Stabilized Gold Nanoparticles Research Articles

Stability and SERS signal strength of laser-generated gold, silver, and bimetallic nanoparticles at different KCl concentrations

Noble metal nanoparticles, specifically gold and silver, are extensively utilized in sensors, catalysts, surface-enhanced Raman scattering (SERS), and optical-electronic components due to their unique localized surface plasmon resonance (LSPR) properties. The production of these nanoparticles involves various methods, but among the environmentally friendly approaches, laser ablation stands out as it eliminates the need for toxic chemicals during purification. However, nanoparticle aggregation poses a challenge in laser ablation, necessitating the addition of extra materials that contaminate the otherwise clean process. In this study, we investigate the effectiveness of a biocompatible material, potassium chloride (KCl), in preventing particle aggregation. Although salt is known to trigger aggregation, we observed that certain concentrations of KCl can slow down this process. Over an eight-week period, we examined the aggregation rate, extinction behavior, and stability of gold, silver, and hybrid nanoparticles generated in different KCl concentrations. Extinction spectra, SEM images, SERS signal strength, and zeta potential were analyzed. Our results demonstrate that laser ablation in water and salt solutions yields nanoparticles with a spherical shape and a negative zeta potential. Importantly, we identified the optimal concentration of potassium chloride salt that maintains solution stability and SERS signal strength. Adsorbed chloride ions on silver nanoparticles were evidenced by low-frequency SERS band near 242 cm−1. A better understanding of the effect of KCl concentration on the properties of noble metal nanoparticles can lead to improved generation protocols and the development of tailored nanoparticle systems with enhanced stability and SERS activity.

Visualization and quantitative detection of foodborne Salmonella Typhimurium by functionalizing cysteamine (CS) stabilized gold nanoparticles (CS-AuNPs@phage)

Visualization and quantitative detection of foodborne Salmonella Typhimurium by functionalizing cysteamine (CS) stabilized gold nanoparticles (CS-AuNPs@phage)

Enhanced Stability of Gold Nanoparticles with Thioalkylated Carboxyl-Terminated Ligands for Applications in Biosensing

Enhanced Stability of Gold Nanoparticles with Thioalkylated Carboxyl-Terminated Ligands for Applications in Biosensing

One-step synthesis of stable gold nanoparticles using Aspergillus austwickii CO1 and its application in colorimetric detection of Mg2+ ion

One-step synthesis of stable gold nanoparticles using Aspergillus austwickii CO1 and its application in colorimetric detection of Mg2+ ion

Nanoformulation of dasatinib cannot overcome therapy resistance of pancreatic cancer cells with low LYN kinase expression.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most difficult to treat tumors. The Src (sarcoma) inhibitor dasatinib (DASA) has shown promising efficacy in preclinical studies of PDAC. However, clinical confirmation could not be achieved. Overall, our aim was to deliver arguments for the possible reinitiating clinical testing of this compound in a biomarker-stratifying therapy trial for PDAC patients. We tested if the nanofunctionalization of DASA can increase the drug efficacy and whether certain Src members can function as clinical predictive biomarkers. Methods include manufacturing of poly(vinyl alcohol) stabilized gold nanoparticles and their drug loading, dynamic light scattering, transmission electron microscopy, thermogravimetric analysis, Zeta potential measurement, sterile human cell culture, cell growth quantification, accessing and evaluating transcriptome and clinical data from molecular tumor dataset TCGA, as well as various statistical analyses. We generated homo-dispersed nanofunctionalized DASA as an AuNP@PVA-DASA conjugate. The composite did not enhance the anti-growth effect of DASA on PDAC cell lines. The cell model with high LYN expression showed the strongest response to the therapy. We confirm deregulated Src kinetome activity as a prevalent feature of PDAC by revealing mRNA levels associated with higher malignancy grade of tumors. BLK (B lymphocyte kinase) expression predicts shorter overall survival of diabetic PDAC patients. Nanofunctionalization of DASA needs further improvement to overcome the therapy resistance of PDAC. LYN mRNA is augmented in tumors with higher malignancy and can serve as a predictive biomarker for the therapy resistance of PDAC cells against DASA. Studying the biological roles of BLK might help to identify underlying molecular mechanisms associated with PDAC in diabetic patients.

