Defect-Engineered Tetragonal ZrO2 Nanoparticles for Biomaterial Interfaces: Green Synthesis, Biointerfacial Interactions, and SERS Biosensing

Abstract

Abstract Zirconia (ZrO2) is a widely used biomaterial in dental and orthopedic applications due to its excellent biocompatibility, chemical stability, and mechanical properties. However, the role of defect structure and phase composition in governing biomolecule–surface interactions at the biointerface remains insufficiently understood. In this work, we demonstrate a synthesis-driven strategy for engineering defect-rich tetragonal ZrO2 nanoparticles via conventional wet-chemical and plant-extract-mediated green routes using Laurus nobilis, Salvia rosmarinus, and Ficus benghalensis. Plant-mediated synthesis using rosemary extract promotes the formation of phase-pure tetragonal ZrO2 with increased surface heterogeneity and a higher density of oxygen vacancy-related defect states. To probe biomolecule–surface interactions, surface-enhanced Raman spectroscopy (SERS) measurements were performed using L-phenylalanine as a model system. This approach provides a simplified model of amino acid adsorption relevant to early-stage protein–surface interactions. Defect-rich tetragonal ZrO2 exhibits enhanced SERS response driven by charge-transfer interactions associated with oxygen vacancies and surface states. This represents one of the first demonstrations of amino-acid-based probing of zirconia SERS substrates in a biomaterial-relevant context, extending beyond conventional symmetric aromatic probe systems. In addition, the materials exhibit photocatalytic activity, interpreted as defect-driven surface reactivity and the ability to generate reactive oxygen species relevant for antibacterial functionality and prevention of biofilm formation at biomaterial interfaces in clinical environments. Overall, this work establishes a structure–property–function framework linking synthesis strategy with defect structure and interfacial performance, providing a framework for the rational design of zirconia-based biomaterials with controlled biointerface functionality.