Types Of Silver Nanoparticles Research Articles

A new approach for discriminating spatially acquired SERS spectra using antiretroviral drug emtricitabine as a test sample

AbstractIn this study, an antiretroviral drug emtricitabine (also known as FTC or Emtriva) was detected and quantified down to 40 ng/ml by using surface‐enhanced Raman spectroscopy (SERS). Its aqueous standards were tested with two types of silver nanoparticles (colloidal and dendritic) using a specially developed aluminum well plate. The SERS spectra were acquired using a Raman scanning device with 30‐μm spatial resolution. The spectral data were analyzed using a new approach for the discrimination of the spatially acquired spectra based on the Quality index (Qi). After the Qi is calculated, the spectral data are sorted based on the Qi. This is followed by selecting only the spectra with a high Qi index and comparing the average of all the spatially acquired spectra. This results in an improvement in the spectral signal‐to‐noise and higher analytical sensitivity of the built calibration curves.

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.

Green synthesis of AgNPs from leaves extract of Saliva Sclarea, their characterization, antibacterial activity, and catalytic reduction ability

Abstract Several technologies are employed for the synthesis of silver nanoparticles, each synthesis technique has advantages and disadvantages, and the best technique relies on the application at hand, the required qualities of the nanoparticles, and the size of the product. But in this article green synthesis were followed. In this research, AgNPs were synthesized using Salvia Sclarea leaf extract in green synthetic routes. The synthesized nanoparticles were examined using UV–vis spectroscopy, powder XRD, SEM, and FT-IR. Here three different type of silver nanoparticles were biosynthesized, AgNPs-1, AgNPs-2, and AgNPs-3 (where composition of AgNO3 and extract were 6:1, 10:1 and 14:1 respectively). The catalytic ability of AgNPs 1–3 was determine in the reduction of nitro-compounds into corresponding amines, where AgNPs-2 was found efficient reductive catalyst. Moreover, antibacterial activities were checked against both gram-positive (Bacillus Suntilis) and gram-negative bacteria (Klebsiella pneumoniae). Upon increasing Ag contents antibacterial activities were found in increasing mode. Which open new era of knowledge for further consideration.

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.

Comparison between the Nature and Activity of Silver Nanoparticles Produced by Active and Inactive Fungal Biomass Forms on Cervical Cancer Cells

Silver nanoparticles (SNPs) can be produced by active and inactive forms of biomass, but their properties have not been compared. Recent research is attempting to reveal their differences in shape, size, amount, antibacterial activity, cytotoxicity, and apoptosis induction. The biomass of Fusarium oxysporum was divided into four groups and pretreated in the following devices: room temperature (RT) and refrigerator (for preparation of active biomass forms), autoclave, and hot air oven (for preparation of inactive biomass forms). Samples were floated in ddH2O, and SNPs were produced after the addition of 0.1699 g/L AgNO3 in the ddH2O solution. SNP production was confirmed by visible spectrophotometry, transmission electron microscopy (TEM) and X-ray diffraction (XRD). SNPs were washed, and their concentration was determined by measuring atomic emission spectroscopy with inductively coupled plasma (ICP-OES). For antibacterial activity, the plate-well diffusion method was used. MTT and Annexin V-FITC/propidium iodide assays were used for cytotoxicity and apoptosis induction, respectively. The maximum absorbance peaks for SNPs pretreated in RT, refrigerator, autoclave, and hot air oven were 404, 402, 412, and 412 nm, respectively. The SNPs produced were almost the same shape and size, and the XRD results confirmed the presence of SNPs in all samples. Due to the differences in the type of bacterial strains used, the SNPs produced showed some differences in their antibacterial activity. The MTT assay showed that the amounts of SNPs in their IC50 dose based on the results of ICP-OES were 0.40, 0.45, 0.66, and 0.44 ppm for the samples pretreated in the hot air oven, autoclave, and refrigerator, and RT, respectively. The apoptosis induction results showed that the biologically engineered SNPs induced more apoptosis (about 34.25%) and less necrosis (about 13.25%). In conclusion, the type and activity of SNPs produced by the active and inactive forms of fungal biomass did not change. Therefore, use of the inactive form of biomass in the future to avoid environmental contamination is reccommended.

Silver Is Not Equal to Silver: Synthesis and Evaluation of Silver Nanoparticles with Low Biological Activity, and Their Incorporation into C12Alanine-Based Hydrogel.

