Abstract
Diabetic wounds are one of the major health issues for people suffering from diabetes. They often do not heal well. The normal healing process is slow or does not work right. These wounds pose a risk to both patients and health care providers. Numerous traditional methods, viz. growth factor administration, cell therapy, gene therapy, wound dressings, skin transplants, and others, are being used to promote wound healing in various types of wounds. Current research focuses on innovative wound dressings that contain biological agents to promote wound healing more quickly. Nano-therapeutics, 3D bioprinting approaches, and stem cell treatment for enhancing curative results with prominence on skin regeneration with negligible side effects are recent innovations in advanced wound care technologies. In this review, the advantages and disadvantages of several cutting-edge and novel approaches viz. cold plasma treatment therapy, extracellular matrix-based techniques, and platelet-rich plasma-based techniques to fostering high-quality wound healing as well as future developments and challenges with these new methods have been reviewed.
Introduction
Globally, diabetic wounds are major and expanding health care concern. In the past few decades, the incidence of diabetes mellitus has rapidly increased, and by 2045, it is predicted that over 700 million people will be suffering from this metabolic disorder.1,2 The development of diabetic wounds is a result of uncontrolled diabetic conditions. These wounds are persistent and complicated, leading to serious consequences including amputations, infections, and significant deterioration in the eminence of living in diabetic people.3,4 The etiology and duration of diabetic wounds are marked by chronic inflammation, poor angiogenesis, high oxidative stress, and a diminished capacity to fight the infections, even more complicated with the existence of advanced glycation end products and modified components of the extracellular matrix (ECM).5,6 Therefore, finding good therapy for diabetic wounds remains a challenge.
Nanotechnology is changing clinical therapy and research. It shows great potential for treating diabetic wounds. This progress offers hope for better treatments.6,7 Nano-therapeutic methods improve wound care. They use nanoparticles to bypass issues with older treatments. This approach offers a better way to heal injuries. Such nanomaterials have multifunctionality, targeted delivery, controlled drug release, and improved biocompatibility. Nano-therapeutics often range in size from 1 to 100 nm. This tiny size makes them well-suited for treating diabetic wounds.8,9 This study intended to highlight the prospect of nanotechnology to transform the area of diabetic wound healing by examining different nanomaterials, delivery strategies, and the insertion of biomaterials. This assessment focuses on providing light on the possibility of nanotechnology to transform the discipline of wound healing for people with diabetes by investigating different nanomaterials, methods of delivery, and the incorporation of biomaterials, thereby upsetting the delicate stability necessary for effective curing of wound.10,11
Physiology of Wound Healing
When skin or other body tissues lose their integrity, a complex biological process takes place, known as wound healing. 12 Various cells, growth hormones, enzymes, and varied ECM components are all necessary for wound healing to repair and restore injured tissues and organs. 13 The process takes place in four different stages, viz. hemostasis, inflammation, proliferation, and remodeling. To prevent disruptions or delays in the healing of wounds, these four stages must be completed in the correct order. 14 Blood clots arise from the biological process identified as hemostasis, which starts as soon as an injury occurs and ends when platelets aggregate at the position of the wound due to their dealings with proteins such as fibronectin and collagen. Soluble fibrinogen is transformed into unsolvable fibrin to stop hemorrhage, and the surrounding tissue produces pro-inflammatory cytokines and growth factors (GFs) that promote the effective curing of wounds. Once the flow of blood has been blocked, the inflammatory phase begins, which involves leukocyte migration to the wounded site to remove debris and infectious microorganisms. 15 Different cells, including lymphocytes, neutrophils, and macrophages, sequentially infiltrate the injured area to prevent infections during this period.16–18 Macrophages have a significant role in the healing process at every stage.19,20 They produce cytokines that cause leukocyte activity, inflammation, and the removal of apoptotic cells. Following the elimination of apoptotic cells, macrophages enter a pro-regenerative state that stimulates fibroblasts and keratinocytes, which leads to tissue regeneration. The inflammatory phase, which causes epithelial cell migration and proliferation, overlaps with the proliferative phase. Epithelial cells and fibroblasts play a crucial role in the development of collagen levels and granulation tissue at the location of the lesion. Fibroblasts are the key players in wound healing because they synthesize collagen, glycol-amino-glycans, and proteoglycans, which are the key elements of the ECM. The production of granulation tissue marks the transition of the wound-curing process from the proliferative phase to the final remodeling phase.16,21
Chronic Hyperglycemia’s Consequences on Cellular Functioning
Chronic hyperglycemia causes a series of harmful effects on numerous kinds of cells that are essential for wound healing. Higher blood sugar levels are scientifically linked to endothelial cell dysfunction, which compromises vasodilation and hinders angiogenesis. Moreover, hyperglycemia interferes with the fibroblast’s regular activity and hinders the production and deposition of collagen, which is necessary for wound healing. Dysregulated inflammatory cells, such as macrophages, can worsen wound repair. This dysregulation prevents the lesion from quickly healing. It keeps the wound from moving into later phases of recovery, and the inflammatory process is extended by this imbalance.
Diminished Angiogenesis in Diabetes-Related Injuries
One important component of wound repair, that is, angiogenesis, is substantially impaired in people with diabetes. Reduced capillary density surrounding the wound is the result of endothelial dysfunction and aberrant signaling pathways brought by chronic hyperglycemia, and due to this, compromised angiogenesis wound receives insufficient oxygen and nutrients. These particular issues are addressed by nano-therapeutic approaches to encourage angiogenesis and restore appropriate vascularization in diabetic wounds.
Compromised Response of Immune for Wound Healing in People with Diabetes
Wound healing requires a balanced immune response. However, diabetes can disrupt this process. High blood sugar can cause too much inflammation that lasts too long. This can cause problems with cytokines and immune cell movement, which can hinder healing. Moreover, delaying the proliferative phase transition, this persistent inflammation worsens tissue damage and creates an environment, which is favorable for infection. Immune dysregulation should be the focus of nano-therapeutic treatments to alter the inflammatory environment and encourage an equitable immune response to facilitate efficient wound healing.
