Using silver nanoparticle to enhance current response of biosensor

Plant-assisted green preparation of silver nanoparticles using leaf extract of Dalbergia sissoo and their antioxidant, antibacterial and catalytic applications

Plant-mediated preparation of silver nanoparticles (AgNPs) is thought to be a more economical and environmentally benign process in comparison to physical and chemical synthesis methods. In the present study, the aqueous leaf extract of Dalbergia sissoo was prepared and utilized to reduce silver ion (Ag+) during the green synthesis of silver nanoparticles (DL-AgNPs). The formation of DL-AgNPs was verified using UV-Vis spectra, exhibiting the surface plasmon resonance (SPR) band at around 450 nm. FT-IR analysis revealed the kinds of phytochemicals that serve as reducing and capping agents while DL-AgNPs are being synthesized. Analysis of scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HR-TEM) images verified the development of spherical and oval-shaped DL-AgNPs, with sizes ranging from 10 to 25 nm. The stability and particle size distribution of synthesized DL-AgNPs were ensured by zeta potential and DLS (dynamic light scattering) investigations. Additionally, X-ray diffraction (XRD) analysis confirmed the crystalline nature of DL-AgNPs. In antioxidant experiments, DL-AgNPs demonstrated significant scavenging capacities of DPPH and ABTS radicals with EC50 values of 51.32 and 33.32 μg/mL, respectively. The antibacterial activity of DL-AgNPs was shown to be significant against harmful bacteria, with a maximum zone of inhibition (21.5 ± 0.86 mm) against Staphylococcus aureus. Furthermore, DL-AgNPs exhibited effective catalytic activity to degrade environment-polluting dyes (methylene blue, methyl orange, and Congo red) and toxic chemicals (p-nitrophenol). The results of all these studies suggested that DL-AgNPs made from the leaf extract of Dalbergia sissoo have merit for application in the environmental and biomedical fields.

Breaking boundaries: Artificial intelligence for pesticide detection and eco-friendly degradation

Pesticides are extensively used agrochemicals across the world to control pest populations. However, irrational application of pesticides leads to contamination of various components of the environment, like air, soil, water, and vegetation, all of which build up significant levels of pesticide residues. Further, these environmental contaminants fuel objectionable human toxicity and impose a greater risk to the ecosystem. Therefore, search of methodologies having potential to detect and degrade pesticides in different environmental media is currently receiving profound global attention. Beyond the conventional approaches, Artificial Intelligence (AI) coupled with machine learning and artificial neural networks are rapidly growing branches of science that enable quick data analysis and precise detection of pesticides in various environmental components. Interestingly, nanoparticle (NP)-mediated detection and degradation of pesticides could be linked to AI algorithms to achieve superior performance. NP-based sensors stand out for their operational simplicity as well as their high sensitivity and low detection limits when compared to conventional, time-consuming spectrophotometric assays. NPs coated with fluorophores or conjugated with antibody or enzyme-anchored sensors can be used through Surface-Enhanced Raman Spectrometry, fluorescence, or chemiluminescence methodologies for selective and more precise detection of pesticides. Moreover, NPs assist in the photocatalytic breakdown of various organic and inorganic pesticides. Here, AI models are ideal means to identify, classify, characterize, and even predict the data of pesticides obtained through NP sensors. The present study aims to discuss the environmental contamination and negative impacts of pesticides on the ecosystem. The article also elaborates the AI and NP-assisted approaches for detecting and degrading a wide range of pesticide residues in various environmental and agrecultural sources including fruits and vegetables. Finally, the prevailing limitations and future goals of AI-NP-assisted techniques have also been dissected.

Diospyros montana mediated reduction, stabilization, and characterization of silver nanoparticles and evaluation of their mosquitocidal potentiality against dengue vector Aedes albopictus

Recent research has focused on nanoparticles. Aedes albopictus is a potential vector that transmits fatal diseases. Recently, Phyto-reduced silver nanoparticles (AgNPs) were shown to be mosquito larvicides. This study aimed to synthesize silver nanoparticles using Diospyros montana leaf extract, characterize them, and test their efficacy as larvicide and pupicide against Ae. albopictus mosquitoes, determine their duration of effectiveness as a larvicide, identify plant compounds that help to synthesize nanoparticles, and assess their effects on non-target organisms. Quercetin, luteolin, kaempferol, gallocatechin gallate, epigallocatechin gallate, and capsaicin are among the novel reducing and capping agents found in D. montana leaf through LCMS analysis. The color shift and distinctive peak in UV-Vis spectroscopy made it simple to see how biogenic AgNPs were produced by converting Ag+ ions into Ag0. Substantial negative value (- 19.10 mv) of zeta potential demonstrated the long-term stability of AgNPs. A moderate range (8.72 - 50.75 nm) of particle size distribution pattern was obtained using the DLS technique. SEM and TEM images depicted the quasi-spherical (or polyhedral) and spherical shape of the nanoparticles, having approximately 16.75 nm average size. Synthesized AgNPs had a low LC90 value (< 10 ppm) for all larval instars and pupae of Ae. albopictus and had negligible mal effect on non-target organisms. Regression equations showed dose-dependent mortality by the positive correlation between mortality rate and AgNPs concentration, and each time the regression coefficient (R2) value was larger than zero. This study shows that D. montana leaf extract is an environment-friendly and sustainable source of an effective reducing and capping agent to synthesize highly stable, ecologically acceptable silver nanoparticles and their application as mosquitocide.

