Search Results (284)

Background/Objectives: Hydrogels infused with silver nanoparticles (AgNPs) are widely used for their antibacterial properties, yet their stability, specifically upon contact with solid growth media (agar), remains poorly explored. This study compared two hydrogel matrices, anionic Carbopol 934 and non-ionic Pluronic F127, incorporating AgNPs of three different sizes. The evaluation focused on colloidal stability and antibacterial efficacy against Gram-positive and Gram-negative bacteria. Methods: In this study AgNPs (~20, ~55, and ~65 nm) were synthesised via a wet-chemical method and characterised by UV–visible spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). AgNPs were incorporated into Carbopol 934 and Pluronic F127 hydrogel matrices. Colloidal stability was monitored over four months of storage and upon contact with tryptic soy agar (TSA). Antibacterial activity was assessed using agar diffusion assays. Results: Showed that both hydrogel systems maintained AgNP stability during storage, comparable to aqueous suspensions. However, upon contact with TSA, aggregation of Carbopol–AgNP hydrogels occurred, whereas Pluronic–AgNP hydrogels remained stable. In antibacterial assays, both hydrogels produced larger zones of inhibition (ZOI) than AgNP suspensions against Gram-negative bacteria (E. coli, P. aeruginosa), with Carbopol–AgNP hydrogels demonstrating superior efficacy in an inverse size-dependent manner. Against Gram-positive bacteria (S. aureus, S. epidermidis), Pluronic–AgNP hydrogels initially showed larger ZOIs due to the polymer’s intrinsic antibacterial activity. However, after correcting for this baseline, Carbopol–AgNP hydrogels exhibited superior net efficacy, with S. epidermidis showing greater susceptibility than S. aureus. Conclusions: While both Carbopol 934 and Pluronic F127 stabilise AgNPs during storage, the matrix type significantly influences behaviour at the biological interface. Carbopol–AgNP hydrogels aggregate upon contact with solid agar yet deliver superior, size-dependent antibacterial activity compared to the stable but less potent Pluronic systems. Full article

Green-synthesized metal nanoparticles are increasingly investigated for their antioxidative, antimicrobial, and stress-protective properties as eco-friendly and cost-effective alternatives to conventional chemical synthesis. Although agri-food wastes represent biomolecule-rich and sustainable resources, they remain less explored as biological matrices for green metal nanoparticle synthesis compared with plant and microbial extracts. The aim of this study was to optimize the synthesis and evaluate the bioactivity of silver nanoparticles derived from bergamot pomace, a polyphenol-rich agri-food waste. Synthesis parameters, including extract concentration, pH, extract-to-metal ratio, temperature, and reaction time, were optimized, and the nanoparticles were characterized by UV–Vis spectroscopy, dynamic light scattering, zeta potential analysis, and electron microscopy (TEM, STEM). ATR-FTIR and proteomic analyses were employed to investigate the molecular mechanisms involved in nanoparticle reduction, capping, and stabilization. The bergamot pomace-based silver nanoparticles exhibited a surface plasmon resonance peak at 430 nm, spherical morphology, good colloidal stability, and average diameters of 15–20 nm, without irreversible aggregation. A putative synthesis mechanism was proposed, involving Ag⁺ bioreduction mediated by polyphenols, ascorbic acid, and oxidoreductase-associated proteins, followed by stabilization through protein corona formation. Seed nanopriming assays on tomato and lettuce, together with in vitro antimicrobial tests against Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria, demonstrated phytostimulatory and antimicrobial effects at very low nanoparticle concentrations. Overall, this study highlights bergamot pomace as a valuable resource for green silver nanoparticle synthesis, supporting its applicability in sustainable agriculture. Full article

