Bioinspired synthesis of multifunctional silver nanoparticles for enhanced antimicrobial and catalytic applications with tailored SPR properties

In the developing nanotechnology world, numerous attempts have been made to prepare the nobel metallic nanoparticles (NPs), which can improve their applicability in diverse fields. In the present work, the biosynthesis of silver (Ag) NPs has been successfully achieved through the medicinal plant extract (PE) of G. resinifera and effectively used for the catalytic and antibacterial applications. The size dependant tuneable surface plasmon resonance (SPR) properties attained through altering precursor concentrations. The X-ray and selected area diffraction pattern for Ag NPs revealed the high crystalline nature of pure Ag NPs with dominant (111) phase. The high-resolution TEM images show the non-spherical shape of NPs shifting from spherical, hexagonal to triangular, with wide particle size distribution ranging from 13 to 44 nm. Accordingly, the dual-band SPR spectrum is situated in the UV–Vis spectra validating the non-spherical shape of Ag NPs. The functional group present on the Ag NPs surface was analysed by FT-IR confirms the capping and reducing ability of methanolic PE G. resinifera. Further, the mechanism of antimicrobial activity studied using electron microscope showed the morphological changes with destructed cell walls of E. coli NCIM 2931 and S. aureus NCIM 5021 cells, when they treated with Ag NPs. The Ag NPs were more effective against S. aureus and E. coli with MIC 128 μg/ml as compared to P. aeruginosa NCIM 5029 with MIC 256 μg/ml. Apart from this, the reduction of toxic organic pollutant 4-NP to 4-AP within 20 min reveals the excellent catalytic activity of Ag NPs with rate constant k = 15.69 s^?1.     

The surface modification of spherical ZnO with Ag nanoparticles: A novel agent,biogenic synthesis,catalytic and antibacterial activities

Nowadays, the industrial wastewater pollutants including toxic dyes and pathogenic microbes have caused serious environmental contaminations and human health problems. In the present study, eco-friendly and facile green synthesis of Ag modified ZnO nanoparticles (ZnO-Ag NPs) using Crataegus monogyna (C. monogyna) extract (ZnO-Ag@CME NPs) is reported. The morphology and structure of the as-biosynthesized product were characterized by field emission scanning electron microscopy (FESEM), X-Ray diffraction (XRD), differential reflectance spectroscopy (DRS), dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS) techniques. TEM and FESEM images confirmed the oval and spherical-like structure of the products with a size of 55–70 nm. The EDS analysis confirmed the presence of Zn, Ag, and O elements in the biosynthesized product. The photocatalytic results showed ZnO-Ag@CME NPs were degraded (89.8% and 75.3%) and (94.2% and 84.7%) of methyl orange (MO) and basic violet 10 (BV10), under UV and sunlight irradiations, respectively. The Ag modified ZnO nanoparticles exhibited enhanced catalytic activity towards organic pollutants, and showed better performance than the pure ZnO nanoparticles under UV and sunlight irradiations. This performance was probably due to the presence of silver nanoparticles as a plasmonic material. Antibacterial activity was performed against different bacteria. ZnO-Ag@CME NPs showed high antibacterial activity against K. pneumoniae, S. typhimurium, P. vulgaris, S. mitis, and S. faecalis with MIC values of 50, 12.5, 12.5, 12.5, and 12.45 µg/mL, respectively. All in all, the present investigation suggests a promising method to achieve high-efficiency antibacterial and catalytic performance.     

Copper-polymer nanocomposite: An efficient catalyst for green Huisgen click synthesis

A new method for Huisgen [3+2] cycloaddition synthesis of 1,4- and 1,4,5-substituted-1H-1,2,3-triazoles was reported. The reaction was catalyzed by the product of thermolysis of copper (II) poly-5-vinyltetrazolate. Heterogeneous catalyst includes copper nanoparticles which supported on polymeric matrix. It presents recovered and recycled catalyst and the catalyzed reaction proceeds in aerobic conditions at room temperature in aqueous media.     