Recent Advances in Applications of Oxidases and Peroxidases Polymer-Based Enzyme Biocatalysts in Sensing and Wastewater Treatment: A Review

Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.

Thermodynamics of the physisorption of capping agents on silver nanoparticles

Nanoscale silver particles have growing applications in biomedical and other technologies due to their unique antibacterial, optical, and electrical properties. The preparation of metal nanoparticles requires the action of a capping agent, such as thiol-containing compounds, to provide colloidal stability, prevent agglomeration, stop uncontrolled growth, and attenuate oxidative damage. However, despite the extensive use of these thiol-based capping agents, the structure of the capping agent layers on the metal surface and the thermodynamics of the formation of these layers remains poorly understood. Here, we leverage molecular dynamics simulations and free energy calculation techniques, to study the behavior of citrate and four thiol-containing capping agents commonly used to protect silver nanoparticles from oxidation. We have studied the single-molecule adsorption of these capping agents to the metal-water interface, their coalescence into clusters, and the formation of complete monolayers covering the metal nanoparticle. At sufficiently high concentrations, we find that allylmercaptan, lipoic acid, and mercaptohexanol spontaneously self-assemble into ordered layers with the thiol group in contact with the metal surface. The high density and ordered structure is presumably responsible for their improved protective characteristics relative to the other compounds studied.

Triangular Silver Nanoplates as a Bioanalytical Tool: Potential COVID-19 Detection

Nanotechnology offers new possibilities in molecular diagnostics, with nanoparticles gaining attention as biosensor upgrades. This study evaluates gold-coated silver nanoplates coated with PEG for enhanced protection, aiming to detect Spike protein with higher sensitivity, and emphasizes the importance of considering complex environments and appropriate controls for specific binding and accurate analysis. The sensitivity of antibody-coated PEGAuTSNPs as tools for immunoassays is demonstrated through fibronectin (Fn)- anti-fibronectin binding within an isolated extracellular matrix as a complex and native environment of Fn. Moreover, the optimal functionalization volume of Spike protein was determined (4 µg/mL of PEGAuTSNP). Anti-Spike was added to confirm binding, while the TJP1 protein was used as a negative control. The same experiment was used in the presence of horse serum to simulate a complex environment. According to Localized Surface Plasmon Resonance analysis and Dynamic Light Scattering size measurements, anti-Spike exhibited a stronger affinity for the nanoplates, causing TJP1 to be replaced by the antibody on the nanoplates' surface. Future research will involve exploring alternative complex environments, filtering larger molecules, and the optimization of immunoassay performance.

Application of Inorganic Nanomaterials in Cultural Heritage Conservation, Risk of Toxicity, and Preventive Measures

Nanotechnology has allowed for significant progress in architectural, artistic, archaeological, or museum heritage conservation for repairing and preventing damages produced by deterioration agents (weathering, contaminants, or biological actions). This review analyzes the current treatments using nanomaterials, including consolidants, biocides, hydrophobic protectives, mechanical resistance improvers, flame-retardants, and multifunctional nanocomposites. Unfortunately, nanomaterials can affect human and animal health, altering the environment. Right now, it is a priority to stop to analyze its advantages and disadvantages. Therefore, the aims are to raise awareness about the nanotoxicity risks during handling and the subsequent environmental exposure to all those directly or indirectly involved in conservation processes. It reports the human-body interaction mechanisms and provides guidelines for preventing or controlling its toxicity, mentioning the current toxicity research of main compounds and emphasizing the need to provide more information about morphological, structural, and specific features that ultimately contribute to understanding their toxicity. It provides information about the current documents of international organizations (European Commission, NIOSH, OECD, Countries Normative) about worker protection, isolation, laboratory ventilation control, and debris management. Furthermore, it reports the qualitative risk assessment methods, management strategies, dose control, and focus/receptor relationship, besides the latest trends of using nanomaterials in masks and gas emissions control devices, discussing their risk of toxicity.

