Citrate-capped Silver Nanoparticles Research Articles

Case study of freezing-induced loading of silver nanoparticles into vaterite microcrystals

Hybrid materials composed of porous vaterite CaCO3 microcrystals loaded with functional inorganic nanoparticles are actively studied with respect to various practical applications. Recently, freezing-induced loading method was demonstrated as a versatile and effective approach for preparation of vaterite-based functional hybrid microparticles. However, despite of its high efficiency, the effect of nanoparticle concentration on the freezing-induced loading process and the structural properties of the resulted hybrids were not studied previously. Herein, for the first time, we have evaluated the feasibility of the conventional adsorption models to describe the freezing-induced loading of citrate-capped silver nanoparticles (AgNPs). The fitting of the dependence of the loading capacity of vaterite crystals on the residual concentration of AgNPs to two- or three-parameter models revealed that the best fit was obtained with the Freundlich model (R2 = 0.969), suggesting non-uniform deposition of AgNPs and interparticle agglomeration (Freundlich n > 1). This was confirmed with electron microscopy and elemental analysis demonstrating the formation and growth of AgNP aggregates on the CaCO3 surface with increasing initial nanoparticle concentration. Overall, the reported findings are valuable for a better understanding of the freezing-induced loading process and for further optimization of the preparation of vaterite-based functional hybrid microparticles.

Comparing silver and gold nanoislands’ surface plasmon resonance for bisacodyl and its metabolite quantification in human plasma

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles’ coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15–240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.

Silver nanoparticles enhanced enzyme-linked immunosorbent assay (ELISA) detection of cancer testis antigens (CTAs).

The Enzyme-Linked Immunosorbent Assay (ELISA) has been a cornerstone technique in laboratory medicine for over 55 years, relying on the specific binding of antibodies to antigens. ELISA's widespread use stems from its ability to detect low concentrations, its specificity, reproducibility, and potential for high-throughput screening. However, its sensitivity has limitations, prompting the exploration of innovative methods to improve the limit of detection (LOD). Nanoparticles provide a promising platform for enhancing ELISA sensitivity. Due to their high surface-to-volume ratio, they offer increased binding sites for capture elements and reporting tags, leading to amplified analytical signals. Recent studies have demonstrated improved sensitivity in ELISA through nanoparticle application, yielding faster detection times and enhanced sensitivities. This study investigates the potential of 50 nm citrate-capped silver nanoparticles to enhance ELISA's performance in quantifying cancer testis antigens (CTAs). In our study, we used the Human NY-ESO-1 ELISA kit (for research purposes) to determine the concentration of CTAs in randomly selected samples from healthy (n=89) and oncological (n=80) subjects, aged 18-75. We employed 50 nm citrate-capped silver nanoparticles (AGCB50-1M, BioPure Silver Nanoparticles - bare citrate, nano-Composix, San Diego, CA, USA). ELISA reactions followed the manufacturer's instructions, and data processing aligned with the same guidelines. Absorbance (OD) measurements occurred at 450 nm, influencing nanoparticle selection. Each ELISA well contained 5 ml of nanoparticles' stock solution with specified concentrations. CTAs concentrations were derived from the standard curve through CurveExpert Basic software. Statistical analysis was performed using SPSS v. 27 software, with p-values indicating significance if <0.03. The study adhered to Helsinki Declaration principles and received ethical approval. Participants provided informed written consent. The increased concentration values of CTAs for healthy individuals and cancer patients were determined in the case of the application of silver nanoparticles. The usage of nanoparticles can enhance the sensitivity of the ELISA method and positively influence its specific detection limit.

Ultrasensitive colorimetric detection of creatinine via its dual binding affinity for silver nanoparticles and silver ions.

