PLGA-coated drug-loaded nanotubes anodically grown on nitinol

This study evaluates the use of nanotubes (NTs) as a matrix for local drug delivery modified by a biodegradable polymeric coating on medical-grade nitinol (NiTi alloy) surfaces. For this purpose, NiTi was anodized within parameters that promote the formation of NTs, ultrasonicated, annealed and impregnated with vancomycin hydrochloride. To improve bioperformance, poly(lactic-co-glycolic acid) (PLGA) was also deposited on the drug-loaded NTs. The samples were characterized in terms of structure, wettability, drug delivery, corrosion and cytocompatibility. Scanning electron microscopy and water contact angle measurements signify the formation of open-top homogeneous NTs of 600- 700 nm in length and ~30 nm in diameter with improved hydrophilicity. The bare antibiotic-impregnated NTs exhibit a burst release of about 49% of the loaded drug in the first 6 h of soaking in a physiological medium, followed by the entire drug diffusing out before 96 h. The PLGA coating effectively controls the burst release of vancomycin to 26% and retains almost 50% of the loaded drug beyond 7 days. The kinetics of the different vancomycin-release stages is also correlated to several well-established models. As a comparative criterion of metallic ions leaching kinetics, the corrosion resistance of nitinol is found to be reduced by the formation of the NTs, while the PLGA coating enhances this electrochemical feature. Due to the alteration of the drug delivery and corrosion protection, the PLGA-coated vancomycin-impregnated sample presents a higher dental pulp stem cell viability in comparison to both the bare drug-loaded and non-loaded NTs. In conclusion, PLGA-coated vancomycin-loaded NT-covered NiTi can be effectively used as a controlled drug-delivery device, while having a drug-release dosage within the therapeutic window and a minimal negative effect on biocompatibility.