Surface modification for improving immunoassay sensitivity

Immunoassays are widely performed in many fields such as biomarker discovery, proteomics, drug development, and clinical diagnosis. There is a growing need for high sensitivity of immunoassays to detect low abundance analytes. As a result, great effort has been made to improve the quality of surfaces, on which the immunoassay is performed. In this review article, we summarize the recent progress in surface modification strategies for improving the sensitivity of immunoassays. The surface modification strategies can be categorized into two groups: antifouling coatings to reduce background noise and nanostructured surfaces to amplify the signals. The first part of the review summarizes the common antifouling coating techniques to prevent nonspecific binding and reduce background noise. The techniques include hydrophilic polymer based self-assembled monomers, polymer brushes, and surface attached hydrogels, and omniphobicity based perfluorinated surfaces. In the second part, some common nanostructured surfaces to amplify the specific detection signals are introduced, including nanoparticle functionalized surfaces, two dimensional (2D) nanoarrays, and 2D nanomaterial coatings. The third part discusses the surface modification techniques for digital immunoassays. In the end, the challenges and the future perspectives of the surface modification techniques for immunoassays are presented.

Molluscicidal and antioxidant activities of silver nanoparticles on the multi-species of snail intermediate hosts of schistosomiasis

BACKGROUND

Schistosomiasis, also known as bilharzia, is the second important parasitic disease after malaria. The present study aimed to evaluate the molluscicidal effects of silver nanoparticles on Biomphalaria alexandrina, B. glabrata, Oncomelania hupensis, snail intermediate hosts of intestinal schistosomes (i.e. Schistosoma mansoni and S. japonicum), along with the changes their antioxidant enzymes.

METHODS

Silver (Ag) nano powder (Ag-NPs) was selected to test the molluscicidal effects on three species of freshwater snails. Exposure to Ag-NPs induced snail mortality and the LC50 and LC90 values of Ag-NPs for each snail species were calculated by probit analysis. Control snails were maintained under the same experimental conditions in dechlorinated water. Snail hemolymph was collected to measure the levels of antioxidant enzymes, such as total antioxidants capacity (TCA), glutathione (GSH), catalase (CAT) and nitric oxide (NO). In addition, the non-target organism, Daphnia magna, was exposed to a series of Ag-NPs concentration, similar to the group of experimental snails, in order to evaluate the LC50 and LC90 and compare these values to those obtained for the targeted snails.

RESULTS

The results indicated that Ag-NPs had a molluscicidal effect on tested snails with the variation in lethal concentration. The LC50 values of Ag-NPs for B. alexandrina snails exposed for 24, 48, 72 hrs and 7 days were 7.91, 5.69, 3.83 and 1.91 parts per million (ppm), respectively. The LC50 values for B. glabrata snails exposed for 24, 48, 72 hrs and 7 days were 16.55, 10.44, 6.91 and 4.13 ppm, respectively, while the LC50 values for O. hupensis snails exposed for 24, 48, 72 hrs and 7 days were 46.5, 29.85, 24.49 and 9.62 ppm, respectively. Moreover, there is no mortality detected on D. magna when exposed to more than double and half concentration (50 ppm) of Ag-NPs during a continuous period of 3 hrs, whereas the LC90 value for B. alexandrina snails was 18 ppm. The molluscicidal effect of the synthesized Ag-NPs seems to be linked to a potential reduction of the antioxidant activity in the snail's hemolymph.

CONCLUSIONS

Synthesized Ag-NPs have a clear molluscicidal effect against various snail intermediate hosts of intestinal schistosome parasites and could potentially serve as next generation molluscicides.

Ratiometric electrochemical immunoassay for procalcitonin based on dual signal probes: Ag NPs and Nile blue A

In order to determine procalcitonin, a sandwich-type ratiometic electrochemical immunosensor was developed by differential pulse voltammetry (DPV). Due to high chemical stability and good biocompatibility, graphitic carbon nitride (g-C₃N₄) could be used as feasible supporter to carry silver nanoparticles (Ag NPs) with an obvious oxidative peak (measured typically at + 0.3 V vs. SCE). Ag NPs loaded onto g-C₃N₄ were not only beneficial to prevent the agglomeration of Ag NPs, but also favorable to improve the electron transfer velocity of g-C₃N₄. Moreover, the g-C₃N₄-Ag NPs as the matrix could immobilize primary antibody by Ag-N bond. Nile blue A (NBA), an excellent redox probe based on the redox reaction with two-electrons, provides a current signal at - 0.38 V (vs. SCE). Zr-based metal organic framework (UiO-67), an ideal framework material with large specific surface area and high porosity, could absorb the substantial water-soluble NBA by electrostatic adsorption. The UiO-67 modified by NBA (NBA-UiO-67) owned admirable biocompatibility and was a qualifying marker to load the secondary antibody. For the immunosensor, the current ratio of NBA to Ag NPs (I_NBA/I_{Ag NPs}) was increased as the concentrations of PCT increased. Under the optimum conditions, the linear range of the immunosensor was 0.005 to 50 ng/mL; the detection limit was 1.67 pg/mL (S/N = 3), which reflected the excellent analytical performance of the sensor. The proposed immunosensor strategy is a simple and dependable platform, with great application potential in biometric analysis.

