In situ conjugation of silver nanoparticles with silane-functionalized TiO2 nanoparticles for antibacterial applications

TiO2 and Ag nanoparticles (NPs) are the two commonly employed inorganic materials in nanomedicine and in recent years, they have attracted growing interest in antibacterial applications. To enhance their biological efficacy, they can be used together in a single nanoplatform [1]. However, the TiO2-Ag conjugation is still challenging due to the aggregation issues, and it needs more studies to develop stable nanohybrids from these two components. One of the promising strategies is to employ biocompatible silane linkers to conjugate TiO2 with Ag nanoparticles to keep them stable in aqueous media. In this research, (3-mercaptopropyl)trimethoxysilane (3MPTMS) was applied as a bifunctional linker bearing soft –SH and hard –O parts in its structure to mediate the chemical conjugation of Ag to TiO2NPs. More importantly, this silane linker improves the biocompatibility of the resultant TiO2-Ag nanoconjugate. In brief, commercially available TiO2NPs with a size of 10-35 nm were firstly functionalized with 3MPTS (hydrolyzed form of 3MPTMS) with sol-gel method through the chemical attachment of titania with the –O moiety of the silane linker. Then Ag ions were coordinated to the free –SH groups on the TiO2-3MPTS surface followed by reduction to the AgNPs forming the final TiO2-3MPTS-Ag nanohybrid. For both Ag+ reduction and AgNPs stabilization, different reducing agents/stabilizers were investigated. The stability, size, morphology, and chemical composition of the nanohybrid were evaluated by UV-Vis, FT-IR, ATR, SEM-EDS, DLS, and XPS characterizations. Thanks to multidisciplinary collaborations, the in vitro antibacterial studies of TiO2-3MPTS-Ag are in progress.