Types Of AgNPs Research Articles

Surface Charge-Modulated Toxicity of Cysteine-Stabilized Silver Nanoparticles.

The toxicity of silver nanoparticles (AgNPs) depends on their physicochemical properties. The ongoing research aims to develop effective methods for modifying AgNPs using molecules that enable control over the processes induced by nanoparticles in both normal and cancerous cells. Application of amino acid-stabilized nanoparticles appears promising, exhibiting tunable electrokinetic properties. Therefore, this study focused on determining the influence of the surface charge of cysteine (CYS)-stabilized AgNPs on their toxicity towards human normal B (COLO-720L) and T (HUT-78) lymphocyte cell lines. CYS-AgNPs were synthesized via the chemical reduction. Transmission electron microcopy (TEM) imaging revealed that they exhibited a quasi-spherical shape with an average size of 18 ± 3 nm. CYS-AgNPs remained stable under mild acidic (pH 4.0) and alkaline (7.4 and 9.0) conditions, with an isoelectric point observed at pH 5.1. Following a 24 h treatment of lymphocytes with CYS-AgNPs, concentration-dependent alterations in cell morphology were observed. Positively charged CYS-AgNPs notably decreased lymphocyte viability. Furthermore, they exhibited grater genotoxicity and more pronounced disruption of biological membranes compared to negatively charged CYZ-AgNPs. Despite both types of AgNPs interacting similarly with fetal bovine serum (FBS) and showing comparable profiles of silver ion release, the biological assays consistently revealed that the positively charged CYS-AgNPs exerted stronger effects at all investigated cellular levels. Although both types of CYS-AgNPs have the same chemical structure in their stabilizing layers, the pH-induced alterations in their surface charge significantly affect their biological activity.

Comparison of Escherichia coli Responses to Different Silver Nanoparticles with Different Particle Sizes and Surface Coatings

AbstractAgNPs are widely used for their excellent antimicrobial properties, whereas the cytotoxicity they possess makes them an unignorable environmental problem. Considering the impact of particle size and surface coating on the antibacterial properties, four types of AgNPs are selected: citrate‐coated 20 nm (C20), polyvinylpyrrolidone‐coated 20 nm (P20), citrate‐coated 100 nm (C100), and polyvinylpyrrolidone‐coated 100 nm (P100) AgNPs. All four AgNPs significantly affect the ribosome pathway, with stronger binding of large and small subunits. 20 nm and 100 nm AgNPs both affected the biosynthesis and metabolism of several amino acids (including arginine, glycine, serine, threonine, glyoxylic acid, and dicarboxylic acid). P20 and C100 exposure affected bacterial chemotaxis and flagellar motility. This study preliminarily explained the response mechanism of E. coli to AgNPs with different properties, which provided a theoretical basis for predicting the response mechanism of E. coli to metal nanoparticles with similar properties.

Metal-enhanced fluorescence (MEF) effect based on silver nanoparticles with different UV spectra on a surface carbon dot-based novel dry platform

In this work, to enhance the fluorescence quantum yield of carbon dots (CDs), a novel metal-enhanced fluorescence (MEF) structure was designed by decorating CDs on silver nanoparticle (AgNPs) film. The glass slide-AgNPs (GS-AgNPs) structure was fabricated using the electrostatic adsorption method, and the AgNPs-CDs structures were prepared by the direct drying method, which then formed the GS-AgNPs-CDs composite structure. In this structure, the MEF effect was found to be size dependent by changing the 5 types of AgNPs with different sizes. And the MEF effect also decreased as the distance between the AgNPs and CDs increased by using polyvinylpyrrolidone (PVP) to separate the AgNPs and CDs. This hybrid structure can be used as a fluorescence detection platform and the recorded fluorescence intensity of GS-AgNPs 428 nm-CDs achieved a maximum enhancement factor (EF) of 31.72. Considering the high enhancement factor, this system may become promising to find potential applications in biochemical assay fields.