This review work highlights the eco-friendly synthesis and application of biomass-derived silica gel (SG)-supported metallic nanoparticles (MNPs), primarily focusing on their potential for sustainable drinking water disinfection and utilizing abundant biomass waste, such as agricultural residues, to extract silica through processes like pyrolysis, chemical treatment, or hydrothermal methods, creating a versatile support with high surface area, porosity, and biocompatibility. MNPs, notably silver, copper, zinc, etc., are immobilized onto these silica frameworks via green synthesis techniques, including plant extract-mediated methods, chemical reduction, and sol–gel processes, resulting in nanocomposites with controlled size, distribution, and enhanced stability. These MNPs are known for their potent antimicrobial activity, capable of inactivating a broad spectrum of pathogens like Staphylococcus aureus and Escherichia coli. Silica gel supports mitigating issues such as nanoparticle aggregation and leaching, thus improving reusability and environmental safety. The synthesis parameters of nanoparticle size, concentration, surface chemistry, and contact time directly influence disinfection efficacy, while biomass-based supports offer advantages including cost-effectiveness, environmentally benign production, and minimal pollution. Incorporating biomass-derived silica gel-supported AgNPs into water treatment systems presents a promising, sustainable alternative to conventional chemical methods like chlorination and ultraviolet (UV) irradiation, which can generate hazardous byproducts. These nanocomposites demonstrate significant potential in resource-limited settings due to their high surface area, porosity, and reusability, although concerns such as nanoparticle leaching, toxicity, scalability, and environmental impact warrant further investigation. Overall, biomass-supported MNPs represent an innovative frontier in water purification technology, aligning with principles of green chemistry and sustainability. Emphasizing the importance of optimizing synthesis protocols and assessing long-term safety, this review underscores their capacity to advance eco-friendly water disinfection strategies that can improve public health and promote sustainable water management practices worldwide. Full article

Silver nanoparticles were biosynthesized using the culture supernatant of Staphylococcus sp. YRA, a strain isolated from Colombian mining sediments. Synthesis was optimized at 1 mM AgNO₃, pH 7, 40 °C and 7 μg/mL extract, producing spherical, protein-capped AgNPs with primary sizes in the tens-of-nanometers range (~35–90 nm by SEM), while DLS indicated larger hydrodynamic diameters (~250–320 nm) consistent with aggregation in suspension (ζ-potential −16.6 mV). These nanoparticles remained stable over 6 months. Characterization by UV–Vis, SEM, AFM, EDS and FTIR confirmed extracellular protein-mediated reduction and capping. The AgNPs showed antibacterial activity against multidrug-resistant clinical isolates (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella bongori, Enterococcus spp.), with inhibition zones of 8–16 mm at 400–1000 μg/mL. Biofilm formation was reduced by >50% at 700 μg/mL in both Gram-positive and Gram-negative strains. In Phaseolus vulgaris (P. vulgaris), low concentrations (5–100 μg/mL) increased growth and chlorophyll content, while 500 μg/mL caused moderate inhibition. FTIR analysis identified amide and thiol groups from bacterial enzymes as capping agents. These results suggest Staphylococcus sp. YRA as a bacterial platform for AgNPs production with antibiofilm activity against MDR pathogens and acceptable phytotoxicity profile for potential applications. Full article

The accurate monitoring and dynamic analysis of metal ions are of considerable practical significance in environmental toxicology and life sciences. Colorimetric analysis and surface-enhanced Raman scattering (SERS) sensing technologies, utilizing the aggregation effect of gold and silver nanoparticles (Au/Ag NPs), have emerged as prominent methods for rapid metal ion detection. While sharing a common plasmonic basis, these two techniques serve distinct yet complementary analytical roles: colorimetric assays offer rapid, instrument-free visual screening ideal for point-of-care testing (POCT), whereas SERS provides superior sensitivity and structural fingerprinting for precise quantification in complex matrices. Furthermore, the synergistic integration of these modalities facilitates the development of dual-mode sensing platforms, enabling mutual signal verification for enhanced reliability. This article evaluates contemporary optical sensing methodologies utilizing aggregation effects and their advancements in the detection of diverse metal ions. It comprehensively outlines methodological advancements from nanomaterial fabrication to signal transduction, encompassing approaches such as biomass-mediated green synthesis and functionalization, targeted surface ligand engineering, digital readout systems utilizing intelligent algorithms, and multimodal synergistic sensing. Recent studies demonstrate that these techniques have attained trace-level identification of target ions regarding analytical efficacy, with detection limits generally conforming to or beyond applicable environmental and health safety regulations. Moreover, pertinent research has enhanced detection linear ranges, anti-interference properties, and adaptability for POCT, validating the usefulness and developmental prospects of this technology for analysis in complicated matrices. Full article