A new type of silver nanoparticles (AgNPs) was prepared and comprehensively studied. Scanning electron microscopy (SEM) and dynamic light scattering (DLS) analyses indicated that 24 nm AgNPs with narrow size distribution were obtained while Z-potential confirms their good stability. The composites of the obtained AgNPs with nontoxic-nature-inspired hydrogel were formed upon cooling of the aqueous solution AgNPs and C12Ala. The thermal gravimetric analysis (TGA) and the differential scanning calorimetry (DSC) do not show significant shifts in the characteristic temperature peaks for pure and silver-enriched gels, which indicates that AgNPs do not strongly interact with C12Ala fibers, which was also confirmed by SEM. Both AgNPs alone and in the assembly with the gelator C12Ala were almost biologically passive against bacteria, fungus, cancer, and nontumor human cells, as well as zebra-fish embryos. These studies proved that the new inactive AgNPs-doped hydrogels have potential for the application in therapy as drug delivery media.

Microfluidic paper-based colorimetric quantification of malondialdehyde using silver nanoprism toward on-site biomedical analysis: a new platform for the chemical sensing and biosensing of oxidative stress.

Malondialdehyde (MDA) is a critical product of polyunsaturated adipose acid peroxidation and represents a common biomarker of oxidative stress. The effect of different MDA concentrations on human biofluids reflects pathological changes, which has been seen in diverse types of sickness, such as leukemia, diabetes, cancer, cardiovascular disease, and age-related macular degeneration and liver disease. In this study, different types of silver nanoparticles, including silver nanoprism (AgNPrs), silver nanowires (AgNWs), and silver nanospheres (AgNSs), were synthesized and used for the chemosensing of MDA by colorimetric and spectrophotometric methods. Colorimetric tests were performed to identify malondialdehyde in the solution as well as the one-droplet-based microfluidic paper substrate as a miniaturization device for the monitoring of analytes in human real samples. The analytical quantification of the MDA was done using the UV-Vis method. Also, the utilization of the designed chemosensor for the analysis of MDA in real sample was evaluated in human urine samples. Using the spectrophotometric method, MDA was deformed in the linear range of 0.01192 to 1.192 mM with a low limit of quantification of 0.12 μM. Essential significant features of this study include the first application of AgNPrs with high stability and great optical properties without any reagent as an optical sensing probe of MDA and optimized OD-μPCD toward on-site and on-demand MDA screening in real samples diagnosis and the innovative time/color semi-analytical recognition strategy. Moreover, the prepared OD-μPCD decorated by AgNPrs could be a prized candidate for commercialization due to the benefits of the low-cost materials used, like paper and paraffin, and portability. This innovative process led to uniform hydrophilic micro-channels on the surface of cellulose, without the use of a UV lamp, clean room, and organic solvents. This report could be a pioneering work, inspiring simple and effective on-site semi-analytical recognition devices for harmful substances or illegal drugs, which simply consist of a piece of lightweight paper and one drop of the required reagent.

Chemical Structure of Stabilizing Layers of Negatively Charged Silver Nanoparticles as an Effector of Shifts in Soil Bacterial Microbiome under Short-Term Exposure.

In this work, we have assessed the exposure of soil bacteria from potato monoculture to three types of silver nanoparticles (AgNPs) as well as silver ions (Ag+ ions) delivered in the form of silver nitrate and a commercially available fungicide. The diversity of the soil microbial community, enzymatic activity, and carbon source utilization were evaluated. It was found that only the fungicide significantly limited the abundance and activity of soil bacteria. Silver ions significantly reduced bacterial metabolic activity. In turn, one type of AgNPs prepared with the use of tannic acid (TA) increased bacterial load and activity. There was found in all AgNPs treated soils (1) a greater proportion of all types of persistent bacteria, i.e., Bacillus, Paenibacillus, and Clostridium; (2) a visible decrease in the proportion of Nocardioides, Arthrobacter, and Candidatus Solibacter; (3) almost complete depletion of Pseudomonas; (4) increase in the number of low-frequency taxa and decrease in dominant taxa compared to the control soil. Despite the general trend of qualitative changes in the bacterial community, it was found that the differences in the chemical structure of the AgNP stabilizing layers had a significant impact on the specific metabolic activity resulting from qualitative changes in the microbiome.

