An Analysis of the Chemical and Physical Properties of a Silver Carboxylate Titanium-Dioxide Polydimethylsiloxane Antimicrobial Matrix on Orthopedic Implant Materials

Abstract

Introduction:

The use of silver (Ag) as an antimicrobial agent has gained attention for its multimodal mechanisms of activity. We have previously demonstrated the efficacy of a 95% titanium dioxide (TiO₂) and 5% polydimethylsiloxane (PDMS) silver carboxylate (AgCar)–eluting chemistry, which has been shown to prevent bacterial adherence, proliferation, and biofilm formation on orthopedic implants and prosthetic liners. This project examines the physical and chemical properties of AgCar on polyether ether ketone (PEEK) implant materials and silicone prosthetic liners, which are prone to bacterial colonization.

Methods:

PEEK implants were coated with varying concentrations of matrix, AgCar, or both. To determine physical properties, we used water contact angle for hydrophilicity, atomic force microscopy for surface roughness averages, and graphite furnace atomic absorption spectroscopy for Ag elution rate. For durability studies, silicone was coated and examined for compressive, frictional, and wear rate properties.

Results:

All implants demonstrated hydrophobicity in the presence of the matrix, AgCar, or both; in contrast, uncoated (UNC) PEEK implants were found to be hydrophilic. The 95% 10× matrix exhibited a delayed and extended elution of AgCar into solution compared with other solutions. Implant surface roughness increased as AgCar concentrations increased. Durability studies found no notable differences between UNC and 95% 10× coated implants.

Conclusion:

Consistent with previous work, the 10× AgCar coating demonstrated the best results for inhibitory behavior on two distinct fronts: mechanically, through roughness and increased hydrophobicity, and chemically, through AgCar elution activity. Furthermore, the 10× coating will likely not impair the durability or elasticity of the implant within the body or silicone prosthetic liners. Thus, the 95% TiO₂:5% PDMS matrix doped with a 10× AgCar concentration is a prime candidate for clinical application consideration.