Abstract:
Biologically synthesized nanomaterials and their industrial utilization have become an integral
part of bionanotechnology. There is an increasing demand for silver nanoparticles (Ag-NPs) due
to its wide properties in various fields of biomedical science including bio-sensing, drug delivery
etc. Thus, the aim of the current study was to synthesize Ag-NPs by reducing the silver ions
present in the silver nitrate (AgNO3) solution by green method to enhance antibacterial activity
of a common medicinal plant Azadirachta indica. Initially, pure cultures of four gram positive
(gm +ve) and eight gram negative (gm -ve) pathogenic bacteria were evaluated against the crude
plant (leaf and bark) extracts and based on their susceptibility, two gm +ve and four gm -ve
bacterial strains were finally selected. In case of crude extract, the highest zone of inhibition
(13.00±1.00 mm) was observed against Staphylococcus aureus when treated with leaf samples,
whereas it was 14.83±2.26 mm when treated with barks. Afterwards, Ag-NPs has been
synthesized following greener method and the formation of Ag-NPs was confirmed by visual
observation (colour change from pale yellow to dark brown) followed by Ultra-Violet Visible
(UV-VIS) spectroscopy. Later, plant extracts with synthesized Ag-NPs were tested against same
six bacterial strains and the obtained zone of inhibitions were compared with those of crude
extract. As expected, both leaf and bark extracts showed increased zone of inhibition than
previous. In this case, the diameter of the highest zone of inhibition was found 27.33±1.36 mm
against S. aureus when treated with leaf extracts containing Ag-NPs and it was30.00±2.60 mm
against the same bacterial strain. In case of bark extract with Ag-NPs. Finally, minimum
inhibitory concentration (MIC) test was performed using both crude and Ag-NPs containing
plant extracts. Significant differences were observed in MIC values between both types of plant
extracts. The MIC value was found 0.312 mg/ml for both crude leaf and bark extracts and 0.078
mg/ml and 0.039 mg/ml for leaf and bark extract containing Ag-NPs, respectively. So, it could
be concluded that the eco-friendly A. indica extracts (leaf and bark) can be used as an effective
reducing agent for the synthesis of Ag-NPs and thus the antimicrobial activity of the selected
medicinal plant can be enhanced by synthesized nanoparticles. |
