In Situ Bioorthogonal Generation of Therapeutics in Mitochondria Using a Guanidine-Rich Molecular Transporter

Bioorthogonal catalysis involves abiotic metal-mediated reactions in living systems without interfering with natural biochemical processes, enabling intracellular generation of imaging and therapeutic agents. Transition metal catalysts (TMCs) are prime candidates for bioorthogonal processes but face challenges in biocompatibility, solubility, and stability. Targeting TMCs to specific organelles is another hurdle. This study introduces a novel bioorthogonal catalyst (Cat 34) consisting of a Ru complex as TMC, triphenylphosphonium (TPP) for mitochondria-targeting, and a guanidine-rich molecular transporter for cellular delivery. Under biologically relevant media, Cat 34 showed good stability and the ability to convert a prodye (Rho-alloc) into its fluorescent form (Rho). Confocal microscopy studies displayed efficient cellular uptake and mitochondria targeting ability of Cat 34. Additionally, Cat 34 activated a prodrug (NIC-alloc) in mitochondria leading to mitochondrial impairment and cellular apoptosis. Overall, Cat 34 enabled rapid cellular uptake, bioorthogonal reactions, and in situ activation of prodyes/prodrugs at targeted organelles for therapeutic and diagnostic applications.