Creatinine is an important biomarker for the diagnosis of chronic kidney disease (CKD). Recently, it has been reported that the concentration of salivary creatinine correlates well with the concentration of serum creatinine, which makes the former useful for the development of non-invasive and point-of-care (POC) detection for CKD diagnosis. However, there exists a technical challenge in the rapid detection of salivary creatinine at low concentrations of 3-18 μM when using the current kidney function test strips as well as the traditional methods employed in hospitals. Herein, we demonstrate a simple, sensitive colorimetric assay for the detection of creatinine with a limit-of-detection (LOD) down to the nanomolar level. Our approach utilises the dual binding affinity of creatinine for citrate-capped silver nanoparticles (Ag NPs) and Ag(i) ions, which can trigger the aggregation of Ag NPs and thus lead to the colour change of a sample. The quantitative detection of creatinine was achieved using UV-Vis spectroscopy with a LOD of 6.9 nM in artificial saliva and a linear dynamic range of 0.01-0.06 μM. This method holds promise to be further developed into a POC platform for the CKD diagnosis.

Fluorometric and colorimetric platforms for rapid and sensitive hydroxychloroquine detection in aqueous samples

The detection of pharmaceuticals has been an active area of research with numerous application areas ranging from therapeutic and environmental monitoring to pharmaceutical manufacturing and diagnostics. And, the emergence of COVID-19 pandemic has increased the demand for detection of certain active pharmaceutical ingredients such as Hydroxychloroquine (HCQ) mainly due to their increased manufacturing and usage. In this study, we present two optical, fluorometric and colorimetric, detection platforms for the rapid and sensitive detection of HCQ. These platforms take advantage of the interactions between the highly fluorescent dye Thioflavin T (ThT) and Tel24 G-quadruplex (G4) DNA structure, as well as the salt-induced aggregation behavior of negatively charged citrate-capped silver nanoparticles (Cit-AgNPs) in the presence of HCQ. In the fluorometric method, the addition of HCQ led to a significant and rapid decrease in the fluorescence signal of the ThT + Tel24 probe. In the colorimetric method, HCQ induced the aggregation of Cit-AgNPs in the presence of NaCl, resulting in a noticeable color change from yellowish-gray to colorless. Under the optimized conditions, the colorimetric platform exhibited a linear range of 18.0–240.0 nM and a detection limit of 9.2 nM, while the fluorometric platform showed a linear range of 0.24–5.17 μM and a detection limit of 120 nM. The selectivity of the proposed optical methods towards the target analyte was demonstrated by evaluating the response to other structurally similar small molecules. Finally, the practical applicability of both detection systems was confirmed by analyzing HCQ-spiked human urine samples that yielded average recoveries ranging from 75.4 to 110.2 % for the fluorometric platform and 86.9–98.2 % for the colorimetric platform. These results indicate the potential of the developed methods for HCQ detection in complex matrices.

Modulation of salt stress through application of citrate capped silver nanoparticles and indole acetic acid in maize

The present study was conducted to determine the effect of indole acetic acid (IAA) and Citrate Capped Silver Nanoparticles (Cit-AgNPs) on various attributes of maize under induced salinity stress. Seeds of the said variety were collected from Cereal Crop Research Institute (CCRI) Pirsabaq, Nowshera, sterilized and sown in earthen pots filled with 2 kg silt and soil (1:2) in triplicates in the green house of the Botany Department, University of Peshawar. Nanoparticles were analyzed by scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Thermo-gravimetric analysis (TGA) and Differential thermal analysis (DTA). Results of SEM revealed spherical morphology of Cit-AgNPs while EDX showed various elemental composition. TGA showed dominant weight loss up to 300 °C while the DTA showed major exothermic peaks at 420 °C. High Salinity concentration (80 mM) imposed significant detrimental impacts by reducing the agronomic attributes, photosynthetic pigments, osmolytes and antioxidant enzymes, which was remarkably ameliorated by the foliar application of Cit-AgNPs and IAA. Agronomic attributes including leaf, root and shoot fresh and dry weight was improved by 52–74%, 43–69% and 36–79% in individual as well as combined treatments of IAA and NPs. Photosynthetic pigments were amplified by 35–63%, total osmolytes were augmented by 39–68% and antioxidant enzymes including SOD and POD were boosted by 42–57% and 37–62% respectively, in combined as well as individual application. Conclusively, Cit-AgNPs are considered as salt mitigating entities that enhance the tolerance level of crop plants along with IAA, which may be beneficial for the plants growing in saline stressed environment.