Phytotoxicity of Silver Nanoparticles with Different Surface Properties on Monocots and Dicots Model Plants

The aim of the research was to evaluate the effect of three types of silver nanoparticles (AgNPs) with different physicochemical properties and silver ions delivered in the form of silver nitrate (AgNO3) at the concentration of 50 mg L−1 on germination and initial growth of monocots (common wheat, sorghum) and dicots (garden cress, white mustard). The AgNPs were prepared using trisodium citrate (TCSB-AgNPs), tannic acid (TA-AgNPs), and cysteamine hydrochloride (CHSB-AgNPs). They exhibited comparable shape, size distribution, and an average size equal to 15 ± 3 nm which was confirmed with the use of transmission electron microscopy. The electrokinetic characteristics revealed that CHSB-AgNPs have positive, whereas TCSB-AgNPs and TA-AgNPs negative surface charge. First, toxicity of the silver compounds was assessed using the Phytotestkit test. Next, after transferring seedlings to pots, shoot length, leaf surface, shoot dry mass, electrolyte leakage measurement, and photosystem II (PSII) efficiency were determined. AgNPs and silver ions delivered in the form of AgNO3 reduced root and shoots length of common wheat, sorghum, and garden cress; leaves surface of garden cress and white mustard; and shoots dry mass of white mustard. The positively charged CHSB-AgNPs and silver ions delivered in the form of AgNO3 showed the greatest inhibition effect. Moreover, silver ions and positively charged CHSB-AgNPs were more toxic to PSII of model plants than negatively charged TCSB-AgNPs and TA-AgNPs. AgNPs impact differed in the case of monocots and dicots, but the size of the changes was not significant, so it concerned individual parameters. The results revealed the interaction strength, which was generally similar in all tested plants, i.e., increasing negative effect in sequence TCSB-AgNPs < TA-AgNPs < silver ions delivered in the form of AgNO3 < CHSB-AgNPs.

Treatment with Argovit® Silver Nanoparticles Induces Differentiated Postharvest Biosynthesis of Compounds with Pharmaceutical Interest in Carrot (Daucus carota L.).

The global market for plant-derived bioactive compounds is growing significantly. The use of plant secondary metabolites has been reported to be used for the prevention of chronic diseases. Silver nanoparticles were used to analyze the content of enhancement phenolic compounds in carrots. Carrot samples were immersed in different concentrations (0, 5, 10, 20, or 40 mg/L) of each of five types of silver nanoparticles (AgNPs) for 3 min. Spectrophotometric methods measured the total phenolic compounds and the antioxidant capacity. The individual phenolic compounds were quantified by High Performance Liquid Chromatography (HPLC) and identified by –mass spectrometry (HPLC-MS). The five types of AgNPs could significantly increase the antioxidant capacity of carrots’ tissue in a dose-dependent manner. An amount of 20 mg/L of type 2 and 5 silver nanoparticle formulations increased the antioxidant capacity 3.3-fold and 4.1-fold, respectively. The phenolic compounds that significantly increased their content after the AgNP treatment were chlorogenic acid, 3-O-caffeoylquinic acid, and 5′-caffeoylquinic acid. The increment of each compound depended on the dose and the type of the used AgNPs. The exogenous application of Argovit® AgNPs works like controlled abiotic stress and produces high-value secondary bioactive compounds in carrot.

Garcinia mangostana Shell and Tradescantia spathacea Leaf Extract- Mediated One-pot Synthesis of Silver Nanoparticles with Effective Antifungal Properties

Background: The feasibility of plant extracts for metallic nanoparticle fabrication has been demonstrated. Each plant species impacts differently on formed nanoparticles, thus specific plants need to be explored in detail. Objective: Continuing the fabrication of nanoparticles using green method, Garcinia mangostana shell and Tradescantia spathacea leaf extract are exploited as reducing sources to form two types of silver nanoparticles (GMS-AgNPs and TSL-AgNPs) less than 50 nm. Methods: Structural characterization of GMS-AgNPs and TSL-AgNPs was performed by ultravioletvisible spectrophotometry (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectrometer (EDAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Antifungal tests of GMS-AgNPs and TSL-AgNPs were performed with Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. Results: UV-vis spectra with the 440-nm peak demonstrate the silver nanoparticle formation. FTIR analysis shows the GMS-AgNPs and TSL-AgNPs modified by organic functional groups. The SEM and TEM images indicate that the GMS-AgNPs are spherical shaped with rough edged, while the TSL-AgNPs are spherical shape with smooth surface. The GMS-AgNP average size (15.8 nm) is smaller than TSL-AgNP (22.4 nm). In addition, antifungal tests using Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum reveal that GMS-AgNPs and TSL-AgNPs can significantly inhibit the proliferation of these fungal strains. Conclusion: Garcinia mangostana shell and Tradescantia spathacea leaf extract as renewable and eco-friendly resources playing a dual role for nanoparticle biosynthesis create GMS-AgNPs and TSL-AgNPs with high antifungal efficiency for biomedical or agricultural applications.

