Environmental and antimicrobial properties of silver nanoparticles synthesized using Azadirachta indica Juss leaves extract

Elucidating antibiofilm as well as photocatalytic disinfection potential of green synthesized nanosilver against multi-drug-resistant bacteria and its photodegradation ability of cationic dyes

BACKGROUND

Bioinspired nanomaterials have widely been employed as suitable alternatives for controlling biofilm and pathogens due to their distinctive physico-chemical properties.

METHODOLOGY

This study explored the antibiofilm as well as photocatalytic potential of silver (Ag) nanoparticles (NPs) synthesized using the cell-free supernatant of Lactobacillus acidophilus for the disinfection of multi-drug-resistant (MDR) strains of enteroaggregative E. coli (EAEC), Salmonella Typhimurium, S. Enteritidis and methicillin-resistant Staphylococcus aureus (MRSA) on exposure to LED light. In addition, the removal of toxic cationic dyes i.e., methylene blue (MB), rhodamine B (RhB) and crystal violet (CV) was explored on exposure to sunlight, LED and UV lights.

RESULTS

Initially, the synthesis of AgNPs was verified using UV- Vis spectroscopy, X-ray diffraction and transmission electron microscopy. The synthesized AgNPs exhibited MIC and MBC values of 7.80 and 15.625 µg/mL, respectively. The AgNPs exhibited significant inhibition (P < 0.001) in the biofilm-forming ability of all the tested MDR isolates. On exposure to LED light, the AgNPs could effectively eliminate all the tested MDR isolates in a dose-dependent manner. While performing photocatalytic assays, the degradation of RhB was observed to be quite slower than MB and CV irrespective of the tested light sources. Moreover, the sunlight as well as UV light exhibited better photodegradation capacity than LED light. Notwithstanding the light sources, RhB followed zero-order kinetics; however, MB and CV followed primarily second-order kinetics.

CONCLUSION

The green synthesized AgNPs were found to be an effective photocatalytic as well as antifouling candidate that could be applied in therapeutics and wastewater treatment.

Construction of Ag/CdZnS QDs nanocomposite for enhanced visible light photoinactivation of Staphylococcus aureus

With increasing use of antibiotics, the development of antibiotic-resistant pathogens poses a serious threat to human health and the environment. Photocatalytic inactivation of these harmful pathogens is one of the novel and non-antibiotic treatments. The study fabricated Ag NPs decorated CdZnS QDs via a facile and biological co-precipitation method using L. camara plant extract as a green alternative to treat the toxic chemicals. The fabricated Ag/CdZnS QDs (NCs) were prepared for the efficient treatment of antibiotic-resistant pathogens as they raise a major global concern. The fabricated NCs were characterized with various characterization techniques to verify its physicochemical properties. The fabricated NCs have shown excellent photo-sterilization performance of 97 % against S. aureus. The excellent activity was attributed to the decoration of Ag NPs on CdZnS QDs as it helped in shortening band gap, improved visible light absorption ability, increased active sites, and boosted photogenerated electron/hole pairs stability. Radical trapping experiment and ESR analysis indicated the involvement of •OH and h+ in the photoinactivation of bacteria. The photo sterilization reaction of NCs was carried out under different environmental conditions, including light and dark conditions and different pH conditions. The experiment was carried out in sewage-treated water in order to test the real-time application, and the fabricated NCs achieved excellent 95.9 % photo-inactivation of S. aureus cells in sewage treated water and the Chemical Oxygen Demand (COD) of the system was increased after photo inactivation treatment. The fabricated NCs have also shown excellent reusable efficiency of 95% after six runs and the photostability and anti-corrosive nature of NCs were confirmed. The study provides an insight for the employment of photocatalysis for the sterilization of pathogens in real time aquatic environment across the globe.

Biosynthesis of Silver Nanoparticles Using Azadirachta indica and Their Antioxidant and Anticancer Effects in Cell Lines