Comparative antibacterial potential of silver nanoparticles prepared via chemical and biological synthesis

New and improved approaches are urgently needed to fight the increasing number of multi-drug resistant bacteria. The antibacterial effect of silver nanoparticles (AgNPs) prepared by standardized chemical and biological syntheses is compered here. Biological systems included extracts of Opuntia ficus-indica mucilage and extracellular growth broth of Aspergillus niger and Bacillus megaterium. The nanoparticles were characterized by infrared spectroscopy, IR, and transmission electron microscopy. All of the AgNPs shared characteristic IR peaks and had an average size of 20–60 nm. The AgNPs were mainly spherical regardless of synthetic path. The synthesis based on the extracellular broth of the fungus, due to the highest biomass and active compounds concentration, resulted in a high yield of nanoparticle formation. These AgNPs also exhibited the highest inhibition zone against Salmonella typhimurium and Staphylococcus aureus. The syntheses reported here have no significant influence on AgNPs physical characteristics, as compared to literature, but represent processes with shorter reaction time. Additionally, the fungal based nanoparticles have superior antibacterial characteristics.     

Nature-inspired biogenic synthesis of silver nanoparticles for antibacterial applications

In recent decades, nanotechnology has been empowered as a new and developing interdisciplinary region of science and innovation that coordinates material science and biology. Nanoscience and nanotechnology open up new streets of examination that are helpful in synthesizing novel nanomaterials with remarkable applications. Among different metal nanomaterials, silver nanoparticles (AgNPs) attracted the attention of researchers due to their versatile antibacterial characteristics and biological properties. Biogenically synthesizing AgNPs from plants and microorganisms seems to be a highly promising alternative for developing a technology that is both environmentally benign and fast. Plants and microorganisms' ability to synthesize AgNPs has mostly remained untapped, and the lack of investigation is due to the vast variety of plants and microorganisms. This review aims to describe the current progress in various synthetic techniques for AgNPs and their potential for antibacterial applications. It discusses biogenic synthetic approaches, the role of various metabolites in the growth processes of AgNPs with antibacterial implications, bactericidal mechanisms, and the influence of operational parameters on AgNPs synthesis. Furthermore, the present status, critical challenges, and future outlook of AgNPs will be explored, which will definitely affect their present and future scenarios. We believe that by focusing readers' attention on nature-inspired, biogenically synthesized AgNPs and their bactericidal applications, this review will enable them to formulate a new perspective.     

Biosynthesis,characterization, biological and photo catalytic investigations of Elsholtzia blanda and chitosan mediated copper oxide nanoparticles

Bio synthesis of nanoparticles using plant parts has gained considerable attention, given the fact that the method is green, environment friendly, cheaper, simple and involves no hazardous substances. The present study involves the green synthesis of copper oxide nanoparticles (CuO NPs) using chitosan and the aqueous leaf extract of Elsholtzia blanda, an aromatic medicinal herb. The synthesized E.blanda-chitosan mediated copper oxide nanoparticles (CPCE) and E. blanda mediated copper oxide nanoparticles (PCE) were subjected to different characterization techniques, Ultraviolet–visible (UV–Vis), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX), High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED). The absorbance peaks in UV–Vis spectroscopy at 286 nm and 278 nm for CPCE and PCE respectively indicated the formation of nanoparticles. TEM and SEM employed for studying the surface morphology showed rod-like and spherical morphology bearing average size of 47.71 nm for CPCE and 36.07 nm for PCE. The antibacterial activities of the prepared nanoparticles were tested against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Salmonella typhi by agar well diffusion method. The results indicate that CuO NPs possess effective antibacterial potential against all tested bacteria with a maximum zone of inhibition of 18 mm for Enterococcus faecalis. Antioxidant studies revealed the highest DPPH scavenging activity of 89% at 25 μg/mL concentration of the nanoparticles. The percentage of the photo catalytic degradation of Congo red was found to be 95% after 10 h.     

