Chitosan hydrogel coatings on Ti-6Al-4V alloy for sustained drug release and corrosion protection in simulated inflammatory and acute inflammatory environments

This study reports a dual-function betamethasone-loaded chitosan hydrogel coating for Ti-6Al-4V implants, designed to combine localized anti-inflammatory drug delivery with corrosion protection under inflammation-relevant environments. The hydrogel formed a porous and continuous coating on the titanium alloy surface, while sandblasted, large-grit, acid-etched (SLA) pretreatment produced a roughened substrate topography that improved coating anchoring. FTIR analysis indicated that betamethasone was mainly physically entrapped within the chitosan hydrogel network rather than covalently bonded. The coated samples exhibited sustained betamethasone release over 30 days, with a biphasic release profile consisting of an initial faster release followed by a slower prolonged release stage. Release was accelerated under more acidic and oxidative conditions, whereas SLA-supported coatings showed a more controlled release behavior. Electrochemical results demonstrated that the hydrogel coating improved the corrosion resistance of Ti-6Al-4V by shifting the corrosion response toward more stable behavior, reducing corrosion current density, and increasing impedance. This protective effect was most pronounced for coatings deposited on SLA-treated substrates, indicating the importance of interfacial integrity in maintaining barrier performance. ICP-MS analysis further confirmed that hydrogel-coated samples released lower amounts of Ti, Al, and V ions than uncoated substrates, even under the most aggressive simulated acute inflammatory condition. Overall, the results show that combining SLA pretreatment with betamethasone-loaded chitosan hydrogel coating is a promising strategy for developing drug-eluting titanium implant surfaces with improved corrosion resistance and reduced metal ion release under inflammatory conditions.