PEGylated Heterofunctional Dendrimers Enable Multivalent Diclofenac Delivery for ROS-Driven Anticancer Activity

Cancer drug development faces escalating costs and limited success, driving interest toward drug repurposing strategies. Diclofenac, a widely used nonsteroidal anti-inflammatory drug (NSAID) with emerging anticancer potential, exhibits poor aqueous solubility and rapid systemic clearance, limiting its chemotherapeutic suitability. Here, we engineered PEGylated heterofunctional polyester dendrimers (HFDs) as modular nanocarriers that enable controlled multivalent presentation of diclofenac through orthogonal chemistry. Diclofenac was conjugated within the dendritic interior using copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) while peripheral PEGylation was introduced through anhydride esterification. First- and second-generation constructs, G1-(Dicl)₃-(mPEG)₆ and G2-(Dicl)₉-(mPEG)₁₂, assembled into amphiphilic core-shell nanostructures with hydrodynamic diameters of 170-330 nm and well-defined drug loading. G1-(Dicl)₃-(mPEG)₆ demonstrated the strongest therapeutic performance, reducing viability by 50-70% in MCF-7, U-87 MG, and PANC-1 cancer cells at 1-10 μM while maintaining >95% viability in noncancerous fibroblasts. This represents a >20-fold improvement in therapeutic index compared to free diclofenac. G2-(Dicl)₉-(mPEG)₁₂ displayed potent but cell-line-dependent activity, with highest efficacy in MCF-7 cells. Both dendrimers required 10-100× lower concentrations than free diclofenac to induce comparable reactive oxygen species (ROS) levels, with G1 producing 3-4-fold ROS elevation at 10 μM and G2 achieving similar induction at 0.1 μM. Mechanistic analysis confirmed ROS-mediated cytotoxicity as a key contributing pathway and correlated directly with cytotoxicity across various cancer models. These findings establish HFDs as an adaptable nanomedicine platform for repurposing clinically approved drugs, with G1 dendrimer providing the optimal balance of efficacy, selectivity, and translational potential.