Wound Curing in Diabetes
Diabetes affects the stages of wound healing as well as prevents the onset of the proliferative stage of wound curing, which inhibits the formation of mature granulation tissues. Additionally, diabetic wounds stay in the inflammatory stage for a longer period than usual.13,22
Compared with regular wound healing, a larger number of inflammatory macrophages stay at the location of damage in diabetic wounds for a longer time. These macrophages generate a higher ratio of pro-inflammatory cytokines, including interleukin (IL)-6 and tumor necrosis factor (TNF)-α, and create reactive oxygen species (ROS) that cause chronic inflammation. These actions stimulate proliferative factors necessary for effective wound healing. However, the increased load of apoptotic cells causes inefficient efferocytosis (phagocytosis of apoptotic cells) by macrophages, which disrupts the common cytokine cascade. A higher proportion of pro-inflammatory cytokines, viz. TNF-α, IL-1, and matrix metalloproteinase-9, lowers levels of anti-inflammatory signals (CD206, transforming growth factor [TGF]-β, insulin growth factor [IGF]-1, and IL-10) may cause uneven fibroblast and keratinocyte death along with the reduction in angiogenesis.23–25
Diabetic wound healing is hindered by both external and intrinsic factors. Recurrent trauma and ongoing mechanical stress can worsen the process of healing and lead to the development of ulcers.26,27 Diabetic wound healing gets delayed for several reasons, including neuropathy, weakened immune system, microbial infection, low oxygen levels, and low GF activity.13,14,28 The typical wound healing process involves a mass of cells, including mast cells, keratinocytes, fibroblasts, neutrophils, macrophages, and endothelial cells. These cells release several GFs and cytokines that are vital for hastening the curing of wounds. Macrophage polarity is altered by elevated blood sugar, and this is one of the main reasons for compromised wound healing. Diabetic wounds showed several abnormalities, including persistent release of pro-inflammatory cytokines, a delayed angiogenic response, and decreased neutrophil, macrophage, and fibroblast activity.29,30
Sensory impairment related to temperature, pressure, and lesions can lead to consequences of diabetic wounds. The absence of discomfort combined with inappropriate vasodilator auto-regulation slows down the healing process of wounds. Diabetic wounds can induce sadness and mental stress in addition to restricting an individual’s ability to move. 22
Types of Diabetic Wound Dressings
By promoting better granulation and re-epithelialization, facilitating water transport, and creating a moist environment, wound dressings accelerate the healing process. They could be used with antimicrobial or medicinal substances to effectively treat wounds. 13 Comfeel®, Granuflex®, and Duoderm® are frequently used diabetic wound care products in the market. However, their use in treating infected wounds raises serious concerns because they may cause maceration to the surrounding tissues. Two hydrogels used to treat wounds are Intrasite Gel and Aquaform; however, their application in diabetic foot lesions in patients with limb ischemia is limited. 31
Films are translucent, sticky substances that are frequently applied during wound care. Their transparency makes it easier to track wound healing without disturbing the wounded area or the dressing. 32 They permit gases such as carbon dioxide, oxygen, and water vapor to pass through the injured area and surrounding air. High elasticity and flexibility, as well as ease of fabrication in the appropriate size, are a few advantages of film-based dressing materials.33,34
Hydrogels are frequently utilized in wound healing and tissue engineering and are produced by cross-linking synthetic or natural polymers chemically or physically. When compared with their dry weight, they may absorb a large amount of water molecules because of their 3D polymeric network. Their ability to retain an excessive amount of moisture at the wound site sets them apart from all other wound dressing materials. 35 To shorten the time needed for wound closure, they could formulate in various shapes and sizes and encapsulate growth hormones, cells, and antimicrobial agents. Because hydrogel can maintain a moist environment, it promotes granulation and re-epithelization, two processes that are important for tissue regeneration. 36
A group of nanofibers with sizes ranging from nanometer to micrometer is called a nano-fibrous dressing. Nanofibers can be developed by a variety of techniques; however, the electrospinning process is one of the most widely used because of its many advantages, including affordability, convenience of use, adaptability, porosity control, and mechanical property tuning. After applying to the wound, the nanofibers were simply removed without harming the area where they were applied.37–40 They can be filled with different bioactive compounds to treat wounds. Nanofibers can mimic the natural ECM. Even they also provide the right conditions for cell adhesion and proliferation, which promotes the wound healing process.41,42
Hydrophilic and hydrophobic foam with bio-adhesive properties is the most common wound dressing material. The hydrophobic layer allows gaseous exchange, and water vapor penetration, however, stops liquids from entering the wound bed needlessly. Foam-based wound dressings have the benefit of being able to absorb excess wound exudate volume and maintain the proper moisture content.43,44 The quantity of wound exudates that foam can absorb varies depending on the overall thickness of the wound. However, dry wounds with lesser exudates shouldn’t use foams.45,46
The very porous, freeze-dried polymers used in wafer-based wound dressings have properties like foams. After absorbing the wound’s exudate, wafers turn it hooked on a gel or viscous solution that creates a damp environment. 47 Wafers for biomedical purposes were developed using polymers, such as sodium alginate and xanthan gum. Wounds heal more quickly thanks to the wafer’s ability to absorb wound exudate, which also helps to lower fluid accumulation and microbial infection. 48
Sponge pores are linked, making it soft and pliable. Because they are porous, they have exceptional swelling capacity, which is ideal for a material used to make wound dressings. Many sponges are made using different polymers to transport medicinal chemicals to effectively treat diabetic wounds. It has been shown that sponges protect the wound site from bacterial infection and facilitate cell migration. Sponge fibroblast migration is facilitated by their interconnected pores, which accelerates wound closure.13,49
Novel Strategies for Diabetic Wound Healing
In the realm of wound healing research, new developments in technology have greatly expanded our knowledge of assessment and treatment strategies.
The paradigm shift from treating dry wounds to moist ones, stimuli-responsive wound dressings, GF-based therapy, nanotherapeutics, tissue-engineered skin, gene therapy, bioengineered human skin replacements, and stem cell therapy have all fundamentally changed the path of advancement in this field. Furthermore, the progression of innovative technologies some platelet-rich plasma (PRP) treatment, 3D bioprinting, and ECM-based methods has opened the door to customized wound healing. However, there are still issues with diagnosing and treating persistent wounds. Consequently, therapeutic approaches that consider these factors for wound healing are more useful, economical, and benefit-to-risk. This section will cover a few novel and inventive wound healing treatment modalities that are currently being researched and utilized, as well as their advantages and disadvantages.
Nano-therapeutics for the healing of diabetic wounds
Nanotechnology has developed new opportunities in the search for novel treatments to address the complex problems related to diabetic wounds. With an emphasis on metallic nanoparticles, we reviewed a number of the remarkable nanomaterials that have emerged as promising options for repairing diabetic wounds. To encourage wound healing in lesions that were difficult to heal, previous approaches employed systemic administration of antibiotics, antimicrobial agents, and other local medication applications. These methods do, however, have several drawbacks, such as inadequate drug diffusion into the underlying skin tissues and the development of bacterial resistance with prolonged antibiotic use.50,51 Nano carriers are therapeutically significant in wounds because of their minuscule size (between 10 and 100 nm) and physical and chemical characteristics that allow for intracellular drug transport, improved penetration, and degradation stability.52,53 Furthermore, the high encapsulation efficiency of nano carriers of different drugs and biomolecules enhances delivery efficiency for relevance in wound healing and skin regeneration. 54 Strategies based on nano-therapeutics offer several benefits for managing microbial contamination in persistent wounds. The benefits include better medication bioavailability and half-life, better drug diffusion across tissue barriers and bacterial biofilms, enhanced drug–microbe interactions, and the ability to elevate drug concentrations at the infection site. 55 Figure 1 shows various nano-therapeutic methods using nanomaterials used for the healing of diabetic wounds.
Schematic representation of various nano-therapeutic methods using nanomaterials for diabetic wound healing.
Metallic nanoparticles
Gold nanoparticles
Gold nanoparticles (AuNPs) are a class of metallic nanomaterials that may help people with diabetes heal their wounds. AuNPs have antioxidant and anti-inflammatory properties that can be especially accommodating for diabetic wounds. These nanoparticles can improve surroundings for wound healing by lowering oxidative stress and excessive inflammation. 56 AuNPs can be used as drug delivery platforms, enabling the controlled release of therapeutic medications at the wound site. While reducing systemic adverse effects, this focused medication delivery can improve the effectiveness of wound healing therapy. Li et al. conjugated AuNPs with keratinocyte growth factor (KGF), which is usually limited by instability. Designed to enhance the healing of diabetic wounds limited by instability and designed to enhance the diabetic wound healing. This resulted in improved binding affinity and increased stability, which increased wound recovery in diabetic animals. 57 AuNPs are also employed in photothermal treatment as well as function as medication carriers. These nanoparticles produce heat when confronted with near-infrared light, used to mark and eliminate microbial infections in the wound.
Silver nanoparticles
Silver nanoparticles (AgNPs) provide a comprehensive healing strategy for diabetic wounds, which are more prone to infections 58 because of their strong antibacterial action. They can effectively fight off a wide range of pathogens, such as fungi, bacteria, and even those who are resistant to antibiotics. Because AgNPs have antibacterial properties, they can help lower the risk of infections in diabetic wounds, which can lead to major issues. 59 Silver nanoparticles have shown strong antibacterial properties against a variety of human pathogens, comprising S. aureus, E.coli, B. subtilis, and S. typhi, in a dose-dependent manner. Moreover, the AgNPs demonstrated the capacity to inhibit the production of resistance genes, which might improve the efficacy of medications. 60 Additionally, researchers have found that AgNPs have anti-inflammatory qualities. One characteristic of diabetic wounds is chronic inflammation, which slows the healing process. By modifying the inflammatory response, AgNPs may hasten the termination of inflammation and encourage the next phases of wound healing. AgNPs have also been demonstrated to promote angiogenesis, which facilitates the revascularization of the injured area and increases the accessibility of oxygen and nutrients. 61 AgNPs are appealing options for diabetic wound care because of their multifaceted properties, which include antibacterial, anti-pro-angiogenic, and inflammatory activities that cooperate to encourage healing and reduce the risk of issues related to these challenging wounds.