Inhalation exposure to silver nanoparticles induces hepatic inflammation and oxidative stress, associated with altered renin-angiotensin system signaling, in Wistar rats

Silver nanoparticles (AgNPs) have become increasingly popular in the biomedical field over the last few decades due to its proven antibacterial property. Previous scientific studies have reported that one of the major organs responsible for detoxification of AgNPs is the liver. The liver is also the primary organ responsible for secretion of angiotensinogen (AGT), a key signaling molecule involved in the renin-angiotensin system (RAS), which plays an important role in maintaining cardiac output and vascular pressure. The aim of this study was to assess any potential changes in the RAS-associated gene signaling, inflammatory response, and hepatocellular toxicity resulting from AgNP exposure. To do this, 6-week-old, male Wistar rats were exposed to a subacute inhalation exposure of AgNP (200 ppb/days over 4 h/days exposure, for 5 d) and their livers were analyzed for alterations in RAS components, inflammation, and oxidative stress. Real time qPCR analysis showed that AgNP-exposure resulted in a significant increase in hepatic AGT, angiotensin converting enzyme (ACE)-1, and ACE-2 mRNA expression. Expression of inflammatory markers interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were also upregulated with AgNP-exposure, compared to controls. Furthermore AgNP-exposure mediated a significant increase in hepatic expression of catalase, and superoxide dismutase, and oxidative stress, as assessed via 8-Oxo-2'-deoxyguanosine staining. Increased oxidative stress was associated with increased monocyte/macrophage-2 staining in the liver of AgNP-exposed rats. Such findings indicate that subacute inhalation exposure to AgNPs mediate increased hepatic RAS signaling, associated with inflammation, macrophage infiltration, and oxidative stress.

Modular terpene synthesis enabled by mild electrochemical couplings

The synthesis of terpenes is a large field of research that is woven deeply into the history of chemistry. Terpene biosynthesis is a case study of how the logic of a modular design can lead to diverse structures with unparalleled efficiency. This work leverages modern nickel-catalyzed electrochemical sp²-sp³ decarboxylative coupling reactions, enabled by silver nanoparticle-modified electrodes, to intuitively assemble terpene natural products and complex polyenes by using simple modular building blocks. The step change in efficiency of this approach is exemplified through the scalable preparation of 13 complex terpenes, which minimized protecting group manipulations, functional group interconversions, and redox fluctuations. The mechanistic aspects of the essential functionalized electrodes are studied in depth through a variety of spectroscopic and analytical techniques.

Review on recent progress in metal-organic framework-based materials for fabricating electrochemical glucose sensors

Diabetes is a type of disease that threatens human health, which can be diagnosed based on the level of glucose in the blood. Recently, various MOF-based materials have been developed as efficient electrochemical glucose sensors because of their tunable pore channels, large specific surface area well dispersed metallic active sites, etc. In this review, the significance of glucose detection and the advantages of MOF-based materials for this application are primarily discussed. Then, the application of MOF-based materials can be categorized into two types of glucose sensors: enzymatic biosensors and non-enzymatic sensors. Finally, insights into the current research challenges and future breakthrough possibilities regarding electrochemical glucose sensors are considered.

Versatile Design of Functional Organic-Inorganic 3D-Printed (Opto)Electronic Interfaces with Custom Catalytic Activity

The ability to combine organic and inorganic components in a single material represents a great step toward the development of advanced (opto)electronic systems. Nowadays, 3D-printing technology has generated a revolution in the rapid prototyping and low-cost fabrication of 3D-printed electronic devices. However, a main drawback when using 3D-printed transducers is the lack of robust functionalization methods for tuning their capabilities. Herein, a simple, general and robust in situ functionalization approach is reported to tailor the capabilities of 3D-printed nanocomposite carbon/polymer electrode (3D-nCE) surfaces with a battery of functional inorganic nanoparticles (FINPs), which are appealing active units for electronic, optical and catalytic applications. The versatility of the resulting functional organic-inorganic 3D-printed electronic interfaces is provided in different pivotal areas of electrochemistry, including i) electrocatalysis, ii) bio-electroanalysis, iii) energy (storage and conversion), and iv) photoelectrochemical applications. Overall, the synergism of combining the transducing characteristics of 3D-nCEs with the implanted tuning surface capabilities of FINPs leads to new/enhanced electrochemical performances when compared to their bare 3D-nCE counterparts. Accordingly, this work elucidates that FINPs have much to offer in the field of 3D-printing technology and provides the bases toward the green fabrication of functional organic-inorganic 3D-printed (opto)electronic interfaces with custom catalytic activity.

