De Novo Zwitterionic Strategy of Ultra-stable Chemiluminescent Probes: Highly Selective Sensing Singlet Oxygen in FDA-approved Phototherapy

Abstract

Singlet oxygen (¹O₂), as a fundamental hallmark in photodynamic therapy (PDT), enables ground-breaking clinical treatment in ablating tumors and killing germs. However, the accurate in vivo monitoring of ¹O₂ remains a significant challenge in probe design, primary difficulties arising from inherent photo-induced side reactions with poor selectivity. Herein, we report a generalizable zwitterionic strategy for ultra-stable near-infrared (NIR) chemiluminescent probes that ensure a highly specific [2+2] cycloaddition between fragile electron-rich enolether unit and ¹O₂ in both cellular and dynamic in vivo domains. Innovatively, zwitterionic chemiluminescence (CL) probes undergo a conversion into an inert ketone excited state with an extremely short lifetime through conical intersection (CI), thereby affording sufficient photostability and suppressing undesired photoreaction. Remarkably, compared with a well-known commercial ¹O₂ probe SOSG, the zwitterionic probe QMI exhibited an ultra-high signal-to-noise ratio (SNR, over 40-fold). Of particular significance is that the zwitterionic CL probes demonstrate excellent selectivity, high sensitivity and outstanding photostability, thereby making a breakthrough in real-timely tracking the FDA-approved 5-ALA mediated in vivo PDT process in living mice. This innovative zwitterionic strategy paves a new pathway for high-performance NIR chemiluminescent probes and high-fidelity feedback on ¹O₂ for future biological and medical applications.

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