Electrochemical impedance spectroscopy detection of lysozyme based on electrodeposited gold nanoparticles

A simple, highly sensitive, and label-free electrochemical impedance spectroscopy (EIS) aptasensor based on an anti-lysozyme-aptamer as a molecular recognition element, was developed for the detection of lysozyme. Improvement in sensitivity was achieved by utilizing gold nanoparticles (AuNPs), which were electrodeposited onto the surface of a gold electrode, as a platform for immobilization of the aptamer. To quantify the amount of lysozyme, changes in the interfacial electron transfer resistance (R_et) of the aptasensor were monitored using the redox couple of an [Fe(CN)₆]^3−/4− probe. The R_et increased with lysozyme concentration. The plot of R_et against the logarithm of lysozyme concentration is linear over the range from 0.1 pM to 500 pM with a detection limit of 0.01 pM. The aptasensor also showed good selectivity for lysozyme without being affected by the presence of other proteins.     

Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions

Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu²⁺. The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu²⁺ ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu²⁺ and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions.     

Size sorting of citrate reduced gold nanoparticles by sedimentation field-flow fractionation

Gold nanoparticles (GNPs) have been synthesized through the citrate reduction method; the citrate/gold(III) ratio was changed from 1:1 up to 10:1 and the size of the resulting nanoparticles was measured by sedimentation field-flow fractionation (SdFFF). Experimental data showed that the GNPs size decreases in the ratio range 1:1–3:1 and then increases from 5:1 to 10:1 passing through a plateau region in between, and is almost independent of the precursor solution concentrations. In the zone of minimum diameters the synthetic process does not produce monodispersed GNPs but often multiple distributions, very close in size, are observed as evidenced by the particle size distributions (PSDs) derived from the SdFFF fractograms. UV–vis spectrophotometry, being the most common technique employed in the optical characterization of nanoparticles suspensions, was used throughout this work. A confirmation of the nucleation–aggregation–fragmentation mechanism was inferred from the cross-correlation between UV–vis and SdFFF results.     

Direct Determination of Urinary Lysozyme Using Surface Plasmon Resonance Light-Scattering of Gold Nanoparticles

The purpose of this study was to establish a simple and sensitive analytical method for lysozyme using Plasmon Resonance Light-Scattering (PRLS) technique with Gold Nanoparticles (AuNPs) as the probe. Nanomolar level of lysozyme induced AuNPs aggregation with enhanced PRLS. For 1.4 nM citrate-capped AuNPs (13 nm in diameter), the linear range of the calibration curve was 15-50 nM with a detection limit of 13.1 nM for lysozyme. Six nanomolar lysozyme can produce an observable PRLS enhancement. Most potential interfering substances present in urine had a negligible effect on the determination. The interference from human serum albumin in the urinary sample can be reduced by precipitating the albumin with ethanol at pH 4.8-4.9. The 90.1-118.2% recovery was achieved for 8 individual lysozyme-spiked urinary samples. This simple and sensitive method for lysozyme does not require sample clean-up and AuNPs modification, thus provided an alternative for urinary lysozyme determination.     

金纳米微粒作探针共振瑞利散射光谱法测定盐酸异丙嗪

在pH 1.8～3.0的酸性介质中,质子化的盐酸异丙嗪(PMZ)可与带负电荷的金纳米微粒依靠静电和疏水作用相互结合,导致共振瑞利散射(RRS)强度显著增强,其最大散射峰位于368 nm,并在284,440,498 nm处有明显的散射峰,在选定的测量波长下,盐酸异丙嗪在0.04～0.10μg/mL的浓度范围内与RRS强度成正比,该法具有高的灵敏度,其检出限为1.34 ng/mL。考察了体系的RRS光谱特征,研究了适宜的反应条件、影响因素,研究了共存物质的影响,据此建立了金纳米微粒作探针RRS法测定盐酸异丙嗪的新方法。     

A sensitive resonance light scattering spectrometry of trace Hg with sulfur ion modified gold nanoparticles

A new resonance light scattering (RLS) spectrometric method for mercury ions (Hg²⁺) in aqueous solutions with sulfur ion (S²⁻) modified gold nanoparticles (Au-NPs-S) has been developed in this contribution. It was found that S²⁻ at the surface of Au-NPs resulting from the surface modification can interact with Hg²⁺ to form very stable S-Hg-S bonds when Hg²⁺ concentration is lower than that of S²⁻, resulting in the aggregation of Au-NPs-S and causing enhanced RLS signals. The enhanced RLS intensities (ΔI_RLS) characterized at 392 nm were found to be proportional to the concentration of Hg²⁺ in the range of 0.025-0.25 μmol L⁻¹ with a detection limit (3σ) of 0.013 μmol L⁻¹. Our results showed that this approach has excellent selectivity for Hg²⁺ over other substances in aqueous solutions.     