Zinc oxide nanoparticles
Among their many applications, zinc oxide nanoparticles (ZnONPs) have demonstrated potential in the management of diabetic wounds. ZnONPs are effective against a range of bacterial strains that are commonly connected to diabetic wound infections due to their potent antibacterial properties. 62 They can help reduce the risk of wound complications by inhibiting the growth of bacteria and the formation of biofilms. ZnONPs have anti-inflammatory properties similar to those of other metallic nanoparticles. By lowering inflammation, these nanoparticles may contribute to the development of a more favorable wound healing environment, potentially speeding up the healing of diabetic ulcers. 63 It has been demonstrated that ZnONPs encourage epithelialization, which can hasten the healing process of diabetic wounds. One of the most important phases of wound closure is epithelialization, which is the process of creating a new epidermal surface over the wound. 64
Polymeric nanoparticles
Chitosan nanoparticles
The natural polymer chitin, which is present in crab shells, is the source of chitosan nanoparticles, which have drawn interest due to its wound healing, biodegradable, and biocompatible qualities. 65 Since chitosan nanoparticles are naturally antibacterial, they can effectively combat a variety of diseases. In the management of diabetic wounds, where infections are a continual concern, this polymer is extremely helpful. It could be revealed that chitosan nanoparticles stimulate the growth of keratinocytes and fibroblasts; these crucial cells effectively contribute to wound healing. Diabetic ulcers may heal more quickly because of this accelerated cell proliferation. Algandaby et al. investigated the effects of Teucrium polium (TP) loaded chitosan nanoparticles on wound healing in diabetic rats. According to their findings, TP boosts the production of collagen, granulation tissue, wound closure, epithelium regrowth, and angiogenic factors, as well as also reducing the oxidative stress and inflammation. Moreover, chitosan nanoparticles have hemostatic qualities that help stop bleeding from the injury region quickly. When diabetic foot ulcers are deep and have a limited vascular supply, this can be especially helpful. Younas et al. presented a brand-new pullulan-based smart microneedle patch that contains moxifloxacin, thrombin, and lidocaine-loaded nanoparticles. This patch exhibits quick wound healing, prolonged antibacterial activity, and hemostasis/analgesia. 66 Through several methods, chitosan nanoparticles hold great promise for treating chronic wounds in people with diabetes.
PLGA nanoparticles
PLGA nanoparticles, also known as poly(lactic-co-glycolic acid) nanoparticles, are biocompatible and biodegradable polymeric carriers that have demonstrated potential in the fields of wound healing and medication delivery. 67 Therapeutic agents can be delivered to the wound site locally and continuously through PLGA nanoparticles with exceptional controlled drug release capabilities. 68 The efficiency of several wound healing substances, including cells, GFs, antibacterial, and anti-inflammatory medications, could be improved by this controlled release. The PLGA@IL-8/acellular dermal matrix (ADM) scaffold may be an efficient delivery system for exogenous cells in diabetic wound treatment, based on prior research conducted by Zhang et al., which employed PLGA nanoparticles laden with the anti-inflammatory feature and angiogenic cytokine IL-8; these nanoparticles were integrated with ADM to boost the differentiation, multiplication, and survival of mesenchymal stem cells (MSCs) in diabetic injuries. This led to an improvement in wound healing and tissue regeneration. 69 The gradual breakdown of PLGA nanoparticles into harmless byproducts eliminates the need for extraction or removal post-drug discharge, aligning with this biodegradability’s aim of minimizing patient discomfort and intervention. The bioavailability of enclosed therapeutic agents improved through their tiny size. When treating diabetic wounds, this is especially beneficial because effective treatment relies on achieving the ideal dosage levels at the wound site. Researchers used PLGA-PEI/nitric oxide (NO) nanoparticles to provide NO to wounds infected with methicillin-resistant S. aureus (MRSA) biofilm. This is a frequent problem in patients with diabetes, and sustained NO administration is essential because of its restricted diffusion and short lifespan. Nanoparticles showed strong antibacterial property due to their robust adherence for biofilm framework and extended NO release. By spreading the biofilm and lowering the bacterial burden, these nanoparticles hasten wound healing in mice with diabetes and provide potential effective treatment for chronic wounds infected by biofilm. 70 Using iron oxide-loaded galactose-modified PLGA nanoparticles, Wei et al. created F@GP, a novel drug delivery system that specifically targets senescent cells in diabetic wounds, promoting cell proliferation and causing ferroptosis to hasten wound healing. 71 The development of new therapeutic approaches for the healing of diabetic wounds is generally made possible by PLGA nanoparticles, which offer unique properties for targeted treatment, controlled drug delivery, and enhanced tissue regeneration.
Lipid-based nanoparticles
Liposomes
Liposomes are circular vesicles with an aqueous core surrounded by lipid bilayers. These lipid-based nanoparticles are attractive for treating diabetic wounds because of their qualities. Since liposomes are biodegradable and biocompatible, their application to wounds reduces the possibility of toxicity or unfavorable responses. 72 Their compatibility with biological systems enhances their usefulness for wound healing functions. Liposomes are an efficient way to encapsulate a variety of medicinal substances, including growth hormones, antibiotics, and anti-inflammatory drugs. This encapsulation enhances therapy outcomes by enabling controlled and accurate drug delivery to the wound site. 73 Liposomes interact with cells near the wound region more easily due to their lipid bilayers, which is resemble to cell membranes. This characteristic improves the ability of medications or bioactive substances to enter tissues, especially those with poor circulation, frequently observed in diabetic wounds. In an earlier study, red blood cell membrane–mimicking liposomes holding curcumin (RC-Lips) were developed to effectively adsorb α-hemolysin, lessen its damage to keratinocytes, facilitate liposome uptake into macrophages, control M2 macrophage polarization, and promote wound healing in mice with diabetes by downregulating IL-1β and IL-10 overexpression. 74 Liposomes offer encapsulated medications that protect them from enzymatic activity and degradation in the wound area. During the journey to the wound site, this protection helps keep therapeutic substances effective. For example, purpurolide C produced from Penicillium purpurogenum inhibits the activation of inflammatory macrophages to enhance wound healing in people with diabetes. However, its low solubility and instability make it difficult to utilize. In an in vivo study, liposome-encapsulated PDTPTBT effectively kills several bacteria, with MRSA and E. coli, under near infra-red radiation (NIR) irradiation, resulting in membrane harm and cytoplasm outflow. This shows its potential in dealing with multidrug-resistant bacterial infections, particularly in reducing mortality and speeding wound healing in a diabetic skin infection model. 75 Liposomes have recently shown promise as efficient delivery systems for gene therapies to target cells in diabetic wounds. 76 This novel strategy has a lot of potential for accurately regulating the expression of important genes concerned with wound healing progression, including those linked to tissue regeneration, inflammation, and angiogenesis. As cutting-edge technologies evolve, liposomes will provide customized treatments to address particular issues with wound healing in diabetic processes.
Solid lipid nanoparticles
Solid lipid nanoparticles (SLNs) offer special benefits and are made of lipids in a solid form at room temperature. 77 First, SLNs provide sustained drug release characteristics, assuring that therapeutic medicines stay at the wound site for an extended period. Chronic diabetic wounds that need ongoing care may benefit most from this controlled release pattern. Because of its great drug-loading capacity, SLNs may encapsulate a sizable quantity of medicinal drugs. Arantes et al. have reported a chitosan film integrated with SLN–all trans-retinoic acid in their prior work. This film effectively loaded high-efficiency medications and encouraged the controlled release of the drug, suggesting that it may be used as a viable therapy for diabetic wounds. 78 When diabetic wounds need topical therapy to get to deeper layers of tissue, SLN’s ability to improve medication penetration through the epidermis and into the wound bed is crucial. By controlling the activity of bacteria and oxidative damage, embedding sesamol within SLNs not only improves its long-term stability as well as withholding in the skin but also boosts its efficacy in opposition to skin pathogens and significantly enhances its capacity to cure wounds.