Nanostructured systems based on pluronics to carry gold nanoparticles and methylene blue aiming for multimodal therapy

The rise of multidrug-resistant microorganisms has become a cause of concern in the biomedical field. In this sense, this study focuses on the development of an effective treatment for infectious diseases mediated by Multimodal Therapy, combining Photodynamic Therapy (PDT), and Photothermal Therapy (PTT). The system involves the synthesis and stabilization of gold nanoparticles (AuNPs) in Pluronic® micelles of F-127 and P-84, combined with the Methylene Blue (MB) aiming effects against microorganisms. It is noteworthy that the AuNPs were synthesized in situ in the copolymer using the solid dispersion technique. These copolymers were strategically chosen for evaluation purposes with our study involving P-123 previously published in this journal. Thus, the effect of the length of the PEO and PPO blocks can be delineated concerning the synthesis of AuNPs. In this case, copolymer F127 has PPO blocks identical to P-123 while P-84 has PEO blocks compatible with P-123. Characterization of the formulations included electronic absorption spectroscopy, dynamic light scattering, and transmission electron microscopy. Fluorescence quenching studies by Stern Volmer plots indicated the location of the MB in the hydrophilic corona of the micelles. In general, was verified that reducing the PEO/PPO ratio favors the formation of AuNPs, possibly due to the greater number of reducing sites per unit mass of the polymer. The formulations remained stable for at least 15 days, and photothermal studies showed a temperature increase of at least 11 °C. The photothermal effect proved reversible after three heating–cooling cycles, revealing a synergy between MB and AuNPs in heat generation, hindered by increased irradiance and rapid photobleaching of MB. The in vitro susceptibility tests with Candida albicans and Staphylococcus aureus demonstrated effective inhibition of the microorganisms. The result shows that AuNPs for itself do not affect the fungal/bacteria lineage. However, the MB/AuNPs combination samples, showed excellent fungal and bacterial inhibition at low drug concentrations.

Highly stable and efficient gold nanoparticles films facilitated by thiourea for catalytic reduction of nitrophenol in water

Water pollution from nitrophenol, a common nitrogen-containing aromatic pollutant, is becoming increasingly significant. Making the conversion of nitrophenol to the less toxic and more easily biodegradable aminophenol is a promising strategy to treat industrial wastewater. A simple and efficient method for treating nitrophenol was investigated using gold nanoparticles (AuNPs) with thiourea and fabricating AuNPs films via filtration for the first time. The prepared AuNPs film with nanoporous structure exhibits good structural stability and excellent catalytic activity. The results show that the optimal concentration of adding thiourea is 20 μg/mL, and the optimal concentration of adding NaBH4 is 1000 mM. After treatment with 20.0 μg/mL thiourea, the prepared AuNPs film catalyzes the degradation of 1.0 mM 2-nitrophenol to 2-aminophenol in just 150 sec. The AuNPs film provides a high density of active sites at the interface, and its stable nanoporous structure brings the substrate nitrophenol closer to the active center, thus enhancing the efficiency of catalytic reduction. Besides, the AuNPs films treated with thiourea still maintained good catalytic performance after seven cycles of catalysis and the catalytic efficiency is still as high as 90%. The thiourea-treated AuNPs film sets a precedent for the innovation of novel catalysts that is a very promising industrial strategy for reducing nitrophenol to aminophenol, offering significant economic advantages.

Effect of Thermo- and pH-Sensitive Block Copolymer Structure and Composition on the Synthesis and Stabilization of Gold Nanoparticles.

Homopolymers of poly[N-(2-(diethylamino)ethyl) acrylamide] exhibit the ability to adsorb onto the surface of preformed or growing gold nanoparticles. The resulting hybrid materials possess a pH and thermo-sensitive nature. Consequently, their optical properties can be modulated by manipulating either the temperature or the pH. Moreover, introducing monomers based on poly(N-isopropyl acrylamide) into block or random statistical polymers enables further modulation of the thermosensitive properties. These copolymers, employed for the in-situ synthesis and/or stabilization of gold nanoparticles, lead to hybrid materials whose properties and/or particle size depend on the polymer composition and microstructure: statistical polymers emerge as superior stabilizing agents compared to their block counterparts at a constant composition.

Role of SiO2 in tailoring stability and nonlinear optical behaviour of gold nanoparticles in glass

In the present work, a new approach is introduced to mitigate the loss of gold nanoparticles while preparing the glass through the traditional melt-quench technique. The role of refractory material i.e. SiO2 in loss reduction is studied by comparing the results obtained for bismuth borate (40Bi2O3:60B2O3) and borosilicate (40Bi2O3:40B2O3:20SiO2) glasses containing gold nanoparticles of different sizes (10 nm, 40 nm and 100 nm). The particle density and thermal stability obtained from FESEM and DTA, respectively, increase considerably with the presence of SiO2 as one of the components of glass composition. The nonlinear optical behaviour of both systems in non-resonant regions has been obtained using the Z-scan technique. In addition, the suitability of the prepared glasses for optical limiting and switching applications has been analysed.