Silver nanoparticles cross-linked polyimide aerogels with improved high temperature microstructure stabilities and high mechanical performances

Nanoparticles can be considered as effective cross-linkers for PI aerogels. In order to investigate the effect of different nanoparticle-cross-linkers on the performances of aerogels, two types of silver nanoparticles, AgNPs (Ag nanoparticles) and AgNShs (Ag nanosheets) were modified via PATP (p-aminothiophenol) as cross-linkers and then added into PAA (polyamic acid) solution derived from BPDA (3, 3′, 4, 4′-biphenyltetracarboxylic dianhydride) and ODA (4, 4′-diaminodiphenyl ether) to form wet gel. The wet gel was processed with supercritical CO 2 drying to fabricate cross-linked polyimide aerogels. Raman, XPS and TG-IR were carried out to prove successful modification of silver nanoparticles. The as-prepared aerogels had densities around 0.2 g cm −3 . Nitrogen adsorption desorption tests and mechanical tests were conducted to characterize the performance of aerogels at room temperature and high temperature (above 150 °C). The results showed that comparing to pure PI aerogels, aerogels cross-linked with silver nanoparticles had higher compressive strength and Young's modulus, which comes to 3.4 MPa and 52.7 MPa, respectively. Besides, silver nanoparticles cross-linked aerogels also had better high temperature stability in both size and microstructure comparing to pure PI aerogels. With remarkable mechanical properties and high temperature microstructure stabilities, these aerogels show potential in many areas of application. • Two kinds of silver nanoparticles are aminated and served as cross-linkers of PI aerogels. • Aerogels added with 5 wt % cross-linker have the highest mechanical properties among aerogels with similar densities. • Silver nanoparticles cross-linked aerogels have better high temperature microstructure stability than pure PI aerogels.

Simultaneous Antibacterial and Antibiofilm Activities of three Types of Silver Nanoparticles against Human Bacterial Pathogens.

Emergence of antibiotic resistant bacteria result in an approximately 550,000 deaths from bacterial infections annually. Several studies reported interesting antibacterial and anti-biofilm activities of silver nanoparticles synthesized by different physical, chemical and biological methods as an alternative to antibiotics. However, the resultant nanoparticles were varying in size, shape, and had different antibacterial and antibiofilm activities with different concentrations. Moreover, previous studies had investigated the antibacterial and antibiofilm activities in separate protocols and didn’t investigate the real-time or dual effect of silver nanoparticles on both planktonic and sessile cells within single protocol. This study aimed to synthesize silver nanoparticles through three methods and analyzing the simultaneous antibacterial and antibiofilm activities against planktonic and sessile bacterial cells. Three methods were applied to analyze silver nanoparticles and used to investigate the dual effect against bacterial biomass and biofilm formation. The results showed that synthesized silver nanoparticles cause significant inhibition to bacterial cell biomass and bacterial biofilm formation when compared with controls at low concentration. Significant Higher antibiofilm activity than antibacterial activity was observed at very low concentration (0.0125 µg/ ml). The antibacterial and antibiofilm activity do not differ according to the type of bacteria. Whereas, the antibacterial effect differs significantly according to the methods of silver nanoparticles synthesis.

A comparative study of sterically and electro-statically stabilized silver nanoparticles for the determination of muscle relaxant tizanidine: Insights of localized surface plasmon resonance, surface enhanced Raman spectroscopy and electrocatalytic activity

A comparative study of two types of silver nanoparticles was investigated. The effect of the surface chemistry of the studied silver nanoparticles (AgNPs) on their localized surface plasmon resonance was utilized for the quantitative determination of muscle relaxant tizanidine drug. The studied AgNPs are classified according to the type of stabilizing agent used in their synthesis into electrostatically and sterically stabilized AgNPs. The electrostatically-stabilized AgNPs (AA AgNPs) were prepared using ascorbic acid as both reducing and protective agents in alkaline medium. The sterically-stabilized AgNPs type (PEG-AA AgNPs) was prepared using ascorbic acid as a reducing agent and polyethylene glycol as a stabilizing agent at room temperature. The interaction of tizanidine with AgNPs was characterized using four different techniques including, transmission electron microscope, UV–visible spectrophotometric, surface enhanced Raman spectroscopic (SERS) and electroanalytical methods. SERS method was developed to study the relationship between the plasmon resonance and the enhanced power of Raman signal. The electrocatalytic behavior and the interfacial properties of AgNPs were studied using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) on glassy carbon electrode modified with AgNPs. The quantitative determination of tizanidine in pharmaceutical and biological samples was successfully achieved by using AgNPs probe based on spectrophotometric methods. A linear response over the range 10–400 nmol L−1 was obtained. Validation procedures were carried out following International Conference on Harmonization (ICH) guidelines.