Green Biosynthesis of Silver Nanoparticles Utilizing Monstera deliciosa Leaf Extract and Estimation of its Antimicrobial Characteristics

AbstractHerein, single step biosynthesis of silver nanoparticles (AgNPs) is reported by using AgNO3 and Monstera deliciosa (MD) leaf extract. Spherical AgNPs are obtained with difference in particle sizes and antibacterial activities using two sets of MD leaf extract having different heating periods 5 and 10 min. They are characterized by UV–vis spectroscopy, X‐ray diffraction (XRD), Zeta potential, Attenuated Total Reflectance Infrared Spectroscopy (ATR‐IR), and Field Emission Scanning Electron Microscopy (FE‐SEM). Dynamic Light Scattering (DLS) studies propose two types of AgNPs have hydrodynamic diameters of 104 and 80 nm. Nuclear Magnetic Resonance (NMR), Gas Chromatography‐Mass Spectrometry (GC‐MS), and High Resolution−Mass Spectrometry (HR‐MS) studies, which reveal the presence of various phytochemicals found in MD leaf extract. These biomolecules play a vital role as stabilizing and reducing agents to fabricate stable AgNPs. These AgNPs exhibit strong antibacterial activities having effective zone of inhibition for both Gram‐positive (Staphylococcus aureus, Bacillus subtilis) and Gram‐negative (Escherichia coli, Pseudomonas aeruginosa) microorganisms, nonetheless AgNPs against different fungi (Penicillium sp., Aspergillus flavus, Fusarium oxysporum, Rhizoctonia solani) show non‐antifungal characteristics because of their inert nature. This study suggests that AgNPs can be used in treating bacterial infections and drug delivery also for several therapeutic and diagnostic applications.

Bacteriogenic synthesis of morphologically diverse silver nanoparticles and their assessment for methyl orange dye removal and antimicrobial activity.

Nanotechnology and nanoparticles have gained massive attention in the scientific community in recent years due to their valuable properties. Among various AgNPs synthesis methods, microbial approaches offer distinct advantages in terms of cost-effectiveness, biocompatibility, and eco-friendliness. In the present research work, investigators have synthesized three different types of silver nanoparticles (AgNPs), namely AgNPs-K, AgNPs-M, and AgNPs-E, by using Klebsiella pneumoniae (MBC34), Micrococcus luteus (MBC23), and Enterobacter aerogenes (MBX6), respectively. The morphological, chemical, and elemental features of the synthesized AgNPs were analyzed by using UV-Vis spectroscopy (UV-Vis), Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy-dispersive spectroscopy (EDX). UV-Vis absorbance peaks were obtained at 475, 428, and 503 nm for AgNPs-K, AgNPs-M, and AgNPs-E, respectively. The XRD analysis confirmed the crystalline nature of the synthesized AgNPs, having peaks at 26.2°, 32.1°, and 47.2°. At the same time, the FTIR showed bands at 599, 963, 1,693, 2,299, 2,891, and 3,780 cm-1 for all the types of AgNPs indicating the presence of bacterial biomolecules with the developed AgNPs. The size and morphology of the AgNPs varied from 10 nm to several microns and exhibited spherical to porous sheets-like structures. The percentage of Ag varied from 37.8% (wt.%) to 61.6%, i.e., highest in AgNPs-K and lowest in AgNPs-M. Furthermore, the synthesized AgNPs exhibited potential for environmental remediation, with AgNPs-M exhibiting the highest removal efficiency (19.24% at 120 min) for methyl orange dye in simulated wastewater. Further, all three types of AgNPs were evaluated for the removal of methyl orange dye from the simulated wastewater, where the highest dye removal percentage was 19.24% at 120 min by AgNPs-M. Antibacterial potential of the synthesized AgNPs assessment against both Gram-positive (GPB) Bacillus subtilis (MBC23), B. cereus (MBC24), and Gram-negative bacteria Enterococcus faecalis (MBP13) revealed promising results, with AgNPs-M, exhibiting the largest zone of inhibition (12 mm) against GPB B. megaterium. Such investigation exhibits the potential of the bacteria for the synthesis of AgNPs with diverse morphology and potential applications in environmental remediation and antibacterial therapy-based synthesis of AgNPs.