One Step Production of Silver-Copper (AgCu) Nanoparticles

AgCu nanoparticles were prepared through hydrogen-reduction-assisted Ultrasonic Spray Pyrolysis (USP) and the Hydrogen Reduction (HR) method. The changes in the morphology and crystal structure of nanoparticles were studied using different concentrated precursors. The structure and morphology of the mixed crystalline particles were characterized through X-ray diffraction analysis (XRD), scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDS). The average particle size decreased from 364 nm to 224 nm by reducing the initial solution concentration from 0.05 M to 0.4 M. These results indicate that the increase in concentration also increases the grain size. Antibacterial properties of nanoparticles against Escherichia coli were investigated. The obtained results indicate that produced particles show antibacterial activity (100%). The AgCu nanoparticles have the usage potential in different areas of the industry.

Nano-sized Metal and Metal Oxide Modified Electrodes for Pharmaceuticals Analysis

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The electrochemical analysis offers a number of important advantages such as providing information on pharmaceuticals analysis and their in vivo redox processes and pharmacological activity. The interest in developing electrochemical sensing devices for use in clinical assays is growing rapidly. Metallic nanoparticles can be synthesized and modified with various chemical functional groups, which allow them to be conjugated with antibodies, ligands, and drugs of interest.

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In this article, the novel developments to enhance the performance of sensor modified with metal nanoparticles of pharmaceuticals were reviewed. A discussion of the properties of metal nanostructures and their application in drug analysis is presented. Their application as a modifier agent in determining low levels of drugs in pharmaceutical dosage forms and biological samples is discussed. It has been found that the electrocatalytic effect of the electrode, sensitivity and selectivity were increased using various working electrodes modified with nano-sized metal, metal oxide and metal/metal oxide particles.

Synthesis of biologically active silver nanoparticles using N-containing compounds: the dual role of semicarbazones

Semicarbazone-type Schiff bases have been demonstrated to play an important role in the synthesis of metal nanoparticles by an easy, simple and convenient protocol. The chosen semicarbazones act as reducing as well as capping agents.

Silver nanoparticle in biosensor and bioimaging: Clinical perspectives

Recent developments in nanotechnology promoted the production of nanomaterials with various shapes and sizes by utilizing interdisciplinary researches of biology, chemistry, and material science toward the clinical perspectives. In particular, gold and silver (Ag) are noble metals that exhibit tunable and unique plasmonic properties for the downstream applications. Ag exhibits higher thermal and electrical conductivities, and more efficient in the electron transfer than gold with sharper extinction bands. In addition, modified Ag nanoparticle is more stable in water and air. With all these above features, Ag is an attractive tool in various fields, including diagnosis, drug delivery, environmental, electronics, and as antimicrobial agent. In particular, applications of Ag nanoparticle in the fields of biosensor and imaging are prominent in recent days. Enhancing the specific detection of clinical markers with Ag nanoparticle has been proved by several studies. This review discussed the constructive application of Ag nanoparticle in biosensor and bioimaging for the detection of small molecule to larger whole cell in the perspectives of diagnosing diseases.

Anxiety determination by antibody-conjugated nanoparticles on an interdigitated electrode sensor

This work focused on the detection of cortisol on an interdigitated electrode sensor surface using an anti-cortisol antibody. To improve immobilization, antibodies were conjugated with silver nanoparticles and attached to the surface of the sensor. Cortisol interacted in a dose-dependent manner on the antibody-immobilized sensor surface, and current changes were observed. Linear regression analysis was performed by a 3σ calculation, and the limit of detection fell into the range of 0.01 and 0.1 ng/mL. The sensitivity of cortisol was calculated to be 0.01 ng/mL and the sensor discriminated against other hormones, namely norepinephrine and progesterone, with higher selectivity for cortisol. This result represented the selective detection of cortisol with high performance, which can help to determine anxiety disorders.

A highly sensitive enzyme-less glucose sensor based on pnictogens and silver shell–gold core nanorod composites

A novel pnictogen-based composite, pnictogen–Au@AgNRs, for the development of a highly sensitive non-enzymatic glucose sensor.

