Abstract
In the present study, silver nanoparticles (AgNPs) were synthesized using both the chemical and biological methods and conjugated with Pyrenacantha grandiflora extracts. These were then characterized and evaluated for antimicrobial activities against multi-drug resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumonia, and Escherichia coli. Nanoparticles were analyzed with UV-visible spectrophotometer, transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX). Silver nanoparticles, P. grandiflora extracts, and the conjugates were also analyzed with Fourier transform infrared spectroscopy (FTIR). As a result, quasi-sphere-shaped AgNPs with sizes ranging from 5 to 33 nm and spherically shaped AgNPs with sizes ranging from 3 to 25 nm were formed from chemical and biological synthesis, respectively. A well diffusion assay showed that the activity of silver nanoparticles was most improved with acetone extract against all tested bacteria with diameters in the range of 19–24 mm. The lowest MIC value of 0.0063 mg/mL against MRSA was observed when biologically synthesized AgNPs were conjugated with acetone and water extracts. Chemically synthesized silver nanoparticles showed the lowest MIC value of 0.0063 mg/mL against E. coli when conjugated with acetone and methanol extracts. This study indicates that silver nanoparticles conjugated with P. gandiflora tubers extracts exhibit strong antibacterial activities against multi-drug resistant bacterial pathogens. Therefore, biosynthesized conjugates could be utilized as antimicrobial agents for effective disease management due to the synergistic antibacterial activity that was observed.
Highlights
The present study focused on the evaluation of the antibacterial activity of Pyrenacantha grandiflora Baill extracts when conjugated with silver nanoparticles against problematic pathogenic bacteria (Staphylococcus aureus (MRSA), Escherichia coli, Klebsiella pneumoniae)
The microorganisms that were used in this study include Magnetospirillum magnetotacticum MS-1 (DSMZ, Braunschweig, Germany) which was grown in a modified chemically defined growth medium supplemented with Isogro (Merck, Modderfontein, South Africa), methicillin-resistant Staphylococcus aureus (ATCC 25,923), and methicillin-susceptible Staphylococcus aureus (ATCC 33,594) sub-cultured on mannitol salt agar, Escherichia coli (ATCC 35,218 and 25,922) sub-cultured on MacConkey agar, and Klebsiella pneumonia (ATCC 700,603) subcultured on nutrient agar (Rochelle, silver nanoparticles-acetone extract (SA))
Synthesis and characterization of P. grandiflora acetone and water extracts conjugated with silver nanoparticles were successfully carried out in this study
Summary
There is an urgent need for novel antibacterial agents. Research has focused on developing several strategies to address this issue. This has been done by trials in making novel antibacterial agents or artificially adjusting the action of existing/momentarily effective antibiotics [1]. Medicinal plants and silver nanoparticles are emerging to address the challenge due to their efficacy as antimicrobial agents. A number of studies have proved that silver nanoparticles possess antimicrobial, antiinflammatory, anti-angiogenic, anticancer, and antiviral properties with several advantages, 4.0/)
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