Gold nanoparticle-based selective and efficient spectrophotometric assay for the insecticidemethamidophos.

Areliable, rapid, and inexpensive nano-sized chemosensor is presentedfor methamidophos (MET)-an insecticide. Poly(lactic acid) (PLA)-stabilized gold nanoparticles (AuNPs) were synthesized by a simple one-pot, two-phase chemical reduction method. The synthesized PLA-AuNPs were subsequently employed for selective, efficient, and quantitative detection of MET. MET is one of the highly toxic pesticides used for eradication of agricultural and urban insects. Upon the addition of MET, the wine-red color of PLA-AuNPs swiftly transformed into greyish-blue, further corroborated by a significant bathochromic and hyperchromic shift in the SPR band. The presence of other interfering insecticides, metal salts, and drugs did not have any pronounced effect on quantitative MET detection. The detection limit, the quantification limit, and linear dynamic range of MET utilizing PLA-AuNPs were 0.0027µM, 0.005µM, and 0.005-1000µM, respectively. ThePLA-AuNP-based assay renders an efficient, rapid, accurate, and selective quantification of MET in food, biological, and environmental samples. The proposed sensor provides an appropriate platform for fast and on-the-spot determination of MET without requiring a well-equipped lab setup.

Synthesis of AuNPs in microemulsion and nano-emulsion systems using aqueous extract of C. chayamansa leaves as reducing agent

This paper explores the synthesis and characterization of gold nanoparticles using various microemulsion and nano-emulsion systems. The pseudo-ternary system consists of an aqueous phase / Brij O10: 1,2-hexanediol (1:1) / castor oil; the aqueous phases include the aqueous extract of Chaya Maya (Cnidoscolus chayamansa) leaves or aqueous extract of Chaya maya leaves combined with the inorganic gold precursor. Chaya maya extract act as a reducing agent for gold (III) ions. The influence of aqueous phase content and surfactant concentration on gold nanoparticles size, morphology, and stability is investigated. Dynamic Light Scattering, Scanning Transmission Electron Microscopy, and UV-Vis spectroscopy are employed to analyze the synthesized gold nanoparticles. The sizes of the gold nanoparticles obtained were influenced by the system composition and are within the range of 19–40 nm. Results indicate that increasing the aqueous phase content generally leads to larger nanoparticle sizes, while higher surfactant concentrations yield smaller nanoparticles. A transition from microemulsion to nano-emulsion is observed at a specific aqueous phase content, marking a shift in nanoparticle size distribution and growth behavior. Additionally, microemulsion and nano-emulsion systems provide stability to gold nanoparticles, as evidenced by measured Zeta potentials indicating negatively charged surfaces conducting to colloidal stability. Also, remark that the use of organometallic precursors is no needed to obtain very good results on nanoparticle size and shape when O/W systems are used to this end. These findings highlight the potential of tailored microemulsion and nano-emulsion systems formulated with low-toxic components for controlling gold nanoparticles properties under mild conditions, contributing to the development of advanced gold nanoparticles-based materials with enhanced functionalities, with implications for diverse applications.

Ultra-stable and highly reactive colloidal gold nanoparticle catalysts protected using multi-dentate metal oxide nanoclusters

Owing to their remarkable properties, gold nanoparticles are applied in diverse fields, including catalysis, electronics, energy conversion and sensors. However, for catalytic applications of colloidal gold nanoparticles, the trade-off between their reactivity and stability is a significant concern. Here we report a universal approach for preparing stable and reactive colloidal small (~3 nm) gold nanoparticles by using multi-dentate polyoxometalates as protecting agents in non-polar solvents. These nanoparticles exhibit exceptional stability even under conditions of high concentration, long-term storage, heating and addition of bases. Moreover, they display excellent catalytic performance in various oxidation reactions of organic substrates using molecular oxygen as the sole oxidant. Our findings highlight the ability of inorganic multi-dentate ligands with structural stability and robust steric and electronic effects to confer stability and reactivity upon gold nanoparticles. This approach can be extended to prepare metal nanoparticles other than gold, enabling the design of novel nanomaterials with promising applications.

Light-enhanced catalytic activity of stable and large gold nanoparticles in homocoupling reactions.