Ag-carried CMC/functional copolymer/ODA-Mt wLED-treated NC and their responses to brain cancer cells

The subject of this work is synthesis and characterization of novel multifunctional nanocomposite (8/2A-NC) consisting (1) carboxymethyl cellulose (CMC) as a matrix biopolymer and poly (maleic acid-alt-acrylic acid) as a reactive synthetic partner matrix polymer; (2) octadecyl amine montmorillonite (ODA-MMT) reactive organoclay provide intercalated silicate layers structures and aqueous colloidal dispersing medium, and MMT as carriers and targeting agents for anticancer agents in drug delivery systems, respectively. ODA as a intercalated surfactant finely dispersed 8/2A NC and its compatibility with matrix polymers via the interfacial polarization (complexing) and functionalization of matrix polymers by amine (ODA) and carboxylic acids from both the CMC and copolymer; (3) silver nanoparticles (AgNPs) as in-situ generated onto matrix polymers with unique nano-size and morphology parameters was synthesized. Important material science and bioengineering aspects of these investigations included (a) novel approach in synthetic pathways; (b) effects of physical and chemical structural rearrangements; (c) effects of Light Emitting Dioda (LED)-treatment on the FT-IR spectra, XRD reflection parameters, SEM-TEM morphology and nano-size and diameter distribution of AgNPs onto matrix polymers; (d) positive effect of LED-treatment of 8/2A nanocomposite and its response to the MIAPaCa-2 and U87 human brain cancer cell lines were evaluated. Novel 8/2A-NC multifunctional drug consisting unique positive, intercalating and encapsulated core-shell morphology structures, nano-size (5.6 nm) and narrow diameter distribution (94%) of AgNPs onto matrix polymers [silver NPs (0.25%) in 8/2A NC (25%)] with highest volume of contact area compared with used cancer micro-cells show lowest cell viability as an excellent anticancer platform. 8/2A-NC is a novel multifunctional drug with intercalating and encapsulated core-shell morphology structures consisting of positively charged, non-randomly distributed AgNPs with a large contact area and low diameters (5-6 nm). The anticancer properties of (This factor is not conformed experimentally in work) this drug can be explained by the following structural factors: 8/2A-NC contains a combination of active sites from protonated hydroxyl, carboxyl and amine groups; Ag⁺-cations and ODA-MMT with high physical and chemical surface areas. We suggest this material be further explored for anti-cancer testing.

Effect of Phenolic Compounds on the Synthesis of Gold Nanoparticles and its Catalytic Activity in the Reduction of Nitro Compounds

Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl₄ with polyphenols from tea extracts, which act as both reducing and capping agents. The obtained AuNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). They act as highly efficient catalysts in the reduction of various aromatic nitro compounds in aqueous solution. The effects of a variety of factors (e.g., reaction time, type and amount of reducing agent, shape, size, or amount of AuNPs) were studied towards the optimization of the processes. The total polyphenol content (TPC) was determined before and after the catalytic reaction and the results are discussed in terms of the tea extract percentage, the size of the AuNPs, and their catalytic activity. The reusability of the AuNP catalyst in the reduction of 4-nitrophenol was also tested. The reactions follow pseudo first-order kinetics.

Trophic transfer of citrate, PVP coated silver nanomaterials, and silver ions in a paddy microcosm

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO₃) for 14 days under two exposure regimes (a single high-dose exposure; 60 μg L^-1 and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 μg L^-1 × 3 = 60 μg L^-1). Most Ag ions from AgNO₃ had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO₃ in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO₃ between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO₃ between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO₃ in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Silver Nanoparticles Synthesized Using Wild Mushroom Show Potential Antimicrobial Activities against Food Borne Pathogens

The present study demonstrates an economical and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using the wild mushroom Ganoderma sessiliforme. The synthesis of AgNPs was confirmed and the products characterized by UV-visible spectroscopy, dynamic light scattering spectroscopy and X-ray diffraction analysis. Furthermore, Fourier transform infrared spectroscopy (ATR-FTIR) analysis was performed to identify the viable biomolecules involved in the capping and active stabilization of AgNPs. Moreover, the average sizes and morphologies of AgNPs were analyzed by field emission scanning electron microscopy (FE-SEM). The potential impacts of AgNPs on food safety and control were evaluated by the antimicrobial activity of the synthesized AgNPs against common food-borne bacteria, namely, Escherichia coli, Bacillus subtilis, Streptococcus faecalis, Listeria innocua and Micrococcus luteus. The results of this study revealed that the synthesized AgNPs can be used to control the growth of food-borne pathogens and have potential application in the food packaging industry. Moreover, the AgNPs were evaluated for antioxidant activity (aDPPH), for biocompatibility (L-929, normal fibroblast cells), and for cytotoxic effects on human breast adenosarcoma cells (MCF-7 & MDA-MB231) to highlight their potential for use in a variety of bio-applications.

