Design and characterization of a photoactivatable manganese-porphyrin based nanozyme for biomedical and environmental...

Nanozymes have emerged as versatile, enzyme-mimicking nanomaterials with broad applications in catalysis, biology, and medicine. In this work, we report the design and characterization of a novel photoactivatable nanozyme constructed from silicon dioxide nanoparticles (SiO₂-NP) coated by a layer-by-layer assembly of a water-soluble porphyrin, a Mn(II)EDTA complex, and several alternating layers of cationic and anionic polymers. Upon irradiation with visible light, the porphyrin efficiently generates singlet oxygen, which subsequently oxidizes Mn(II) to Mn(III), producing an active redox intermediate that confers potent pseudo-oxidase activity to the system. Comprehensive morphological and compositional analyses confirmed the successful production of the nanoparticle, and mechanistic studies revealed the sequence of photoinduced reactions responsible for its catalytic behavior. Furthermore, cytotoxicity assays in mammalian cells demonstrated that the nanozyme is non-toxic in the absence of light, while irradiation after incubation induces cell damage, primarily due to the generation of singlet oxygen. These results establish a versatile photosensitive nanozyme platform with adjustable oxidation capacity and potential applications in biomedicine, environmental remediation, and photoinduced catalytic processes.