Click-Controlled Photo-Uncaging: Click-Assembly of Platinum-Based Photoactive Protecting Groups for Light-Triggered Bioactive Molecule Release

Abstract

We introduce click-controlled photouncaging, an innovative approach that synergizes click ligation with photocleavage to achieve biorthogonal, light-triggered bioactive molecule release across visible to near-infrared (NIR) wavelengths. Central to this approach is a novel amine protection and deprotection strategy utilizing Pt(IV) complexes. In this strategy, an azide-bearing clickable Pt(IV) moiety acts as a protecting group for amine-containing molecules (the ″cargo″) via a carbamate linkage. Subsequently, click ligation with a DBCO-tagged fluorescent antenna positions the antenna near the Pt(IV) core, transforming it into a photoactive protecting group (PPG) that can be fine-tuned to respond to visible or NIR light. When exposed to light, the antenna drives the photoreduction of the Pt(IV) linker, triggering deprotection and subsequently releasing the cargo molecule. To validate this approach, three Pt(IV) complexes were synthesized featuring amine-containing fluorescent reporters (coumarin, BODIPY) and a therapeutic molecule (Exatecan), and their functionality was validated in solution and cell cultures. Overall, this work introduces a novel, user-friendly, and versatile chemical tool for bioorthogonal, light-controlled activation of molecules in complex biological environments.