Enhanced resonance light scattering properties of gold nanoparticles due to cooperative binding

The interaction of 11-mercaptoundecanoic acid capped gold nanoparticles (MUA-GNPs) with europium ions and aminoacids has been studied by UV-Vis spectrophotometry, fluorescence, confocal fluorescence microscopy, resonance light scattering and TEM. Results demonstrated that hyper-Rayleigh scattering emission occurs upon the addition of lysine to the MUA-GNPs–Eu(III) system, thus providing an inherently sensitive method for lysine determination. The effects of geometrical factors of the gold nanoparticles (aspect ratio, particle size, cluster formation) and the surrounding medium (pH) on this behavior are discussed. The cooperative binding interactions of Eu³⁺ and lysine with gold nanoparticles permitted the discrimination of lysine from other amino acids. The probable mechanism for the spectral changes and the enhanced resonance light scattering observed is outlined. Figure Gold nanoparticle resonance light scattering plasmon enhancement through cooperative binding with europium and lysine     

Homogeneous immunoassay based on gold nanoparticles and visible absorption detection

A sensitive homogeneous immunoassay, using human serum albumin (HSA) as a model analyte coupled with simple visible absorption detection, has been developed. The new assay is based on the use of gold nanoparticles functionalized with the target protein, which compete with the analyte for the binding of a specific polyclonal antibody. The binding of antibodies to the functionalized nanoparticles determines a shift of the visible absorption maximum of the gold colloid, and quantification of the analyte could be obtained as the competitive inhibition of the binding of antibodies to the nanoparticles. The proposed immunoassay has been optimized and successfully applied to measuring HSA in human urine samples, in which results agreed well with those obtained by a nephelometric reference method.     

Rapid synthesis of bovine serum albumin-conjugated gold nanoparticles using pulsed laser ablation and their anticancer activity on hela cells

Nanoscience research aims to produce nanoparticles without adverse effects for medical applications. The pulsed laser ablation (PLA) technique was utilized in this study to synthesize gold nanoparticles (AuNPs) using bovine serum albumin (BSA) in simulated body fluid (SBF) at the fundamental wavelength of the Nd: YAG laser (1064 nm). BSA acted as a stabilizer, reducing and capping agent to produce spherically shaped AuNPs (diameter 3–10 nm). The successful synthesis of AuNPs was confirmed through color changes and UV–vis spectroscopy. The agglomeration and precipitation of AuNPs are attributed to the presence of BSA in the solution, and electrostatic repulsion interactions between BSA and Au nanoclusters. The effect of salt concentration of SBF on BSA stability as well as the interaction of BSA conjugated AuNPs to form complexes was studied using molecular dynamic simulations. Our results show that the stability of AuNPs-BSA conjugates increase with the salt concentration of BSA. Moreover, the synthesized AuNPs exhibit low toxicity and high biocompatibility, supporting their application in drug delivery. Investigation of the cytotoxic effect of the synthesized AuNPs show that normal fibroblast cells (L929) remain intact after treatment whereas a dose-dependent inhibition effect on the growth of cervix cancer cells (HeLa) is observed. In general, this study presents an effective, environmentally-friendly, and facile approach to the synthesis of multifunctional AuNPs using the PLA technique, as a promising efficacious therapeutic treatment of cervical cancer.     