In the present study, silver nanoparticles (Ag-NPs) were synthesized using Azadirachta indica extract and evaluated for their in vitro antioxidant activity and cytotoxicity efficacy against MCF-7 and HeLa cells. The silver nanoparticles (Ag-NPs) were formed within 40 min and after preliminary confirmation by UV-visible spectroscopy (peak observed at 375 nm), they were characterized using a transmission electron microscope (TEM) and dynamic light scattering (DLS). The TEM images showed the spherical shape of the biosynthesized Ag-NPs with particle sizes in the range of 10 to 60 nm, and compositional analysis was carried out. The cytotoxicity and antioxidant activity of various concentrations of biosynthesized silver nanoparticles, Azadirachta indica extract, and a standard ranging from 0.2 to 1.0 mg/mL were evaluated. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) activity of the biosynthesized Ag-NPs and aqueous leaf extract increased in a dose-dependent manner, with average IC₅₀ values of the biosynthesized Ag-NPs, aqueous leaf extract, and ascorbic acid (standard) of 0.70 ± 0.07, 1.63 ± 0.09, and 0.25 ± 0.09 mg/mL, respectively. Furthermore, higher cytotoxicity was exhibited in both the MCF-7 and HeLa cell lines in a dose-dependent manner. The average IC₅₀ values of the biosynthesized Ag-NPs, aqueous leaf extract, and cisplatin (standard) were 0.90 ± 0.07, 1.85 ± 0.01, and 0.56 ± 0.08 mg/mL, respectively, with MCF-7 cell lines and 0.85 ± 0.01, 1.76 ± 0.08, 0.45 ± 0.10 mg/mL, respectively, with HeLa cell lines. Hence, this study resulted in an efficient green reductant for producing silver nanoparticles that possess cytotoxicity and antioxidant activity against MCF-7 and HeLa cells.

Development of Wash-Durable Antimicrobial Cotton Fabrics by In Situ Green Synthesis of Silver Nanoparticles and Investigation of Their Antimicrobial Efficacy against Drug-Resistant Bacteria

An environment friendly and wash-durable silver nanoparticle treatment of cotton fabrics was carried out by in situ reduction of silver nitrate using Azadirachta indica leaf extract. The wash durability of the silver nanoparticles treatment on the cotton fabric was improved by pretreating the fabrics by mercerization and by adopting hydrothermal conditions of 120 °C temperature and 15 psi pressure for the in situ synthesis. The silver nanoparticle treated fabrics were characterized using scanning electron microscopy, colorimetric analysis and inductively coupled plasma mass spectroscopy. The coating of silver nanoparticles was seen to be dense and uniform in the scanning electron micrographs of the treated fabrics. An evaluation of the antibacterial efficacy of the silver nanoparticle treated fabric against antibiotic-resistant Gram-positive and Gram-negative strains was carried out. The antibacterial efficacy was found to be the highest against Bacillus licheniformis, showing 93.3% inhibition, whereas it was moderate against Klebsiella pneumoniae (20%) and Escherichia coli (10%). The transmittance data of a UV spectrophotometer (290–400nm) was used for measuring the UV protection factor of the silver nanoparticle treated fabrics. All the silver nanoparticle treated fabrics showed good antimicrobial and UV protection activity. The treatment was also seen to be durable against repeated laundering. This paper contributes the first report on a novel green synthesis approach integrating mercerization of cotton fabrics and in situ synthesis of nanoparticles under hydrothermal conditions using Azadirachta indica leaf extract for improved wash durability of the multifunctional fabric.

Facile green synthesis of non-genotoxic, non-hemolytic organometallic silver nanoparticles using extract of crushed, wasted, and spent Humulus lupulus (hops): Characterization, anti-bacterial, and anti-cancer studies

Since the last few decades, the green synthesis of metal nanoparticles was one of the most thrust areas due to its widespread application. The study proposed using wasted and unusable Humulus lupulus (Hops) extract to synthesize silver nanoparticles for biomedical application. The environment around us gives us many scopes to use the waste from environmental sources and turn it into something valuable. The spent Hops extract was used to synthesize silver nanoparticles (AgNP@HOPs), and the synthesized product exhibited an excellent therapeutic effect in terms of anti-bacterial and anti-cancer agents. The synthesis was optimized considering different factors like time and the concentration of AgNO₃. The silver nanoparticles were characterized in detail using different characterization techniques XRD, DLS, TEM, BET, XPS, Raman Spectroscopy, SEM, EDAX, AFM, which revealed the uniqueness of the silver nanoparticles. The average hydrodynamic size was found to be 92.42 ± 2.41 with a low polydispersity index. The presence of Ag-C and Ag-O bonds in the AgNP@HOPs indicated that it is composed of organo-silver and silver oxides. The nanoparticles were found to be spherical with an average size of 17.40 nm. The AgNPs were lethal to both E. coli and S. aureus with a MIC-50 of 201.881 μg/mL and 213.189 μg/mL, respectively. The AgNP@HOPs also exhibited an anti-cancer effect with an IC-50 of 147.175. The AgNP@HOPs exhibited less cytotoxicity and genotoxicity against normal cells and exhibited superior haemocompatibility (major criteria for drug selection). There are indeed various reports on the synthesis of silver nanoparticles, but this study proposes a green method for producing non-genotoxic, non-hemolytic organometallic silver nanoparticles using waste material with considerable therapeutic index from the environmental source with potential application in the medical industry. This work could be taken forward for in-vivo studies and for pre clinical studies.

