Dynamic palladium speciation governs prodrug activation by nanoparticles in vitro and in vivo

This work investigates palladium nanocatalysts for C-O bond cleavage of propargyl (Proc) and allyl (Alloc) carbamates of coumarin, rhodamine, and doxorubicin. Catalytic performance was evaluated using colloidal Pd(0) and Pd(II) nanoparticles, across buffered media, cell cultures, and mouse models. In aqueous buffers, Pd(II)-NPs showed higher activity toward Proc substrates, while Alloc substrates remained largely unreactive. In cellular environments, however, both nanoparticle systems promoted efficient uncaging of Alloc and Proc derivatives, consistent with dynamic palladium speciation under biological relevant conditions. Among the system evaluated, the Pd(0)-NPs/Alloc-DOX combination elicited the strongest reduction in cell viability while maintaining low intrinsic toxicity, thus emerging as the most robust platform for in vivo evaluation. In murine tumor models, Pd(0)-NPs combined with Alloc-DOX significantly reduced tumor growth compared to controls and individual treatments. In contrast, Proc-DOX displayed comparable antitumor effects in the presence and absence of palladium, suggesting partial activation through endogenous pathways. These findings highlight that catalytic outcomes are governed not only by palladium oxidation state but also by dynamic speciation and biological microenvironment.