Polymeric-protein-MOF nanoparticles with stimuli-responsive disassembly and highly reproducible synthesis

Metal-organic frameworks (MOFs), such as zeolitic imidazolate framework-8 (ZIF-8), offer a promising platform for therapeutic protein delivery due to their biocompatibility and tunable degradation properties. However, the clinical translation of protein-loaded MOFs has been limited by poor colloidal stability and a lack of robust, stimulus-responsive release mechanisms. Here, we present a proof-of-concept colloidally stable nanoparticle system composed of poly(acrylic acid) (PAA), bovine serum albumin (BSA), ZIF-8 and copper (Cu) or iron (Fe) ions, PAA@Cu/FeBSA@c-ZIF-8, designed for H₂O₂-responsive, multimodal therapeutic delivery. Through iterative design, we stabilised protein-loaded ZIF-8 nanoparticles with PAA and doped the system with Cu or Fe to enable Fenton-based H₂O₂ sensitivity. Upon exposure to biologically relevant H₂O₂ concentrations (40-100 µM), PAA@CuBSA@c-ZIF-8 and PAA@FeBSA@c-ZIF-8 nanoparticles release encapsulated BSA and the doped transition metal ions, demonstrating potential for protein therapy in tandem with reactive oxygen species (ROS)-mediated cytotoxicity. The PAA@BSA@c-ZIF-8, PAA@CuBSA@c-ZIF-8 and PAA@FeBSA@c-ZIF-8 exhibit consistent physiochemical properties across independent operators and scales, including particle size, ζ potential, and cargo release, as well as cytotoxicity. Importantly, we identify ROS production, measured by 2',7'-dichlorodihydrofluorescein diacetate response, as a key critical quality attribute correlating with therapeutic potency. This work establishes a reproducible, H₂O₂-responsive nanoplatform towards application in cancer therapy and supports the broader use of quality attribute metrics in nanoparticle development.