Green Synthesis, Characterization and Antibacterial Activity of Silver Nanoparticles Using Amorphophallus paeoniifolius Leaf Extract

Biosynthesis and antibacterial activity of silver nanoparticles using Flos Sophorae Immaturus extract

The current study proposes a green synthesis method for silver nanoparticles (Ag NPs) using various concentrations of Flos Sophorae Immaturus extract as reducing and capping agents. The UV-Visible (UV-Vis) spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) were used to characterize resulting brown nanopowder. The as-prepared Ag NPs had a high negative zeta potential value of ∼ -38 mv, indicating the existence of electrostatic stabilization. The average sizes of ∼27.8 nm, 28.5 nm, 34.3 nm and 36.5 nm were measured by TEM. Moreover, FTIR and XPS analyses validated the production and chemical composition of Ag NPs from silver nitrate. The antibacterial activity of Ag NPs was examined against E. coli, P. aeruginosa, and S. aureus using agar well diffusion and the minimum inhibitory concentration (MIC) method. The antibacterial activity of the as-prepared Ag NPs from 4 mL extract was excellent against E. coli, P. aeruginosa, and S. aureus and the MIC values were 31.250, 15.625, and 31.250 mg/L, respectively. Based on these results, this study proposes a practical approach for the synthesis of Ag NPs in the industry and medical fields.

Proteomic Response of Aedes aegypti Larvae to Silver/Silver Chloride Nanoparticles Synthesized Using Bacillus thuringiensis subsp. israelensis Metabolites

Simple Summary

Aedes aegypti is a vector of important mosquito-borne diseases. Green synthesized nanoparticles (NPs) have been used to control the larvae of mosquitoes including A. aegypti. However, the molecular responses of A. aegypti larvae to green synthesized NPs remain unexplored. This work analyzed protein expression in A. aegypti larvae in response to treatment using green synthesized silver/silver chloride nanoparticles (Ag/AgCl NPs) based on two-dimensional polyacrylamide gel electrophoresis. Fifteen differentially expressed protein spots were selected for identification using mass spectrometry. The results showed that the six upregulated proteins in A. aegypti larvae responsible for green synthesized Ag/AgCl NP treatment were involved in mitochondrial dysfunction, DNA and protein damage, inhibition of cell proliferation, and cell apoptosis, implying the modes of actions of Ag/AgCl NPs. This finding has provided greater insight into the possible mechanisms of green synthesized Ag/AgCl NPs on the control of A. aegypti larvae.

Abstract

Silver/silver chloride nanoparticles (Ag/AgCl NPs) are an alternative approach to control the larvae of Aedes aegypti, a vector of mosquito-borne diseases. However, the molecular mechanisms of Ag/AgCl NPs to A. aegypti have not been reported. In this work, Ag/AgCl NPs were synthesized using supernatant, mixed toxins from Bacillus thuringiensis subsp. israelensis (Bti), and heterologously expressed Cry4Aa and Cry4Ba toxins. The images from scanning electron microscopy revealed that the Ag/AgCl NPs were spherical in shape with a size range of 25–100 nm. The larvicidal activity against A. aegypti larvae revealed that the Ag/AgCl NPs synthesized using the supernatant of Bti exhibited higher toxicity (LC₅₀ = 0.133 μg/mL) than the Ag/AgCl NPs synthesized using insecticidal proteins (LC₅₀ = 0.148–0.217 μg/mL). The proteomic response to Ag/AgCl NPs synthesized using the supernatant of Bti in A. aegypti larvae was compared to the ddH₂O-treated control. Two-dimensional gel electrophoresis analysis revealed 110 differentially expressed proteins, of which 15 were selected for identification using mass spectrometry. Six upregulated proteins (myosin I heavy chain, heat shock protein 70, the F₀F₁-type ATP synthase beta subunit, methyltransferase, protein kinase, and condensin complex subunit 3) that responded to Ag/AgCl NP treatment in A. aegypti were reported for NP treatments in different organisms. These results suggested that possible mechanisms of action of Ag/AgCl NPs on A. aegypti larvae are: mitochondrial dysfunction, DNA and protein damage, inhibition of cell proliferation, and cell apoptosis. The findings from this work provide greater insight into the action of green synthesized Ag/AgCl NPs on the control of A. aegypti larvae.