Sunlight and microwave catalyzed comparative biosynthesis of silver nanoparticles using in-vitro and in-vivo biomass of Fagonia schweinfurthii Hadidi, its antibacterial activity and phytotoxicity

In the present study, we explore the potential of Fagonia schweinfurthii Hadidi (FS) in-vivo plant material and in-vitro-grown callus as a bio-template for AgNPs synthesis, highlighting its eco-friendly and bio-inspired sustainable approach. The comparative efficacy of natural plant material and its callus culture was assessed for AgNP synthesis by employing both sunlight and microwave irradiation as separate synthesis methods. This yielded four distinct types of AgNPs denoted as CS-AgNPs, PS-AgNPs, CM-AgNPs, and PM-AgNPs. Sunlight-irradiated AgNP synthesis optimized at near to neutral pH (6.6), whereas microwave-assisted synthesis needed a basic pH for synthesis. Optimization of these AgNPs involved varying concentrations of AgNO3, plant aqueous extract (PAE), and callus aqueous extract (CAE) of FS, exposure time to sunlight and microwave radiation, as well as pH adjustments. The particle size of these AgNPs ranged from 5 to 30 nm, having a crystalline nature with a similar fringe width of 0.22 nm, as observed from HR-TEM analysis. These AgNPs showed significant antibacterial properties against the clinical isolates with λmax 420 nm. Importantly, CAE outperformed PAE for the biosynthesis of AgNPs, mainly in the presence of sunlight-producing CS-AgNPs. These CS-AgNPs are rapidly synthesized, well dispersed and stable, showing significant antibacterial activity, and the least environmental phytotoxicity. It promoted the number of secondary roots, seedling DW, and TWC with 100% seed germination. This highlights their sustainable features for exploring industrial eco-friendly nonmanufacturing of AgNPs using callus culture and sunlight irradiation.

Evaluating the efficiency of silver nanoparticles prepared using <i>Pseudomonas fluorescens</i> and <i>Bacillus thuringiensis</i> subsp. <i>tenebrionis</i> in controlling eggs and adults of <i>Callosobruchus maculatus</i> (F.) (Coleoptera: Bruchidae)

This study aimed to evaluate the efficiency of silver nanoparticles (AgNPs) which are prepared biologically by two bacterial species, Bacillus thuringiensis tenebrionis (Btt) and Pseudomonas fluorescens (P.f) to control southern cowpea beetle insect, Callosobruchus maculatus. Many features of the prepared nanoparticles were examined, and the results obtained showed that the highest absorption value of AgNPs was at 262 nm. Whereas the results of FTIR analysis showed that several compounds played a role in the silver ions reduction process, which included alcohol, alkane, primary amine, and amine group. The scanning electronic microscopic images showed that the average diameter of nanoparticles which was created by P.f was 48.52 nm, while it was 56.08 nm for the nanoparticles prepared by Btt. The study showed no significant differences between the activity of both AgNP types against C. maculatus eggs, while a significant preference was recorded for the activity of Btt AgNPs against the C. maculatus adults. The highest percentage of unhitched eggs was 53.8% recorded at 3000 ppm concentration, while Btt AgNPs gave 59.6% at 3000 ppm. The highest mortality rate of the adults who were treated by Btt AgNPs was 58.8 % at 3000 ppm concentration, while it was recorded 50% at 3000 ppm with P.f AgNPs treatment. The current study demonstrates the efficiency of biologically prepared AgNPs in controlling C. maculatus insect life stages, which encourages using of these nanoparticles as a modern strategy in management of insect pests.

Biological activity of silver nanoparticles synthesized using viticultural waste

This research paper presents a novel approach to the green synthesis of silver nanoparticles (AgNPs) using viticultural waste, allowing to obtain NP dispersions with distinct properties and morphologies (monodisperse and polydisperse AgNPs, referred to as mAgNPs and pAgNPs) and to compare their biological activities. Our synthesis method utilized the ethanolic extract of Vitis vinifera pruning residues, resulting in the production of mAgNPs and pAgNPs with average sizes of 12 ± 5 nm and 19 ± 14 nm, respectively. Both these AgNPs preparations demonstrated an exceptional stability in terms of size distribution, which was maintained for one year. Antimicrobial testing revealed that both types of AgNPs inhibited either the growth of planktonic cells or the metabolic activity of biofilm sessile cells in Gram-negative bacteria and yeasts. No comparable activity was found towards Gram-positives. Overall, pAgNPs exhibited a higher antimicrobial efficacy compared to their monodisperse counterparts, suggesting that their size and shape may provide a broader spectrum of interactions with target cells. Both AgNP preparations showed no cytotoxicity towards a human keratinocyte cell line. Furthermore, in vivo tests using a silkworm animal model indicated the biocompatibility of the phytosynthesized AgNPs, as they had no adverse effects on insect larvae viability. These findings emphasize the potential of targeted AgNPs synthesized from viticultural waste as environmentally friendly antimicrobial agents with minimal impact on higher organisms.