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the influence of synthesis conditions on phase composition, morphology, and antimicrobial efficiency. The obtained powders were characterized by ATR-FTIR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD analysis revealed that drying at 120 °C led to oxide-rich systems dominated by Ag₂O, with minor contributions from metallic Ag and carbonate species, while calcination at 550 °C resulted in complete phase transformation into highly crystalline metallic silver. SEM observations demonstrated that precursor concentration and synthesis assistance strongly affect particle size, aggregation degree, and surface morphology. Ultrasound- and microwave-assisted synthesis promoted finer crystallite sizes and more homogeneous particle distributions compared to non-assisted routes. The antibacterial activity was evaluated against Escherichia coli (Gram-negative) and Clostridium perfringens (Gram-positive, anaerobic, spore-forming). Oxide-rich samples, particularly Ox.Ag/2 M, exhibited rapid and complete bacterial inactivation within 30 min, while metallic silver samples showed time-dependent antibacterial behavior, achieving full inhibition after 4 h. The results demonstrate that antibacterial efficiency is governed by a synergistic interplay between silver oxidation state, nanoscale morphology, and surface reactivity. These findings highlight the potential of tailored silver-based nanomaterials as effective antibacterial materials for biomedical, food safety, and environmental applications. Full article

Valsartan (Val)—a lipophilic non-peptide angiotensin II type 1 receptor antagonist—is highly effective against hypertension and displaying limited solubility in water (3.08 μg/mL), thereby resulting in low oral bioavailability (23%). The limited water solubility of antihypertensive drugs can pose a challenge, particularly for rapid and precise administration. Herein, we synthesize and characterize valsartan-containing silver nanoparticles (Val-AgNPs) using Mangifera indica leaf extracts. The physicochemical, structural, thermal, and pharmacological properties of these nano-conjugates were established through various analytical and structural tools. The spectral shifts in both UV-visible and FTIR analyses indicate a successful interaction between the valsartan molecule and the silver nanoparticles. The resulting nano-conjugates are spherical and within the size range of 30–60 nm as revealed in scanning electron-EDS and atomic force micrographs. The log-normal distribution of valsartan-loaded nanoparticles, with a size range of 30 to 60 nm and a mode of 54 nm, indicates a narrow, monodisperse, and highly uniform particle size distribution. This is a favorable characteristic for drug delivery systems, as it leads to enhanced bioavailability and a consistent performance. Dynamic Light Scattering (DLS) analysis of the Val-AgNPs indicates a polydisperse sample with a tendency toward aggregation, resulting in larger effective sizes in the suspension compared to individual nanoparticles. The accompanying decrease in zeta potential (to −19.5 mV) and conductivity further supports the idea that the surface chemistry and stability of the nanoparticles changed after conjugation. Differential scanning calorimetry (DSC) demonstrated the melting onset of the valsartan component at 113.99 °C. The size-dependent densification of the silver nanoparticles at 286.24 °C correspond to a size range of 40–60 nm, showing a significant melting point depression compared to bulk silver due to nanoscale effects. The shift in Rf for pure valsartan to Val-AgNPs suggests that the interaction with the AgNPs alters the compound’s overall polarity and/or its interaction with the stationary phase, complimented in HPTLC and HPLC analysis. The stability and offloading behavior of Val-AgNPs was observed at pH 6–10 and in 40% and 80% MeOH. In addition, Val-AgNPs did not reveal hemolysis or significant alterations in blood cell indices, confirming the safety of the nano-conjugates for biological application. In conclusion, these findings provide a comprehensive characterization of Val-AgNPs, highlighting their potential for improved drug delivery applications. Full article

