Antibacterial activity of cotton fabrics treated with sulfadimidine azo dye/chitosan colloid

Abstract

A series of sulfadimidine dyes has been synthesized via coupling of sulfadimidine diazonium salt with N-substituted anilines in acetic acid. This series was embedded in a chitosan colloid and applied to the surface of cotton fabric by using the pad-dry cure technique. The cotton fabric treated with sulfadimidine dye/chitosan was characterized by infrared spectra and scanning electron microscope images. The antibacterial activities of the prepared cotton fabric samples treated with chitosan and/or sulfadimidine dye/chitosan against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were evaluated.

Introduction

It has been known for many years that the azo compounds are the most widely used class of dyes due to their versatile application in various fields such as the dyeing of textile fibers, the coloring of different materials, in biological-medical studies, and advanced applications in organic synthesis [1–3]. In recent years, biodegradable polymeric systems have gained importance in the design of surgical devices, artificial organs, drug delivery systems with different routes of administration, carriers of immobilized enzymes and cells, biosensors, ocular inserts, and materials for orthopedic applications [4]. These polymers are classified as either synthetic (polyesters, polyamides, polyanhydrides) or natural (polyamino acids, polysaccharides) [5]. Polysaccharides-based polymers represent a major class of biomaterials, which include agarose, alginate, carageenan, dextran and chitosan.

Chitosan, 2-amino-2-deoxy-(1-4)-β-D-glucpyranose, is a cationic biopolymer produced by alkaline N-deacetylation of chitin. Chitosan has found many biomedical applications, including tissue engineering, owing to its biocompatibility, low toxicity, and degradation in the body by enzymes such as chitosanase and lysozyme [6], which has opened up avenues for modulating drug release in vivo in the treatment of various diseases. These chitosan-based delivery systems range from microparticles to nanoparticles [7] to gel [8] and film [9]. Further, gels and films of chitosan have been used for oral delivery of chlorhexidine digluconate in the treatment of fungal infections [10].

The film-forming property of chitosan has found many applications in tissue engineering and drug delivery by virtue of its mechanical strength and rather slow biodegradation [11]. Some drug-loaded chitosan films are emerging as naval drug delivery systems [12,13], and films appear to have potential for local sustained delivery of cancer chemotherapeutic agents.

Several major classes of synthetic antimicrobial agents are used in the textile industry. Antimicrobial agents should possess broad spectrum biocidal properties, be safe for use, and highly effective against antibiotic resistant microorganisms including those that are commonly involved in hospital-acquired infections. The synthetic antimicrobial agents are very effective against a range of microbes and give durable effect on textiles [14–16]. In view of the above background information, we now report on the successful synthesis of some sulfadimidine dyes 4a-d and their application to cotton fabrics via encapsulation into chitosan film and coating on the cotton fabric surface.

Experimental

Materials

Scoured and bleached cotton fabrics (125 g/m²) were kindly supplied by Misr El-Mehalla Spinning and Weaving Co., Egypt. Chitosan with a molecular weight of 7,50,000 Da and a deacetylation degree of 85% were purchased from Fluka and used as received. Acetic acid analytical grade, N,N-dimethylaniline, N,N-diethylaniline, N-ethylaniline, N-benzyl-N-ethylaninline, and sulfadimidine were purchased from Sigma-Aldrich (Steinheim, Germany).

Synthesis of sulfadimidine dyes 4a-d

General procedure

A well-stirred solution of sulfadimidine 1 (2.78 g, 0.01 mole) in 3 mL concentrated hydrochloric acid (HCl) and 4 mL H₂O was cooled in an ice-bath and diazotized with the solution of NaNO₂ (0.7 g in 5 mL H₂O). The cold diazonium solution was added slowly to a well-stirred solution of N-substituted anilines 3a (1.49 g, 0.01 mole), 3b (1.21 g, 0.01 mole), 3c (1.21 g, 0.01 mole), or 3d (2.11 g, 0.01 mole) in 20 mL acetic acid at (0–5°C). The reaction mixture was stirred for another 2 h. The crude product was filtered off, dried well, and recrystallized from an ethanol-benzene mixture to give the corresponding dyes 4a-d [17].

Preparation of sulfadimidine dye/chitosan solution

A mixture of chitosan powder 1% (w/v) and the corresponding sulfadimidine dye (0.5 g) was suspended in acetic acid (2% v/v). Then, the mixture was stirred vigorously with a high-speed homogenizer for 30 min to obtain the sulfadimidine dye/chitosan colloidal solution.

Application of sulfadimidine dye/chitosan to cotton fabric

The cotton fabric was padded in the sulfadimidine dye/chitosan colloidal solution to wet pick up of 100%; padded fabric was dried at 80°C. The dried fabric samples were cured in an oven at 150°C for 4 min. The cured fabric samples were then washed with alkaline water for 30 min at 60°C and then washed several times with tap water and finally dried. Thus, prepared cotton fabrics were characterized by scanning electron microscopy (SEM) using JXA-840 an electron probe microanalyzer-JEOL.