Synthesis and applications of silver nanoparticles

Over the past few decades, nanoparticles of noble metals such as silver exhibited significantly distinct physical, chemical and biological properties from their bulk counterparts. Nano-size particles of less than 100 nm in diameter are currently attracting increasing attention for the wide range of new applications in various fields of industry. Such powders can exhibit properties that differ substantially from those of bulk materials, as a result of small particle dimension, high surface area, quantum confinement and other effects. Most of the unique properties of nanoparticles require not only the particles to be of nano-sized, but also the particles be dispersed without agglomeration. Discoveries in the past decade have clearly demonstrated that the electromagnetic, optical and catalytic properties of silver nanoparticles are strongly influenced by shape, size and size distribution, which are often varied by varying the synthetic methods, reducing agents and stabilizers. Accordingly, this review presents different methods of preparation silver nanoparticles and application of these nanoparticles in different fields.     

Diethylmethyl chitosan as an antimicrobial agent: Synthesis, characterization and antibacterial effects

Chitosan with excellent biodegradable and biocompatible characteristics has received attention as an oral drug delivery vehicle. A quaternized chitosan (i.e., N-diethylmethyl chitosan, DEMC) was prepared based on a modified two-step process via a 2² factorial design to optimize the preparative conditions. DEMC was fully characterized using FTIR and ¹H-NMR spectroscopies. As calculated using NMR-based data, high degree of quaternization was achieved through the optimized two-step process. The highly quaternized biopolymeric derivative was subjected to microbial experiments. The antimicrobial activities of chitosan and DEMC against Escherchia coli were compared by calculation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Our data indicates that although the antimicrobial activity of DEMC is higher than that of chitosan in acetic acid medium, the both compounds are pH dependent and an increase in concentration of acetic acid results in a significant decrease in both MIC and MBC.     

Green synthesis of silver nanoparticles using olive leaf extract and its antibacterial activity

The silver nanoparticles (AgNPs) synthesized using hot water olive leaf extracts (OLE) as reducing and stabilizing agent are reported and evaluated for antibacterial activity against drug resistant bacterial isolates. The effect of extract concentration, contact time, pH and temperature on the reaction rate and the shape of the Ag nanoparticles are investigated. The data revealed that the rate of formation of the nanosilver increased significantly in the basic medium with increasing temperature. The nature of AgNPs synthesized was analyzed by UV–vis spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis (TGA). The silver nanoparticles were with an average size of 20–25 nm and mostly spherical. The antibacterial potential of synthesized AgNPs was compared with that of aqueous OLE by well diffusion method. The AgNPs at 0.03–0.07 mg/ml concentration significantly inhibited bacterial growth against multi drug resistant Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli). This study revealed that the aqueous olive leaf extract has no effect at the concentrations used for preparation of the Ag nanoparticles. Thus AgNPs showed broad spectrum antibacterial activity at lower concentration and may be a good alternative therapeutic approach in future.     

Green synthesis of AgNPs from aqueous extract of Oxalis corniculata and its antibiofilm and antimicrobial activity

