Highly sensitive SERS probe for mercury(II) using cyclodextrin-protected silver nanoparticles functionalized with methimazole

We have developed a surface-enhanced Raman scattering (SERS) probe for the determination of mercury(II) using methimazole-functionalized and cyclodextrin-coated silver nanoparticles (AgNPs). These AgNPs in pH 10 solution containing sodium chloride exhibit strong SERS at 502 cm^?1. Its intensity strongly decreases in the presence of Hg(II). This effect serves as the basis for a new method for the rapid, fast and selective determination of trace Hg(II). The analytical range is from 0.50 μg L^?1 to 150 μg L^?1, and the limit of detection is 0.10 μg L^?1. The influence of 11 metal ions commonly encountered in environmental water samples was found to be quite small. The method was applied to the determination of Hg(II) in spiked water samples and gave recoveries ranging from 98.5 to 105.2 % and with relative standard deviations of <3.5 % (n?=?5). The total analysis time is <10 min for a single sample.

Highly sensitive methanol chemical sensor based on undoped silver oxide nanoparticles prepared by a solution method

We have prepared silver oxide nanoparticles (NPs) by a simple solution method using reducing agents in alkaline medium. The resulting NPs were characterized by UV–vis and FT-IR spectroscopy, X-ray powder diffraction, and field-emission scanning electron microscopy. They were deposited on a glassy carbon electrode to give a sensor with a fast response towards methanol in liquid phase. The sensor also displays good sensitivity and long-term stability, and enhanced electrochemical response. The calibration plot is linear (r ²?=?0.8294) over the 0.12?mM to 0.12?M methanol concentration range. The sensitivity is ~2.65?μAcm^?2?mM^?1, and the detection limit is 36.0?μM (at a SNR of 3). We also discuss possible future prospective uses of this metal oxide semiconductor nanomaterial in terms of chemical sensing.

Highly sensitive fluorescence quantification of picloram using immunorecognition liposome

Picloram is a widely used chlorinated herbicide, which is quite persistent and mobile in soil and water with adverse health and environmental risks. A simple and efficient method with high sensitivity and good selectivity was developed in this work to analyze picloram. The aldehyde group functionalized quartz glass plate was used to catch picloram by Schiff base reaction, and reacted with the liposomes-labeled antibody. The fluorescein isothiocyanate (FITC) solution was encapsulated in the liposomes. After being released from the liposomes, the fluorescence of FITC was measured by a fluorimeter. It was found that the fluorescence intensity is linearly correlated to the logarithm of picloram concentration, ranging from 1.0 × 10⁻⁴ to 100 ng mL⁻¹, with a detection limit of 1.0 × 10⁻⁵ ng mL⁻¹. Picloram concentration in real wastewater samples were accurately measured by the proposed method and HPLC, the results of the two methods were approximately the same. The proposed method showed high sensitivity and good selectivity, and could be an efficient tool for picloram quantitative analysis.     

Highly sensitive detection of microRNA by chemiluminescence based on enzymatic polymerization

We have developed a new methodology for miRNA assay using chemiluminescence imaging by poly(U) polymerase catalyzed miRNA polymerization. This method is very sensitive with a 50 fM limit of detection, which is comparable to or better than current assay methods. Multiplex detection for miRNA can be easily realized by introducing different capture probes onto the biosensor array, which will make it highly versatile for various research purposes.     

Highly sensitive biomolecule detection on a quartz crystal microbalance using gold nanoparticles as signal amplification probes.

