Next-Generation Autocatalysis-Integrated Antibody-Bioorthogonal Catalyst Conjugates for Amplified Cell-Surface Antigen Imaging and Targeted In Situ Prodrug Activation

Abstract Immunoassays and antibody–drug conjugates (ADCs) rely on specific antigen–antibody recognition for biomarker detection and targeted cancer therapy; however, their practical performance is often hampered by low antigen abundance, which yields weak readout signals or insufficient local drug concentrations. Autocatalytic bioorthogonal reactions offer an attractive route to achieve exponential signal amplification, but existing CuAAC-based autocatalytic systems suffer from slow multistep ligand assembly and fluorophore self-quenching that degrade signal-to-background ratios. Herein, we report a next-generation autocatalysis-integrated bioorthogonal catalyst-linked immunosorbent assay (BCLISA) employing bis(triazolylmethyl)aminopropyne (DTTA) as a key autocatalytic precursor. Unlike the prior tripropargylamine (TPA) system that demands three successive CuAAC events for ligand formation, DTTA assembles active tris(triazolylmethyl)amine ligands via only one single CuAAC reaction with 7-azidocoumarin (7AC), incorporating merely one coumarin moiety per ligand to mitigate fluorescence self-quenching. Benefiting from accelerated kinetics and suppressed self-quenching, DTTA-mediated autocatalysis enables sensitive in vitro detection of recombinant HER2 and BK polyomavirus VP1 antigens, outperforming commercial ELISA kits. Functionalized with n-octyl lipid tails, DTTA-C8 anchors autocatalytic cascades onto living cell membranes, allowing confocal imaging and quantitative measurement of low-abundance cell-surface antigens free from endogenous enzyme interference. Furthermore, autocatalytically generated copper catalytic centers drive local CuAAC-mediated prodrug cyclization to produce cytotoxic agents. Distinct from conventional ADC approaches that pursue high drug-to-antibody ratios, our strategy achieves targeted in situ drug activation without heavy antibody modification, retaining native antibody-binding capacity and eliciting antigen-selective cancer-cell death. This work illustrates the utility of rationally optimized autocatalytic bioorthogonal cascades to couple antibody-based molecular recognition with exponential chemical amplification for both diagnostic and therapeutic applications.