Synergistic Effects of Hydroxyapatite and Graphene Oxide in Nanocomposites: Deciphering the Bio–Nano Interface and Antibacterial Efficacy

ABSTRACT Hydroxyapatite nanoparticles (HAp NPs) are promising for biomedical applications but are constrained by low mechanical strength, agglomeration, limited intrinsic antibacterial activity, and potential cytotoxicity from rapid ion release. To address these limitations, HAp, graphene oxide (GO), and HAp:GO nanocomposites were synthesized and comprehensively characterized by zeta potential, PXRD, FTIR, Raman, SEM‐EDS, and HR‐TEM. Biointerfacial behavior was probed utilizing BSA as a model protein using UV–visible, fluorescence, CD spectroscopy, and AFM. BSA exposure produced reproducible changes in absorbance and fluorescence and increased surface roughness of the HAp:GO nanocomposite, consistent with adsorption. Adsorption isotherm analysis revealed Langmuir behavior for HAp but Freundlich behavior for GO and HAp:GO, indicating heterogeneous, multilayer binding on the nanocomposite surface. Kinetic data fitted a pseudo‐second‐order model for all nanomaterials, consistent with chemisorption, while Stern–Volmer and Hill analyses indicated mixed quenching. CD spectroscopy showed substantially smaller perturbations of BSA secondary structure upon interaction with HAp:GO than with HAp NPs or GO, even at elevated nanomaterial concentrations, indicating enhanced preservation of native protein conformation. Antibacterial activity against dental‐caries bacteria demonstrated comparatively stronger bactericidal efficacy of HAp:GO relative to the individual components. These results highlight HAp:GO nanocomposites as biointerfacially compatible, antimicrobial nanomaterials, shows preliminary indications for dental and orthopedic applications.