Organic nanoparticles
Extracellular vesicles
Small, membrane-bound particles called extracellular vesicles (EVs) are released by an assortment of cell types, containing immune and stem cells, and are essential for tissue healing and intercellular communication. 79 The EVs released from cells in diabetic wounds may differ from those in normal wounds. Through identifying surface KRT14 as a consistent marker and proving their decreased number and changed composition in wounds with diabetes, Guda et al. established an innovative technique to isolate and distinguish keratinocyte-originated EVs (hExoκ) from an individual’s chronic wound fluid. This suggests that EVs may play a role in the chronicity of diabetic wounds and offers important insights into how EVs malfunction in diabetic hurdles. 80 Nonetheless, EVs derived from healthy cells or organs have great potential as organic carriers of bioactive compounds including GFs, nucleic acids, and cytokines. These molecules can promote regenerative processes such as angiogenesis, the production of collagen, and cell movement; all are essential for the healing of diabetic wounds. 81 EVs solve many problems associated with cell transplantation by providing a cell-free substitute for conventional cell-based treatments. Because of their compact size, they may be administered more easily and delivered precisely to the wound site. 82 Immune cells and MSCs are two examples of cell types from which EVs are extracted and customized to meet the unique requirements of each patient. The newly developed EVs were enhanced to make them more beneficial. The healing of diabetic wounds has been greatly enhanced by their modification to efficiently absorb miR146a and adhere to a silk fibroin patch, for instance. 83 Additionally, EVs can be added to biomaterials for extended release, enhancing the material’s efficacy and durability. One useful treatment for diabetic wounds is the incorporation of macrophage consequent EVs in a new hydrogel system, which combines anti-swelling and photothermal properties, scavenges ROS, suppresses inflammation, and increases angiogenesis. 84 In general, EVs provide a possible therapeutic option for diabetic wounds.
Nanofibers
Nanofibers are essential tools for the healing of diabetic wounds because of their very small diameters, measured in signaling. 13 These microscopic fibers improve wound care in several ways. They are highly good at absorbing medications and other therapeutic molecules because of their huge surface area, which enables effective treatment delivery straight to the wound region. 85 By providing co-loading ability, biocompatibility, and controlled discharge features, chitosan-based nanofibers have a nanocapsule-in-nanofiber framework developed in a prior study to efficiently load both hydrophilic and hydrophobic drugs, improving the management of challenging wounds. 86 Moreover, the ECM’s structure and function may be replicated by nanofibers, resulting in a supportive atmosphere that promotes tissue development, cell attachment, and mobility. 87 To sustain long-lasting therapy benefits, nanofiber-based coverings are used to discharge GFs or drugs gradually over time. Additionally, these fibers serve as barriers that shield wounds from infections while maintaining moisture, essential for healing. 88 They can even be shaped into 3D to aid in the healing of more severe wounds. For instance, Huang and colleagues developed a 3D chitosan/polyvinyl alcohol–tannic acid nanofiber sponge that provides a fluffy, extremely porous structure that enhances hemostatic properties, water handling, and antibacterial and antioxidant properties without the need for antibiotics. This sponge is assured for use in medical wound dressing applications in the future. 89 Finally, a lot of nanofibers are biodegradable, breaking down into innocuous compounds as the wound heals, minimizing the need for repeated replacement of dressings and other medical procedures. 90
Covalent organic frameworks and metal organic frameworks in the healing of diabetic wound
The potential of two new nanomaterials, covalent organic frameworks (COFs) and metal organic frameworks (MOFs), for a variety of applications, including the management of diabetic wounds, has attracted attention. 91 These materials belong to a larger class of crystalline porous materials, valued for their special structural properties and biological tissue compatibility that qualify them for use in medical settings.
Recent advances in biomedical research have led to the development of new treatment methods using MOFs, and they exhibit encouraging promise in tackling the particular difficulties associated with diabetic wound curing. The MOF/Gel antioxidant system is one such advancement that aims to aid rats with diabetes in healing chronic wounds. 92 This approach incorporates an MOF nanozyme that functions similarly to an antioxidant enzyme into a hydrogel. In chronic diabetic wounds, the MOF/Gel constantly scavenges ROS, modifying the oxidative stress microenvironment and promoting the passage from the inflammatory to the proliferative phases. This therapy has shown promise as a secure and practical solution for therapeutic needs, with efficacy equivalent to that of human epidermal growth factor (EGF) gel, a commonly used clinical medication for wound treatments. Engineered therapeutic hydrogels are another noteworthy strategy that uses MOFs’ antioxidative and oxygen-generating properties to improve diabetic wound healing. 93 Natural polymers and a catalase mimic nanozyme generated from MOF used to develop these hydrogels, which absorb high ROS and cooperatively produce oxygen. This strategy speeds up the healing process by shielding vital cells in the skin from ROS and hypoxia-mediated apoptosis thus encouraging a change in the activity of macrophages from a pro-inflammatory into an anti-inflammatory state. Additionally, there have been outstanding outcomes from the use of multifaceted nano-platforms such as Au NCs@PCN treating bacterially contaminated diabetic ulcers. 94 These systems use zirconium-based MOFs and gold nanoclusters to produce ROS and photothermal impacts when exposed to NIR laser light, which efficiently kills bacteria and drastically lowers wound covering in rats with diabetes. The development of permeable MOF liquids, including zeolitic imidaizolate-91 (ZIF-91) porous liquid, represents a breakthrough in diabetic wound care medication delivery systems. 95 When cross-linked with altered gelatin to create hydrogels, these liquids have a high capacity for loading curcumin with a prolonged release, that promotes healing. New permeable MOF microneedle patches that can distribute NO in a photothermal-responsive manner are being developed. 96 These patches speed up vascularization and tissue regeneration by promoting a deeper NO supply to the wound site. Conclusively, incorporating MOFs into diabetic wound treatment presents a multifaceted strategy that tackles oxidative stress, bacterial infection, and inflammation, and it has significant potential to improve the results of chronic diabetes wounds. These groundbreaking therapies represent a major step forward in addressing the shortcomings of existing treatments and lay the groundwork for further developments in the management of diabetic wounds.
Conversely, COFs encompass a stiff organic structure developed by covalent bonding. These frameworks are distinguished by their robustness, predictable architecture, and adaptability in changing their characteristics to meet particular requirements. COFs have demonstrated promise in improving regulated medication release and promoting tissue repair processes in diabetic wound healing. Their precise structure allows for the design of their physical and chemical properties, which influences how drugs are released and transported. 97 This control is essential for developing methods of delivery that are tailored to the unique needs of diabetic wounds, with an emphasis on the right dosage and timing of therapeutic agents. 98 A novel nano agent was developed in aprior study using 2D reductive COF covered with signal engineered exosomes for treating diabetic wound through reduction of inflammation, oxidative stress and promoting angiogenesis to get rid of bacterial infection. This nano-agent showed notable improvements over traditional treatments. 99 In another study, an innovative therapeutic gel that combines COFs and microalgae was developed to address the intricate problems of diabetes-related chronic wound repair. Through promoting angiogenesis, reducing inflammation, and releasing oxygen helps in wound healing. Clinical results support the effectiveness of this approach for intensive wound care. 100
Clustered regularly interspaced short palindromic repeats revolution
A genome editing technique that may precisely mark various genomic regions to fix or damage a particular gene has been made possible by the clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) system. 101 Numerous applications of the Cas9 and other Cas systems have been made to identify therapeutic targets, develop animal models, determine the roles of genes, and ultimately generate gene treatment. Moreover, this technique has been utilized to reduce the warning signs of several diseases. 102 Since CRISPR/Cas9 technology may mobilize and utilize a wide range of molecules as mediators for healing without triggering an immune response, it may be useful for chronic wound healing. 103 Therefore, compared with existing gene-editing approaches, this technology has made it feasible to access genomic targets to change the wound microenvironment more precisely and with incredibly slight off-target alteration. In one case, BMMSCs were genetically re-programmed ex vivo to express excessive platelet-derived growth factor (PDGF)-B and facilitate healing in recent studies. 104 According to other researchers, fibroblasts from people with dystrophic epidermolysis bulbosa, a condition that causes skin lesions that heal slowly, had certain genes fixed. 105 However, rather than reprogramming the cells of the wound bed by local CRISPR/Cas9 administration, the future of this technique is probably going to lie in ex vivo re-programming of cells to be injected or placed in dressings over expressing GFs or pro-healing cytokines.
