Dual-Receptor Targeted Imaging of Cancer Cells with a Bioorthogonal Iridium(III)-Based Probe

Luminescence probes targeting specific membrane receptors are powerful imaging tools for cancer detection and image-guided surgical navigation. However, conventional single receptor targeting probes often suffer from low specificity and high background interference, limiting their effectiveness in accurately imaging cancer cells. Herein, we developed two dual receptor-mediated luminescent iridium(III) complexes for precise cancer cell imaging using a bioorthogonal activation approach. We strategically designed these probes to target two different biomarkers on the membrane: the benzenesulfonamide group in the N^N ligand targets carbonic anhydrase IX (CAIX), while the biotin moiety linked to endo-9-hydroxymethyl-bicyclo[6.1.0]non-4-yne (BCN) targets the biotin receptor. Complexes 1 and 2 exhibit 16- and 29-fold luminescence enhancement after reacting with BCN-Biotin, with rapid second-order rate constants (k₂) of 3.5 × 10⁵ M^–1 s^–1 and 8.7 × 10³ M^–1 s^–1, respectively. Notably, complex 2 can sensitively and specifically detect cancer cells overexpressing CAIX, as verified by multiple biochemical experiments. On the other hand, complex 2 showed negligible luminescence in cell lines with low expression of CAIX, demonstrating its ability to discriminate cancer cells. Overall, this work demonstrates the promising potential of dual receptor-mediated iridium(III) complexes based on the bioorthogonal activation strategy for the accurate and specific imaging of cancer cells.