Bioinspired α-MnO2 Nanostructures Derived from Nyctanthes arbor-tristis: Biointerface-Mediated Selective Anticancer Activity and Mechanistic Insights

Abstract Biointerface engineering of nanomaterials through sustainable synthesis offers a promising strategy for developing phytochemical-associated functional nanostructures. In this study, a phytochemical-mediated approach was developed for the sustainable synthesis of α-MnO2 nanostructures using Nyctanthes arbor-tristis leaf extract. The synthesized nanostructures were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). HRTEM analysis revealed crystalline α-MnO2 nanostructures with an average particle size of 17.66 nm, while XPS analysis indicated the presence of Mn2+, Mn3+, and Mn+4 surface chemical states. The in vitro cytotoxic activity of the synthesized α-MnO2 nanostructures was evaluated against MCF-7 human breast cancer cells using the MTT assay and phase-contrast microscopy. The nanostructures exhibited a concentration-dependent reduction in MCF-7 cell viability, with an estimated IC50 of approximately 55 μg mL–1 under the experimental conditions employed. Molecular docking and network-pharmacology analyses identified cyclin-dependent kinase 1 (CDK1) as a potential molecular target associated with the investigated phytochemicals; however, this computational prediction requires experimental validation. Overall, this study demonstrates a plant-mediated route for the synthesis of crystalline α-MnO2 nanostructures with a phytochemical-associated surface and provides preliminary in vitro evidence of their cytotoxic activity against MCF-7 cells. Further comparative and mechanistic studies are required to establish the contribution of the phytochemical-associated fraction, α-MnO2 core, and their interfacial interactions to the observed biological activity.