3D bioprinting-based strategies
Several therapy techniques have been widely used to treat both acute and chronic wounds during the past 20 years. However, the majority of the available treatment techniques required human labor, and the length of time needed to cover big wounds or burns impeded their effectiveness. To get beyond this restriction, 3D bioprinting has become a fast and elevated throughput automation technique in recent decades to deal with regenerative medicine’s problems, such as wound healing. A possible method for creating biocompatible artificial skins is the 3D bioprinting process, which is an additive manufacturing method that involves precisely depositing GFs, biomaterials, proteins, and live cells layer by layer. 3D bioprinted skin constructs offer significant advantages for wound healing and skin regeneration as well as they allow for faster and more automated production, which reduces both time and costs. These constructs are flexible, enabling the introduction of various cells and biomolecules that support pigmentation, nerve growth, and blood vessel formation. They enable the precise placement of different biomaterials and cells in specific locations. Lastly, these constructs can be produced on a large scale while maintaining good flexibility and adaptability.106–108 Because numerous cells and biomaterials are precisely deposited, the bioprinted skin analogs intimately resemble the architecture and heterogenicity of genuine skin. 109 Several requirements must be met by the bioprinted skin structures for them to function and be composed. Initially, it should be possible for bioprinted skin replacements to transfer wound exudates and nutrients. The ability to specifically deposit a range of skin cells, including keratinocytes, fatty tissue cells, fibroblasts, melanocytes, and Langerhans cells, at specific levels and places at the second need for bioprinted equivalents. Conclusively, the bioprinted configuration must be strong, biocompatible, biodegradable, and proficient to withstand external stresses and pressures that exist in in vivo settings. Its mechanical, porosity, and degrading characteristics must closely resemble those of the natural skin.110,111 The four primary bioprinting methods being used for skin tissue rejuvenation and cutaneous healing of wounds are as follows. Based on their initial prototypes, bioprinting technologies include extrusion-based, droplet on-demand (inkjet)-based, laser-based, and stereolithography-based techniques.112–115 Extrusion-based bioprinting (EBB) techniques are the most widely used technologies for skin bioprinting because of their many benefits, including their high printing momentum, affordability, convenience, ability to replicate complex tissues, and capacity to print a broad variety of viscous biomaterials. 116 Pneumatic pressure, screw-based, microfluidic, or piston processes are often used in EBB to extrude uninterrupted stands of bio-inks by conducting a nozzle to deposit the predesigned, geometrically distinct, and 3D multifaceted patterns of skin. 117
One drawback of the EBB approach is that it frequently has clogging issues with various types of nozzle types. The bioprinting methods offer several advantages and disadvantages that require development in provisions of bioprinting device designs and procedures. The use of hybrid bioprinting systems that combine two or more bioprinting technologies, as well as newer and/or enhanced bioprinting expertise, can help overcome the limits of bioprinting technologies. Examples of novel and enhanced versions of current bioprinting technology are computed axial lithography (CAL), multimaterial multi-nozzle 3D printing (MM3D), and continuous liquid interface production (CLIP).118–120 Because CLIP-based bioprinting has a 100-fold quicker printing speed than traditional stereolithography (SLA) printing techniques and uses an oxygen-permeable window beneath the UV projection to develop a “no polymerization zone,” it ensures a continuous SLA process. 119 To print multilayer skin constructions on a wider scale, CLIP may be expanded to use biocompatible photopolymers, visible light-based methods, and other photoinitiators. Instead of employing the traditional layer-by-layer method, MM3D premised bioprinting uses a voxel-by-voxel method with a customized printhead that can switch among up to eight different materials at high frequency. 120 The advantages of this bioprinting technique for the tissue of skin printing include the preservation of stiffness differences throughout the length and width of any particular layer as well as between layers. In comparison to CLIP, which was developed in 2015, this bioprinting technique and CAL were developed in 2019 for skin bioprinting applications. In order to employ this bioprinting technique for skin tissue regeneration, more research is therefore required. Another innovative method for 3D bioprinting is called CAL, which employs volumetric building instead of the more conventional layer-by-layer approach. 118 When using 3D bioprinting techniques, biomaterial ink, also referred to as bio-ink, is another crucial element for successful skin engineering and wound healing.121,122
Biomaterial ink contains all the components of bio-ink except the cells, whereas bio-inks encompass biomaterials, cells, and GFs/biomolecules. For skin bioprinting, a variety of biomaterial hydrogels such as gelatin, collagen, chitosan, silk fibroin, alginate, cellulose, and hyaluronic acid, as well as synthetic biopolymers, are used to enhance the mechanical characteristics of bioprinted structures.123,124 Whether biopolymers are synthetic or natural, all bio-inks should have a few essential characteristics. These characteristics include mechanical stability, good printing ability, biocompatibility, high availability, biodegradability, and the capacity to retain high form fidelity during the bioprinting process. Moreover, the use of living cells in bio-inks might affect the immunological response following implantation, and due to this reason, this crucial factor should be kept in mind when selecting cells. Moreover, primary skin cells, such as melanocytes, fibroblasts, keratinocytes, or stem cells, are ideal for skin bioprinting because they can fabricate skin constructions while retaining all biological functions. 125 Viscoelastic behavior is another fundamental characteristic of bio-ink that impacts cell movement, proliferation, and ECM remodeling in addition to skin bio printability. 126 According to research, the first bioprinted skin was developed in 2009 using bio-ink derived from human dermal fibroblasts and collagen hydrogel. 127 Research indicates that the first bioprinted skin was produced in 2009 using collagen hydrogel and bio-ink made from human dermal fibroblasts. 128 Binder et al. developed skin replacements for wound healing using a 3D inkjet bioprinter and human keratinocytes and fibroblasts. 129 There have been major developments in skin bioprinting that utilize different types of bio-inks and bioprinting techniques. The issue of donor and surgical requirements is resolved by using 3D bioprinted skin corresponding as a substitute to conventional skin transplants for the regeneration of skin tissue structure with appendages.106,130 Additionally, a variety of chronic and non-healing lesions, including diabetic foot ulcers caused by pressure, venous ulcers, and burn wounds, have been treated using this new skin bioprinting method. In a previous study, a portable 3D bioprinting device was created to heal full-thickness burn wounds in pig models with less scarring. 131 In situ, bioprinting of skin tissue sheets is made possible by this portable bioprinter, which preserves the heterogeneity and compositional differences of the cells in the various skin layers. Several biopolymers, including collagen, alginate, and hyaluronic acid hydrogels, as well as epidermal and dermal skin cells, are used in this technique to bioprint skin. An undulating pattern of the distinctive dermal–epidermal junction was developed in a different study, coupled with a full-thickness human skin counterpart that was structurally and biomechanically identical to native skin. 132 An angiogenic 3D-bioprinted peptide patch was created in a recent study to promote skin wound healing. Here, the QHREDGS peptide was covalently coupled with the biocompatible biopolymers gelatin methacryloyl and hyaluronic acid methacryloyl to facilitate bioprinting. In both in vitro and in vivo, the bioprinted peptide-containing patch showed enhanced angiogenesis, their biocompatibility, and wound healing. 133 Figure 2 shows new developments in 3D bioprinting and high throughput and screening platforms.
New developments in 3D bioprinting technology, bioinks for better healing of wounds, in vitro disease models, and the creation of high-throughput drug screening platforms.
