Titania and silica nanoparticles coupled to Chlorin e6 for anti-cancer photodynamic therapy.

In this study, light-sensitive photosensitizers (Chlorin e6, Ce6) were linked to TiO and SiO nanoparticles (NPs) in order to develop new kinds of NP-based drug delivery systems for cancer treatment by PDT. TiO or SiO NPs were modified either by the growth of a polysiloxane layer constituted of two silane reagents ((3-aminopropyl)triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS)) around the core (PEGylated NPs: TiO@4Si-Ce6-PEG, SiO@4Si-Ce6-PEG) or simply modified by APTES alone (APTES-modified NPs: TiO-APTES-Ce6, SiO-APTES-Ce6). Ce6 was covalently attached onto the modified TiO and SiO NPs via an amide bond. The absorption profile of the hybridized NPs was extended to the visible region of the light. The physicochemical properties of these NPs were explored by TEM, HR-TEM, XRD, FTIR and zeta potential. The photophysical characteristics including the light absorption, the fluorescence properties and the production reactive oxygen species (O and HO) were also addressed. In vitro experiments on glioblastoma U87 cells were performed to evaluate the photodynamic efficiency of the new hybridized NPs. The cells were exposed to different concentrations of NPs and illuminated (λ = 652 nm, fluence rate 10 J/cm). In contrast to the PEGylated NPs, the APTES-modified nanosystems were found to be more efficient for PDT. An interesting photodynamic effect was observed in the case of TiO-APTES-Ce6 NPs. After illumination, the viability of U87 was decreased by 89% when they were exposed to 200 μg/mL of TiO-APTES-Ce6 NPs, which corresponds to 0.22 μM of Ce6. The same effect can be obtained with free photosensitizer but using a higher concentration of 10 μM of Ce6.