Citrate-stabilized Silver Nanoparticles Research Articles

Evaluation of extraction and storage conditions for quantification and characterization of silver nanoparticles in complex samples by single particle-ICP-MS

The extraction of nanoparticles (NPs) from complex matrices and subsequent storage can potentially alter the NPs physicochemical properties and hinder cross-study comparisons. Most NP extraction methods are designed and tested at high nanoparticle concentrations, although (eco)toxicological and regulatory monitoring programs require methods capable of analyzing NPs at environmentally relevant concentrations (lower ppb range). In this study, we investigated how extraction methods affect the characteristics of PVP coated and citrate-stabilized silver NPs (AgNPs) spiked into soil, sewage sludge, and biological samples at environmentally relevant concentrations using Single Particle Inductively Coupled Plasma Mass Spectrometry spICP-MS). Further we investigated the impact of storage temperature (-80°C to 21°C) and storage duration (1-28 days) on the particle characteristics such as particle size.We found that aqueous AgNPs samples with low ionic strength media retained their original characteristics (like particle size, particle concentration and particle-based Ag mass) when preserved at 4°C for up to 28 days. AgNPs dispersed in high ionic strength media were however better preserved at -80°C. Among the extraction agents, tetrasodium pyrophosphate was more efficient in extracting AgNPs from soil and sewage sludge matrices, while Proteinase K was more suitable for biological samples from organisms (earthworms or fish).Although our study focused only on AgNPs, it provides crucial information to aid interlaboratory comparisons and data interpretation for (eco)toxicological studies.

Green synthesis of stable and biocompatible silver nanoparticles with natural flavonoid apigenin

The synthesis of silver nanoparticles has been carried out, controlling the size and using only apigenin as a reducing and coating agent. Unlike citrate-stabilized silver nanoparticles, the apigenin-coated nanoparticles are very stable in physiological environments. This unique stability is a result of a thick polyphenolic coating on the surface of the particles, which has been observed by electron microscopy. Based on Raman scattering, the phenolic coating originates from apigenin. Hemolysis induced by nanoparticles is less than 1% up to a concentration of 64 μg/ml and less than 5% up to a concentration of 128 μg/ml. These particles do not cause significant toxicity in human dermal fibroblast cells up to a concentration of 256 μg/ml. In the evaluation of the antioxidant properties of particles, it was found that they have antioxidant behavior up to a concentration of 32 μg/ml and pro-oxidant behavior at higher concentrations. Considering the biocompatibility of these nanoparticles, many biomedical applications can be considered for them.

Rapid and Visual Detection of Vitamin C Based on Sodium Citrate-Stabilized Silver Nanoparticles

Ensuring the vitamin C requirements are met through dietary intake or supplements is essential for health. In this study, a simple and rapid visual detection method for semi-quantitative analysis of vitamin C was proposed based on sodium citrate-stabilized silver nanoparticles (SC-AgNPs). As a validation of SC-AgNPs as a colorimetric sensor for vitamin C, color changes were observed gradually, shifting from transparent yellow to deep brown after the addition of vitamin C at various concentrations. That is also supported by an increase in absorption intensity at the peak wavelength of 417 nm, which was analyzed using a UV-Vis spectrophotometer. Based on the spectral approach method, the linear relationship between absorbance values and vitamin C is in the range of 0-4.2 mM, with a coefficient correlation of 0.99 and sensitivity of 0.95/mM. Furthermore, the feasibility of the SC-AgNPs for vitamin C detection in healthy beverages and tablet pharmaceuticals has been investigated.

Label-Free Citrate-Stabilized Silver Nanoparticles-Based, Highly Sensitive, Cost-Effective, and Rapid Visual Method for the Differential Detection of Mycobacterium tuberculosis and Mycobacterium bovis.

