ABSTRACT
Treatment of microbial infections is becoming a challenge due to the resistance exhibited by several antimicrobial agents. Metal nanoparticles have been shown to be effective in the eradication of microorganisms. This research was carried out to synthesize and characterize a cost-effective Vernonia amygdalina copper oxide nanoparticles (VA-CuONPs) using Vernonia amygdalina leaf extract and investigate its in vitro antimicrobial properties using clinical bacterial and fungal isolates.
Phytochemical analysis of V. amygdalina was carried out to determine the bio-molecules that served as reducing agent during the synthesis of VA-CuONPs. VA-CuONPs were synthesized by heating a mixture of 80 ml of 0.01 M Copper sulphate pentahydrate and 20 ml of V. amygdalina aqueous extract at 60oC for 30 minutes. The VA-CuONPs were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and particle size analysis using zetasizer. The antimicrobial activities of VA-CuONPs and V. amygdalina, separately and in combination, were evaluated by agar disc diffusion method against Staphylococcus aureus, Escherichia coli and Candida albicans. Ampicillin and fluconazole were used as reference antibacterial and antifungal agents, respectively.
Phytochemical analysis of the plant extract revealed the presence of saponin, flavonoid, phenol, glycoside, terpenoid and alkaloid. Synthesis of VA-CuONPs was achieved using V. amygdalina leaf extract with a mean size of 1207 nm.The FTIR spectroscopy identified the bioactive functional groups such as the hydroxyl groups which are responsible for the stability of the bioreduced VA-CuONPs. SEM image showed VA-CuONPs with leaf-like and undefined shape morphology. The nanoparticles were in the nanometer dimension and exhibited significant antimicrobial activity (P < 0.05) against the tested microbes. However, the standard drug, ampicillin, showed a higher antibacterial activity against S. aureus and E. coli with the zone of inhibition (ZOI) of 13.10 ± 0.38 mm and 11.80 ± 0.12 mm, respectively. Fluconazole had no antifungal activity against C. albicans while V. amygdalina demonstrated antibacterial activity against S. aureus and E. coli but lacked antifungal activity against C. albicans. The plant extract had a higher antibacterial activity when compared to VA-CuONPs while the VA-CuONPs had a higher antifungal activity when compared to the plant extract. Ampicillin had a higher antibacterial activity when compared to the nanoparticles. However, the combination of VA-CuONPs and fluconazole showed remarkable antifungal activity with ZOI of 11.29 ± 0.57 mm. When VA-CuONPs were combined with ampicillin, a lower antibacterial activity was observed while the mixture of the VA-CuONPs and the plant extract exhibited significant antifungal activity with ZOI of 10.37 ± 0.72 mm (P < 0.05). A simple, reproducible, and economical VA-CuONPs have been successfully synthesized using V. amygdalina leaf extract. The findings indicate that VA-CuONPs could be used as an antimicrobial agent and drug delivery system. It has the potential of reversing the resistance associated with fluconazole.