The silver nanoparticles OC-AgNPs, synthesized from the aqueous extract of Oxalis corniculata (OC), showed antiviral activity against Herpes Simplex Virus-1 (HSV-1), and anti-biofilm, and antibacterial activities against human isolates of six multi-drug resistant (MDR) bacteria - Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, and Pseudomonas aeruginosa. The OC-AgNP was characterized by UV-Vis and FTIR spectroscopy; while its morphology and distribution were determined by transmission electron microscopy (TEM). The results revealed that the biogenic OC-AgNPs are spherical with an average diameter of 40 nm and has shown UV-Vis peak at 445 nm. The cytotoxicity and safety of OC-AgNP has been evaluated by MTT assay in Vero cells and triple-negative human breast cancer MDA-MB-468 cells. The plaque reduction assay has been used to test the antiviral activity against HSV-1F. The anti-biofilm activity was assessed by crystal violet staining, followed by light and confocal microscopy; while the antibacterial activity was determined by conventional disk-diffusion and broth-dilution methods. Moreover, the mechanism of anti-biofilm and antibacterial activity was examined by Field Emission Scanning Electron Microscopy (FESEM). The CC₅₀ (cytotoxicity) on Vero cells was 300 μg/ml; while the survival percentage of MDA-MB-468 cells was 27.12% at 20 μM and 80.97% at 100 μM of, respectively. The OC-AgNP showed moderate antiviral activity against HSV-1F at EC₅₀ of 25 μg/ml; but significantly inhibited the biofilm produced by Pseudomonus aeruginosa and Escherichia coli at 25-50 μg/ml; while at 30-50 μM we observed the dose-dependent lowering of fluorescence intensity under light and confocal microscope. Interestingly, the OC-AgNPs demonstrated significant antibacterial activity against Pseudomonas aeruginosa (20 mm), Klebsiella pneumoniae (15 mm), Escherichia coli (12 mm), Salmonella typhi (10 mm), Streptococcus pyogenes (11 mm) and Staphylococcus aureus (10 mm) with Minimum Inhibitory Concentration (MIC) of 0.65–0.90 μM (0.11- 0.153 μg), respectively. Further, the FESEM micrograph showed disruption of membrane structure with the damage of cell membrane integrity of Pseudomonus aeruginosa at its MIC.     

Green synthesis and characterization of spherical copper nanoparticles as organometallic antibacterial agent

A facile and green route for the synthesis of copper nanoparticles (Cu NPs) has been achieved using green tea extract as a reducing, capping and stabilizing agent. UV–visible spectra gave surface plasmon resonance at 560 nm. The Cu NPs were characterized using various techniques. The size of the Cu NPs was about 20 nm. Antibacterial activity of biogenic Cu NPs were investigated against bacterial species Staphylococcus aureus , Bacillus subtilis , Pseudomonas aeruginosa and Escherichia coli and compared based on diameter of inhibition zone in disc diffusion assay and minimum inhibitory concentration and minimum bactericidal concentration of NPs dispersed in liquid cultures. The NPs showed better inhibitory activity against Gram‐positive bacteria (S. aureus and B. subtilis ) compared to Gram‐negative bacteria. Toxicity of the NPs was evaluated against animal cell line using MTT assay.     

Development of proof of concept for prostate cancer detection: an electrochemical immunosensor based on fullerene-C60 and copper nanoparticles composite film as diagnostic tool

Screening of Prostate-specific antigen (PSA) in human blood is the most common approach to diagnose prostate cancer. The joint application of biology and electrochemistry has shown a tremendous rise in research towards the development of electrochemical diagnostic tools for various diseases. The present study demonstrates the development of an effective immunosensing platform incorporating hydroquinone (HQ) immobilized, fullerene-C₆₀ and copper nanoparticles (CuNPs) composite film on glassy carbon electrode (HQ@CuNPs-reduced-fullerene-C₆₀/GCE) for the selective, quick and trace detection of PSA. In order to fabricate immunosensor sequential immobilization of primary antibody (Ab₁), blocking agent (bovine serum albumin (BSA)), antigen (prostate-specific antigen (PSA)) and secondary antibody (Ab₂) tagged with horseradish peroxide (HRP) was carried out on HQ@CuNPs-reduced-fullerene-C₆₀/GCE. Electrochemical characterization and the signal response of immunosensor were tested using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergetic effect of fullerene-C₆₀ and CuNPs, the novel nanocomposite film exhibited excellent catalytic activity towards hydrogen peroxide (H₂O₂) reduction for greatly amplified immunosensing signals. HQ@CuNPs-fullerene-C₆₀/GCE exhibited a well-defined redox peak and accelerated electrochemical reduction of H₂O₂ without any interference of dissolved oxygen and false-positive result in phosphate buffer solution (PBS) at pH 7.0. The parameters influencing the electrochemical response were optimized. Under the optimized conditions, wide linearity between PSA concentrations and current responses ranging from 0.005 ng/mL to 20 ng/mL with the lower detection limit of 0.002 ng/mL was obtained at the proposed immunosensor. The clinical applicability of the proposed immunosensor was successfully tested in serum and urine samples. Results revealed that the proposed immunosensor may create new boundaries in the identification of PSA in human blood samples.     

