Biogenic Synthesis of Silver Nanoparticles using Lasiosiphon eriocephalus (Decne): In vitro Assessment of their Antioxidant, Antimicrobial and Cytotoxic Activities

Abstract

Introduction: The emergence of novel nanobiomedicine has transformed the management of various infectious as well as non-infectious diseases.Lasiosiphon eriocephalus, a medicinal plant, revealed the presence of active secondary metabolites and biological potentials.

Objective: The present study was aimed to demonstrate the biosynthesis of silver nanoparticles using L. eriocephalus leaf extract (LE-AgNPs) and their biological properties, such as antioxidant, antibacterial and anticancer potential.

Methods: The biosynthesized LE-AgNPs were characterized by UV-Visible spectroscopy, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction, and Fourier transform infrared spectroscopy (FTIR) analysis. The antibacterial activity was checked by minimum inhibitory concentration (MIC) and zone of inhibition assays against Gram-positive and Gram-negative bacteria. The anticancer potential of biogenic LE-AgNPs was checked by cytotoxicity and genotoxicity assay against human cervical adenocarcinoma (HeLa) and human breast adenocarcinoma (MCF-7) cells.

Results: UV-visible spectroscopy confirmed the formation of silver nanoparticles by measuring the surface plasmon resonance peak of the colloidal solution at 410-440 nm. The results of SEM and TEM revealed the distribution and spherical shape of 20-50 nm sized AgNPs. XRD spectrum confirmed the characteristic peaks at the lattice planes 110, 111, 200, 220 and 311 of silver which confirmed the crystalline nature of biosynthesized LE-AgNPs. FTIR spectrum of plant extract and biogenic LE-AgNPs was recorded in between 1635-3320 cm^-1 which confirmed stretching vibrations of possible functional groups C=C and O-H, responsible for the reduction of silver ions to silver nanoparticles. The in vitro antioxidant potential of LE-AgNPs was evaluated using DPPH (IC₅₀ = 26.51 ± 1.15 μg/mL) and ABTS radical assays (IC₅₀ =74.33 ± 2.47 μg/mL). The potential antibacterial effects of LE-AgNPs confirmed that 92.38 ± 2.70% growth inhibition occurred in E. coli in response to 0.1mg/mL concentration of LE-AgNPs followed by P. aeruginosa (75.51 ± 0.76), S. aureus (74.53 ± 1.26) and K. pneumoniae (67.4 ± 3.49). The cytotoxicity results interpreted that the biogenic silver nanoparticles exhibited strong dose and time dependent cytotoxicity effect against selected cancer cell lines where IC₅₀ concentration of LE-AgNPs required to inhibit the growth of HeLa cells after 24 h exposure was 4.14 μg/mL and MCF7 cells 3.00 μg/mL, respectively. Significant DNA fragmentation was seen in the DNA extracted from HeLa and MCF-7 cells exposed to more than 2.5 to 10 μg/mL concentrations of LE-AgNPs.

Conclusion: The overall findings from the present investigation indicated that the AgNPs synthesized using L. eriocephalus exerted strong biological potentials such as antioxidant, antimicrobial and extensive cytotoxicity and genotoxicity activities.

Keywords: Lasiosiphon eriocephalus; antibacterial activity; anticancer; antioxidants; cytotoxicity; genotoxicity.