Fig. 8 Nanomaterials modified with porphyrin photosensitizers to enhance PDT. Enhanced light capture efficiency increases1O2 production
Ferreira and co-workers synthesized two different shapes of gold nanostructures (spherical and rod-like) and formed colloidal hybrid systems with 5,10,15,20-tetrakis(N-methylpyridinium-4-yl) porphyrin tosylate salt(H2TM4PyP(OTs)4) (POR) that should be used in the visible light range for photodynamic therapy(Ferreira et al. 2017). Electron paramagnetic resonance (EPR) experiments combined with spin trapping were used to detect the production of reactive oxygen species and to evaluate the efficiency of these novel hybrid systems as photosensitizers. The results show that the hybrid systems composed of Au NRs and POR have a higher efficiency of 1O2 production relative to the other components by about one order of magnitude. This effect is due to the enhanced local electric field around the Au NRs, which leads to an increase in light absorption by the photosensitizer, resulting in an effective energy transfer to the oxygen molecules forming1O2. On this basis, Duman and co-workers investigated nanocomposites of 5,10,15,20-tetrakis(1-methyl 4-pyridinio) porphyrin tetra(p -toluenesulfonate) (TMPyP) with Au NRs as nanocarrier systems for PDT and fluorescence imaging(Demir Duman et al. 2020). To confer biocompatibility and promote cellular uptake, NRs were wrapped with polyacrylic acid (PAA) and effectively loaded with cationic porphyrins by electrostatic interaction. The nanocomposites were tested in 2D monolayer culture and 3D compressed head and neck squamous cell carcinoma (HNSCC) collagen structures after incubation in light. The results showed that loading TMPyP onto Au NRs under in vitro cell culture conditions increased the absorption and emission intensity of the photosensitizer and promoted the production of1O2 under light irradiation. Under short-term light exposure, the TMPyP-loaded NRs exhibited higher phototoxicity compared with the same concentration of free photosensitizer.