Bionanocomposite of Au decorated MnO2 via in situ green synthesis route and antimicrobial activity evaluation

Green synthesis gaining a significant importance for the preparation of nanoparticles (NPs) and NPs-based biocomposites gained much attention in biological applications. In the current study, gold (Au) nanoparticles were prepared via green approach using cinnamon extract. The Au nanocomposite (NC) was prepared with MnO₂ nanofiber mesh structure. The NC was characterized by XRD, SEM, FT-IR, EDX, UV–visible and DLS techniques. The MnO₂ nanofibers diameter was in 10–25 nm range, which was arranged in a mesh form and Au NPs was combined with nanofibers randomly. The MnO₂-Au NC antimicrobial activity was measured against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus strains. The antimicrobial activity of MnO₂-Au NC was highly promising against tested microorganisms in comparison to control (ciprofloxacin, a standard drug). The antimicrobial activity of MnO₂-Au NC was found in following order; > S. aureus > E. coli > P. aeruginosa with the zones inhibition of 22, 18 and 15 (mn), respectively. The MIC (minimum inhibitory concentration) values were 316, 342 and 231 (µg/mL) for E. coli, P. aeruginosa and S. aureus, respectively. In view of promising antimicrobial activity, the MnO₂-Au NC prepared via green approach could have potential applications in medical field and future study can be engrossed on the biocompatibility evaluation of MnO₂-Au NC using bioassays.     

Pseudo five-component process for the synthesis of functionalized tricarboxamides using CuI nanoparticles as reusable catalyst

An efficient and multicomponent method has been developed for the synthesis of functionalized tricarboxamides at room temperature using CuI nanoparticles as catalyst. This method involved fivecomponent coupling reactions of Meldrum's acid, isocyanides with aromatic aldehydes and amines at room temperature. Atom economy, wide range of products, excellent yields in short time and mild reaction conditions are some of the important features of this protocol. Notably, this catalyst could be recycled and reused for several times without significantly decreasing the catalytic activity.     

Corallocarpus epigaeus mediated synthesis of ZnO/CuO integrated ZrO2 nanoparticles for enhanced in-vitro antibacterial,antifungal and antidiabetic activities

Zirconia based nanocomposites have attracted much research attention in recent years due to their exceptional biomedicinal activities. Rhizome extracts of Corallocarpus epigaeus based ZrO₂/CuO–ZnO nanocomposite were green synthesized in a facile synthesis strategy. The nanocomposites were examined with XRD technique for their structural information and FT-IR technique for surface functional group analysis. Electron microscopic images aided to elucidate the CuO and ZnO nanoparticles decorated ZrO₂ nanostructures. UV–vis absorption spectroscopic studies of the nanocomposite revealed the characteristic UV absorption of ZrO₂ and enhanced visible region absorption for the incorporated nanoparticles. Antibacterial and antifungal studies indicated enhanced activity of nanocomposites over the pristine zirconia nanoparticles. ZrO₂/CuO–ZnO nanocomposite had exhibited about 75% of α-amylase inhibition activity, whereas pristine ZrO₂ nanoparticles had exhibited only 57% suggesting the worthwhile application in the antidiabetic activity of the nanocomposite.     