The characterization and biomedical modification of bentonite clays from the Kalzhat deposit (Kzh), which is situated in Kazakhstan’s Zhetysu region, are the main objectives of this work. In order to improve the raw material’s structural qualities, the montmorillonite fraction was enriched, and coarse impurities were eliminated using the Salo method. The presence of meso- and micropores that guarantee high dispersity and specific surface area, as well as the prevalence of montmorillonite and kaolinite, was all confirmed by physicochemical analysis. Particle size measurements indicated finely dispersed structures with a propensity to aggregate, whereas thermal analysis demonstrated resilience under heating. After effective functionalization with silver nanoparticles, a porous hybrid system with improved surface reactivity was produced. These enhancements demonstrate the modified bentonite’s usefulness as a multifunctional carrier for the immobilization and controlled release of pharmaceuticals, with potential uses in drug delivery systems, antimicrobial coatings, and wound-healing materials. The material has potential use in sorption and environmental protection technologies in addition to its biomedical application. Overall, Kzh’s structural and functional performance is greatly improved by the combination of purification and functionalization with silver nanoparticles, highlighting its promise as a useful element in the development of next-generation polymer–composite systems. Full article

Thanks to both endogenous and exogenous antioxidants (AOs), the antioxidant defense system ensures redox homeostasis, which is crucial for protecting the body from oxidative stress and maintaining overall health. The food industry also exploits the antioxidant properties to prevent or delay the oxidation of other molecules during processing and storage. There are many classical methods for assessing antioxidant capacity/activity, which are based on mechanisms such as hydrogen atom transfer (HAT), single electron transfer (SET), electron transfer with proton conjugation (HAT/SET mixed mode assays) or the chelation of selected transition metal ions (e.g., Fe²⁺ or Cu¹⁺). The antioxidant capacity (AOxC) index value can be expressed in terms of standard AOs (e.g., Trolox or ascorbic acid) equivalents, enabling different products to be compared. However, there is currently no standardized method for measuring AOxC. Nanoparticle sensors offer a new approach to assessing antioxidant status and can be used to analyze environmental samples, plant extracts, foodstuffs, dietary supplements and clinical samples. This review summarizes the available information on nanoparticle sensors as tools for assessing antioxidant status. Particular attention has been paid to nanoparticles (with a size of less than 100 nm), including silver (AgNPs), gold (AuNPs), cerium oxide (CeONPs) and other metal oxide nanoparticles, as well as nanozymes. Nanozymes belong to an advanced class of nanomaterials that mimic natural enzymes due to their catalytic properties and constitute a novel signal transduction strategy in colorimetric and absorption sensors based on the localized surface plasmon resonance (LSPR) band. Other potential AOxC sensors include quantum dots (QDs, <10 nm), which are particularly useful for the sensitive detection of specific antioxidants (e.g., GSH, AA and baicalein) and can achieve very good limits of detection (LOD). QDs and metallic nanoparticles (MNPs) operate on different principles to evaluate AOxC. MNPs rely on optical changes resulting from LSPR, which are monitored as changes in color or absorbance during synthesis, growth or aggregation. QDs, on the other hand, primarily utilize changes in fluorescence. This review aims to demonstrate that, thanks to its simplicity, speed, small sample volumes and relatively inexpensive instrumentation, nanoparticle-based AOxC assessment is a useful alternative to classical approaches and can be tailored to the desired aim and analytes. Full article

In this work, a stable silver nanoparticle (AgNPs) with strong surface plasmon resonance absorption (Abs) signals was synthesized using light-wave technology. In the absence of aptamers, AgNPs can aggregate in a given concentration of salt solution, resulting in significant changes in color. After adding the aptamer (Apt), it was observed that the aptamer can coordinate with AgNPs and adsorb on the surface of AgNPs, thereby maintaining the stability of the nanosol. In the presence of mercury ions (Hg²⁺), their high-affinity reaction with the aptamer compromised the latter’s protective effect on AgNPs, causing the color of the system to change again. Based on this, a simple and rapid new Abs method for detecting Hg²⁺ can be constructed. The linear range was 2.5 × 10⁻³–10.00 μmol/L, and the detection limit (DL) of the system was 2.03 nmol/L. Full article