Validating the direct photocatalytic activity of colloidal plasmonic nanoparticles is challenging due to their limited stability and needed support materials that can often contribute to the chemical reactions. Stable gold nanoparticles (AuNPs) with tunable sizes are prepared across porous polymer particles without any chemical bonds where the resulting composite particles exhibit intense surface plasmon resonances (SPRs) in the visible region. These composite particles are then tested as photocatalysts under a broadband solar-simulated light source to examine the contribution degree of photothermal heating and SPR coming from the incorporated AuNPs in the C-C bond forming homocoupling reaction. Generally, the thermal and photothermal heating are the main driving force to increase the reactivity of relatively smaller AuNPs (~ 44 nm in diameter) with a narrower SPR band. However, the SPR-induced catalytic activity is much greater for the composite particles containing larger AuNPs (~ 87 nm in diameter) with a broader SPR. As the polymer particle matrix does not influence the catalytic activity (e.g., inducing charge delocalization and/or separation), the unique SPR role of the colloidal AuNPs in the catalytic reaction is assessable under light irradiation. This study experimentally demonstrates the possibility of evaluating the direct contribution of SPRs to photocatalytic chemical reactions.

Insitu synthesis of gold nanospheres immobilised carboxymethyl cellulose-based conductive hydrogel bioink for 3D bioprinting technology

Electrically conductive bioink (ECB) improves the cellular electrical coupling which increases the propagation of cells in bioprinted 3D scaffolds for developing biomimetic architectures. The preparation of ECB predominantly relies on synthetic organic polymers and inorganic nanomaterials, which have certain limitations such as cytotoxicity, weak mechanical stability, and non-biodegradability. The current study focuses on synthesising an ECB immobilised with gold nanospheres (GNS) within the carboxymethyl cellulose (CMC) polymer to eliminate the drawbacks of ECB preparation. Insitu reduction of gold into stable gold nanoparticles within the CMC hydrogel polymer matrix imparted better conductivity without compromising the bioink properties for 3D bioprinting technology.

Detection of Femtomolar Amyloid-β Peptides for Early-Stage Identification of Alzheimer's Amyloid-β Aggregation with Functionalized Gold Nanoparticles.

Progressive amyloid-β (Aβ) fibrillar aggregates have long been considered as the pathogenesis of Alzheimer's disease (AD). Biocompatible and stable cysteine-Aβ peptide-conjugated gold nanoparticles (Cys-Aβ@AuNP) are demonstrated as suitable materials for detecting subfemtomolar Aβ peptides in human plasma. Incubation with Aβ peptides causes the Cys-Aβ@AuNP to aggregate and changes its absorption spectra. The spectral change is especially apparent and noticeable when detecting subfemtomolar Aβ peptides, and the aggregates contain only two or three AuNPs. Cys-Aβ@AuNP can also be used to identify early-stage Aβ oligomerization, which is not possible using the conventional method, in which the fluorescence of thioflavin-T is measured. The ability to detect Aβ oligomerization can facilitate therapeutics for AD. In addition, the binding of Aβ peptides by Cys-Aβ@AuNP in combination with centrifugation redirects the conventional Aβ aggregation pathway and can effectively inhibit the formation of toxic Aβ oligomers or fibrils. Therefore, the proposed Cys-Aβ@AuNP can also be used to develop effective therapeutic agents to inhibit Aβ aggregation. The results obtained in this study are expected to open revolutionary ways to both detect and inhibit Aβ aggregation at an early stage.

New retinoblastoma (RB) drug delivery approaches: anti-tumor effect of atrial natriuretic peptide (ANP)-conjugated hyaluronic-acid-coated gold nanoparticles for intraocular treatment of chemoresistant RB.

Intraocular drug delivery is a promising approach for treatment of ocular diseases. Chemotherapeutic drugs used in retinoblastoma (RB) treatment often lead to side effects and drug resistances. Therefore, new adjuvant therapies are needed to treat chemoresistant RBs. Biocompatible gold nanoparticles (GNPs) have unique antiangiogenic properties and can inhibit cancer progression. The combination of gold and low-molecular-weight hyaluronan (HA) enhances the stability of GNPs and promotes the distribution across ocular barriers. Attached to HA-GNPs, the atrial natriuretic peptide (ANP), which diminishes neovascularization in the eye, is a promising new therapeutic agent for RB treatment. In the study presented, we established ANP-coupled HA-GNPs and investigated their effect on the tumor formation potential of chemoresistant RB cells in an in ovo chicken chorioallantoic membrane model and an orthotopic in vivo RB rat eye model. Treatment of etoposide-resistant RB cells with ANP-HA-GNPs in ovo resulted in significantly reduced tumor growth and angiogenesis compared with controls. The antitumorigenic effect could be verified in the rat eye model, including a noninvasive application form via eye drops. Our data suggest that ANP-HA-GNPs represent a new minimally invasive, adjuvant treatment option for RB.