Stem cell therapy-based strategies
Stem cells can differentiate into numerous cell types and have a long-term capability for self-renewal, they have attracted a lot of interest in regenerative medication for wound recovery and regeneration of skin. 134 Progenitor cells and stem cells have drawn a lot of interest among cell treatments for wound healing, and because of the stem cell’s flexibility, surviving stem cells around wound sites also cure wounds. Additionally, stem cell-based therapy has demonstrated significant promise in the management of chronic wounds that cannot be resolved by conventional therapies. Stem cell-based therapy for chronic wounds uses many mechanisms, including immune process stimulation, inflammatory process management, and GF interactions and activities, to accelerate vascularization and re-epithelialization. 135 In recent years, several stem cell-based clinical and preclinical studies have shown significant effects on the quality of wound healing.136,137 The capacity of stem cell-based wound therapy to release GFs and pro-regenerative cytokines to promote the regeneration of skin during the recovery process of chronic wounds is primarily accountable for its therapeutic perspective. 138
Furthermore, autologous stem cells promote angiogenesis, have a good differentiation prospective, and are generally well-accepted by patients with few side effects. Stem cells are an excellent option to aid in the natural process of healing by promoting the proliferation of cells and hastening wound contraction due to their amazing capacity to differentiate into any other type of cell. Previous studies have shown that stem cells aid in the healing of wounds by indirectly and directly stimulating the epidermal tissue’s resident cells, releasing active chemicals, reducing inflammation, and remodeling the ECM. 139 Among the several types of stem cells, MSCs, embryonic stem cells (ESCs), and the currently researched induced pluripotent stem cells (iPSCs) are the main sources of stem cells utilized for wound healing and regeneration of skin. 140 Because of the ethical issues involved, ESCs were not widely used as a source of stem cells for repairing wounds. MSCs continue to be the mainly compelling source of stem cells for curing wounds due to their capacity to control inflammation, improve angiogenesis and granulation tissue creation, have antibacterial properties, lessen scarring, and encourage fibroblasts.141,142 MSCs can be derived from a wide range of sources, including adipose tissue, amniotic fluid, bone marrow, umbilical cord blood, and Wharton’s jelly stem cells. MSCs facilitate movement to the wound location and stimulate angiogenesis, GF/cytokine discharge, and re-epithelialization, all of which are significant steps in the four stages of wound healing. In the first-ever human investigation, bone marrow-derived MSCs were used to treat severe burn injuries, neo-vascularization and pain alleviation followed by skin grafting. 143 Burned patients with 80% total body surface area and hypertrophic scarring were treated with their bone marrow stem cells implanted in the wound surface in a related investigation. The patients were then covered with an acellular dermis support matrix. 144 Stem cell transplantation led to improved angiogenesis, altered ECM, and decreased wound contraction. A second study was also carried out to treat diabetic ulcers, which are chronic wounds that do not heal, using skin fibroblasts, autologous bone marrow-derived MSCs, and biodegradable collagen membranes (Coladerm). Improved vascularization and a decrease in wound size were observed after 29 days of dual therapy. 145 Table 1 mentions the several stem cell-based treatments for faster wound healing.
An Overview of Several Stem Cell-Based Treatments for Faster Wound Healing
According to a recent study, MSC transplantation enhanced cutaneous wound healing by releasing vascular endothelial growth factor (VEGF) through paracrine signaling. Although MSCs show promise in cell-therapy-based wound care strategies, there are still several drawbacks, including limited viability upon implantation and long-term protection. Several strategies have been used to increase the transplanted MSCs post-implantation existence.151,152 Kamolz et al. delivered MSCs to the wound site using Matrigel with Matriderm. Moreover, the development of this strategy included GFs in the scaffolds to enhance wound healing and vascularization.153,154 These studies show that adding GFs to scaffold-based delivery methods and stem cells improves the wound healing effect. Furthermore, to hasten the healing of chronic wounds, a number of compelling clinical trials have been conducted using scaffold-based delivery systems and stem cells.138,155 Furthermore, promoting the best possible tissue regeneration and wound repair requires MSC guidance. Halloysite (aluminosilicate clay mineral) nanotube-coated 3D-printed polylactic acid demonstrated the beneficial effects of MSC orientation on wound healing using this technique. 156
Another study revealed that a 3D-printed poly-caprolactone scaffold seeded with MSCs and covered with nanocellulose promoted cellular proliferation and differentiation for the wound healing process. 157 Adipose-derived MSCs are also often used in applications of wound healing because of their ease of access, low invasiveness, and lack of ethical restrictions.148,158 Exosomes produced from adipose-derived MSCs have recently demonstrated rapid wound healing by reducing the inflammatory phase, leading to a considerable increase in the rate of wound contraction.159,160 By increasing cell proliferation and collagen deposition, umbilical cord blood stem cells, another source of MSCs, have shown encouraging therapeutic benefits in the control of chronic wounds in people with diabetes. 161 In the field of regenerative medicine, iPSCs, a novel stem cell source, have been released to address the limitations of MSCs and ESCs.138,162,163
EVs: A cell-free healing method for wound
EVs are sophisticated, compact cell-to-cell communication networks that allow many cell types to share information in the form of proteins, lipids, or species of nucleic acid. EVs were initially identified in 1983,164,165 and they were dubbed “exosomes” 166 in 1989. These days, tiny EVs that are discharged from the inside of any cell through the multivesicular endosomal pathway are referred to as “exosomes” (exos). Exosomes are one type of EVs that cells produce together with apoptotic bodies and microvesicles, also known as ectosomes. The size and cargo content (proteins, RNA, etc.) of microvesicles, exos, and apoptotic bodies vary from one another; exos range in size from 30 to 150 nm, microvesicles vary from 100 to 1000 nm, and apoptotic bodies range from 50 to 5000 nm. 167 The cellular source must be taken into account while creating EV therapies for wound healing applications. Inflammatory cell-derived EVs and MSC-derived EVs drive distinct biological processes. Because of their proven signal-modulatory activity and regenerative ability, MSCs-EVs are the primary focus of EV utilization in wound healing applications.168,169 The great majority of EV-based medicinal strategies are developed as topical, subcutaneous, intramuscular, or intravenous injections. However, because of their high clearance rate, EVs administered by injection may not perform as intended. 170 Only a few numbers of in vivo EV-loaded techniques have undergone testing with encouraging outcomes. Fang et al. developed a hydrogel (HydroMatrix®) that was encapsulated with human umbilical cord MSCs-Exos. The study revealed a reduction in myofibroblast accumulation and scar formation compared with the control group. 171 Micro-RNA-126-overexpressing SMSCs-Exos in a chitosan-based hydrogel demonstrated significantly increased angiogenesis and quick re-epithelialization in comparison to the control group and dressing without Exos. 172 In contrast to control and Exos-free hydrogel groups, another in vivo method employing a chitosan/silk GMSCs-Exos-loaded hydrogel showed excellent swelling and moisture retention qualities along with improved collagen deposition, re-epithelialization, nerve density, and microvessel. 173 Moreover, recently, a multifocal strategy utilizing a healing hydrogel (chitosan and methylcellulose) loaded with adipose tissue-derived mesenchymal stem cells (ATMSC) exosomes has been reported. Comparing the Exos-loaded system with the control and Exos-free systems, the former improved wound closure rates, re-epithelialization, angiogenesis, and collagen deposition. 174 Henriques-Antunes and colleagues found that the HA hydrogel loaded with human umbilical cord blood mononuclear cells enhanced the closure kinetics of wounds that received one or more Exos doses. These values were similar to those achieved with Regranex®. Increased neovascularization, improved re-epithelialization, and changes in the expression of seven miRNAs on various stages of wound healing were all linked to this pro-healing activity. They also demonstrated that giving the same total dosage of Exos in multiple doses produced more beneficial effects than giving it all at once. 175
Alginate and methyl cellulose/chitosan, two additional Exos-loaded hydrogels, were recently developed and demonstrated promising results in a full-thickness cutaneous wound model. Wang et al.’s cellulose/chitosan hydrogel showed remarkable self-healing and biocompatibility qualities. Additionally, exosome-loaded hydrogels derived from placental MSCs demonstrated decreased cell death and enhanced angiogenesis in db/db animals. On day 15, hair follicles and glands were even visible in the repaired region of the Exos-loaded hydrogel group, which was packed with neotissues. 176 Exos from ATMSCs were added to the alginate hydrogels developed by Shafei et al. In summary, the manufactured system’s biodegradable and biocompatible nature was demonstrated by its physical and biochemical characteristics. Furthermore, the hydrogel loaded with Exos enhanced neovessel formation, collagen production, and wound healing in the affected region. 177
Recent research has shown that when EVs made from various cell types are administered locally or transported in dressings, they can both accelerate wound healing. However, several factors varied significantly, including variations in the cellular background, the separation process, and/or the quantification technique, aside from the fact that EVs were extracted from culture-conditioned media in the overwhelming majority of investigations. As a result, there were probably different proportions of different EV populations and different levels of lipid and protein pollutants.167,178 Moreover, this lack of standardization is exacerbated by variations in dose units. Given these and other particular concerns related to clinical translation, it is evident that additional preclinical research is required to clarify the exact mechanisms governing the effects mediated by such as yet-to-be-well-defined, heterogeneous, and little-understood EVs.
