A New Polymer Nanoprobe Based on Chemiluminescence Resonance Energy Transfer for Ultrasensitive Imaging of Intrinsic Superoxide Anion in Mice

Despite significant developments in optical imaging of superoxide anion (O2•–) as the preliminary reactive oxygen species, novel visualizing strategies that offer ultrahigh sensitivity are still imperative. This is mainly because intrinsic concentrations of O2•– are extremely low in living systems. Herein, we present the rational design and construction of a new polymer nanoprobe PCLA-O2•– for detecting O2•– based on chemiluminescence (CL) resonance energy transfer without an external excitation source. Structurally, PCLA-O2•– contains two moieties linked covalently, namely imidazopyrazinone that is capable of CL triggered by O2•– as the energy donor and conjugated polymers with light-amplifying property as the energy acceptor. Experiment results demonstrate that PCLA-O2•– exhibits ultrahigh sensitivity at the picomole level, dramatically prolonged luminescence time, specificity, and excellent biocompatibility. Without exogenous stimulation, this probe for the first time in situ visualizes O2•– level differences between normal and tumor tissues of mice. These exceptional features ensure that PCLA-O2•– as a self-luminescing probe is an alternative in vivo imaging approach for ultralow level O2•–.