Hexaconazole, a triazole-class fungicide, demonstrates broad-spectrum protective and therapeutic activity against fungal pathogens, particularly those from Basidiomycota and Ascomycota, such as brown spot and powdery mildew. Despite its efficacy in controlling Actinidia brown spot disease in kiwifruit, excessive hexaconazole residues pose significant health risks due to its high toxicity. To address this challenge, a rapid analytical method for detecting hexaconazole residues in kiwifruit was developed using surface-enhanced Raman spectroscopy (SERS). The methodology employed silver colloid (C-AgNPs) as the active substrate and 1 mol/L NaCl as the aggregation agent, optimized through systematic testing, resulting in an optimal volume ratio of 400:225 between C-AgNPs and hexaconazole solution and a sequential mixing order of C-AgNPs + NaCl + Hexaconazole, followed by a 20 min incubation period. The characteristic Raman peak at 1584 cm⁻¹ was identified as the spectral signature for hexaconazole quantification. Analytical validation revealed a linear detection range of 0.25–2.25 mg/L (R² = 0.9870), precision with a relative standard deviation (RSD) of 1.7%, and an average recovery rate of 88.40–105.50%, confirming the method’s robustness. This approach enables rapid, non-destructive analysis with minimal sample pretreatment, offering high sensitivity and stability. This method demonstrates great potential for detecting hexaconazole residues in agricultural products. Full article

Gold–silver nanoshells (GS-NSs) are hollow spherical nanoparticles with an alloyed Ag-Au shell. GS-NSs exhibit a tunable localized surface plasmon resonance (LSPR) in the visible to near-IR wavelengths as a function of composition and shell thickness and offer greater stability across pH ranges compared to other metal nanoparticles. These properties make GS-NSs promising materials for diagnostics, photothermal therapy, and photocatalysis. However, current research has explored GS-NSs only in aqueous systems, since they immediately aggregate in other solvents, limiting their utility. This paper provides an in-depth study of the choice and effect of non-thiol ligands on the stability and phase-transfer of GS-NSs from aqueous to non-aqueous solvents, such as ethylene glycol, tetrahydrofuran, dichloromethane, and toluene. Ligand exchange for functionalization of GS-NSs was performed with Triton X-100 (TX100), sodium stearate (NaSt), polyvinylpyrrolidone (PVP), and hydroxypropyl cellulose (HPC), prior to phase-transfer. The nanoparticles were phase-transferred to the non-aqueous solvents, and the stability of the colloids in the various solvents before and after functionalization was recorded with UV–visible spectroscopy, dynamic light scattering (DLS), zeta potential (ζ), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The study was also extended to include silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) to evaluate broad-range applicability. Among the ligands studied, HPC functionalization demonstrated the widest range of phase-transfer stability across 21 days for all three particle systems studied. UV–vis spectroscopy demonstrated sustained LSPR integrity after HPC functionalization in EG, THF, and DCM. SEM, TEM, and hydrodynamic size measurements by DLS further confirmed no aggregation in EG, THF, and DCM but suggested possible twinning or clustering in the solution. Overall, this work successfully identified non-toxic alternatives to expand the LSPR stability of citrate-synthesized metal nanoparticles in organic solvents. Full article