Ecotoxicity of different-shaped silver nanoparticles: Case of zebrafish embryos

As the worldwide application of silver nanomaterials in commercial products increases every year, and concern about the environmental risks of such nanoparticles also grows. A clear understanding of how different characteristics of nanoparticles contribute in their toxic behavior to organisms are imperative for predicting and control nanotoxicity. Within our research, we investigated the toxic effect of two types of silver nanoparticles (spherical and flat Ag nanoparticles) on zebrafish (Danio rerio) embryos. Particular interest was paid to proper characterization of Ag nanoparticles initially and during the experiment. A proper test medium was found and used for ecotoxicity evaluation. The behavior of flat silver nanoparticles with respect to embryos of zebrafish was analyzed and compared to the ecotoxicity of silver ionic form (AgNO3). Both types of nanoparticles showed a more pronounced toxic effect to Danio rerio embryos than silver ions (AgNO3), while silver nanoplates were more harmful than Ag nanospheres. While previous investigations showed that toxicity of Ag nanoparticles can be explained by the presence of Ag+ in solution of silver nanoparticles, our results demonstrate that the harmful effects of nanosilver may be associated with silver nanoparticles themselves than with ionic silver released into solution.

Fabrication of Nanocomposite Scaffolds Including Metal Nanoparticles for Tissue Engineering Applications

This study presents the findings of a research on fabricating composite nanofibrous mats including silver and copper nanoparticles for tissue engineering applications. For this purpose, two different types of silver nanoparticles (soluble starch capped silver nanoparticles, sodium alginate capped silver nanoparticles) and two different types of copper nanoparticles (soluble starch capped copper nanoparticles, sodium alginate capped copper nanoparticles) were successfully incorporated into polyvinyl alcohol (PVA) fibers through electrospinning process. Characterization studies with x-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma spectrometer (ICP) were conducted to determine physical and structural properties of the obtained nanofiber mats. According to SEM analysis it was observed that interconnected and randomly-oriented nanofibers were successfully generated. Additionally, XRD and FTIR studies proved the existence of silver nanoparticles and hydroxapatite on the nanofiber mats immersed in simulated body fluid (SBF) for 7 days. The results indicated that long term silver ion release was achieved. Overall results showed that these nanofibrous mats can be good candidates as multifunctional scaffolds for tissue engineering applications.

Ag Nanoparticles Drop-Casting Modification of Screen-Printed Electrodes for the Simultaneous Voltammetric Determination of Cu(II) and Pb(II).

A new silver nanoparticle modified screen-printed electrode was developed and applied to the simultaneous determination of Pb(II) and Cu(II). Two different types of silver nanoparticles with different shapes and sizes, Ag nanoseeds and Ag nanoprisms, were microscopically characterized and three different carbon substrates, graphite, graphene and carbon nanofibers, were tested. The best analytical performance was achieved for the combination of Ag nanoseeds with a carbon nanofiber modified screen-printed electrode. The resulting sensor allowed the simultaneous determination of Pb(II) and Cu(II) at trace levels and its applicability to natural samples was successfully tested with a groundwater certified reference material, presenting high reproducibility and trueness.

