Green Synthesis of Copper Nanoparticles from the Aqueous Extract of Lonicera japonica Thunb and Evaluation of Its Catalytic Property and Cytotoxicity and Antimicrobial Activity

In this study, copper nanoparticles with an average particle size of 2-4 nm were synthesized using the green extract of <i>Lonicera japonica</i> Thunb. The catalytic activity and dye degradation efficiency of Cu NPs were evaluated using ultraviolet spectroscopy. To confirm that Cu NPs can continuously remove organic dyes, this study used Cu/Lj-C composite material adsorbed on cotton balls as a simulated bed to study the cyclic catalytic activity of Cu NPs for the reduction of methylene blue by sodium borohydride (NaBH₄). The experiment showed that after multiple cycles, it can also quickly and effectively reduce methylene blue. To evaluate the toxicity of Cu NPs, experiments were conducted using HUVEC and MC3T3-E1 cells. The median lethal doses (LD₅₀) were 37.64 µg/mL and 7.50 µg/mL. The synthesized Cu NPs also exhibited antibacterial efficacy against <i>Aspergillus niger</i> (fungus), <i>Staphylococcus aureus</i> (Gram-positive bacteria), <i>Escherichia coli</i> (Gram-negative bacteria), and <i>Candida albicans</i> (yeast).