SERS of Human Red Blood Cells in Non-Resonant Conditions: Benefits, Limitations, and Complementary Tools (CytoViva and GFAAS)

Herein, Raman and surface-enhanced Raman spectroscopies (SERS) were successfully employed to establish the chemical interactions of citrate-capped silver nanoparticles (AgNPs, 10–15 nm) with human red blood cells (RBCs). The Raman/SERS spectra offered spectral evidence for the cellular uptake of AgNPs and the subsequent change in the conformation of the most abundant component, hemoglobin (Hb), from oxyhemoglobin to deoxyhemoglobin. The spectral characterization of AgNPs’ interactions with other RBC biomarkers (membrane proteins and lipids) was impeded by the dominant Hb bands, even for non-resonant Hb conditions. CytoViva hyperspectral imaging and graphite furnace atomic absorption spectroscopy (GFAAS) served as complementary tools to effectively address the challenges related to a single excitation line (632.8 nm) and the resolution of the confocal Raman microscope (0.5–1.0 µm). CytoViva confirmed the RBC-AgNP interactions through hyperspectral signatures and facilitated the label-free localization of AgNPs extracellularly and intracellularly. Irreversible agglutination of RBCs was noted after 24 h of exposure, raising concerns about the toxicity of AgNPs of biocompatible citrate coatings. GFAAS validated the Raman/SERS results by quantifying the proportion of AgNPs absorbed by RBCs, which was significant (~48% AgNPs by mass), mostly at the membrane (60% RBCs), and size dependent (no large AgNPs or AgNP-aggregates in RBCs, after 12–24 h).

The detection of IgG class antibodies against SARS-CoV-2 nucleocapsid protein by application of nanoparticles.

Enzyme-linked immunosorbent assay (ELISA) is a widely used biochemical analytical method for the detection of a biomarker, through a specific antigen-antibody reaction. A common with ELISA is the amount of concrete biomarkers falling below the detection limit. Thus, the approach that will contribute to enhanced sensitivity of enzyme-linked immunosorbent assay is of great importance for medical practice. To address this issue, we used nanoparticles to improve the detection limit of traditional ELISA. 80 samples were used, for which the presence of IgG antibodies against SARS-CoV-2 nucleocapsid protein were already determined qualitatively. We tested the samples using an in vitro ELISA kit [SARS-CoV-2 IgG ELISA, COVG0949 (NovaTec, Leinfelden-Echterdingen, Germany)]. Additionally, we tested the same sample with the same ELISA kit but with the addition of 50 nm diameter citrate-capped silver nanoparticles. The reaction was performed, and data were calculated according to manufacturer guidelines. To measure ELISA results absorbance (optical density - OD) at 450 nm was read. Greater absorbance values have been revealed in case of silver nanoparticles application (66 cases, 82.5%, p<0.05). ELISA with application of nanoparticles classified 19 equivocal cases as positive and 3 equivocal ones as negative, 1 negative case as equivocal. Our findings suggest that nanoparticles can be used to improve the sensitivity of ELISA method and increase the detection limit. Thus, it is logical and desirable to enhance the sensitivity of ELISA method by application of nanoparticles; the approach is low cost and with a positive impact on accuracy.

Effect of post-synthesis betanin functionalized silver nanoparticles on the cellular oxidative mechanism and biofilm formation in Staphylococcus aureus

Eliciting oxidative stress and interference with biofilm formation by silver nanoparticles (AgNPs) comprise some of the postulated mechanisms of bacteria destruction. Plant extracts are commonly employed both as reducing agents and stabilizers of green-synthesized AgNPs. This yields a broad nanoparticle size distribution and unpredictable coating arising from diverse biomolecules and oxidation products in the final reaction mixture, which makes the comparison of different experiments exploiting green synthesised AgNPs as antimicrobial agents tricky. The current study synthesised citrate-capped silver nanoparticles (CtAgNPs) with a diameter of 37.9±8.6 nm functionalized via ligand exchange with betanin. Subsequently, the betanin silver nanoparticles (BtnAgNPs) ability to perturb the cellular oxidative stress defence mechanism of Staphylococcus aureus American Type Culture Collection (ATCC) 12600 and biofilm-forming properties were evaluated. Treatment with a minimum inhibitory concentration (MIC) of BtnAgNPs (12.5ppm) promoted reactive oxygen species accumulation and significantly reduced superoxide dismutase (SOD) and catalase activities. Furthermore, BtnAgNPs at sub-minimum inhibitory concentrations (SubMICs) to MIC range (0.39-12.5 ppm) inhibited the establishment of biofilms in a concentration-dependent manner. The study advocates for synthesis protocols that produce precise-sized nanoparticles followed by selective biomolecule functionalization for better antimicrobial efficacy comparative studies between AgNPs bearing different coatings in future experiments.

