Enhanced Antimicrobial Activity of Biofunctionalized Zirconia Nanoparticles

The effective interactions of nanomaterials with biological constituents play a significant role in enhancing their biomedicinal properties. These interactions can be efficiently enhanced by altering the surface properties of nanomaterials. In this study, we demonstrate the method of altering the surface properties of ZrO₂ nanoparticles (NPs) to enhance their antimicrobial properties. To do this, the surfaces of the ZrO₂ NPs prepared using a solvothermal method is functionalized with glutamic acid, which is an α-amino acid containing both COO^- and NH₄ ⁺ ions. The binding of glutamic acid (GA) on the surface of ZrO₂ was confirmed by UV-visible and Fourier transform infrared spectroscopies, whereas the phase and morphology of resulting GA-functionalized ZrO₂ (GA-ZrO₂) was identified by X-ray diffraction and transmission electron microscopy. GA stabilization has altered the surface charges of the ZrO₂, which enhanced the dispersion qualities of NPs in aqueous media. The as-prepared GA-ZrO₂ NPs were evaluated for their antibacterial properties toward four strains of oral bacteria, namely, Rothia mucilaginosa, Rothia dentocariosa, Streptococcus mitis, and Streptococcus mutans. GA-ZrO₂ exhibited increased antimicrobial activities compared with pristine ZrO₂. This improved activity can be attributed to the alteration of surface charges of ZrO₂ with GA. Consequently, the dispersion properties of GA-ZrO₂ in the aqueous solution have increased considerably, which may have enhanced the interactions between the nanomaterial and bacteria.