The influence of chitosan's molecular weight, concentration, and dissolution method on the properties of electrophoretically deposited coatings on the Ti13Nb13Zr alloy surface

In this study, the effects of molecular weight (high, medium, and low), concentration (0.1 and 0.5 %) and dissolution method (in a rarely used hydroxyacetic acid and utilizing a novel CO₂ saturation) of chitosan on the microstructure, chemical composition, wettability, surface roughness, adhesion, corrosion resistance and antibacterial activity of chitosan coatings electrophoretically deposited (10 V, 1 min) on β titanium alloy Ti13Nb13Zr were investigated. Microstructural analysis showed that low molecular weight chitosan at low concentrations formed uniform coatings while increasing these parameters resulted in uneven coatings with agglomerates. Energy-dispersive X-ray and Fourier transform infrared spectroscopy analyses confirmed the presence of chitosan on all coated samples. Higher concentrations of chitosan yielded thicker coatings. Wettability tests confirmed hydrophilic properties for all samples, with contact angles around 70°. Surface roughness varied with chitosan concentration, showing increased roughness for higher concentrations. Adhesion tests showed the highest critical load for high molecular weight chitosan coatings with a concentration of 0.1 %. Corrosion tests revealed that low molecular weight chitosan coatings provided the best protection. Antimicrobial assays showed that chitosan coatings prepared using acid dissolution had strong bactericidal activity against both Gram-positive and Gram-negative bacteria, while those prepared using CO₂ saturation showed limited bacteriostatic activity. These findings suggest that chitosan coatings, especially those prepared using acid dissolution, hold promise for biomedical applications requiring corrosion resistance and antibacterial properties.