Greener synthesis of zinc oxide nanostructures using selected amino acids for assessment of antibacterial activity

Background: This study presents a simple and eco-friendly green synthesis approach for the preparation of amino acid–assisted zinc oxide nanostructures (ZnONSs). Objectives: The objectives of synthesizing amino acid-assisted ZnONSs were to evaluate their antibacterial applications. Methods: Among the amino acids selected are Arginine, aspartic acid, cystine, and lysine. These amino acids were used as capping and stabilizing agents to tailor the structural and surface properties of ZnONSs. The synthesized nanostructures were characterized using X-ray diffraction (XRD), UV–Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) and disk diffusion method for antibacterial activity analysis. Results: XRD analysis confirmed the formation of ZnO with altered crystallinity due to amino acid incorporation, while UV–Vis spectroscopy verified successful synthesis of ZnONSs. FTIR spectra demonstrated effective surface functionalization by amino acid–related functional groups, and SEM revealed amino acid-dependent morphological variations, including rod- and flower-like structures with increased surface area. EDS further verified the predominance of Zn in the samples. The disk diffusion study confirmed effective antibacterial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), with performance varying according to the amino acid used during synthesis. Among the samples, arginine-assisted ZnONSs demonstrated superior antibacterial efficacy, likely due to enhanced surface functionalization and electrostatic attraction with negatively charged bacterial cell membranes. Conclusion: This work highlights amino acid-assisted green synthesis as a promising route for developing eco-friendly ZnO-based antibacterial nanomaterials.