Tuberculosis poses a global health challenge, and it demands improved diagnostics and therapies. Distinguishing between Mycobacterium tuberculosis (M. tb) and Mycobacterium bovis (M. bovis) infections holds critical "One Health" significance due to the zoonotic nature of these infections and inherent resistance of M. bovis to pyrazinamide, a key part of the directly observed treatment, short-course (DOTS) regimen. Furthermore, most of the currently used molecular detection methods fail to distinguish between the two species. To address this, our study presents an innovative molecular-biosensing strategy. We developed a label-free citrate-stabilized silver nanoparticle aggregation assay that offers sensitive, cost-effective, and swift detection. For molecular detection, genomic markers unique to M. tb and M. bovis were targeted using species-specific primers. In addition to amplifying species-specific regions, these primers also aid the detection of characteristic deletions in each of the mycobacterial species. Post polymerase chain reaction (PCR), we compared two highly sensitive visual detection methods with respect to the traditional agarose gel electrophoresis. The paramagnetic bead-based bridging flocculation assay successfully discriminates M. tb from M. bovis with a sensitivity of ∼40 bacilli. The second strategy exploits citrate-stabilized silver nanoparticles, which aggregate in the absence of amplified dsDNA on the addition of sodium chloride (NaCl). This technique enables the precise, sensitive, and differential detection of as few as ∼4 bacilli. Our study hence advances tuberculosis detection, overcoming the challenges of M. tb and M. bovis differentiation and offering a quicker alternative to time-consuming methods.

Fluorescence quenching of fluorescein dye using silver nanoparticles

Fluorescence quenching is indeed a versatile and widely used technique in various scientific disciplines, including chemistry, biology, and medicine. It provides valuable information about the behaviour of small molecules in organized systems and offers insights into the properties of the microenvironments surrounding the fluorescent probe and quencher molecules. In the present work, we report the synthesis of citrate-stabilized silver nanoparticles and also investigate the effect of the prepared silver nanoparticles on the fluorescence luminous intensity of fluorescein dye with different concentrations of silver nanoparticles. The UV–visible spectrometer is used to study the absorption properties of silver nanoparticles. We have obtained a single surface plasmon resonance band, which indicates the isotropic nature of particles. The particle size was obtained from the absorption spectra, using the Mie scattering theory. The luminous intensity of fluorescein dye was found to be quenched in addition to silver nanoparticles. The morphological analysis is done using SEM.

A systematic study of SERS spectra of cationic Raman dyes adsorbed on citrate-stabilized silver nanoparticles

The adsorption (kinetics and signal stability) of cationic triarylmethane dyes and an acridine derivative with various counter-ions on citrate-stabilized hydroxylamine-reduced silver sols was studied using SERS spectroscopy. The influence of the method of nanoparticle synthesis, as well as the composition and ionic strength of the medium on the stability of nanoparticle–dye complexes was investigated.

A Systematic Study of the Surface-Enhanced Raman Scattering Spectra of Cationic Raman Dyes Adsorbed on Citrate-Stabilized Silver Nanoparticles

A Systematic Study of the Surface-Enhanced Raman Scattering Spectra of Cationic Raman Dyes Adsorbed on Citrate-Stabilized Silver Nanoparticles

Influences of Plasma Plume Length on Structural, Optical and Dye Degradation Properties of Citrate-Stabilized Silver Nanoparticles Synthesized by Plasma-Assisted Reduction.

Citrate-capped silver nanoparticles (Ag@Cit NPs) were synthesized by a simple plasma-assisted reduction method. Homogenous colloidal Ag@Cit NPs solutions were produced by treating a -trisodium citrate-deionized water with an atmospheric-pressure argon plasma jet. The plasma-synthesized Ag@Cit NPs exhibited quasi-spherical shape with an average particle diameter of about 5.9−7.5 nm, and their absorption spectra showed surface plasmon resonance peaks at approximately 406 nm. The amount of Ag@Cit NPs increased in a plasma exposure duration-dependent manner. Plasma synthesis of Ag@Cit NPs was more effective in the 8.5 cm plume jet than in the shorter and longer plume jets. A larger amount of Ag@Cit NPs were produced from the 8.5 cm plume jet with a higher pH and a larger number of aqua electrons, indicating that the synergetic effect between plasma electrons and citrate plays an important role in the plasma synthesis of Ag@Cit NPs. Plasma-assisted citrate reduction facilitates the synthesis of Ag@Cit NPs, and citrate-capped nanoparticles are stabilized in an aqueous solution due to their repulsive force. Next, we demonstrated that plasma-synthesized Ag@Cit NPs exhibited a significant degradation of methylene blue dye.