An insight into the mechanism of antibacterial activity by magnesium oxide nanoparticles

The exact mechanism behind the antibacterial efficacy of nanoparticles has remained unexplored to date. This study aims to shed light the mechanism adopted using magnesium oxide nanoparticles prepared in ethyl alcohol against gram-negative and gram-positive bacterial cells, and the generation of reactive oxygen species (ROS) is proposed to be the dominant mechanism. This paradigm is supported by the quantification of the hydroxyl radical and superoxide anions produced in the nanoparticle treated and untreated bacterial solutions, and by the reduction of the antibacterial efficiency after the addition of a radical scavenger. The production of free Mg2+ ions from the nanoparticle is supposed to be the causative agent behind this uncontrolled ROS generation, resulting in excessive oxidative stress, which the antioxidants of the bacterial cells are unable to nullify, leading to cell damage. The amount of proteins, carbohydrates and lipids leaked due to the distortion of the cellular membrane is also quantified, and it is observed that their leakage trend varies on the structure of the bacterial cell. FESEM images taken at certain time intervals show the gradual internalization of the nanoparticles, and increasing rupture of bacterial cell membranes, leading to cell necrosis.

Green Synthesis of Gold and Silver Nanoparticles by Using Amorphophallus paeoniifolius Tuber Extract and Evaluation of Their Antibacterial Activity

In this report, we discussed rapid, facile one-pot green synthesis of gold and silver nanoparticles (AuNPs and AgNPs) by using tuber extract of Amorphophallus paeoniifolius, and evaluated their antibacterial activity. AuNPs and AgNPs were synthesized by mixing their respective precursors (AgNO₃ and HAuCl₄) with tuber extract of Amorphophallus paeoniifolius as the bio-reducing agent. Characterization of AuNPs and AgNPs were confirmed by applying UV-vis spectroscopy, field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDS). From UV-vis characterization, surface plasmon resonance spectra were found at 530 nm for AuNPs and 446 nm for AgNPs. XRD data confirmed that both synthesized nanoparticles were face-centered cubic in crystalline nature, and the average crystallite sizes for the assign peaks were 13.3 nm for AuNPs and 22.48 nm for AgNPs. FTIR data evaluated the characteristic peaks of different phytochemical components of tuber extract, which acted as the reducing agent, and possibly as stabilizing agents. The antibacterial activity of synthesized AuNPs and AgNPs were examined in Muller Hinton agar, against two Gram-positive and four Gram-negative bacteria through the disc diffusion method. AuNPs did not show any inhibitory effect, while AgNPs showed good inhibitory effect against both Gram-positive and Gram-negative bacteria.

Review on Methodologies Used in the Synthesis of Metal Nanoparticles: Significance of Phytosynthesis Using Plant Extract as an Emerging Tool

Nanosized particles, with a size of less than 100 nm, have a wide variety of applications in various fields of nanotechnology and biotechnology, especially in the pharmaceutical industry. Metal nanoparticles [MNPs] have been synthesized by different chemical and physical procedures. Still, the biological approach or green synthesis [phytosynthesis] is considered as a preferred method due to eco-friendliness, nontoxicity, and cost-effective production. Various plants and plant extracts have been used for the green synthesis of MNPs, including biofabrication of noble metals, metal oxides, and bimetallic combinations. Biomolecules and metabolites present in plant extracts cause the reduction of metal ions into nanosized particles by one-step preparation methods. MNPs have remarkable attractiveness in biomedical applications for their use as potential antioxidant, anticancer and antibacterial agents. The present review offers a comprehensive aspect of MNPs production via top-to-bottom and bottom-to-top approach with considerable emphasis on green technology and their possible biomedical applications. The critical parameters governing the MNPs formation by plant-based synthesis are also highlighted in this review.