各向异性金纳米粒子的制备及其在催化中的应用

尽管有关金纳米粒子催化的研究工作很多,但其中大多数都是采用传统的浸渍法将金盐负载到载体上、共沉淀或沉积-沉淀法制得负载的纳米粒子,但这些方法并未吸收最新的纳米技术。最近,金催化剂的研究者开发了在胶态悬浮液中制取金属纳米粒子,然后进行固载,从而使得单金属和双金属催化剂的催化活性和形貌控制取得较大进展。另一方面,最近十年出现了金纳米粒子合成的高级控制技术,得到了许多各向异性的金纳米粒子,且很容易制得新的形貌,可以控制纳米粒子的表面原子配位数和光学特性(可调的等离子体带),这些都与催化密切相关。这些形貌包括纳米棒、纳米星、纳米花、树枝状纳米结构或多面体纳米粒子等。除了高度关注各向异性金纳米粒子的最新开发的制备方法和性质,本综述也清楚地总结了这些纳米粒子独特的催化性能,以及通过提供更高催化性能的金催化剂、控制暴露的活性位,以及热、电和光催化的鲁棒性和可调性,从而给多相催化领域带来令人惊奇的潜在变革。     

Resonance Rayleigh scattering spectral method for the determination of raloxifene using gold nanoparticle as a probe

When gold nanoparticles were being prepared by sodium citrate reduction method, citrate anions self-assembled on the surface of gold nanoparticles to form supermolecular complex anions with negative charges, and protonated raloxifene (Ralo) was positively charged and could bind with the complex anions to form larger aggregates through electrostatic force and hydrophobic effects, which could result in the remarkable enhancement of the resonance Rayleigh scattering intensity (RRS), and the appearance of new RRS spectra. At the same time, the second-order scattering (SOS) and frequency-doubling scattering (FDS) intensities were also enhanced. The maximum wavelengths were located near 370 nm for RRS, 520 nm for SOS, and 350 nm for FDS, respectively. Among them, the RRS method had the highest sensitivity and the detection limit was 5.60 ng mL⁻¹ for Ralo, and its linear range was 0.05-2.37 μg mL⁻¹. A new RRS method for the determination of trace Ralo using gold nanoparticles probe was developed. The optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism and the reasons for the enhancement of RRS were discussed.     

Interaction of gold nanoparticles with mitochondria

Mitochondrion is one of the most important organelles in cells with several vital responsibilities. The consequence of a deficiency in the function of mitochondrion could result with the wide range of diseases and disorders. In this study, we investigated the feasibility of utilizing surface-enhanced Raman scattering (SERS) to understand the mode of interaction of gold nanoparticles (GNPs) with mitochondria. The living lung cancer cells and the isolated mitochondria from these cells were treated with gold colloidal suspension for SERS experiments. The AFM images of the mitochondria confirmed that the treatment did not cause substantial damage to mitochondria. The localization of GNPs in living cells is investigated with confocal microscopy and found that GNPs form aggregates in the cytosol away from the mitochondria. However, SERS spectra obtained from isolated mitochondria and living cells indicate that GNPs escaped from the endosomes or entered into the living cell through another route may be in contact with mitochondria in a living cell. The findings of this study indicate that SERS can be used for mitochondrial research.     

Physico-chemical characterization and anti-laryngeal cancer effects of the gold nanoparticles

Most recently, gold nanoparticles due to anticancer properties have been considered in medical science. So the aim of the study was green synthesis of gold nanoparticles using Ocimum basilicum extract and its anticancer activity. The prepared Au nanoparticles were characterized by advanced physicochemical techniques like Fourier Transformed Infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD) and UV–vis spectroscopy study. It has been established that Au nanoparticles have a spherical shape with a mean diameter from 19 to 44 nm. In the cellular and molecular part of the recent study, the treated cells with Au nanoparticles were assessed by MTT assay for 48 h about the cytotoxicity and anti-human laryngeal cancer properties on normal (HUVEC) and cancer (HEp-2, TU212, KB, UM-SCC-5, UM-SCC-11A and UM-SCC-11B) cell lines. In the antioxidant test, the IC50 of Au nanoparticles and BHT against DPPH free radicals were 228 and 208 µg/mL, respectively. The IC50 of Au nanoparticles were 174, 231, 179, 143, 230, and 216 µg/mL against HEp-2, TU212, KB, UM-SCC-5, UM-SCC-11A and UM-SCC-11B cell lines, respectively. The viability of malignant cell lines reduced dose-dependently in the presence of Au nanoparticles. It appears that the anti-cancer effect of Au nanoparticles e to their antioxidant effects.     