Some peculiarities of the response of microalga Porphyridium cruentum to the action of citrate-stabilized silver and gold nanoparticles

The article presents the results regarding some peculiarities of the response of microalga Porphyridium cruentum to the action of citrate-stabilized silver and gold nanoparticles with sizes of 10 nm and 20 nm. It has been established that the tested nanoparticles added to the cultivation medium of microalga P. cruentum at the beginning of lag phase did not change significantly its productivity during the cultivation cycle. The effect of this type of nanoparticles on the chlorophyll a and β - carotene synthesis during the cultivation of porphyridium is manifested depending on the size and concentrations applied.

Genotoxicity of physical silver nanoparticles, produced by the HVAD method, for Chinchilla lanigera genome

Each year, growing demand for silver nanoparticles (AgNP) contributes to the search for alternative methods of their production. Stable AgNP with antibacterial properties, low toxicity to the environment and living organisms are especially valued. In the study presented here, an attempt was made to assess the toxicity of two AgNP solutions produced using the HVAD method to the Chinchilla lanigera genome. The AgNO3 solution was the indicator and reference for the harmfulness of AgNP. The study was carried out in vitro on bone marrow cells isolated from Chinchilla lanigera bones. The genotoxicity was assessed by comet assay, following the treatment of cells with three silver solutions: unstable and sodium citrate-stabilized silver nanoparticles, as well as silver nitrate at three concentrations (5, 10 and 20 µg/L), after 3, 6 and 24 h. Based on the percentage of the DNA content in the comet tail and the tail moment, an increase in cell DNA integrity disruption was demonstrated in all tested variants: of solution, exposure time and concentration, compared to the control sample. A statistically significant correlation was determined between the level of induced DNA breaks and the concentration of the active solutions and the duration of their activity. A solution of silver nanoparticles stabilized with sodium citrate was shown to have the most harmful effect on bone marrow cells. Silver nitrate demonstrated a level of toxicity similar to these particles. Further studies are necessary to directly compare the genotoxic properties of AgNP produced using the HVAD method and the chemical method under the same conditions.

Fabrication and surface-enhanced Raman scattering properties of thin-film assemblies of classified silver nanoparticles

The classification of citrate-stabilized silver nanoparticles was performed by a combination of centrifugation and redispersion. Repeated classification processes led to a convergence of similarly sized nanoparticles, which in turn decreased their size deviations. This tendency corresponds to the change in the zeta potentials of the silver nanoparticles. Densely packed sphere-shaped silver nanoparticle thin-film assemblies were fabricated by a liquid–liquid interfacial precipitation process using appropriately classified silver nanoparticles. The surface-enhanced Raman scattering efficiencies of these thin-film assemblies of silver nanoparticles were varied and could be optimized by the number of classification processes.

Synthesis of Citrate-Stabilized Silver Nanoparticles Modified by Thermal and pH Preconditioned Tannic Acid.

Silver nanoparticles (AgNPs) may be synthesized by many different methods, with those based on the thermal reduction of silver salts by citric acid or citric acid/tannic acid being amongst the most commonly used. These methods, although widely used and technically simple, can produce particles in which the size, polydispersivity and morphology can vary greatly. In this work nearly mono-dispersed spherical AgNPs have been synthesized via a one-step reduction method by using sodium citrate and varying quantities of Tannic Acid (TA), which was thermally conditioned prior to use in the growth process. It was found that the final size can be further tailored by controlling the amount of TA and the thermal conditioning of the TA at 60 °C at different time points, which changes the size and polydispersivity of AgNPs. To better understand the origin of this effect, optical spectroscopic analysis and 1H NMR of the TA following mild thermal conditioning of the solution have been done. Comparison of thermally conditioned TA and TA exposed to basic pH shows that similar chemical modifications occur and consequently produce similar effects on growth when used in the synthesis of AgNPs. It is proposed that thermal preconditioning of the TA introduces either chemical or structural changes, which decrease the final particle size under a given total silver content.