Citrate capped silver nanoparticles as naked-eye colorimetric sensor for sensitive and rapid detection of cysteine in biological and environmental samples

The use of citrate capped silver nanoparticles (Cit/Ag NPs) as a highly selective and fast colorimetric sensor for the determination of cysteine by UV–Vis spectrophotometric detection was described in the present work. The colorimetric recognition strategy was based on the significant change in the surface plasmon resonance (SPR) band of Cit/Ag NPs from 403 to 550 nm with cysteine. By adding cysteine to the Cit/Ag NPs solution, the color of the solution rapidly changed from yellow to red in a short time of 1 min. This is attributed to the aggregation of citrate-capped Ag NPs induced by cysteine due to the formation of the strong covalent Ag–S bond and electrostatic binding. With this strategy, a linear relationship between the A550/A403 extinction ratio and Cys concentrations was obtained in the range of 0.01–100 μM with a coefficient of determination of 0.9931 and a limit of detection of 5.1 nM. The proposed method was successfully applied for detection of cysteine in biological and environmental samples with significant recovery rates in the range of 95.5–105.1% and the relative standard deviation (RSD) lower than 5.5%.Therefore, the Cit/Ag NPs as a chemical sensor in colorimetry assay is simple, very fast, easy synthesis, highly selective and sensitive, a single-step process, and mainly cost-effective, providing a possibility to develop an analysis in real-time and an effective rapid detection way for monitoring and visualizing Cys.

Identification of milk quality and adulteration by surface-enhanced infrared absorption spectroscopy coupled to artificial neural networks using citrate-capped silver nanoislands

Milk is one of the most important multicomponent superfoods owing to its rich macronutrient composition. It requires quality control at all the production stages from the farm to the finished products. A localized surface plasmon resonance optical sensor based on a citrate-capped silver nanoparticle (Cit-AgNP)–coated glass substrate was developed. The fabrication of such sensors involved a single-step synthesis of Cit-AgNPs followed by surface modification of glass slides to be coated with the nanoparticles. The scanning electron microscope micrographs demonstrated that the nanoparticles formed monolayer islands on glass slides. The developed surface-enhanced infrared absorption spectroscopy (SEIRA) sensor was coupled to artificial neural networking (ANN) for the qualitative differentiation between cow, camel, goat, buffalo, and infants’ formula powdered milk types. Moreover, it can be used for the quantitative determination of the main milk components such as fat, casein, urea, and lactose in each milk type. The qualitative results showed that the obtained FTIR spectra of cow and buffalo milk have high similarity, whereas camel milk resembled infant formula powdered milk. The most difference in FTIR characteristics was evidenced in the case of goat milk. The developed sensor adds several advantages over the traditional techniques of milk analysis using MilkoScan™ such as less generated waste, elimination of pre-treatment steps, minimal sample volume, low operation time, and on-site analysis.Graphical abstract

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.

Citrate capped silver nanoparticles as an instantaneous colorimetric selective sensor for neomycin and thiamine in wastewater

A simple colorimetric selective detection of antibacterial and vitamin drugs has been performed using citrate capped silver nanoparticles.

