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.