Singlet Oxygen Afterglow Therapy with NIR-II Fluorescent Molecules

Improving singlet oxygen (O-1(2)) lifespan by fractionated delivery in dark and hypoxic conditions is a better way to achieve enhanced phototherapeutic efficacy. Herein, three boron dipyrromethene (BODIPY) dyes are synthesized to demonstrate that anthracence-functionalized BODIPY, namely ABDPTPA is an efficient heavy-atom-free photosensitizer for the reversible capture and release of O-1(2). The spin-orbit charge-transfer intersystem crossing of ABDPTPA promises a high O-1(2) quantum yield of 60% in dichloromethane. Under light irradiation, the anthracene group reacts with O-1(2) to produce endoperoxide. Interestingly, after termination of irradiation, the endoperoxide undergoes thermal cycloreversion to produce O-1(2), and regenerates the anthracene module to achieve O-1(2) afterglow, which results in a prolonged half lifetime of O-1(2) for 9.2 min. In vitro cytotoxicity assays indicate that ABDPTPA nanoparticles have a low half-maximal inhibitory concentration (IC50) of 3.6 mu g mL(-1) on U87MG cells. Further, the results of near-infrared-II fluorescence-imaging-guided phototherapy indicate that ABDPTPA nanoparticles can inhibit tumor proliferation even at a low dose (200 mu g mL(-1), 100 mu L) without any side effects. Therefore, the study provides a generalized O-1(2) afterglow strategy to enhance phototheranostics for complete tumor regression.

Automated summary

The synthesized ABDPTPA is an efficient heavy-atom-free photosensitizer that can improve the lifespan of O-1(2) under dark and hypoxic conditions. Its high O-1(2) quantum yield and ability to promote O-1(2) awakening make it suitable for phototherapy to enhance tumor regression.