Protein-Bound Uremic Toxins Quantification by a Colorimetric Sensor Based on the Oxidation of Silver Nanoparticles

This work shows a colorimetric sensor based on albumin bound to citrate-capped silver nanoparticles. The sensor capability of detecting protein-bound uremic toxins, such as indoxyl sulfate and p-cresylsulfate, is demonstrated. These uremic toxins enhance the oxidation of citrate-capped silver nanoparticles by hydrogen peroxide, affecting the localized surface plasmon resonance and allowing the proposed colorimetric sensing method. The method exhibits a linear response for indoxyl sulfate and p-cresylsulfate concentrations ranging from 15 to 100 mg/L with resolutions of 0.56 mg/L and 0.41 mg/L and expanded uncertainties for a confidence level of 95% of 17.23 mg/L and 12.55 mg/L, respectively. Limits of detection and quantification of 5.7 mg/L and 19 mg/L for indoxyl sulfate and of 3.2 mg/L and 10.7 mg/L for p-cresylsulfate were obtained for p < 0.05. These characteristics of the colorimetric method allow for a distinction between total normal and total uremic blood concentrations, which reported levels are (0.54 ± 4.00) mg/L and (37.07 ± 26.50) mg/L for indoxyl sulfate and (1.87 ± 2.31) mg/L and (23.00 ± 16.90) mg/L for p-cresylsulfate. Besides, this novel sensor significantly reduces costs of analysis and facilitates the quantification of those toxins. The interaction between albumin and citrate-capped silver nanoparticles was also investigated by Raman spectroscopy.

Optimization of localized surface plasmon resonance hot spots in surface-enhanced infrared absorption spectroscopy aluminum substrate as an optical sensor coupled to chemometric tools for the purity assay of quinary mixtures.

Surface-enhanced infrared absorption spectroscopy offers an alternative to conventional IR spectroscopy and utilizes the signal enhancement exerted by the plasmon resonance of nanostructured metal thin films. Citrate-capped silver nanoparticles were prepared in a single-step method, and their morphology was identified using transmission electron microscopy, scanning electron microscopy, ultraviolet/visible spectrophotometry, and Zetasizer. Thenanoparticles generatedwere deposited on the surface of cheap aluminum slides for different durations aiming for the selection of the best time producing a thin film, suitable to act as a lab-on-a-chip SEIRA substrate. These substrates werecoupled to partial least squares regression tools for simultaneous resolving of the quinary mixture in commercial dosage forms of bisoprolol, perindopril, bisoprolol acid degradation product, bisoprolol alkali degradation product, and perindoprilat in concentration ranges of 15-75, 60-300, 15-55, 12-60, and 20-80μg/mL with limits of detection values of 0.69, 3.43, 0.97, 1.25, and 1.09μg/mL, respectively. Overall, we could demostrate that thelocalized surface plasmon resonance sensor coupled to chemometrics providescheap, simple, selective, multiplex, rapid, and molecular specific procedures for impurity detection, which would be beneficial in many applications for quality control and quality accuracy of active pharmaceutical ingredients.

Development a simple and sensitive method for determination low trace of nickel by local surface plasmon resonance of citrate capped silver nanoparticles

Nickel is a toxic transition metal which can create serious problems in health of humans and wildlife. Thus determination of nickel in environmental samples like waters is important and inevitable. In this research a simple and sensitive method for determination of nickel in water was described based on aggregation of citrate capped silver nanoparticles. Silver nanoparticles were prepared by reduction of silver nitrate with sodium borohydride. Cefixime was as chelating agent in the assay and when nickel was added to the mixture of citrate capped silver nanoparticles and cefixime, color of citrate capped silver nanoparticles changed from light yellow to red that depend on Ni2+ concentration. As a result of aggregation, local surface plasmon resonance (LSPR) band of silver nanoparticles around 395 nm decreased and a new peak appeared in 550 nm. Control experiments with 10 other ions carried out and did not a distinct change in color or spectrum. Under optimized conditions, linear relationship between Ni2+ concentrations and the absorbance ratio of A550/A395 and limit of detection were found in the range of 2.70 µmol L-1 to 17.10 µmol L-1 and 0.80 µmol L-1, respectively. The method was applied in tap and well waters that indicate the colorimetric method has acceptable accuracy and good stability.

Study of the Stability of Citrate Capped AgNPs in Several Environmental Water Matrices by Asymmetrical Flow Field Flow Fractionation.

Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible behavior in the environment for short times since mixturing (up to 180 min). Ultrapure (UPW), bottled (BW1, BW2), tap (TW), transitional (TrW) and sea water (SW) matrices were assayed. Observations were compatible with the aggregation of AgNPs, a change in the plasmon band and a size growth with time were done. Fractograms showed different evolution fingerprints in the function of the waters and batches. The aggregation rate order was BW2, SW, TrW, BW1 and TW, being BW2 the lowest and TW the highest. NP aggregation can be induced by increasing the salt concentration of the medium, however transitional and sea waters did not follow the rule. Both matrices presented a lower aggregation rate in comparison with other aqueous matrices with much lower ionic strength (BW1 and TW), which can be explained by the potential presence of dissolved organic matter and/or the high concentration of halides providing their stabilization and passivation, respectively. AF4 provides relevant information with respect to static DLS and UV-Vis Spectroscopy showing that at least two populations of aggregates with different sizes between them, depending on both, the mixture time for a given matrix and type of water matrix for the same time.

Are Smaller Nanoparticles Always Better? Understanding the Biological Effect of Size-Dependent Silver Nanoparticle Aggregation Under Biorelevant Conditions.

PurposeSilver nanoparticles (AgNPs) are one of the most commonly investigated nanomaterials, especially due to their biomedical applications. However, their excellent cytotoxic and antimicrobial activity is often compromised in biological media due to nanoparticle aggregation. In this work, the aggregation behavior and the related biological activity of three different samples of citrate capped silver nanoparticles, with mean diameters of 10, 20, and 50 nm, respectively, were examined.MethodsFollowing nanoparticle synthesis and characterization with transmission electron microscopy, their aggregation behavior under various pH values, NaCl, glucose, and glutamine concentrations, furthermore in cell culture medium components such as Dulbecco’s Modified Eagle’s Medium and fetal bovine serum, was assessed through dynamic light scattering and ultraviolet-visible spectroscopy.ResultsThe results indicated that acidic pH and physiological electrolyte content universally induce micron-scale aggregation, which can be mediated by biomolecular corona formation. Remarkably, larger particles demonstrated higher resistance against external influences than smaller counterparts. In vitro cytotoxicity and antimicrobial assays were performed by treating cells with nanoparticulate aggregates in differing stages of aggregation.ConclusionOur results revealed a profound association between colloidal stability and toxicity of AgNPs, as extreme aggregation led to the complete loss of biological activity. The higher degree of aggregation resistance observed for larger particles had a significant impact on the in vitro toxicity, since such samples retained more of their activity against microbes and mammalian cells. These findings lead to the conclusion that aiming for the smallest possible nanoparticles might not be the best course of action, despite the general standpoint of the relevant literature.

Chitosan/heparin blends in ionic liquid produce polyelectrolyte complexes that quickly adsorb citrate-capped silver nanoparticles, forming bactericidal composites

We present chitosan (CHT)/heparin (HP) polyelectrolyte complexes (PECs) that quickly adsorb citrate-capped silver nanoparticles (AgNPs). CHT/HP blends in ionic liquid ([HMIm][HSO4]) form durable PECs after precipitation in water. CHT/HP PECs have positive Zeta potentials (higher than +20 mV). They adsorb citrate-capped AgNPs (Zeta potential of - 12.25 mV) synthesized from Turkevich's method. PEC/AgNPs composites are characterized by spectroscopic, thermal, and microscopy analyses. AgNPs on the PEC surfaces are confirmed by transmission electron microscopy. PECs adsorb AgNPs from aqueous suspensions, achieving ≈ 95% of removal (17.18 μg of AgNPs per milligram of PEC) after only 10 min. The pseudo-second-order kinetic model adjusted well to the experimental data. The PECs release approximately 11.80 μg/mg Ag+ (66%) compared to the initial adsorbed AgNPs content (17.18 μg/mg) after 7200 min at pH 2.0. The PECs present low swelling degrees (between 130 and 150%), supporting high stability in water. PEC/AgNPs composites promote significant bactericidal activity toward Staphylococcus aureus and Escherichia coli between 0.25 and 0.5 mg/mL. This study shows a new strategy to create hybrid polysaccharide/AgNPs composites. PECs can stabilize the AgNPs and release Ag+ ions, supporting antimicrobial materials.

Spectrophotometric determination of buspirone HCl and doxazosin mesylate using citrate-capped silver nanoparticles

Spectrophotometric determination of buspirone HCl and doxazosin mesylate using citrate-capped silver nanoparticles