Exploration of Thermally Activated Delayed Fluorescence (TADF)-Based Photoredox Catalyst To Establish the Mechanisms of Action for Photodynamic Therapy.

The mechanisms of action (MoA) have been proposed to further reduce the O2 dependence of photodynamic therapy (PDT) significantly. However, the triplet states of traditional photosensitizers are relatively short and also are easily deactivated by the quenching of H2O or O2. This is not conducive for the electron transfer in the photocatalytic process and poses a great obstacle to establish the MoA. Therefore, we selected and synthesized a zirconium(IV) complex (Zr(MesPDPPh)2) reported by Milsmann to address this issue. The specific symmetric and intact geometry endowed Zr(MesPDPPh)2 NPs with long-lived triplet excited state (τ = 350 µs), desired sensitized ability, and improved anti-interfering performance on O2, which was matched with the requirements of photoredox catalyst significantly. The results showed that while PDT (I) and PDT (II) could be achieved simultaneously by leveraging Zr(MesPDPPh)2 NPs, it also could be served as a rare example of thermally activated delayed fluorescence (TADF)-based photoredox catalyst to implement the MoA of PDT. It involved the oxidation of NADH and the establishment of catalytic cycle collaborating by O2 and cytochrome c (cyt c) in normoxia and hypoxia, respectively. As a result, the oxygen-free PDT and tumor-growth inhibition was realized.

Real-time visualization of the fluctuations in HOBr with AIE fluorescent probes during myocardial ischemia-reperfusion injury.

Two fluorescent probes (QM-S and QM-Se) featuring AIE properties were developed. The increased intracellular hypobromous acid (HOBr) in cardiomyocytes during MIRI was revealed with these probes. It was also observed that MIRI might be alleviated by combating oxidative stress, as well as inhibiting inflammation and ferroptosis, which could mediate oxidative stress.

Cyano-substituted stilbene (CSS)-based conjugated polymers: Photophysical properties exploration and applications in photodynamic therapy.

Conjugated polymers (CPs) have attracted great attention due to their excellent optical properties (such as large absorption cross section, signal amplification, high photostability etc.). As representative electron acceptors and organic small molecules which are easy to be synthesized and modified, cyano-substituted stilbene (CSS) derivatives are widely used to construct photoelectrical materials. Despite donor-acceptor (D-A) conjugated polymers based on CSS have been applied in sensing and super-resolution imaging, systematic studies about the effects of different CSS structures on the photophysical properties of CPs have rarely been reported. Therefore, we have synthesized a series of D-A conjugated polymer nanoparticles (CP NPs) based on different CSS units, and found that the photophysical properties of CP NPs including the bandgap and ΔES-T were closely associated with the structure of CSS derivatives. Moreover, the introduction of tetraphenylethylene (TPE) can relieve the aggregation-caused quenching (ACQ) effects of CSS conjugated polymers to varying degrees. The theoretical calculation further corroborated that by regulating the number and distribution of cyanide groups in the repeating units, the stronger D-A strength resulted in a redshift in the emission spectrum and the more efficient capacity of total ROS (1O2, O2•- and •OH) generation. We then selected CP6-TAT NPs, with the near infrared (NIR) emission and best ФPS, to characterize its performance in photodynamic therapy (PDT). It was revealed that CP6-TAT NPs can be regarded as an ideal candidate for PDT. The results provided a new reference for regulating the structure-effect relationship of CPs and a comprehensive method for constructing photosensitizers based on CPs.