Hydrothermal synthesis of copper based nanoparticles: antimicrobial screening and interaction with DNA.

Abstract Copper based nanoparticles (Cu-based NPs) of different compositions and sizes have been hydrothermally synthesized by varying the reaction time in the presence of the biocompatible surfactants polyoxyethylene (20) sorbitan laurate (Tween 20) and polyethylene glycol 8000 (PEG 8000). Effective control of the above synthetic parameters gave rise to Cu, Cu 2 O and Cu/Cu 2 O NPs of 10–44 nm. The antibacterial activity of the NPs was screened against Gram-positive ( Bacillus subtilis , Bacillus cereus , Staphylococcus aureus ) and Gram-negative ( Xanthomonas campestris , Escherichia coli ) bacteria. The Cu-based NPs induce pDNA degradation in a dose-dependent manner as well as extensive ds CT-DNA degradation. Cu 2 O NPs of 16 nm and 12 nm exhibit the lowest IC 50 values (2.13 μg/mL and 3.7 μg/mL) against B. cereus and B. subtilis , respectively. The agarose gel electrophoresis of ds CT-DNA treated with Cu 2 O NPs demonstrated degradation at high concentration. In lower concentrations, viscosity measurements indicated groove binding. In regard to the enhanced antibacterial effect and specificity of Cu 2 O NPs against the Gram-positive strains, the activity pathway was further explored and ROS production and lipid peroxidation verified. The released copper ions 5.15 mg/L in distilled water and 16.32 mg/L in nutrient medium, found below the critical value to inhibit bacterial growth and thus nanosized composition effect is predominant.