SYNTHESIS OF SILVER NANOPARTICLES FROM SILVER NITRATE SOLUTION USING GREEN TEA EXTRACT (CAMELIA SINENSIS) AS BIOREDUCTOR

The synthesis of silver nanoparticles with micro size is highly required in antibacterial fields. The biorefinery material is highly potential as a bioreductor which is applied in the synthesis of nanoparticles. The bioreductor is made from green tea leaves extraction using aquadest to extract its active substance, the catechin which is derived from polyphenol. The polyphenol can reduce the synthesis of silver nanoparticles naturally. The result of FTIR analysis from green tea leaves extract containing polyphenol shown in the uptake functional groups is -OH group located in 3425 cm-1, C=O group located in 1635 cm-1, C=C group located in 1527, and 1442 cm-1 , and C-O group located in 1234 cm-1. The precursors of AgNO3 was used as the main synthetic material. The synthetic condition was resulted from the reaction between the extraction of green tea extract and AgNO3 as the precursors in the variation of synthetizing time. The heating process during synthesizing is done in 50 ?C along with stirring to foster the creation of silver nanoparticles. The analysis result of XRD shows that silver nanoparticles has the diffraction peaks in the angle of 2 theta that are 44.08, 64.40, and 77.51. The types of silver nanoparticles is Ag0 nanoparticles with face-centered cubic crystal structure. Based on TEM analysis, the size and particle size distribution can be determined using image J. The distribution shows that the longer synthesizing time, the bigger nanoparticles produced. With synthesizing times at 24 hours, 6 hours, 3 hours, and 2 hours produce average particle size of 26.4 nm; 9.2 nm; 8.4 nm; and 7.4 nm respectively.

Novel metal nanoparticle-enhanced fluorescence for determination of trace amounts of fluoroquinolone in aqueous solutions

Metal-enhanced fluorescence of fluoroquinolones (FQs) was first observed in aqueous solutions. In addition, a new type of silver nanoparticles (AgNP) was synthesized with simple and easy synthetic processes and environmentally friendly compounds. The effects of different concentrations of AgNPs on the fluorescence behaviours of ciprofloxacin (CIP), enrofloxacin (ENR) and lomefloxacin (LMF) in aqueous solutions were investigated, respectively. The experimental results demonstrated that the fluorescence peak shapes and the locations of the features in the excitation and emission spectra for each FQ that was mixed with AgNPs were almost the same as those of the standard FQs. An enhancement or quenching of the fluorescence can also be observed, depending on the exact conditions. Compared with the identical control samples that lack AgNPs, the fluorescence of each FQ in aqueous solutions was greatly enhanced by AgNPs with concentrations at a volume ratio of 5%. Moreover, at the optimum AgNP concentration, novel sensitive fluorometric methods for the separate determination of trace amounts of CIP, ENR and LMF in aqueous solutions were established. Under optimal experimental conditions, the linear dynamic ranges for the determination of CIP, ENR and LMF concentrations varied from 0.025 to 1.0mgL−1, 5.0 to 160ngL−1 and 0.01 to 0.8mgL−1, and the limits of detection were 90, 5 and 6ngL−1, respectively; the relative standard deviation was less than 1.2% (n = 9). The experimental recovery results for the determination of CIP, ENR and LMF in aqueous solutions ranged from 99% to 102%, 90% to 103% and 92% to 107%, respectively. Compared with the established method in which no AgNPs were added, the quantitation limits of the silver nanoparticle-enhanced fluorometric methods were approximately 2-fold lower for CIP, 2.6-fold lower for ENR and 4-fold lower for LMF. Significantly, the novel silver nanoparticle-enhanced fluorometric methods were successfully applied to directly determine CIP, ENR and LMF concentrations in pharmaceutical preparations, demonstrating the methods’ advantages of simplicity, sensitivity and low cost.

Toxicity of silver nanoparticles towards tumoral human cell lines U-937 and HL-60

The toxicity of three types of silver nanoparticles towards histiocytic lymphoma (U-937) and human promyelocytic cells (HL-60) was studied. The nanoparticles were synthesized in a chemical reduction method using sodium borohydride. Trisodium citrate and cysteamine hydrochloride were used to generate a negative and positive nanoparticle surface charge. The evaluation of cell viability, membrane integrity, antioxidant activity and the induction of inflammation were used to evaluate the difference in cellular response to the nanoparticle treatment. The results revealed that the cysteamine-stabilized (positively charged) nanoparticles (SBATE) were the least toxic although they exhibited a similar ion release profile as the unmodified (negatively charged) nanoparticles obtained using sodium borohydride (SBNM). Citrate-stabilized nanoparticles (SBTC) induced superoxide dismutase (SOD) activity in the HL-60 cells and total antioxidant activity in the U-937 cells despite their resistance to oxidative dissolution. The toxicity of SBNM nanoparticles was manifested in the disruption of membrane integrity, decrease in the mitochondrial functions of cells and the induction of inflammation. These findings allowed to conclude that mechanism of silver nanoparticle cytotoxicity is the combination of effects coming from the surface charge of nanoparticles, released silver ions and biological activity of stabilizing agent molecules.