Photodynamic Therapy

Abstract

In 1903, Von Tappeiner and Jesionek [...]

Complexed Photosensitizer of Hypericin with G-Quadruplex: Structure-Dependent Behavior

“…Hypericin has been shown to have a high quantum yield of triplet formation (0.5−0.7). 19,20 The assignment of these transient absorption bands at 450−550 and 630−800 nm to triplet state 3 Hyp* can be confirmed by their accelerated quenching in the presence of O 2 , with the lifetime being shortened to ∼2.14 μs (Figure S1A,B). Moreover, the absorption spectra of triplet 3 Hyp* obtained here in DMSO are consistent with that obtained in ethanol solution.…”

“…19,20 The assignment of these transient absorption bands at 450−550 and 630−800 nm to triplet state 3 Hyp* can be confirmed by their accelerated quenching in the presence of O 2 , with the lifetime being shortened to ∼2.14 μs (Figure S1A,B). Moreover, the absorption spectra of triplet 3 Hyp* obtained here in DMSO are consistent with that obtained in ethanol solution. 19 However, as shown in Figure S2, the characteristic triplet signal of Hyp is absent in water solution, owing to the We thus testify that Hyp can bind with the water-soluble Gquadruplex to form a complexed photosensitizer.…”

“…Moreover, the overhang base at the 5′-end is found to affect the binding extent, possibly due to the hydrogen-bonding interaction between Hyp and overhang base at this site. Importantly, the 1 O 2 quantum yields for different Hyp/G-quadruplexs are derived using methylene blue as a reference standard, revealing a consistent trend that the better the Hyp/G4 binding, the longer the triplet 3 Hyp* lifetime and the higher the efficiency to produce singlet oxygen. These results clearly reveal the conformational effect of the G-quadruplex on the binding behavior and photosensitizing activity of Hyp/G-quadruplex.…”

“…Second, we performed transient spectroscopy utilizing the triplet excited state as sensitive reporters. Presumably, the decay lifetimes of triplet 3 Hyp* are highly sensitive to the confined environment where Hyp binds to Gquadruplex; thereby, they should make it possible to distinguish a different binding mode. 23−25 If Hyp is sandwiched between two c-kit2 with a 1:2 binding ratio, the triplet 3 Hyp* lifetime should be longer than that of the 1:1 binding ratio, due to the better two sides' protection from bulk O 2 quenching.…”

“…Hypericin (Hyp) (Scheme A), a natural polycyclic quinone pigment, is one of the major active constituents of hypericum with diverse biological activities, such as antiviral, antiretroviral, anticancer, proteasome inhibition, antidepressant, anti-inflammatory, and photodynamic activities. , As Hyp preferentially accumulates in cancerous tissues, it is currently being investigated as a promising photosensitizer for use in the photodynamic therapy of cancer and as a dye in fluorescence imaging of cancer. As a photosensitizer, under the combined action of oxygen and a laser of appropriate wavelength, cytotoxic reactive oxygen species (ROS), particularly singlet oxygen ( 1 O 2 ), are generated via electron or energy transfer pathways, resulting in the ablation of tumor. − …”