New approaches for enhancing the photosensitivity, antibacterial activity, and controlled release behavior of non-porous silica-titania nanoplatforms

This research presents a new approach for the synthesis of inorganic nano-platforms containing >2 layers. Nano-platforms were characterized using scanning electron microscopy, X-ray diffraction, fluorescence and Fourier transform infrared spectroscopy, fluorescence microscopy, dynamic light scattering, thermogravimetric analysis, Brunauer-Emmett-Teller, etc. Since it has been reported that the maximum tolerable dose of non-porous silica nanoparticles (NPs) in in-vivo studies is higher than that of mesoporous silica, the non-porous silica was prepared. Curcumin (CUR) was trapped between the surfaces of the spherical non-porous silica and titania NPs (<100 nm) as both fluorescent and therapeutic agents, thus resulting in increased loading capacity of the non-porous silica NPs, as well as providing significant photosensitivity, antibacterial activity, and controlled release. In addition, the surface of NPs was enriched with Methyl violet-10B (MV-10B), and Rhodamine B (RhB). Silica@CUR@titania exhibited approximately 9-fold higher fluorescence intensity than silica@CUR NPs. This finding enabled us to design nano-platforms with minimum toxic effect due to low contents of RhB for bioimaging applications. The antimicrobial efficiency of nano-platforms was evaluated against P. aeruginosa, E. coli, S. typhimurium, K. pneumonia, S. epidermidis, S. aureus, B. subtilis, B. cereus, and E. faecalis. It was concluded that titania markedly lowered the minimum inhibitory concentration values (MICs) of CUR against all bacteria except B. subtilis and P. aeruginosa. Theoretical simulation was also performed to clarify the accumulation of functionalized NPs in tumor tissue.