*3.2.3 Drug release silane coatings*

On the other hand, bacterial infections or inflammations are one of the reasons for biomedical implants failure. Bacteria can form recalcitrant biofilms on implant surfaces, resisting conventional antibiotic treatments. As a consequence, the entire implant must be removed to allow an efficacious antibiotic treatment. Thus, it is necessary to find an effective local drug-releasing coating to simultaneously provide high anticorrosion and antibacterial ability for Mg alloys. Sol-gel coatings have attracted great attention since they offer the possibility to introduce antibiotics in the coating, and also to control the mechanism and kinetics of the drug release. Under this context, Xue et al. [75] designed a composite coating on AZ31 Mg alloy by depositing a drug-loaded coating obtained by crosslinking ciprofloxacin (CIP) (antibacterial drug) and polymethyltrimethoxysilane (PMTMS) as precursors. Cyto-compatibility and antibacterial performance of the coating were probed using in-vitro cytotoxicity tests (MTT), live/dead cell staining, and plate counting method. The results showed that the coating displayed a controllable long-term drug release ability against *Staphylococcus aureus* and *Escherichia coli*, implying that this coating provides a new approach for the anti-infection Mg bone implants. Although this coating system showed a good antibacterial performance, the drugreleasing time of the coating was too long to be used in the human body, since the period in the wound healing cycle is normally 1–2 weeks.

This approach can be a promising alternative, but it is necessary to continue studying ways to shorten drug-release time by modifying the synthesis of the sol. The control of the sol-gel synthesis and processing parameters together with the selection of the precursors are key issues.