Recently, interest in multifunctional materials has increased; therefore, we developed a system that combines biocompatibility, gradient changing, and antibacterial properties. We aim to combine these properties in the development of a biomimetic system based on hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HA) by incorporating silver nanoparticles (Ag NPs) into HA matrices, leveraging their antimicrobial effects, while also exploring their role as drug-release triggers (which absorb infrared (IR) light of 808–960 nm, convert it to heat energy to induce localized heating, and cause a structural leak for drug release) to unmodified HA, which cannot be activated by IR in significant amounts. Limited diffusion aggregation is used to form HA (enhanced with glycine or produced with different outer electrolytes) by diffusing calcium phosphates through Na₂HPO₄-agar. The composite is then packed with tetracycline and a deposition of polyelectrolytes (PE). The combination of polydiallyldimethylammonium chloride (PDADMAC) and heparin forms a robust PE. Infrared light (808 nm, 1.4 mW/cm²) was utilized as energy source for non-invasive and on-demand drug release. Physical and chemical characterization of HA was carried out. Glycine did not affect the p-factor of the resulting rings, which is equal to ca. 1.00. NIR increased release rates 2.1-fold (k = 39.21 compared to 18.22). High glycine concentrations reduce HA crystallinity (94 to 30%), result in a 12.5% increased drug-loading capacity, and increase solubility (5× control). NIR reduced the Korsmeyer–Peppas release exponent (n) from 0.42 (Fickian) to 0.11 (PE-coated HA-Ag), confirming the photothermal disruption of diffusion barriers due to the presence of silver nanoparticle peaks in the composition. Full article

The synthesis of silver nanoparticles (AgNPs) using sustainable and non-toxic methods has become an important research focus due to the limitations of conventional chemical approaches, which often involve hazardous reagents and produce unstable products. In particular, the effects of reaction conditions on the quality and stability of AgNPs obtained via green synthesis remain insufficiently understood. This study addresses this gap by examining the influence of pH and temperature on the synthesis of AgNPs using Rosmarinus officinalis extract as both reducing and stabilizing agents. UV-vis spectroscopy and TEM analysis revealed that optimal conditions for producing uniform, stable, and spherical AgNPs were achieved at pH 8, with a narrow size distribution (~17.5 nm). At extreme pH values (≤3 or ≥13), nanoparticle formation was hindered by aggregation or precipitation, while elevated temperatures mainly accelerated reaction without altering particle morphology. HRTEM and SAED confirmed the crystalline face-centered cubic structure, and colloids synthesized at pH 8 showed excellent stability over 30 days. Overall, the results demonstrate that precise pH control is critical for obtaining high-quality AgNPs via a simple, scalable, and environmentally friendly approach. Their stability and homogeneous size highlight potential applications in biomedicine, food packaging, and sensing, where reproducibility and long-term functionality are essential. Full article

The growing accumulation of non-biodegradable petrochemical plastics and increasing food waste present urgent environmental and public health challenges. This study addresses both issues by developing biodegradable food packaging films from agar and starch, enhanced with antimicrobial properties by incorporating silver nanoparticles. The innovation of this work is the synthesis of novel agar–starch–silver nanoparticle coatings, where the contained nanoparticles were produced via green methods using two agro-industrial by-products of Greek olive oil production—olive stone extract and olive mill wastewater—as reducing agents. The morphology of the novel coatings was confirmed using transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, revealing nanoscale particles with variable sizes. Additional film characterization was performed through Fourier-transform infrared spectroscopy, scanning electron microscopy coupled with energy-dispersive spectroscopy, and surface profilometry. Infrared spectroscopy analysis suggested the presence of functional groups responsible for nanoparticle stabilization, while energy-dispersive X-ray spectroscopy revealed silver aggregation in both olive stone extract and olive mill wastewater-derived films. Profilometry showed that films with olive mill wastewater-based nanoparticles had a rougher surface than those synthesized from olive stone extract. Antibacterial efficacy was tested against Escherichia coli (Gram-negative) and Staphylococcus epidermidis (Gram-positive) using a spot-on-film assay with high (10⁶ CFU/film) and low (10³ CFU/film) bacterial loads. After 72 h of incubation at 4 °C, both film types showed strong antibacterial activity at high bacterial concentrations, demonstrating their potential for active food packaging. These findings highlight a promising approach to sustainable food packaging within the circular economy, utilizing agricultural waste to create biodegradable materials with effective antimicrobial functionality. Full article