Most photodynamic therapy (PDT) paradigms
work through the highly
O2-dependent type II photoreaction to generate singlet
oxygen (1O2). The hypoxic microenvironment of
solid tumors severely hampers therapeutic outcomes. Here, we present
a novel design that could transfer the photophysical and photochemical
properties of traditional phthalocyanine-based photosensitizers from
type II photoreaction to efficient type I photoreaction and vibrational
relaxation-induced photothermal conversion. These features enable
the obtained nanostructured phthalocyanine assemblies (e.g., NanoPcAF)
to display excellent phototherapies under both normoxic and hypoxic
conditions. Moreover, NanoPcAF has a high level of accumulation in
tumor tissues after intravenous injection, and 94% of tumor growth
is inhibited in a preclinical model at a NanoPcAF dose of 0.8 nmol
g–1 and light dose of 300 J cm–2.
The photophysical properties, such as the UV-vis absorption spectra, triplet transient difference absorption spectra, triplet excited-state extinction coefficients, quantum yields of the triplet excited state, and lifetimes of the triplet excited state, of 10 novel zinc phthalocyanine derivatives with mono- or tetraperipheral substituents have been systematically investigated in DMSO solution. All these complexes exhibit a wide optical window in the visible spectral range and display long triplet excited-state lifetimes (140-240 mus). It has been found that the complexes with tetrasubstituents at the alpha-positions exhibit a bathochromic shift in their UV-vis absorption spectra, fluorescence spectra, and triplet transient difference absorption spectra and have larger triplet excited-state absorption coefficients. The nonlinear absorption of these complexes has been investigated using the Z-scan technique. It is revealed that all complexes exhibit a strong reverse saturable absorption at 532 nm for nanosecond and picosecond laser pulses. The excited-state absorption cross sections were determined through a theoretical fitting of the experimental data using a five-band model. The complexes with tetrasubstituents at the alpha-positions exhibit larger ratios of triplet excited-state absorption to ground-state absorption cross sections (sigma T/sigma g) than the other complexes. In addition, the wavelength-dependent nonlinear absorption of these complexes was studied in the range of 470-550 nm with picosecond laser pulses. All complexes exhibit reverse saturable absorption in a broad visible spectral range for picosecond laser pulses. Finally, the nonlinear transmission behavior of these complexes for nanosecond laser pulses was demonstrated at 532 nm. All complexes, and especially the four alpha-tetrasubstituted complexes, exhibit stronger reverse saturable absorption than unsubstituted zinc phthalocyanines due to the larger ratio of their excited-state absorption cross sections to their respective ground-state absorption cross sections.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.