Formation of a Highly Stable and Nontoxic Protein Corona upon Interaction of Human α-1-Acid Glycoprotein (AGP) with Citrate-Stabilized Silver Nanoparticles.

Given the importance of protein corona in determining cellular responses to nanoparticles, numerous studies have been devoted to finding stable, biocompatible, and nontoxic protein corona. In this work, the interaction between human α-1-acid glycoprotein (AGP) and citrate-stabilized silver (Ag-CIT) nanoparticles of about 10 nm was methodically studied using molecular docking simulation approach and various experimental techniques. It could be shown that a stable Ag-CIT/AGP bioconjugate was formed with a high binding constant of 109 M-1, several orders of magnitude larger than that of other highly abundant serum proteins. Formation of AGP corona was accompanied by conserving the native conformation of the protein and further associated with a considerable decrease in the cytotoxicity of the silver nanoparticles.

Ultrasensitive Fluorescence Determination of 6-Thioguanine in Biological Samples Based on the Silver Nanoparticle-Mediated Release of Acridine Orange Probe

This article reports a simple, convenient, and very sensitive method for the determination of 6-thio guanine (6-TG). The basic phenomenon in the proposed method is fluorescence resonance energy transfer, where acridine orange (AO) act as a donor and citrate-stabilized silver nanoparticles (AgNPs) as an acceptor. A noncovalent bond between the surfaces of AgNPs and AO was found, and the effect of fluorescence quenching was observed. The fluorescence spectra of AO recovered after further addition of 6-TG are responsible for the aggregation of AgNPs. Under ideal conditions, the linear relationship of 6-TG in the concentration range of 0.005 to 0.04 μM was displayed, and the limit of detection of 6-TG was obtained as 5.3 nM. Under ideal conditions, the linear relationship of 6-TG was displayed in the concentration range of 0.005 to 0.04 μM, and the limit of detection of 6-TG was obtained as 5.3 nM. The proposed method offers a rapid analysis to determine 6-TG in human serum, blood, and urine samples.

СИНТЕЗ ТА АНТИМІКРОБНА АКТИВНІСТЬ НАНОЧАСТИНОК СРІБЛА СТАБІЛІЗОВАНИХ ЦИТРАТ-АНІОНАМИ

Widespread use of synthetic antimicrobial drugs leads to the development of antibiotic resistance of pathogenic strains of microorganisms. Therefore, today researchers are very interested in drugs based on nanoparticles of metals, in particular silver and copper, which have antibacterial, antifungal and antiviral activity. One of the reasons for the high interest of researchers in AgNPs as an antimicrobial agent is the significantly lower toxicity of AgNPs compared to Ag+ ions. High antibacterial efficiency of silver nano¬particles is achieved due to their developed surface, which provides maximum contact with the environment. In addition, such nanoparticles are quite small and are able to penetrate cell membranes, to affect intracellular processes from within. Therefore, the aim of this work was to obtain concentrated colloidal silver solutions stabilized by citrate anions, which simultaneously provide satisfactory stabilization of colloidal silver solutions and are non-toxic, as well as to investigate the antimicrobial action of synthesized AgNPs. The solution of citrate stabilized silver nanoparticles (AgNPs) have been obtained via the reaction of reduction of silver nitrate by hydrazine in alkaline medium in the presence of sodium citrate. AgNPs were investigated using transmission electron microscopy (TEM) and UV-vis spectroscopy and the particles size and particles size distribution (PSD) were determined. It was observed that obtained AgNPs are mainly spherical shape. It was found that the mean diameter and PSD of AgNPs determined using TEM and UV-vis spectroscopy are close and equal to 14 and 5 nm and 15 and 4 nm respectively. Obtained solution was concentrated by evaporation at 70 C under reduced pressure up to achievement of AgNPs concentration equal to 200 mg/L. On the base of comparison of optical properties of initial silver sol and concentrated solution the minority of agglomeration of AgNPs was statement. At the same time AgNO3 test showed no change of UV-vis spectrum of concentrate that points on the absence of reducing agent in the solution; this fact indicate that hydrazine was eliminated from during the evaporation of initial AgNPs solution and obtained concentrate did not consist the toxic impurities. Antimicrobial activity of obtained citrate stabilised AgNPs against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli bacterium was tested using disk diffusion method. It was found that AgNPs shown significant bactericidal effect even at low (25 mg/L) concentration as well as some higher efficiency against Gram-negative bacterium. There was also a slightly higher antimicrobial activity of the drug against gram-negative bacteria Escherichia coli compared with gram-positive bacteria Bacillus subtilis, due to the different structure of cell walls. In particular, the walls of gram-positive bacteria consist mainly of peptidoglycan (murein), and gram-negative bacteria have cell walls with a layer of peptidoglycan and an outer membrane with a lipopolysaccharide component, which is not present in gram-positive bacteria. Based on the studies, it can be concluded that the proposed method of synthesis of AgNPs is suitable for obtaining highly concentrated silver sols. This method of synthesis is simple in hardware design, scalable, and the resulting colloidal solutions are stable and do not contain harmful impurities. Therefore, due to the high antibacterial activity of citrate-anion-stabilized AgNPs against certain types of gram-positive and gram-negative bacteria, it can be recommended for the manufacture of bactericidal drugs for biomedical purposes.

