Influence of synthesis method on physiochemical properties and antibacterial activity of green synthesized CuO nanoparticles from Laurus nobilis L. leaf extracts

Abstract

Copper oxide nanoparticles (CuO NPs) have been extensively utilized across multiple disciplines due to their potent antimicrobial characteristics. This study investigated the synthesis of three distinct CuO nanoparticles through the use of aqueous extracts derived from Laurus nobilis L. leaves. The synthesized CuO NPs were characterized using UV–Vis spectroscopy, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM–EDS), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. Surface plasmon resonance bands in the range of 250–285 nm confirmed the synthesis of CuO NPs. FITR spectrometry results revealed CuO-specific vibrations at the 601 cm⁻¹ band. CuO NPs were uniformly distributed, 10–26 nm in size and spherical shaped, as inferred from SEM and TEM images. According to EDS results, Cu content of the nanoparticles was in the range of 3 %–45 %. The antimicrobial activities against gram-positive and gram-negative bacteria, along with yeast, were assessed using the micro-dilution technique. CuO NP1 did not demonstrate antimicrobial activity against the tested organisms. However, CuO NP2 and CuO NP3 demonstrated inhibitory effects on the growth of all tested organisms at 250 µg mL⁻¹, except E. coli, which was inhibited at 500 µg mL⁻¹. The antimicrobial activities of CuO NPs varied based on their copper content. Molecular docking studies were conducted to estimate the binding affinities of CuO NPs towards proteins that played a role in the virulence and antibiotic resistance of pathogens, which indicated a high affinity for PBP2a, Bam A and listeriolysin proteins. These results are encouraging for the design of CuO NPs containing biocides alone or in a composite form.