Biocomposite Materials Derived from Andropogon halepensis: Eco-Design and Biophysical Evaluation.

This research work presents a "green" strategy of weed valorization for developing silver nanoparticles (AgNPs) with promising interesting applications. Two types of AgNPs were phyto-synthesized using an aqueous leaf extract of the weed Andropogon halepensis L. Phyto-manufacturing of AgNPs was achieved by two bio-reactions, in which the volume ratio of (phyto-extract)/(silver salt solution) was varied. The size and physical stability of Andropogon-AgNPs were evaluated by means of DLS and zeta potential measurements, respectively. The phyto-developed nanoparticles presented good free radicals-scavenging properties (investigated via a chemiluminescence technique) and also urease inhibitory activity (evaluated using the conductometric method). Andropogon-AgNPs could be promising candidates for various bio-applications, such as acting as an antioxidant coating for the development of multifunctional materials. Thus, the Andropogon-derived samples were used to treat spider silk from the spider Pholcus phalangioides, and then, the obtained "green" materials were characterized by spectral (UV-Vis absorption, FTIR ATR, and EDX) and morphological (SEM) analyses. These results could be exploited to design novel bioactive materials with applications in the biomedical field.

Green synthesis of silver nanoparticles using olive mill wastewater and olive stones extract and testing their antimicrobial activities against Escherichia coli and Staphylococcus epidermidis

Abstract Plant mediated synthesis of silver nanoparticles is eco-friendly and of low cost. The synthesis involves a reduction of silver ions and is controlled by several independent factors. In this work, silver nanoparticles (AgNPs) were successfully synthesized using olive stone extract (OSE) and olive mill wastewater (OMW) extract. The nanoparticle synthesis was monitored using the plasmon resonance observed in the UV–Vis absorption spectrum, in which a Voigt profile was fitted. The peak wavelength (λ 0), the peak area (A), and the Full Width at Half Maximum (FWHM) were the fitting parameters and were used as the response. The independent factors were the incubation temperature, the incubation time, the silver nitrate, extract, and sodium hydroxide concentrations. The influence of these factors was investigated ‘two factor at a time’, using interaction plots. Strong interaction was observed between all factors, with sodium hydroxide to have a crucial role. The optimum conditions for silver nanoparticle formation were a) OSE (1% v/v), AgNO3 (2 mM), and NaOH (0.2 mM), and b) OMW (2% v/v), AgNO3 (1 mM), and NaOH (7.9 mM), showing an absorption maximum at 414 nm, and 410 nm, respectively. The mean diameter of AgNPs using OMW, measured with Transmission Electron Microscopy was 12.87 ± 4.84 nm. Both types of AgNPs showed antibacterial action against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli), using the broth microdilution assay. Both nanoparticle types inhibited bacterial growth up to one dilution higher than reference samples.

Antimicrobial Activity of Two Different Types of Silver Nanoparticles against Wide Range of Pathogenic Bacteria.

The emergence of antibiotic-resistant bacteria, particularly the most hazardous pathogens, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. (ESKAPE)-pathogens pose a significant threat to global health. Current antimicrobial therapies, including those targeting biofilms, have shown limited effectiveness against these superbugs. Nanoparticles, specifically silver nanoparticles (AgNPs), have emerged as a promising alternative for combating bacterial infections. In this study, two types of AgNPs with different physic-chemical properties were evaluated for their antimicrobial and antibiofilm activities against clinical ESKAPE strains. Two types of silver nanoparticles were assessed: spherical silver nanoparticles (AgNPs-1) and cubic-shaped silver nanoparticles (AgNPs-2). AgNPs-2, characterized by a cubic shape and higher surface-area-to-volume ratio, exhibited superior antimicrobial activity compared to spherical AgNPs-1. Both types of AgNPs demonstrated the ability to inhibit biofilm formation and disrupt established biofilms, leading to membrane damage and reduced viability of the bacteria. These findings highlight the potential of AgNPs as effective antibacterial agents against ESKAPE pathogens, emphasizing the importance of nanoparticle characteristics in determining their antimicrobial properties. Further research is warranted to explore the underlying mechanisms and optimize nanoparticle-based therapies for the management of infections caused by antibiotic-resistant bacteria.