Evaluation of cell toxicity and DNA and protein binding of green synthesized silver nanoparticles

Silver nanoparticles (AgNPs) were prepared by GREEN chemistry relying on the reduction of AgNO₃ by phytochemicals present in black tea extract. AgNPs were fully characterized by transmission electron microscopy (TEM), ultraviolet-visible spectroscopy ((UV-vis)), X-ray diffraction (XRD) and energy dispersive absorption spectroscopy (EDS). The synthesized AgNPs induced a decrease of the cell viability in a dose-dependent manner with a low IC₅₀ (0.5 ± 0.1 μM) for an ovarian carcinoma cell line (A2780) compared to primary human fibroblasts (IC₅₀ 5.0 ± 0.1 μM). The DNA binding capability of CT (calf thymus) DNA was investigated using electronic absorption and fluorescence spectroscopies, circular dichroism and viscosity titration methods. Additionally, the AgNPs strongly quench the intrinsic fluorescence of BSA, as determined by synchronous fluorescence spectra.

Recent advances in synthetic methods and applications of silver nanostructures

As the advanced functional materials, silver nanoparticles are potentially useful in various fields such as photoelectric, bio-sensing, catalysis, antibacterial and other fields, which are mainly based on their various properties. However, the properties of silver nanoparticles are usually determined by their size, shape, and surrounding medium, which can be modulated by various synthesis methods. In this review, the fabrication methods for synthesizing silver nanoparticles of different shapes and specific size are illustrated in detail. Besides, the corresponding properties and applications of silver nanoparticles are also discussed in this paper.

Potential targetability of multi-walled carbon nanotube loaded with silver nanoparticles photosynthesized from Ocimum tenuiflorum (tulsi extract) in fertility diagnosis

Nanocarrier mediated targeted delivery and biosensing in reproductive health care is a major exploratory domain. This work demonstrates the loading of silver nanoparticle (AgNP) inside the multiwalled carbon nanotube (MWCNT) and their targetability to the intracellular part of the sperm cell for its further application in biosensing based infertility diagnosis. Ocimum tenuiflorum (tulsi extract) mediated photosynthesized AgNP exhibited spherical shape, 5-40 nm size and surface plasmonic resonance at 430 nm. After loading of freshly prepared AgNP into emulsified MWCNT, the loading was confirmed with spectroscopic and microscopic methods. FTIR analysis displayed significant shifting at 3450 cm^-1 (-OH stretching) and 1615 cm^-1 (CNT back bone) which validated the binding of AgNP with MWCNT and interestingly heat flow analysis revealed that Ag loaded MWCNT has greater stability than AgNP. Moreover, AFM based surface profile height analysis clearly showed the loading of AgNP inside MWCNT as surface height of MWCNT increased from 22 to 32 nm, which in turn confirmed the encapsulation of 10 nm size of AgNP inside the tube. Furthermore, surface enhanced Raman spectroscopy (SERS) confirmed the homogeneous loading as there were no changes in D/G ratio. SERS analysis for the interaction of AgNP loaded MWCNT with freshly collected healthy, motile human spermatozoa showed a significant Raman shift at 800-780 cm^-1 (NH₂⁺ twist) and 1050-1060 cm^-1 (vas PO₃^-) for change in DNA packaging process and its stabilizing protein polyamine respectively. Finally, DNA fragmentation and morphological examination confirmed the binding and targetability of AgNP to the sperm nucleus. Improved targeting efficiency and biosenssing ability make AgNP-MWCNT composite suitable in fertility diagnosis.

Facile synthesis of AgNPs on reduced graphene oxide for highly sensitive simultaneous detection of heavy metal ions

Silver nanoparticles grown on reduced graphene oxide (AgNPs/RGO) were successfully synthesized via a facile in situ method.

Comparative analysis of the relative potential of silver, Zinc-oxide and titanium-dioxide nanoparticles against UVB-induced DNA damage for the prevention of skin carcinogenesis

Sunscreen formulations containing UVB filters, such as Zinc-oxide (ZnO) and titanium-dioxide (TiO2) nanoparticles (NPs) have been developed to limit the exposure of human skin to UV-radiations. Unfortunately, these UVB protective agents have failed in controlling the skin cancer incidence. We recently demonstrated that silver nanoparticles (Ag-NPs) could serve as novel protective agents against UVB-radiations. Here our goal was to perform comparative analysis of direct and indirect UVB-protection efficacy of ZnO-, TiO2- and Ag-NPs. Sun-protection-factor calculated based on their UVB-reflective/absorption abilities was the highest for TiO2-NPs followed by Ag- and ZnO-NPs. This was further confirmed by studying indirect protection of UVB radiation-induced death of HaCaT cells. However, only Ag-NPs were active in protecting HaCaT cells against direct UVB-induced DNA-damage by repairing bulky-DNA lesions through nucleotide-excision-repair mechanism. Moreover, Ag-NPs were also effective in protecting HaCaT cells from UVB-induced oxidative DNA damage by enhancing SOD/CAT/GPx activity. In contrast, ZnO- and TiO2-NPs not only failed in providing any direct protection from DNA-damage, but rather enhanced oxidative DNA-damage by increasing ROS production. Together, these findings raise concerns about safety of ZnO- and TiO2-NPs and establish superior protective efficacy of Ag-NPs.

