Dual-locking nanoprobe based on hemicyanine for orthogonal stimuli-triggered precise cancer imaging and therapy

Currently, stimulus-responsive nanomedicines are usually activated by a single cancer-associated biomarker and utilize different image/therapeutic agents for cancer imaging/therapy, which restricts the specificity of nanomedicine and complicates their design. Herein, we report a novel dual-locking theranostic nanoprobe (DL-P) based on near-infrared (NIR) hemicyanine CyNH2 with two orthogonal stimuli of cancer cell lysosomal pH (first "lock")- and lysosome-overexpressed cathepsin B (CTB, second "lock")-triggered NIR fluorescence turn-on and drug activation to improve the specificity of cancer imaging and therapy. The fluorescence of CyNH2 was initially quenched due to intramolecular charge transfer (ICT) but could be selectively activated under the dual-key stimulation of lysosomal pH and CTB to liberate CyNH2, resulting in strong NIR fluorescence turn-on for cancer imaging. Moreover, CyNH2 caused mitochondrial dysfunction to inhibit cancer cell proliferation in the absence of laser irradiation, which can be used in cancer therapy. Compared with previously reported probes that respond to a single stimulus, this dual-locking nanoprobe that is responsive to two orthogonal stimuli triggers with integrated imaging and therapy function in a single agent exhibits increased selectivity and specificity, which provides a prospective strategy for precise cancer imaging and therapy.