Effect of static electricity and thickness of solution blow spun polyamide 6/AgNP nanofibrous membrane on nanoparticle filtration and microbiological activity

The efficient filtration of particulate matter smaller than 0.3 µm is crucial for preventing microbial and viral infections. Nanofiber membranes (NFMs) produced by solution blow spinning (SBS) modified with antimicrobial nanoparticles have emerged as a promising technology for filtration technology. In this context, here we developed novel NFMs produced by SBS using Polyamide 6 (PA6) which was surface functionalized with different types of silver nanoparticles (AgNPs) using a simple immersion procedure. The NFMs thickness was customized to evaluate their performance towards the filtration of NP (nanoparticle) from 30 to 300 nm. The incorporation of AgNPs onto the NFMs was also investigated to test their bactericidal activity against E. coli and S. aureus. The NFMs were physically and chemically characterized using distinct techniques. The filtration efficiency of 30–300 nm NP reached around 93.5 %, where the NFMs thickness played a key role in the filtration efficiency and pressure drop. Furthermore, the presence of static electricity in the NFM inherent to the SBS process also contributed to the greater filtration efficiency of smaller particles. Our results demonstrated that NFMs can be produced through SBS in an easy and scalable way, leading to highly efficient filtration systems, with implications for diverse fields such air purification systems and protective clothing.

Optimizing the microbial synthesis of silver nanoparticles using Gloeophyllum striatum and their antimicrobial potential evaluation

The search for new sources of silver nanoparticles (AgNPs) is highly relevant in many fields. Mycosynthesis seems to be advantageous for large-scale production, and using brown rot fungi might be a promising solution. In this study, AgNP synthesis using Gloeophyllum striatum DSM 9592 was performed under various process conditions. The resulting AgNPs were characterized using UV/Vis, FT-IR, SEM and NTA techniques and their biological activities were determined. It was found that different synthesis conditions changed the production efficiency, which was the highest in 28 s AgNPs. Moreover, temperature and shaking conditions slightly affected the activity of the resulting AgNP types. Gram-negative bacteria were generally more susceptible to the action of AgNPs with MIC values two- or three-fold lower compared to Gram-positive strains. Pseudomonas aeruginosa was the most sensitive among tested strains with a MIC value of 1.56 µg/ml. The research was additionally extended by the biofilm formation assay for this strain. It was found that AgNPs of all types led to a reduction in biofilm-forming capability of P. aeruginosa over the tested concentration range. Haemolytic and cytotoxic activity assays showed that synthesis conditions also affected AgNP toxicity. For instance, 4 ns AgNPs were the least cytotoxic and cause less than 50% reduction of fibroblast viability in the concentration that inhibits the growth of P. aeruginosa completely. These results highlight the possible utility of mycogenic silver nanoparticles as an antibacterial agent in antiseptics or other external treatments.

Microalga Broths Synthesize Antibacterial and Non-Cytotoxic Silver Nanoparticles Showing Synergy with Antibiotics and Bacterial ROS Induction and Can Be Reused for Successive AgNP Batches.

The era of increasing bacterial antibiotic resistance requires new approaches to fight infections. With this purpose, silver-based nanomaterials are a reality in some fields and promise new developments. We report the green synthesis of silver nanoparticles (AgNPs) using culture broths from a microalga. Broths from two media, with different compositions and pHs and sampled at two growth phases, produced eight AgNP types. Nanoparticles harvested after several synthesis periods showed differences in antibacterial activity and stability. Moreover, an evaluation of the broths for several consecutive syntheses did not find relevant kinetics or activity differences until the third round. Physicochemical characteristics of the AgNPs (core and hydrodynamic sizes, Z-potential, crystallinity, and corona composition) were determined, observing differences depending on the broths used. AgNPs showed good antibacterial activity at concentrations producing no or low cytotoxicity on cultured eukaryotic cells. All the AgNPs had high levels of synergy against Escherichia coli and Staphylococcus aureus with the classic antibiotics streptomycin and kanamycin, but with ampicillin only against S. aureus and tetracycline against E. coli. Differences in the synergy levels were also dependent on the types of AgNPs. We also found that, for some AgNPs, the killing of bacteria started before the massive accumulation of ROS.

