Sol–gel synthesis of Ag-doped titania-coated carbon nanotubes and study their biomedical applications

In this paper, we report the formation of new conjugates constituting single-wall nanotube (SWNTs) and multi-wall nanotube (MWNTs) comprising silver-doped titanium dioxide (TiO 2 /Ag) having outstanding antimicrobial and toxic properties. At first, the raw SWNTs and raw MWNTs were chemically treated with sulfuric acid and nitric acid to produce functionalized SWNTs (F-SWNTs) and functionalized MWNTs (F-MWNTs) surface. Then TiO 2 /Ag nanoparticles (NPs) were loaded with F-SWNTs and F-MWNTs using in situ sol–gel technique. The raw SWNTs, raw MWNTs, and conjugates’ samples were characterized via ultraviolet–visible (UV–Vis) spectrophotometer, Fourier transform infrared (FTIR), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). These measurements confirmed the loading of TiO 2 /Ag NPs on SWNTs and MWNTs walls. The optical band gap of R-SWNTs and R-MWNTs was decreased from 3.74 to 3.6 eV and from 3.9 to 3.64 eV, respectively, after decoration of TiO 2 /Ag. The XRD results confirmed the hexagonal structure of R-SWNTs and R-MWNTs with (002) plane, while the conjugates’ samples showed anatase phase of TiO 2 with (101) plane. The R-SWNTs and R-MWNTs dispersions revealed poor killing ability toward both Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). In contrast, the prepared SWNTs–TiO 2 /Ag and MWNTs–TiO 2 /Ag conjugates exhibited significant inhibitory effect against bacterial strains after 24 h of incubation. The cytotoxicity of these newly developed conjugates was assessed toward uterine cancer (SiHa) cell and normal (WRL68) cell lines. The SWNTs–TiO 2 /Ag and MWNTs–TiO 2 /Ag conjugates were able to selectively kill tumor cells (~ 60 to 40%), whereas less affecting normal cells (~ 10%).