Biogenesis of copper nanoparticles using peel extract of Punica granatum and their antimicrobial activity against opportunistic pathogens

Copper nanoparticles (CuNPs) were biologically synthesized using peel extract of Punica granatum as reducing agent as well as capping agent. On treatment of aqueous solutions of CuSO₄·5H₂O with peel extract of P. granatum, stable CuNPs were formed. UV-Visible spectrophotometer analysis confirmed the formation of CuNPs. The synthesized nanoparticles were characterized with Fourier transform infrared spectroscopy, particles size analyzer and transmission electron microscopy (TEM). The electron microscopy analysis of CuNPs indicated that they ranged in size from 15 to 20?nm. The biologically synthesized CuNPs demonstrated high antibacterial activity against opportunistic pathogens, that is, Micrococcus luteus MTCC 1809, Pseudomonas aeruginosa MTCC 424, Salmonella enterica MTCC 1253 and Enterobactor aerogenes MTCC 2823 in vitro. Nanoparticles synthesized biologically using plant extracts have the potential to serve as possible ecofriendly alternatives to chemical and physical methods for biomedical applications and research.!     

Formulation and characterization of in situ generated copper nanoparticles reinforced cellulose composite films for potential antimicrobial applications

Cellulose was dissolved in aq.(LiOH + urea) solution pre-cooled to –12.5°C and the wet films were prepared using ethyl alcohol coagulation bath. The gel cellulose films were dipped in 10 wt.% Cassia alata leaf extract solution and allowed the extract to diffuse into them. The leaf extract infused wet cellulose films were dipped in different concentrated aq. copper sulphate solutions and allowed for in situ generation of copper nanoparticles (CuNPs) inside the matrix. The morphological, structural, antibacterial, thermal, and tensile properties of dried cellulose/CuNP composite films were carried out. The presence of CuNPs was established by EDX spectra and X-ray diffraction. The composite films displayed higher thermal stability than the matrix due to the presence of CuNPs. Cellulose/CuNP composite films possessed better tensile strength than the matrix. The composite films showed good antibacterial activity against E.coli bacteria. We conclude that good antibacterial activity and better tensile properties of the cellulose/CuNP composite films make them suitable for antibacterial wrapping and medical purposes.     

A green one-pot multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications using silica nanoparticles as reusable catalyst

A one-pot practical, efficient, and environmentally benign multicomponent synthesis of 4H-pyrans and polysubstituted aniline derivatives of biological, pharmacological, and optical applications has been developed using a very mild, neutral, and reusable silica nanoparticles as catalyst. The 4H-pyran derivatives were synthesized by a three component reaction of an aldehyde, malononitrile, and 5,5-dimethyl-1,3-cyclohexanedione or ethyl acetoacetate at room temperature or refluxing in ethanol. Alternatively, polysubstituted anilines were synthesized via a four component reaction of an aldehyde, a ketone, and two equivalents of malononitrile in ethanol.     

Synthesis and spectral studies of [RuCl(CO)(L)(PPh3)(B)] (HL = 2'-hydroxychalcones and B = PPh3, pyridine or piperidine) and their catalytic and biological applications

The reactions of [RuHCl(CO)(PPh3)2(B)] (B = PPh3, pyridine or piperidine) and 2'-hydroxychalcones led to the formation of [RuCl(CO)(PPh3)(L)(B)] (L = chalconate). The new complexes have been characterized by analytical and spectral (IR, electronic, 1H NMR and 31P NMR) data. They have been assigned an octahedral structure. The complexes have been used as catalysts for the aerial oxidation of cinnamyl alcohol. Some of the complexes have been tested in vitro for growth inhibitory activity against the bacteria E. coli, S. typhi and Pseudomonas sp. and the fungi A. fumigatus.     

In situ generation of silver nanoparticles in cellulose matrix using Azadirachta indica leaf extract as a reducing agent

In the present work, silver nanoparticles (AgNPs) were in situ generated in cellulose matrix using leaf extract of Azadirachta indica as a reducing agent. The cellulose/AgNP composite films prepared were characterized by FTIR, X-ray diffraction (XRD), scanning electron microscope, and antibacterial tests. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and spherical in shape with diameter in the range of 61–110?nm. XRD confirmed the formation of AgNPs and Ag–O nanoparticles. The nanocomposite films showed good antibacterial activity against Escherichia coli bacteria.