Chitosan-Nanogold and Chitosan-Nanozinc Electrodeposited Coatings for Biomedical Applications

Bacterial infections represent a significant challenge to the success rate of both short- and long-term titanium implants. Consequently, there is a persistent need for effective strategies to prevent such infections. In this study, chitosan-based coatings modified with gold or zinc nanoparticles, recognized for their antibacterial properties, were electrophoretically deposited (EPD) onto the Ti13Zr13Nb alloy and thoroughly characterized. The effects of EPD voltage, surfactant use, and metallic nanoparticle type and concentration were investigated with regard to the microstructure and properties of the obtained chitosan-based coatings. Incorporating metallic nanoparticles into the chitosan matrix increased surface roughness (from 54 nm to even 146 nm), particularly at higher EPD voltages, resulting in a composite structure containing nanometal clusters. The addition of gold nanoparticles reduced the thickness of the coatings (from 3.90 μm for the chitosan coating with Tween20-3.43 μm); zinc had no effect. Reducing the deposition voltage from 20 V to 10 V resulted in a thickness reduction of around 50% for all tested modifications. The improvement in plastic deformation resistance (indicated by the H³/E² ratio) was demonstrated for gold and zinc coatings deposited at lower voltages (from 0.34 MPa for the chitosan coating with Tween20 to 1.00 MPa for the gold half and 1.78 MPa for the zinc coating). A twofold increase in voltage resulted in a significant enhancement of coating adhesion-by approximately 177% for gold-added coatings and 138% for zinc-added coatings. Biological responses were dependent upon the types and concentrations of nanometals. Nanogold induced erythrocyte hemolysis, whereas nanozinc exhibited no adverse effects. Notably, gold-doped coatings demonstrated antibacterial efficacy against Staphylococcus aureus, while zinc-doped counterparts did not. Both nanometals, however, demonstrated reduced cytocompatibility at higher concentrations. Biological response tests indicated that 2-fold and 4-fold dilutions of the extracted medium do not show cytotoxicity for gold and zinc nanoparticles, respectively. These findings highlight the considerable extent to which coating parameters can be modified by adjusting selected EPD process parameters.