We report here a novel strategy for the high-sensitive detection of target biomolecules with very low concentrations on a quartz crystal microbalance (QCM) device using gold nanoparticles as signal enhancement probes. By employing a streptavidin-biotin interaction as a model system, we could prepare biotin-conjugated gold nanoparticles maintaining good dispersion and long-term stability by controlling the biotin density on the surface of gold nanoparticles that have been investigated by UV-vis spectra and AFM images. These results showed that 10 microM N-(6-[biotinamido]hexyl)-3'-(2'-pyridyldithio)propionamide (biotin-HPDP) was the critical concentration to prevent the nonspecific aggregation of gold nanoparticles in this system. For sensing streptavidin target molecules by QCM, biotinylated BSA was absorbed on the Au surface of the QCM electrode and subsequent coupling of the target streptavidin to the biotin in the sensing interface followed. Amplification of the sensing process was performed by the interaction of the target streptavidin on the sensing surface with gold nanoparticles modified with 10 microM biotin-HPDP. The biotinylated gold nanoparticles were used as signal amplification probes to improve the detection limit, which was 50 ng/ml, of the streptavidin detection system without signal enhancement, and the calibration curve determined for the net frequency changes showed good linearity over a wide range from 1 ng/ml to 10 microg/ml for the quantitative streptavidin target molecule analysis. In addition, the measured dissipation changes suggested that the layer of biotin-BSA adsorbed on the Au electrode and the streptavidin layer assembled on the biotin-BSA surface were highly compact and rigid. On the other hand, the structure formed by the biotinylated gold nanoparticles on the streptavidin layer was flexible and dissipative, being elongated outward from the sensing surface.     

A strand displacement signal amplification-assisted fluorescence assay for sensitive detection of microRNA

MicroRNA is a vital biomarker because of its abnormal expression in the emergence and development of diseases, especially in cancers. Herein, a label-free fluorescent sensing platform is proposed for detecting microRNA-21, coupled with the cascade toehold-mediated strand displacement reaction and magnetic beads. Target microRNA-21 acts as an initiator to trigger the cascade toehold-mediated strand displacement reaction and it outputs double-stranded DNA. After magnetic separation, the double-stranded DNA is intercalated by SYBR Green I, resulting in an amplified fluorescent signal. Under the optimal conditions, a wide linear range (0.5–60 nmol/L) and low limits of detection (0.19 nmol/L) are exhibited. What's more, the biosensor shows great specificity and reliability between microRNA-21 and other microRNAs involved in cancer (microRNA-34a, microRNA-155, microRNA-10b, and let-7a). Owing to the properties of fabulous sensitivity, high selectivity, and simplicity of operator, the proposed method paves a promising way for microRNA-21 detection in cancer diagnosis and biological research.     

Highly sensitive detection of DNA phosphorylation by counting single nanoparticles

DNA phosphorylation is a vital process in the repair, replication, and recombination of nucleic acids. Traditionally, it is assayed by denaturing gel electrophoresis and autoradiography, which are tedious and not sensitive. We report on the development of a sensitive, simple, and economical method for DNA phosphorylation detection and T4 polynucleotide kinase (T4 PNK) activity assay based on marking DNA phosphorylation/biotinylation events by the attachment of fluorescent nanoparticles. Enzyme activity of T4 PNK is measured down to a limit of 5 × 10⁻⁶ U/ml, which is 400 times lower than previous reports. We also studied DNA phosphorylation specificity with different DNA substrates. Furthermore, T4 PNK inhibition by the inhibitor ADP and activation by the activator spermine are shown, demonstrating the potential for high-throughput screening for inhibitors and activators.     

Perfluorocarbon-stabilized silver nanoparticles manufactured from layered silver carboxylates

Perfluorocarboxylate-stabilized silver nanoparticles have been prepared uniformly via the thermal decomposition of layered silver perfluorocarboxylates (AgCO2(CF2)nCF3, n = 10, 12, 14 and 16).     