PRP-based therapy
In regenerative medicine, PRP-based endogenous therapeutic technology has attracted a lot of attention recently due to its potential to promote and speed up tissue regeneration, particularly wound healing.179,180 PRP is an autologous biological product that has more platelets than blood in circulation, meaning it has a greater concentration of GFs, which is necessary for the curing of wounds. 181 Because platelets have a hemostatic effect and encourage the proliferation of skin cells and tissue expansion, PRP, also known as autologous platelet gel, autologous platelet concentrate, or plasma-rich GFs are essential for wound healing. 182 GFs that promote cell migration, propagation, and differentiation for the start of closure of the wound include PDGF, EGF, fibroblast growth factor, TGF-1, IGF-1, KGF, VEGF, and others. Intricate wound healing processes and skin tissue regeneration depend on GFs, which are signaling molecules that influence cellular metabolism. 183 GFs are produced by every type of skin cell, and during the stages of wound healing, different cell types develop various kinds of GFs. Every GF has several effects and regulates cellular functions including angiogenesis, ECM signaling, cell migration, and proliferation, creating the perfect environment and speeding up the healing of wounds. GFs are key to fixing wounds. Yet, one GF isn’t always enough. Chronic wounds, such as diabetic foot ulcers, are hard to heal. This shows that wound healing is complex. 184 PRP technology has several benefits for wound healing, including cost efficiency, safety, and simplicity of use. 185 PRP is prepared using a straightforward centrifugation procedure after being extracted from patient blood. Therefore, it is feasible to regulate the dosage of GFs supplied by PRP by adjusting the centrifugation settings and the activation technique. Because PRP is taken from the same patient (autologous), it is safer to administer and has longer-lasting benefits than traditional treatments. In addition to its potential to lower the financial burden of conventional treatment plans, it may also have antibacterial properties. Furthermore, PRP-based therapy is an option for traditional treatments rather than their replacement. PRP has significant regeneration ability and speeds up the healing process for wounds since it is rich in many GFs. 185 According to one research, PRP-based dressing therapy sped up the healing of skin wounds and encouraged fibroblast and MSC migration and proliferation, which resulted in quicker neo-vascularization in clinical patients. 186 Topical PRP therapy for diabetic foot ulcers led to early wound healing with the development of normal granulation tissue. 187 Topical PRP gel application and subcutaneous autologous PRP injections in nonhealing wounds showed a substantial decrease in the size of the wound, a decrease in inflammation and soreness, and the possibility of safety for all patients receiving treatment with no negative effects.
Cold atmospheric plasma therapy
For the past 20 years, biomedical engineering used plasma-based therapeutic approaches for cancer and ulcers. Thermal and nonthermal (cold) plasma are the two types of plasma, which constitute the fourth state of matter. While nonthermal or cold plasma contains particles that are not in thermal equilibrium, thermal plasma contains all the particles including heavy and electron particles in thermal equilibrium. Because of its advantageous qualities, plasma-based treatment for wound recovery has drawn a lot of interest recently. Since cold plasmas have a lower temperature (40°C) that is suitable for biomedical purposes, they are most frequently used in biomedical research. Cold plasmas are also known as nonthermal plasma, gas plasma, or physical plasma. Comprising neutral particles (neutral atoms and molecules) and charged particles (electrons, various reactive nitrogen species [RNS], and ROS), cold plasma is an ionized gas that is close to room temperature. 188 Furthermore, together with various ions and reactive species, the plasma cocktail’s electric field and UV irradiation mediate biological actions essential for tissue renewal. Plasma developed as a result of an electron bombardment and photons having enough energy to interact with the neutral molecules and atoms in the phase of gas. Cold plasmas are predominantly employed in biomedical research because of their lower temperature (40°C), which is appropriate for biomedical applications. Other names for cold plasma include gas plasma, physical plasma, and nonthermal plasma. Almost at room temperature, cold plasma is an ionized gas made up of neutral particles (neutral atoms and molecules) and charged particles (electrons, different RNS, and ROS). 188 Furthermore, together with various ions and reactive species, the plasma cocktail’s electric field and UV irradiation mediate biological actions essential for tissue renewal. Dielectric barrier discharge (DBD) and non-DBD type atmospheric pressure plasma jet are the two main sources of low-temperature plasma discharge. 189 Furthermore, cold atmospheric plasma (CAP), which uses multimodal modes of action to treat chronic wounds and promote wound healing, is a new intervention. 190 Because cold plasma produces anti-infective ROS and RNS, it can lower the bacterial load and trigger the hemostatic phase of wound healing. Furthermore, cold plasma therapy has been shown to have promise for wound tissue regeneration by inactivating microbial species by producing ROS and RNS. NO is the most prevalent RNS for promoting angiogenesis, ECM signaling, and bacterial load reduction. 191 ROS and NO work together to boost GFs where there are wounds. This helps control how wounds shrink. It also helps skin cells grow back to heal the area. 192
MiR-based approach for curing of wound
Managing chronic wounds involves many different, complex things. So, many treatments exist to help fix these wounds. These therapies help the wounds heal better. Current treatments for long-lasting wounds often don’t work well enough. These wounds can be hard to heal. Better solutions are needed to help people recover. A newly developed treatment strategy for chronic wound healing has attracted a lot of interest recently: miR-based therapy, which includes either miR replacement or inhibitory intervention. 193 Since, they control the expression of messenger RNAs, miRs (short non-coding RNA molecules, about 18–25 nucleotides long), are engaged in several pathological and physiological processes, including metabolism differentiation, and development as well as the healing process of wounds. 194 Moreover, prolonged wound healing results in dysregulation of miR expression that was properly produced throughout the regular wound healing process. MiRs may be an effective target for the healing of chronic wounds, as demonstrated by a prior study that found diabetic wounds overexpressed 18 miRs and downregulated 65 miRs when compared with nondiabetic rats (control wound healing group). 195 MiR-based therapy provides a novel, state-of-the-art approach to dealing with chronic wounds since a single miR may regulate a group of genes. The basis of miR-based treatment for wound care is the capacity of therapeutic miRs to raise the levels of beneficial miRs and lower the levels of detrimental miRs utilizing a variety of strategies. Synthetic double-strand breaks, or miR mimics, can be employed to upregulate stuck beneficial miR oligonucleotides. Conversely, competitive inhibitors called antagomiRs (complementary oligonucleotides) can be used to downregulate harmful miRs. The binding of mimics or antagomiRs is necessary for their successful transport to the target miRNA in various tissues, compatibility, and resistance to destruction. 196 Furthermore, by controlling many signaling pathways, the discovery and investigation of relevant miRs implicated in various stages of wound healing may offer third-generation genetic treatment for the curing of chronic wounds. However, a suitable delivery system design is necessary to ensure miR’s effectiveness as a therapy of gene to get past both intracellular and extracellular obstacles. Table 2 shows the various types of miRs associated with various stages of wound healing.
List of miRs Associated with Various Stages of Wound Healing
NO, nitric oxide.