Synthesis, characterization and photocatalytic application of Sophora mollis leaf extract mediated silver nanoparticles

This study reports green synthesis and characterization of silver nanoparticles (Ag NPs) from Sophora mollis leaf extract. The use of S. mollis extract for preparation of Ag NPs was investigated using different techniques. Dark brown color indicates formation of nanoparticles. Fourier transform infra-red (FTIR) analysis revealed that plant extract act as a reducing and capping agent. Morphological aspects of Ag NPs were ascertained by means of SEM studies. Energy dispersive and FTIR spectroscopy results showed chemical composition and plant extract functionality respectively. X-ray diffraction (XRD) analysis showed particle size of 70 nm. Antibacterial activity of NPs was investigated by disc diffusion and minimum inhibitory concentration method. Antioxidant activity of NPs was shown by DPPH assay. The photo catalytic efficiency of synthesized Ag NPs was evaluated by degradation of methylene blue (MB) dye under UV irradiation. Ag NPs degraded MB dye up to 88% in 160 min. It is concluded that these NPs could be employed for degradation of toxic industrial effluents. Result proved the green synthesis of Ag NPs from S. mollis extract is clean, economical and safe method.

Unveiling the cytotoxicity of phytosynthesised silver nanoparticles using Tinospora cordifolia leaves against human lung adenocarcinoma A549 cell line

Biosynthesis of silver nanoparticles (AgNPs) using plant extract is a cheap, easily accessible and natural process in which the phyto-constituents of the plants act as capping, stabilising and reducing agent. The present study explored the biosynthesis of AgNPs using aqueous leaf extract of Tinospora cordifolia and characterised via various techniques such as Fourier transform infrared, scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray analysis and X-ray diffraction. Here, TEM confirmed the spherical morphology with 25-50 nm size of synthesised AgNPs. Further, anticancer efficiency of AgNPs synthesised using T. cordifolia leaves were evaluated against human lung adenocarcinoma cell line A549 by MTT, trypan blue assay, apoptotic morphological changes using Annexin V-FITC and Propidium iodide (PI), nuclear morphological changes by DAPI (4, 6-diamidino-2-phenylindole dihydrochloride) staining, reactive oxygen species generation and mitochondrial membrane potential determination. Results confirmed the AgNPs synthesised using T. cordifolia leaves are found to be highly toxic against human lung adenocarcinoma cell line A549.

Novel Green Biomimetic Approach for Synthesis of ZnO-Ag Nanocomposite; Antimicrobial Activity against Food-borne Pathogen, Biocompatibility and Solar Photocatalysis

A simple, eco-friendly, and biomimetic approach using Thymus vulgaris (T. vulgaris) leaf extract was developed for the formation of ZnO-Ag nanocomposites (NCs) without employing any stabilizer and a chemical surfactant. T. vulgaris leaf extract was used for the first time, in a novel approach, for green fabrication of ZnO-Ag NCs as a size based reducing agent via the hydrothermal method in a single step. Presence of phenols in T. vulgaris leaf extract has served as both reducing and capping agents that play a critical role in the production of ZnO-Ag NCs. The effect of silver nitrate concentration in the formation of ZnO-Ag NCs was studied. The in-vitro Antimicrobial activity of NCs displayed high antimicrobial potency on selective gram negative and positive foodborne pathogens. Antioxidant activity of ZnO-Ag NCs was evaluated via (2,2-diphenyl-1-picrylhydrazyl) DPPH method. Photocatalytic performance of ZnO-Ag NCs was appraised by degradation of phenol under natural sunlight, which exhibited efficient photocatalytic activity on phenol. Cytotoxicity of the NCs was evaluated using the haemolysis assay. Results of this study reveal that T. vulgaris leaf extract, containing phytochemicals, possess reducing property for ZnO-Ag NCs fabrication and the obtained ZnO-Ag NCs could be employed effectively for biological applications in food science. Therefore, the present study offers a promising way to achieve high-efficiency photocatalysis based on the hybrid structure of semiconductor/metal.

Biological synthesis of metallic nanoparticles (MNPs) by plants and microbes: their cellular uptake, biocompatibility, and biomedical applications

Metallic nanoparticles (MNPs) with their diverse physical and chemical properties have been applied in various biomedical domains. The increasing demand for MNPs has attracted researchers to develop straightforward, inexpensive, simple, and eco-friendly processes for the enhanced production of MNPs. To discover new biomedical applications first requires knowledge of the interactions of MNPs with target cells. This review focuses on plant and microbial synthesis of biological MNPs, their cellular uptake, biocompatibility, any biological consequences such as cytotoxicity, and biomedical applications. We highlighted the involvement of biomolecules in capping and stabilization of MNPs and the effect of physicochemical parameters particularly the pH on the synthesis of MNPs. Recently achieved milestones to understand the role of synthetic biology (SynBiol) in the synthesis of tailored MNPs are also discussed.