Bendable Electro-chemical Lactate Sensor Printed with Silver Nano-particles

Here we report a flexible amperometric lactate biosensor using silver nanoparticle based conductive electrode. Mechanically bendable cross-serpentine-shaped silver electrode is generated on flexible substrate for the mechanical durability such as bending. The biosensor is designed and fabricated by modifying silver electrode with lactate oxidase immobilized by bovine serum albumin. The in-sensor pseudo Ag/AgCl reference electrode is fabricated by chloridization of silver electrode, which evinced its long-term potential stability against a standard commercial Ag/AgCl reference electrode. The amperometric response of the sensor shows linear dependence with lactate concentration of 1~25 mM/L. Anionic selectivity is achieved by using drop-casted Nafion coated on silver electrode against anionic interferences such as ascorbate. This non-invasive electrochemical lactate sensor also demonstrates excellent resiliency against mechanical deformation and temperature fluctuation which leads the possibility of using it on human epidermis for continuous measurement of lactate from sweat. Near field communication based wireless data transmission is demonstrated to reflect a practical approach of the sensor to measure lactate concentration portably using human perspiration.

High second-order nonlinear response of platinum nanoflowers: the role of surface corrugation

Platinum nanoflowers (PtNFs) were elaborated using the seed-mediated growth technique applied to monodisperse platinum nanoparticles (∼3.0 nm) synthesized by the chemical reduction method. The X-ray diffraction pattern confirmed the formation of face-centered-cubic platinum nanocrystals. We report the Harmonic Light Scattering (HLS) properties of PtNFs for six different diameters (∼7.0; 8.0; 10.0; 14.0; 20.0 and 31.0 nm). From these HLS data we infer, for the first time, large hyperpolarizability β values of PtNFs. These very high β values of PtNFs are assigned mainly to highly corrugated surfaces for nanoparticles with irregular shapes.

Plant extract-mediated biogenic synthesis of silver, manganese dioxide, silver-doped manganese dioxide nanoparticles and their antibacterial activity against food- and water-borne pathogens

Silver nanoparticles (AgNPs), manganese dioxide nanoparticles (MnO₂NPs) and silver-doped manganese dioxide nanoparticles (Ag-doped MnO₂NPs) were synthesized by simultaneous green chemistry reduction approach. Aqueous extract from the leaves of medicinally important plant Cucurbita pepo was used as reducing and capping agents. Various characterization techniques were carried out to affirm the formation of nanoparticles. HR-TEM analysis confirmed the size of nanoparticles in the range of 15-70 nm and also metal doping was confirmed through XRD and EDS analyses. FT-IR analysis confirmed that the presence of biomolecules in the aqueous leaves extract was responsible for nanoparticles synthesis. Further, the concentration of metals and their doping in the reaction mixture was achieved by ICP-MS. The growth curve and well diffusion study of synthesized nanoparticles were performed against food- and water-borne Gram-positive and Gram-negative bacterial pathogens. The mode of interaction of nanoparticles on bacterial cells was demonstrated through Bio-TEM analysis. Interestingly, AgNPs and Ag-doped MnO₂NPs showed better antibacterial activity against all the tested bacterial pathogens; however, MnO₂NPs alone did not show any antibacterial properties. Hence, AgNPs and Ag-doped MnO₂NPs synthesized from aqueous plant leaves extract may have important role in controlling various food spoilage caused by bacteria.

Avoiding artefacts during electron microscopy of silver nanomaterials exposed to biological environments

Electron microscopy has been applied widely to study the interaction of nanomaterials with proteins, cells and tissues at nanometre scale. Biological material is most commonly embedded in thermoset resins to make it compatible with the high vacuum in the electron microscope. Room temperature sample preparation protocols developed over decades provide contrast by staining cell organelles, and aim to preserve the native cell structure. However, the effect of these complex protocols on the nanomaterials in the system is seldom considered. Any artefacts generated during sample preparation may ultimately interfere with the accurate prediction of the stability and reactivity of the nanomaterials. As a case study, we review steps in the room temperature preparation of cells exposed to silver nanomaterials (AgNMs) for transmission electron microscopy imaging and analysis. In particular, embedding and staining protocols, which can alter the physicochemical properties of AgNMs and introduce artefacts thereby leading to a misinterpretation of silver bioreactivity, are scrutinized. Recommendations are given for the application of cryogenic sample preparation protocols, which simultaneously fix both particles and diffusible ions. By being aware of the advantages and limitations of different sample preparation methods, compromises or selection of different correlative techniques can be made to draw more accurate conclusions about the data.