Obstacles and Future Perspectives
Interest in better skin wound healing has grown in recent decades. This has led to new treatment methods for quality wound repair. It also encouraged more study of how wounds heal. Although several researches have clarified the fundamental mechanics of wound healing, certain particular mechanisms are still unknown. Many novel and cutting-edge approaches to better and quicker wound healing have been adopted because of enormous scientific and technological breakthroughs. Nowadays, there is a lot of interest in using a nano-therapeutic approach to encourage wound healing and avoid scarring. To provide stimulating effects at every stage of wound healing, nano-therapeutics uses a broad variety of nanomaterials, such as nanoparticles, polymeric micelles, nanofibers, nanoemulsions, and nanogels, either as a treatment device or as a drug delivery vehicle. However, because of their advantageous qualities, several nanomaterial-based approaches have a lot of promise for treating various kinds of chronic wounds. Nevertheless, there are still some issues that need to be resolved before using nano-therapeutics for applications to wound healing. 210 The primary concern in nano-therapeutics is the biological safety of products based on nanomaterials since these materials interact directly with the tissues of the wound. Thus, the risk of transdermal toxicities is linked to nanoparticles that might trigger allergies and irritation to the skin, indicating that the biological safety of nanomaterials should be taken into account before application for wound healing. 210 The stability, shape, size, and concentration of the particles all affect the toxicity associated with nanomaterials. 211 New nanomaterials for wound care must limit skin damage. To reduce skin irritation, a variety of stabilizers should be used, including metal shells, surfactants, covalent adsorption, polymers, electrochemical synthesis, and particle size control technologies.212,213 Chronic wounds often vary greatly. This makes it hard for nanomaterials to help them heal. The inconsistent nature of these wounds limits regeneration and self-healing. Overcoming this limit needs better insight into how biology works. It also means knowing how to make tiny materials for certain kinds of wounds. This knowledge will help wounds heal better. Innovative nano-therapies offer new ways to heal chronic wounds. These methods use advanced tech without drugs. This lowers production costs. It also speeds up clinical use. The high cost of nano-formulations also limits nanomaterial use for wound care in medicine. These materials can be hard for medical facilities to afford. This expense is a major obstacle. Several approaches are being used and investigated to get around this restriction, including lowering the dosage of nanomaterials, adding inexpensive adjuvants to create composite nanomaterials, and using microneedles and organized self-assembly of nanomaterials for the regulated and prolonged release of the loaded medicines.214–216 Moreover, improving nano-formulations and fabrication procedures might be a useful strategy for cutting production costs. The variations in the metabolic and functional characteristics of human and animal systems present another significant obstacle to nano-therapeutic-based techniques. The majority of nanomaterials research uses animals like rats, mice, and rabbits, which have very different skin morphologies and wound healing mechanisms. Despite having similar skin morphologies and characteristics, large animals like pigs and humans are still not frequently used for wound healing treatments. In recent years, nanoparticles have been used in a variety of formulations with a range of medications and techniques; nevertheless, little is known about the processes by which nanomaterials aid in wound healing. The TGF-1/SMAD signaling route (proliferation phase) and macrophage polarization (inflammatory phase) are the most often researched signaling pathways for wound healing with nanomaterials for skin repair and wound healing enhancement. 217 The enhancement of wound healing should be associated with a variety of processes because of using different kinds of nanomaterials with diverse characteristics are used. Thus, future research must investigate novel approaches to gain a better understanding of causes and enhance treatment methods. Additionally, to represent the mechanics of wound recovery in various wound types, signaling and controlled signaling techniques are needed. Even though nanomaterial-based treatment provides advantages in every stage of wound healing, a single nanomaterial cannot be used in every stage since the needs of each stage would differ significantly. The need for a real-time indicator is relevant for the evaluation of wound conditions to mitigate this problem. To achieve this, ZnO nanowires modified by the enzymes urease and uricase have been used to develop self-sufficient implantable electronic skins that monitor a variety of parameters, including temperature, blood pressure, electrolyte metabolites, humidity and so forth, for trans-cutaneous human health detection. 217 Furthermore, with further standardization and optimization techniques, electronic skin might eventually be able to track inflammatory factors, signaling pathway proteins, and pH levels. Nanotechnology and electronic skin have brought about a number of new opportunities for real-time wound healing therapeutic control with the right nanomaterials.
3D bioprinting, a very promising and new technology, is another possible method for enhancing wound healing. Without the need for a lengthy incubation period, 3D bioprinting techniques enable the exact layer-by-layer application of skin structure and functional components directly onto the wound using an in situ bioprinting methodology. Furthermore, combining 3D bioprinting, sensors, and imaging methods will enhance wound healing results and eventually pave the way for precision medicine. For instance, real-time wound status monitoring is made possible by a 3D bioprinted hydrogel dressing that is connected to electrical components. Although the field of skin bioprinting has seen tremendous progress thus far, there are still certain restrictions. The main drawback of using skin bioprinting to cure wounds is needed to get autologous cells for developing skin constructs, which hasn’t been reduced enough yet. It takes less time to treat patients with severe burn injuries. As a result, the current goal of skin bioprinting is to reduce hypertrophic scar tissue and speed up wound healing. Stem cell therapy is a common and effective way to help wounds heal. This method uses different approaches. One way is to change stem cells through gene editing. Another way involves using exosomes that come from stem cells. Researchers are also looking at new sources of stem cells, like iPSCs.Even though the findings of induced pluripotent stem cells and exosomes produced from iPSCs might improve wound healing, there are still several issues with the stem cell’s origin, including genomic instability, possible carcinogenesis, infection risk, immunogenicity, and high processing expenses. Autologous iPSCs produced by nonviral vectors have been employed to combat immunogenicity and cancer risk. Additional research is needed to better understand the safety and dependability of iPSC re-programming technology to extend iPSC-based wound healing treatments. Furthermore, by stimulating skin cells (keratinocytes, fibroblasts, and endothelial cells), rejuvenating senescent cells, inhibiting apoptosis, reducing scar formation, and enhancing angiogenesis, stem cell-derived exosomes using immuno-modulatory and anti-inflammatory properties aid in wound healing. 218 Stem cell exosomes show promise for healing wounds. Yet, their use is limited. We lack high-quality exosomes for medical treatments. This shortage hinders progress in wound care. New tech for making stem cells could help wounds heal better. These stem cells come from other stem cells. Future good manufacturing practice methods will likely make this process even better. This could boost how well stem cells work to fix injuries. Other cutting-edge techniques being used to enhance wound healing include PRP therapy, CAP-based treatment, and ECM-based techniques. The clinical results are inconsistent and mostly depend on several aspects, including manufacturing techniques, decellularization efficiency, and post-decellularization, even though Decm-based strategies employing various matrix formats have shown encouraging results. 219 The cellular sources, which differ substantially in the content to reproduce cellular niches, may also be responsible for variations in the therapeutic results. Collagen is abundant in ECMs formed from stromal cells, whereas endothelial cell-derived ECMs mostly comprise underlying membrane structures (laminin). 220 Most ECM regeneration methods are still in early testing. Often, they are paired with other skin fixes. These include cell therapy or medicine given through hydrogels. Therefore, to fully utilize the potential of ECM-based techniques for chronic wound healing and skin regeneration, additional comprehension and information about the various construction processes, cell sources, and decellularization would be needed. A quick, painless, noninvasive, and safe therapeutic method for hastening wound healing is CAP treatment. The production of RNS and ROS to lower the bacterial load, promotion of quicker cell migration, and quick wound healing with a reduction in the inflammatory phase in the situation of chronic wounds are some of the advantageous effects of CAP therapy for wound care. 221
In addition to promoting wound healing, cold plasma therapy has enormous promise for controlling and avoiding infectious skin illnesses in the future. Since CAP treatment is a relatively new method of promoting wound healing, future research should examine the evaluation of each plasma component in detail as well as the development of better plasma devices to pave the way for efficient wound care. Additionally, by stimulating cellular regeneration processes and modifying the immune system, a PRP-based therapeutic strategy for healing wounds is mediated through the production of platelet-derived GFs and cytokines. Due to variations in each patient’s endogenous and exogenous elements, the PRP-based therapy strategy is individualized and non-standardized. Both endogenous (age, gender, diet, disease-associated systemic variables) and exogenous (cellular composition, anticoagulants) factors affect the quality of PRP. 222 Future research would thus need to take a more comprehensive approach, taking into account the effects of both endogenous and exogenous variables, to fully comprehend the influence of PRP-based therapy on wound healing. This strategy would make it possible to develop more individualized and effective PRP-mediated treatments for the regeneration of skin and wound healing.
Conclusions
In the field of wound care and skin regeneration, treating bigger and more difficult-to-heal chronic wounds continues to be a significant issue, despite the substantial research and improved understanding of wound treatment techniques for high-quality wound healing. No single therapy is enough for the full healing of a wound since wound healing is linked to several cellular and molecular pathways. Numerous cutting-edge and novel treatment approaches, including nano-therapeutics, stem cell research, 3D bioprinting-based approaches, cold plasma therapy, and PRP therapy, have been investigated recently to get around these restrictions and increase our understanding of wound healing. An outline of the many cutting-edge techniques being used today for better wound healing, together with an analysis of their benefits and drawbacks, is mentioned in this article. These methods are used separately or in combination to promote quicker wound healing. Patients with complicated wounds that are difficult to cure now have more options and hope due to these new methods and techniques for speeding up wound healing. Combining new technology with new ideas shows great hope and this leads to better wound healing for every individual.
Footnotes
Authors’ Contribution
Conceptualization, formal analysis, and investigation: G.S. and S.B.M.; Methodology: M.M.; Writing—original draft preparation: M.M. and G.S.; Writing—review and editing and supervision: S.B.M.
Consent for Publication
The consent of all the authors has been taken to publish the research in this journal.
Author Disclosure Statement
No competing financial interests exist.
Funding Information
The authors did not receive support from any organization for the submitted work.