Phenotypic and Genotypic Characterization of Recently Isolated Multidrug-Resistant Acinetobacter baumannii Clinical and Aquatic Strains and Demonstration of Silver Nanoparticle Potency.

This study aims to demonstrate the effectiveness of silver nanoparticles (Ag NPs) on multidrug-resistant (MDR) Acinetobacter baumannii (AB) strains isolated from the clinical and aquatic environment. Three types of Ag NPs were investigated for their antimicrobial, antibiofilm, and antivirulence properties on a total number of 132 AB strains isolated in the same temporal sequence from intra-hospital infections (IHIs), wastewater (WW), and surface water (SW) samples between 2019 and 2022 from different Romanian locations and characterized at the phenotypic and genotypic levels. The comparative analysis of the antimicrobial resistance (AR) profiles according to the isolation source and the geographical location demonstrated a decrease in MDR level in AB recovered from WW samples in 2022 from north-eastern/central/southern regions (N-E/C-W/analyzed strains S): 87.5/60/32.5%. The AB strains were lecithinase, caseinase, amylase, and lipase producers, had variable biofilm formation ability, and belonged to six genotypes associated with the presence of different virulence genes (ompA, csuE, bap, and bfmS). The Ag NPs synthesized with the solvothermal method exhibited an inhibitory effect on microbial growth, the adherence capacity to the inert substratum, and on the production of soluble virulence factors. We report here the first description of a powerful antibacterial agent against MDR AB strains circulating between hospitals and anthropically polluted water in Romania.

Red light enhances the antibacterial properties, biofabrication, and stability of Fagonia indica callus-based silver nanoparticles.

Plant-based nanoparticles can be tuned through the frequency of light for efficient synthesis, structural properties, and antibacterial applications. This research assessed the effect of material type (callus and whole-plant extract) and the interaction with a specific range of light wavelength on AgNP synthesis. All types of AgNPs were characterized by their size, shape, associated functional groups, and surface charge. Interestingly, the size of red light and callus-based AgNPs (RC-AgNPs) was smaller (6.32 nm) compared to 14.59 nm for Ultraviolet light and callus-based AgNPs (UV-C-AgNPs). Zeta potential analysis showed that RC-AgNPs had higher stability (-29.2 mV) compared to UV-C-AgNPs (-16.7 mV). Similarly, red light-based AgNPs had higher Oxidation reduction potential in both whole-plant-based and callus-based AgNPs, indicating a more oxidizing nature compared to those synthesized under UV light. This was confirmed by the lower total phenolic and flavonoid content associated with them and their lower antioxidant activity. The higher antibacterial activities and lower minimum inhibitory concentrations of red light-based AgNPs against highly resistant pathogenic bacteria demonstrated the role of red light in enhancing antibacterial activity. These results indicate that AgNPs synthesized in red light and callus extract are more active compared to those synthesized under other wavelengths and/or in whole-plant extracts.

The Morphology Dependent Interaction between Silver Nanoparticles and Bovine Serum Albumin.

Biological applications of silver nanoparticles (AgNPs) depend on the covalently attached or adsorbed proteins. A series of biological effects of AgNPs within cells are determined by the size, shape, aspect ratio, surface charge, and modifiers. Herein, the morphology dependent interaction between AgNPs and protein was investigated. AgNPs with three different morphologies, such as silver nanospheres, silver nanorods, and silver nanotriangles, were employed to investigate the morphological effect on the interaction with a model protein: bovine serum albumin (BSA). The adsorptive interactions between BSA and the AgNPs were probed by UV-Vis spectroscopy, fluorescence spectroscopy, dynamic light scattering (DLS), Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), and circular dichroism (CD) techniques. The results revealed that the particle size, shape, and dispersion of the three types of AgNPs markedly influence the interaction with BSA. Silver nanospheres and nanorods were capsulated by protein coronas, which led to slightly enlarged outer size. The silver nanotriangles evolved gradually into nanodisks in the presence of BSA. Fluorescence spectroscopy confirmed the static quenching the fluorescence emission of BSA by the three AgNPs. The FTIR and CD results suggested that the AgNPs with different morphologies had different effects on the secondary structure of BSA. The silver nanospheres and silver nanorods induced more pronounced structural changes than silver nanotriangles. These results suggest that the formation of a protein corona and the aggregation behaviors of AgNPs are markedly determined by their inherent morphologies.