Enhanced stability of gold nanoparticles capped with double hydrophilic block copolymers synthesized by eATRP

AbstractIn this study, the gold nanoparticles (Au NPs) are capped with a novel, well‐defined double hydrophilic block copolymer, poly (ethylene glycols)‐block‐poly(mono‐2‐(methacryloyloxy) ethyl succinate) (PEG‐b‐PSEMA). The PEG‐b‐PSEMA, with long side chains and relatively narrow dispersity index, is successfully prepared by aqueous electrochemically mediated atom transfer radical polymerization using a PEG‐Br macroinitiator (Mn≈2000 g mol−1). By simply mixing PEG‐b‐PSEMA and Au precursor before adding reductants, coulombic interactions occur between the Au precursor and the carboxylate group of the PSEMA, as a result dense Au NPs are formed. This enables the Au NPs to remain dispersed even in the presence of temperature variations, pH adjustments, and incubation in organic solvents. Au NPs were endowed by PEG‐b‐PSEMA with more remarkable catalytic activity in organic solvents of 4‐nitrophenol into 4‐aminophenol than by sodium citrate (Au@citrate) and MeO‐PEG‐OH (Au@PEG). In addition, PEG‐b‐PSEMA‐stabilized Au NPs (Au@PEG‐b‐PSEMA) were also tested for the dye degradation property against Rhodamine‐B in only pH 10 basic solution, and over 99% of dye degradation can be achieved in 9 min. PEG‐b‐PSEMA induces coulombic interactions with Au NPs, providing outstanding stability for catalytic applications in organic or specific acidic‐base environments.

Visible light enhanced catalytic activity of Aun subnanoclusters: the importance of d-sp interband transitions.

Polymers can serve as an effective matrix to stabilize gold nanoparticles. These materials offer a continuous light-activated supply of subnanoclusters, which are composed of a few atoms. We report an efficient approach to enhance the catalytic activity of gold subnanoclusters by in situ feeding of these species through the generation of hot carriers via 5d-6s6p interband transitions on PEG-stabilized Au nanoparticles.

Novel RNA genosensor based on highly stable gold nanoparticles decorated phosphorene nanohybrid with graphene for highly sensitive and low-cost electrochemical detection of coconut cadang-cadang viroid.

Coconut cadang-cadang viroid (CCCVd) is an infectious single-stranded RNA (ssRNA) pathogen, which leads directly to the death of a large number of coconut palm trees and heavy economic loss to coconut farmers. Herein, a novel electrochemical impedance RNA genosensor is presented based on highly stable gold nanoparticles (AuNPs) decorated phosphorene (BP) nanohybrid with graphene (Gr) for highly sensitive, low-cost, and label-free detection of CCCVd. BP-AuNPs are environmentally friendly prepared by ultrasonic-assisted liquid-phase exfoliation of black phosphorus, accompanying direct reduction of chloroauric acid. Gr/BP-AuNPs are facilely prepared by the in situ growth of AuNPs onto the BP surface and its nanohybrid with Gr to improve environmental stability of BP. Gr/BP-AuNP-based RNA genosensor is fabricated by immobilizing the thiol-functionalized single-stranded DNA (ssDNA) oligonucleotide probe onto the surface of Gr/BP-AuNP-modified glassy carbon electrode via gold-thiol interactions, which served as an electrochemical genosensing platform for the label-free impedance detection of CCCVd by hybridization between the functionalized ssDNA probe and the complementary CCCVd ssRNA sequence in a wide linear range from 1.0 × 10-11 to 1.0 × 10-7M with a low limit of detection of 2.8 × 10-12M. This work supplies an experimental support and theoretical direction for the fabrication of RNA biosensors based on graphene-like materials and potential application for a specific diagnosis of plant RNA viral disease in Arecaceae planting industry.

Tomography Study and Growth Control of Spiky Gold Nanoparticles

A fundamental understanding of the morphological stability and microstructural characteristics of gold nanoparticles (Au NPs) is crucial for their diverse applications. In this study, spiky Au NPs are prepared by a seed‐mediated approach using citrate‐capped Au nanospheres as seeds. The morphological and microstructural characteristics of the spiky Au NPs are studied using 3D tomography transmission electron microscopy (TEM) analysis. Twin boundaries in all spikes of the Au NPs are identified by straight lines in the TEM images and specific crystallographic orientations. In addition, the analysis reveals that a careful approach is required when evaluating the morphological characteristics of spiky Au NPs using 2D images. A series of spiky Au NPs with sizes ranging from 62 to 323 nm is prepared by precisely controlling the amount of seed solution and first growth solution added during seed‐mediated growth. To elucidate the morphological and microstructural characteristics of the spiky Au NPs, a mechanism for the formation and evolution of the spikes is proposed based on the TEM results.