An alternative model for photodynamic therapy of cancers: Hot-band absorption

Abstract

The sulfonated aluminum phthalocyanine (AlPcS), a photosensitizer for photodynamic cancer therapy (PDT), has an absorption tail in the near-infrared region (700–900 nm) which is so-called hot band absorption (HBA). With the HBA of 800 nm, the up-conversion excitation of AlPcS was achieved followed by the anti-Stocks emission (688 nm band) and singlet oxygen production. The HBA PDT of AlPcS seriously damaged the KB and HeLa cancer cells, with a typical light dose dependent mode. Particularly, the in vitro experiments with the AlPcS shielding solutions further showed that the HBA PDT can overcome a self-shielding effect benefiting the PDT applications.

Unoccupied conduction band of chloroaluminum phthalocyanine

“…Phthalocyanines (Pcs), known as tetrabenzotetraazaporphyrins, mimicking naturally occurring porphyrins, are candidates for important applications, because they are low cost, less hazardous, have excellent thermal and chemical stability, and good optical properties. 1,2) Chloroaluminum phthalocyanine (Cl-AlPc), a metal Pc complex, has been widely used in molecular electronics, 3) photovoltaics, 4,5) gas-sensors, 6) and in photodynamic therapy agents for cancer treatment, 7) among other areas. A Pc ring is composed of highly conjugated 18 π-electron planar aromatic systems, resulting in electron or charge delocalization over the whole molecule.…”

Hot-band absorption assisted single-photon frequency upconversion luminescent nanophotosensitizer for 808 nm light triggered photodynamic immunotherapy of cancer

“…The anti-Stokes luminescence occurs between thermal vibration-rotation levels (S t ) of the ground state (S 0 ) and the first excited state (S 1 ), followed by the emission of higher energy radiation (shorter wavelength) than the excitation photon of lower energy (longer wavelength), defined as hot-band absorption. [30][31][32][33][34] It is characterized by a typical one-photon process in which additional energy is offered by the heat originating from the original Boltzmann distribution of dye molecules. To date, a few FUCL organic fluorophores have been reported for bioimaging and biodetection, [33][34][35][36][37][38] and FUCL technology has also been applied in antitumor therapy.…”

“…To date, a few FUCL organic fluorophores have been reported for bioimaging and bio-detection, 33–38 and FUCL technology has also been applied in antitumor therapy. 30,39–41 Chen et al used sulfonated aluminum phthalocyanine (AlPcS) for in vitro PDT studies with hot-band absorption under 800 nm irradiation. 30 Recently, Peng et al utilized an upconversion photosensitizer with 808 nm laser irradiation to realize deep cancer PDT.…”

“…30,39–41 Chen et al used sulfonated aluminum phthalocyanine (AlPcS) for in vitro PDT studies with hot-band absorption under 800 nm irradiation. 30 Recently, Peng et al utilized an upconversion photosensitizer with 808 nm laser irradiation to realize deep cancer PDT. 40 There is an urgent need to develop novel upconversion photosensitizers to combine FUCL technology and immunotherapy for antitumor photodynamic immunotherapy.…”