Nanobiotechnology is a rapidly growing field that harnesses the unique properties of nanoparticles for various biomedical applications, including antimicrobial agents and drug delivery vehicles [1, 2]. Metal nanoparticles, particularly those synthesized through nanotechnology, have applications in biomedicine, drug delivery systems, energy, agriculture, and antimicrobial/anticancer activities [3–10]. With the rise of bacterial resistance to conventional antibiotics, there is an urgent need to explore alternative antimicrobial agents to combat pathogenic infections, which pose significant global health risks. In this context, mono/bi/tri/multi-metal nanoparticles (MNPs) have been identified to act as promising candidates for antimicrobial applications.
Efforts have been directed towards developing eco-friendly and cost-effective synthesis methods for MNPs. Current synthesis approaches involve chemical reduction processes, microwave-assisted methods, electron irradiation techniques, and plant-mediated biogenic methods [11–20]. However, challenges remain in controlling the stability, yield, and morphology of the as produced MNPs [21–23]. Chemical synthesis methods require substantial energy and cost investments, and they have negative environmental impacts, including pollution, eco-toxicity, and public health hazards.
Among the various synthesis methods, green synthesis/biogenic methods have gained popularity due to their environment friendly nature, low toxicity, cost-effectiveness, and simplicity of synthesis process. These methods utilize plant extracts, such as leaves, fruits, or peels, as well as microorganisms, to reduce and stabilize MNPs [24–27]. While microorganism-based synthesis processes are time-consuming and require complex aseptic conditions, using plant extracts offers a more energy-efficient and may cost-effective practical approach. Plant extracts contain abundant natural biomolecules and complex molecular structures with rich medicinal values that can effectively cap MNPs and enhance their antibacterial properties [28–31].
MNPs are highly sought-after in nanotechnology due to their multifunctional properties, including optical, electrical, catalytic, magnetic, and antimicrobial characteristics, arising from their nano dimensions with large surface area to volume ratio [32–36]. Bimetallic nanoparticles, such as copper-silver (Cu-Ag), form core-shell nanostructures and exhibit multifunctional properties due to the synergistic effects of the constituent metal ions [37–41]. While the synthesis of mono-metallic nanoparticles using the extract of Argyreia Nervosa (AN) plant leaf has been reported, this plant has not yet been utilized for the synthesis of copper-silver bimetallic nanoparticles (Cu-Ag BMNPs)[42–46]. The AN plant is known for its medicinal properties, including anti-inflammatory and stress-reducing effects[47].
This study presents the first-ever utilization of the AN plant leaf green extract as a reducing, capping, and stabilizing agents to synthesize stable Cu-Ag BMNPs. Previous research has demonstrated the efficient antimicrobial activity of AgNPs against E. coli bacteria, and we expect the Cu-Ag BMNPs to exhibit enhanced antibacterial properties[47]. AgNPs have been extensively explored for various technological applications, including antimicrobial agents, drug delivery vehicles, water purification, and the textile industry. They are known for their high stability and low toxicity towards human cells. Despite numerous studies reporting the synthesis and antimicrobial activities of various MNPs, the green synthesis of Cu-Ag BMNPs using the AN plant and their antibacterial properties, as far as knowledge is concerned, have not been investigated. In this work, we synthesized Cu-Ag BMNPs using the AN plant leaf extract and evaluated their antibacterial activities against one of the Escherichia coli serotype known as Enteropathogenic E.coli (EPEC) via disc diffusion and minimum inhibitory concentration (MIC) assays. Our findings provide valuable insights into the potential of these green-synthesized Cu-Ag BMNPs as antibacterial agents. Moreover, we assert that the green synthesis method employed in this study, utilizing the AN plant leaf extract, offers a promising, energy-efficient, and cost-effective approach for large-scale production of Cu-Ag BMNPs for commercial applications.