Tuning of Citrate-Stabilized Laser Ablated Silver Nanoparticles for Glyphosate Detection

The recent advances in nanotechnology can help develop both fast and cost-effective detection techniques to verify if the presence of contaminants in water resources is under safe limits, increasing temporal and geographical test coverage. For a specific analyte, the detection performance of citrate-stabilized silver nanoparticles depends on their chemical affinity, as well as on the ensemble characteristic of the colloid upon its de-stabilization by a mediated aggregation process. This work presents the tuning of citrate-stabilized silver nanoparticles produced by pulsed laser ablation in liquids for glyphosate detection in water. For fixed geometry and laser pulse characteristics, the ablation time, surfactant concentration and interaction pH were studied. The resulting colloidal solutions of silver nanoparticles with glyphosate were interrogated employing optical fiber spectroscopy. Two interrogation techniques which are based on a controlled aggregation of the colloid were used: UV-Vis extinction and Surface Enhanced Raman scattering. Using a calibration curve for low concentrations, the obtained limits of detection for glyphosate in water were $6~\mu \text{M}$ (1.0 mg/L) and $7.5~\mu \text{M}$ (1.3 mg/L), respectively.

PH effect on the synthesis of different size silver nanoparticles evaluated by DLS and their size-dependent antimicrobial activity

ABSTRACT This paper reports citrate-stabilized silver nanoparticles (AgNPs) synthesized by nitrate ion chemical reduction with sodium borohydride, at different pHs (2–9). The AgNPs synthesized by this method exhibited size distribution from 5 to 249 nm, depending on pH, as determined by dynamic light scattering, and morphology spherical, as determined by transmission electron microscopy. In pH range 3–7 occurred aggregation of the nanoparticles. The size distribution depending on pH was determined by dynamic light scattering. The zeta potential was determined, and the colloidal stability was correlated with nanoparticles aggregation at different pHs. The size-dependent antimicrobial activity was evaluated for two solutions, wherein both samples exhibited antimicrobial activity, although the smallest AgNPs without agglomeration have enhanced antimicrobial properties.

Spectroscopic insights into the effect of pH, temperature, and stabilizer on erlotinib adsorption behavior onto Ag nanosurface.

