Biosynthesis of Silver Nanoparticles Using Barleria albostellata C.B. Clarke Leaves and Stems: Antibacterial and Cytotoxic Activity
Authors: Gangaram Serisha , Naidoo Yougasphree , Dewir Yaser Hassan , Singh Moganavelli , Lin Johnson , Nicole Daniels Aliscia , Mendler-Drienyovszki Nóra 
Published: September 2024

Silver nanoparticles (AgNPs) have increasingly gained attention owing to their distinctive physicochemical and biological properties. The objective of the investigation was to biologically synthesize AgNPs using plant extracts from Barleria albostellata. The synthesized AgNPs, obtained from B. albostellata (leaves and stems), were characterized through various techniques including UV-visible spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis, Fourier transform infrared (FTIR) spectral analysis, and nanoparticle tracking analysis (NTA). The antibacterial efficacy of the synthesized AgNPs was evaluated utilizing the disk diffusion method. The cytotoxicity effects of the synthesized AgNPs were determined using the MTT assay (3-[(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide]) in cervical cancer (HeLa), embryonic kidney (HEK293), and breast adenocarcinoma (MCF-7) cell lines. The results indicate that B. albostellata extracts could serve as eco-friendly biofactories for the synthesis of AgNPs. UV-vis spectroscopy of the leaf and stem extracts revealed absorption peaks within the range of 400–450 nm, thereby confirming the synthesis of AgNPs. Elemental Ag was highest in the methanol leaf extracts (16.87 ± 0.89%) and lowest in the powdered stem extracts (7.13 ± 1.44%). Synthesized AgNPs were predominantly spherical in shape. HRTEM revealed that synthesized AgNPs from the methanolic stem extracts (34.32 ± 16.99 nm) were larger in size, while those from the powdered stem extracts were smaller (16.57 ± 5.55 nm). AgNPs synthesized from both the leaf and stem extracts exhibited zeta potential values between −8.8 and −32.1 mV, with hydrodynamics diameters ranging from 34.3 to 111.3 nm. FTIR spectroscopy confirmed the presence of various functional groups on the AgNPs. AgNPs synthesized from the leaf and stem extracts displayed significant antibacterial activity and were sensitive to Gram-negative and Gram-positive bacteria. AgNPs exhibited significant antibacterial activity (diameter of the zone of inhibition) against Pseudomonas aeruginosa (21.67 ± 2.87 mm) in the leaf methanolic extract. Synthesized AgNPs exhibited selective in vitro cytotoxicity against HEK293, HeLa, and MCF-7 cell lines. The IC50 values of the AgNPs synthesized from the various extracts were all above 9 µg/mL. Significant cytotoxic levels (IC50 16.11 and 27.23 µg/mL) were observed for the MCF-7 cell line upon exposure to the methanolic leaf and stem AgNPs. This study recommends the use of medicinal plant extracts in producing economically effective AgNPs, due to their efficient capping. Overall, AgNPs synthesized from B. albostellata extracts comprised novel antibacterial and anticancer agents, and warrant further investigation. Bio-synthesized AgNPs show great potential in the area of nanotechnology and may be used as an affordable, eco-friendly alternative for the delivery of conventional therapeutics.