One step to detect the latent fingermarks with gold nanoparticles

A simple and environment friendly chemical route for detecting latent fingermarks by one-step single-metal nanoparticles deposition method (SND) was achieved successfully on several non-porous items. Gold nanoparticles (AuNPs) synthesized using sodium borohydride as reducing agent in the presence of glucose, were used as working solution for latent fingermarks detection. The SND technique just needs one step to obtain clear ridge details in a wide pH range (2.5-5.0), whereas the standard multi-metal deposition (MMD) technique requires six baths in a narrow pH range (2.5-2.8). The SND is very convenient to detect latent fingermarks in forensic scene or laboratory for forensic operators. The SND technique provided sharp and clear development of latent fingermarks, without background staining, dramatically diminished the bath steps.     

Biological response of hydrogels embedding gold nanoparticles

A nanocomposite hydrogel based on natural polysaccharides and gold nanoparticles (ACnAu) has been prepared and its biological effects were tested in vitro with both bacteria and eukaryotic cells. Antimicrobial tests showed that AC-nAu gels are effective in killing both gram+ (Staphylococcus aureus) and gram- (Pseudomonas aeruginosa) bacteria. LDH assays pointed at a toxic effect towards eukaryotic cell-lines (HepG2 and MG63), in contrast with the case of silver-based hydrogels; cytofluorimetry studies demonstrated an apoptosis-related mechanism induced by increase of ROS intracellular level which leads to cell death after 24 h of direct contact with AC-nAu gels. In vivo biocompatibility has been evaluated in a rat model, investigating the peri-implant soft tissue reaction after 1 month of implantation. The results show that silver-containing samples induced a fibrotic capsule of the same average thickness of the control sample (devoid of nanoparticles) (～50 μm), while in the case of gold containing materials the fibrotic capsule was thicker (～100 μm), confirming a higher biocompatibility for silver-based samples than for gold-based ones.     

Enhanced detection of gold nanoparticles in agarose gel electrophoresis

Gel electrophoresis is a powerful tool in gold nanoparticle (AuNP) research. While the technique is sensitive to the size, charge, and shape of particles, its optimal performance requires a relatively large amount of AuNP in the loading wells for visible detection of bands. We here describe a novel and more sensitive method for detecting AuNPs in agarose gels that involves staining the gel with the common organic fluorophore fluorescein, to produce AuNP band intensities that are linear with nanoparticle concentration and almost an order of magnitude larger than those obtained without staining the gel.     

金纳米粒子的表面等离子体共振吸收光度法研究和分析应用

在阴离子表面活性剂十二烷基苯磺酸钠存在下的水溶液中，基于金纳米粒子产生的表面等离子体共振吸收的原理，提出了一个分光光度方法。结果表明在524nm处的共振吸收强度与金质量浓度在2．4-120μg/mL范围内服从比尔定律。其线性回归方程为：c＝55．58A 0．78，相关系数为0．9998。方法适用于载金炭中的金分析。     

Eco-friendly synthesis of gold nanoparticles using fruit extracts and in vitro anticancer studies

Gold nanoparticles are biocompatible and are having several applications in biomedical Sciences and Engineering. Integration of nanoscience in medicine leads to the development of biomedical products that helps the Society in a faster and safer manner. In the present research work, bioreduction and biofunctionalization of gold nanoparticles are performed with fruit extracts of Aegle marmelos, Eugenia jambolana and soursop. The nanoparticles are characterized using UV–Vis spectroscopy, Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy and Zeta potentiometer. The qualitative phytochemical analysis of the fruit extracts shows the presence of alkaloids, amino acid, flavonoids, phenol, proteins, tannin, reducing sugars and total Sugars. The in vitro anticancer activity was confirmed by MTT assay on the human breast cancer cell line MCF-7 at different concentrations. The flavonoids present in the fruit extracts are potential reducing agent which is responsible for the formation of gold nanoparticles. Stabilization of gold nanoparticles are performed by the carboxylate group present in the proteins. Also, the nanoparticles are held apart from each other by the electrostatic repulsions that exist due to the presence of like charges surrounding the gold nanoparticles. This study proves that the fruit extracts can be used for the synthesis and stabilization of gold nanoparticles. Further, the engineered nanoparticles capped with bioactive compounds are potential anticancer agents against breast cancer cell line MCF-7.