In this study, surface - enhanced Raman spectroscopy (SERS) was applied at the first time for estimation of how pH, temperature, and nanoparticle (NP) stabilizer affect an adsorption behavior of erlotinib (drug approved in a non-small cell lung cancer therapy) onto citrate-stabilized silver nanoparticles (AgNPs). Novel approach to improve cancer therapy assumes application of NPs as an efficient drug delivery system. This strategy requires designing stable drug/nanocarrier conjugates that can effectively interact in the target site. It is also important to perform deeply characterization of a drug orientation on the potential carrier surface and estimation how stable the appeared interaction is. Performed analysis, indicates that pH, temperature, presence of NP stabilizers, and time of incubation have an influence on the occurring adsorption geometry of the drug. However, the observed erlotinib/AgNP interaction remains stable regardless of the applied conditions. These considerations were supported by insightful physicochemical characteristics of the AgNPs and the erlotinib/AgNP conjugates by conducting transmission electron microscopy (TEM) imaging, determination of colloid stability conducted with the use of dynamic light scattering technique (DLS) and measurements of electrophoretic mobility. Such complex approach allows a better understanding of the stability of the erlotinib/AgNP conjugates and provides information how the investigated interaction is affected by the induced perturbations.

Evaluation of the Colorimetric Performance of Unmodified Citrate-Stabilized Silver Nanoparticles for Copper (II) Sensing in Water

In this study, the colorimetric performance of unmodified citrate-stabilized silver nanoparticles (cit-AgNP) for Cu2+ detection was investigated. Cit-AgNP was successfully synthesized using the modified Creighton method with sodium borohydride as reducing agent and trisodium citrate as stabilizing agent. The resulting nanoparticle was yellow in color, characteristic of AgNP. The absorbance peak was determined at 400 nm using UV Vis analysis while for morphology, the particles were spherical in shape with an average diameter of 11 nm determined by TEM analysis. In the presence of increasing Cu2+ concentration, the yellow cit-AgNP turned orange and showed decreasing absorbance at 400 nm with simultaneous emergence of additional peak at 450 nm. These changes were attributed to the nanoparticle aggregation confirmed by TEM analysis. A calibration curve generated showed that the absorbance ratio 450/400 nm is directly proportional to Cu2+ concentration from 0 to 40x10-4 M with good linear fit at R2 = 0.9749. The detection and quantification limits were determined to be 6.59x10-4 M and 21.97x10-4 M, respectively. Overall, the study demonstrated the potential of the assay for Cu2+ sensing application.

Simple and rapid colorimetric sensing of Ni(II) ions in tap water based on aggregation of citrate-stabilized silver nanoparticles

The presence of nickel in our water sources presents a danger to human health and aquatic organisms alike. Therefore, there is a need to detect and monitor nickel concentration in these sources. Current detection methods use instruments that are costly, resource intensive and require skilled personnel. Alternative methods that are simple and fast are needed. This study reports for the first time the development of a simple colorimetric assay for the detection of Ni2+ in aqueous solution using citrate-stabilized silver nanoparticles. Chemical synthesis method was employed using sodium borohydride and trisodium citrate as reducing and stabilizing agents, respectively. The characterization techniques used for obtaining spectral and morphological properties were ultraviolet-visible spectroscopy and transmission electron microscopy. The resultant silver nanoparticle solution was yellow in color and exhibited an absorbance peak at 392 nm. The full width at half maximum value was 57.8 ± 1.3 nm indicating particle monodispersity. For the morphology, the nanoparticles were spherical in shape with an average size of 10.4 ± 4.5 nm. Furthermore, the colorimetric properties of the silver nanoparticles for Ni2+ detection was investigated. Ni2+ was visually detected through a fast solution color change from yellow to orange. Monitoring of the absorbance showed a decrease in the original 392 nm peak and broadening of the surface plasmon absorption band. These changes are attributed to the aggregation of the nanoparticles due to Ni2+ addition which was confirmed by the transmission electron microscopy imaging. The absorption ratio (A510/A392) was plotted against varying Ni2+ concentration and it exhibited a good linear correlation from 0.7 to 1.6 mM with an R2 of 0.9958. The limits of detection and quantification were 0.75 and 1.52 mM, respectively. Additionally, the assay was tested against other common ions and showed excellent selectivity for Ni2+. Finally, the assay was successfully tested to detect Ni2+ in tap water samples with an average difference of 16% from prepared concentrations. Overall, the study showed the potential of using citrate-stabilized silver nanoparticles as a colorimetric reagent for detecting Ni2+ in aqueous solution.