Colorimetric and surface-enhanced Raman scattering method for vanillin detection based on two types of reduced silver nanoparticles

It’s the first time we found that vanillin and 3,3′,5,5′-tetramethylbenzidine (TMB) can reduce Tollens’ reagent to different types of Ag nanoparticles (Ag NPs) because of their different reducibility. Vanillin reduced the Tollens’ reagent to small size of Ag NPs (Ag45 NPs) which was colorless and has the maxmium absorption at 350 nm, while pink large Ag NPs (Ag100 NPs) with the maxmium absorption at 490 nm was reduced by TMB. Based on different types of AgNPs reduced by vanillin and TMB, dual-mode detection of vanillin by colorimetry and surface-enhanced Raman scattering (SERS) was designed. The solution changed from pink to colorless with the increasing concentration of vanillin (within 3 min). On the other hand, the reduced Ag45 NPs shows a high SERS enhancement factor, which can be applied for ultra-sensitive detection of vanillin in situ. The SERS had a low detection limit of 25.8 pM, which was 5-orders lower than the colorimetric method and most previously reported methods. Importantly, It avoids the additional procedures to prepare SERS-active substrates and can be used to discriminate vanillin from ethylvanillin, both of which are very difficult to be distinguished because of their much highly similar structure and property. Therefore, the visual, fast and high-sensitive dual-mode strategy has great potential in food safety assessment.

Predicting the effect of silver nanoparticles on soil enzyme activity using the machine learning method: type, size, dose and exposure time

In this study, machine learning models predicted the impact of silver nanoparticles (AgNPs) on soil enzymes. Artificial neural network (ANN) optimized with genetic algorithm (GA) (MAE = 0.1174) was more suitable for simulating overall trends, while the gradient boosting machine (GBM) and random forest (RF) were ideal for small-scale analysis. According to partial dependency profile (PDP) analysis, polyvinylpyrrolidone coated AgNPs (PVP-AgNPs) had the most inhibitory effect (average of 49.5%) on soil enzyme activity among the three types of AgNPs at the same dose (0.02–50 mg/kg). The ANN model predicted that enzyme activity first declined and then rose when AgNPs increased in size. Based on predictions from the ANN and RF models, when exposed to uncoated AgNPs, soil enzyme activities continued to decrease before 30 d, but gradually rose from 30 to 90 d, and fell slightly after 90 d. The ANN model indicated the importance order of four factors: dose > type > size > exposure time. The RF model suggested the enzyme was more sensitive when experiments were conducted at doses, sizes, and exposure times of 0.01–1 mg/kg, 50–100 nm, and 30–90 d, respectively. This study presents new insights on the regularity of soil enzyme responses to AgNPs.

Differential electrochemical behaviour of phytofabricated and chemically synthesized silver nanoparticles towards hydrogen peroxide sensing**

AbstractSilver nanoparticles (AgNPs) are one of the most widely used nanomaterials for biomedical applications. However, the impact of its synthesis by chemical and plant‐mediated routes on its differential electrochemical behaviour has not been examined till date. Here, we report for the first time the differential study of the electrochemical behaviour of the AgNPs synthesized by different routes. First, the AgNPs were obtained by different routes (chemical and phytofabrication) and extensively characterized to compare their physical properties. Thereafter, a comparison of electron transfer kinetics between chemically synthesized (Ag−C) and phyto‐fabricated (Ag‐Phy) nanoparticles (NPs) has been studied by electrochemical techniques such as potentiodynamic cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To further investigate the electrocatalytic properties of both types of AgNPs, we have used the peroxide moieties (H2O2), and the Ag−C NPs‐based sensor probe has been reported to have four times better sensitivity than the Ag−Phy NPs‐based sensor. The AgNPs modified sensor probes have also been tested in real‐world environments to explore the consistency of their performance in complex matrices by using clinical urine samples, where we found comparable sensitivity to the standard conditions.