Antibacterial activity of cotton containing sulfadimidine dye/chitosan

The antibacterial activity of prepared cotton fabrics was measured according to the AATCC 100-1999, test method against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli).

Results and discussion

Synthesis of sulfadimidine dyes 4a-d

The synthetic procedures adopted to obtain the target compounds are depicted in Scheme (1). A solution of sulfadimidine (1) in concentrated HCl was diazotized with a solution of sodium nitrite and then coupled to substituted anilines 3 in acetic acid to allow the formation of sulfadimidine dyes 4a-d [17]. Scheme 1.

The infrared spectra were recorded on Mattson 5000 spectrometer (λ, cm⁻¹) using the potassium bromide wafer technique (Faculty of Science, Mansoura University) and showed characteristic absorption bands within the ν = 3270–3220 cm⁻¹ corresponding to stretching vibration of NH. The bands within ν = 1519–1492 cm⁻¹ were due to the symmetric vibrations of the azo group. Absorption bands within the ν = 1166–1155 and 1083–1079 cm⁻¹ were attributed to SO₂ of the coupling component (Figure 1).

Figure 1.

Infrared spectra (IR) spectra of sulfadimidine dyes 4a-d.

Infrared spectra analysis and SEM Morphology of Cotton Fabrics Containing Sulfadimidine Dyes/Chitosan

Chitosan film containing sulfadimidine dyes were applied to cotton fabric by using a coating technique. The structures of the four dyes bonded on the fabric were established on the basis of infrared spectra (IR) spectra and SEM. The stretching frequency values of the sulfonyl group in the IR spectra have received special attention which shows absorption peaks within ν = 3431–3342 (broad) cm⁻¹ due to the presence of OH groups of the cellulose fabric. The absorption frequencies within ν = 1508–1494 cm⁻¹ due to the presence of azo group (Figure 2).

Figure 2.

Infrared spectra (IR) spectra of untreated and treated cotton fabrics.

The surface of the untreated, chitosan-coated, and sulfadimidine dyes 4a-d/ chitosan-coated cotton fabrics were morphologically observed by SEM (Figures 3 and 4). From the SEM analysis, it was clear that the formed coating appears smooth and homogeneous on the fabric surface, with absence of any microphase separation. Again, the results obtained here indicate good compatibility between the matrix and the sulfadimidine dyes.

Figure 3.

Scanning electron microscopy (SEM) images of the untreated (a) and chitosan treated cotton (b).

Figure 4.

Scanning electron microscopy (SEM) images of cotton fabrics treated with sulfadimidine dyes 4a-d/chitosan.

Antibacterial activity of the treated cotton fabrics

The treated cotton fabrics were subjected to testing for antibacterial activity using Gram-positive bacteria (S aureus) and Gram-negative bacteria (E coli). The antibacterial activity of prepared cotton samples was measured quantitatively (reduction in bacterial count percent RBC%) according to AATCC Test Method 100-1999 [18,19] (Table 1). The treated cotton fabric with chitosan was also exposed to the same testing.

Table 1.

Antibacterial properties of cotton fabrics coated with sulfadimidine dyes/chitosan.

Coated fabric samples	G + Ve Staphylococcus aureus		G –Ve Escherichia coli
	Count/mL	RBC (%)	Count/mL	RBC (%)
Blank	15 × 107	0.0	17 × 107	0.0
Coated fabric	3 × 107	80.0	5 × 107	70.5
Coated fabric + 4a	11 × 106	96.6	2 × 107	88.2
Coated fabric + 4b	6 × 106	96.0	15 × 106	91.0
Coated fabric + 4c	6 × 106	96.2	13 × 106	92.3
Coated fabric + 4d	6 × 106	98.2	13 × 106	94.3

RBC%: reduction in bacterial count percent.

The data in Table 1 signify that (a) Antibacterial activity of coated fabrics with chitosan film and chitosan film containing different sulfadimidine dyes 4a-d has the following orders: coated fabric samples containing sulfadimidine dyes 4a-d > chitosan coated fabric > untreated fabric, (b) there is a slight difference in antibacterial activity between sulfadimidine dyes 4a-d and they have the decreasing order 4d > 4a > 4c > 4b, and (c) antibacterial activity of prepared sample fabrics against Gram-positive (S aureus) is greater than antibacterial activity against Gram-negative (E coli), most probably due to the fact that Gram-positive bacteria cell walls consist of a single layer, whereas Gram-negative cell wall is a multilayered structure bounded by an outer cell membrane [20].

Conclusions

A set of four sulfadimidine dyes were successfully synthesized, embedded in a chitosan paste, and applied to the surface of cotton fabric. The treated cotton fabric obtained was tested for antibacterial activity against Gram-positive bacteria (S Aureus) and Gram-negative bacteria (E Coli). The treated cotton fabrics showed greater efficacy against S aureus than against E coli.