Mesoporous platinum nanoparticles as high-performance antioxidant and anti-inflammatory nanozymes

Mesoporous platinum nanoarchitectures are attractive functional nanomaterials (e.g., high performance nanozymes), yet sub-20 nm Pt nanoparticles with coating-free surfaces and fully accessible porous structures remain difficult to obtain because most synthetic routes rely on surfactants, polymers, sacrificial metals, or structure-directing agents that poison Pt catalytic surface whilst also impeding access to pores. Here, we report a one-pot aqueous, template-free synthesis of mesoporous Pt nanoparticles enabled by temperature/pressure control in sealed microwave reactors, using only ascorbic acid and citrate as reducing agent and small, removable surface coating, respectively. HAADF-STEM tomography evidences a porous architecture with internal voids distributed throughout the nanoparticle volume, while electrochemical measurements confirm an enhanced electrochemically active surface area consistent with high pores accessibility. The nanoparticles exhibit good dispersion under biologically relevant conditions and efficient cellular uptake, with no cytotoxicity in RAW 264.7 macrophage-like cells. Functionally, these mesoporous Pt nanozymes attenuate LPS-induced oxidative stress and reduce IL-6 secretion, demonstrating potent antioxidant/anti-inflammatory activity. In an in vitro model of atherosclerosis, they further decrease oxidized-LDL uptake and foam-cell formation, indicating a multi-level mitigation of ROS-driven macrophage dysfunction. Overall, this work establishes a straightforward route to clean, sub-20 nm mesoporous Pt nanozymes and highlights their potential for modulating inflammation in ROS-driven diseases.