Highly sensitive fluorescence quantification of irinotecan in biological fluids with the aid of second-order advantage

<正>A rapid,green and highly sensitive excitation-emission matrix(EEM) fluorescence method was proposed for analysis of irinotecan(CPT-11) in biological fluids including human plasma and urine samples of uncalibrated interferences with the aid of second-order advantage.Due to the serious spectral overlapping from biological matrices,the parallel factor analysis(PARAFAC) and the alternating normalization-weighted error(ANWE) have been recommended to perform directly calibration and overcome the problem which makes the traditional fluorospectrophotometer in trouble.Satisfactory results can be achieved.Furthermore, performance of the proposed method was evaluated based on figures of merit and some statistical parameters.The accuracy of both algorithms was validated by the elliptical joint confidence region(EJCR) test.The precision and repeatability were also investigated by the relative standard deviations(RSDs) of intra-day and inter-day.     

Highly sensitive polymerase chain reaction-free quantum dot-based quantification of forensic genomic DNA

Forensic DNA samples can degrade easily due to exposure to light and moisture at the crime scene. In addition, the amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. The accurately quantified extracted genomic DNA is then used as a DNA template in polymerase chain reaction (PCR) amplification for short tandem repeat (STR) human identification. Accordingly, highly sensitive and human-specific quantification of forensic DNA samples is an essential issue in forensic study. In this work, a quantum dot (Qdot)-labeled Alu sequence was developed as a probe to simultaneously satisfy both the high sensitivity and human genome selectivity for quantification of forensic DNA samples. This probe provided PCR-free determination of human genomic DNA and had a 2.5-femtogram detection limit due to the strong emission and photostability of the Qdot. The Qdot-labeled Alu sequence has been used successfully to assess 18 different forensic DNA samples for STR human identification.     

Functionalized gold nanoparticles as nanosensor for sensitive and selective detection of silver ions and silver nanoparticles by surface-enhanced Raman scattering

We have developed a surface-enhanced Raman scattering (SERS) nanosensor firstly for Ag ions and Ag nanoparticles detection based on 2-mercaptoisonicotinic acid (2MNA)-functionalized Au nanoparticles. Ag(+) can coordinate with 2MNA resutling in a variation of its SERS spectrum, which is used as a criterion to determine Ag(+) in a solution. This sensor exhibits a detection limit no more than 25 nM and has a high selectivity against other metal ions. More importantly, it can be directly applied in real sample detection.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al₂O₃ was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield（up to 99%） without any byproducts other than H₂O.The highest activity was obtained over 5 wt%Ag/Al₂O₃ in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H₂ in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

Highly sensitive fluorescence determination of silver ions based on functionalized cadmium telluride nanorods

Microchimica Acta - Water-soluble fluorescent CdTe nanorods (NRs) capped with L-cysteine (Cys) and thioglycolic acid (TGA) were prepared for optical determination of silver ions. These NRs are...     

Highly selective silver nanoparticles based label free colorimetric sensor for nitrite anions

Highly selective label free colorimetric sensor based on AgNPs stabilized by phenolic chelating ligand, N,N′-bis(2-hydroxybenzyl)-1,2-diaminobenzene (1), for NO₂⁻ anions has been developed. Addition of NO₂⁻ showed selective decolourisation of brownish yellow colour of 1-AgNPs with the detection limit of 10⁻⁷ M. Absorption studies showed the complete disappearance of 1-AgNPs peak at 426 nm due to the conversion of AgNPs to silver ions. The presence silver ions were confirmed by white precipitates of AgCl formation with NaCl. The interference studies confirmed the high selectivity of NO₂⁻ sensing in presence of anions as well as cations by 1-AgNPs. A linear relationship was observed between the change of absorption and concentration of NO₂⁻. The present approach could be performed at room temperature and ambient conditions. The practical applications of 1-AgNPs for selective sensing of NO₂⁻ in different water samples such as ground, river, pond and tap water have also been demonstrated.     

纳米金比色法测定多西环素和土霉素

采用柠檬酸钠还原法合成粒径约13nm的纳米金粒子.采用紫外-可见分光光度计、荧光分光光度计研究了纳米金粒子与多西环素/土霉素分子的相互作用;通过改变缓冲溶液、纳米金粒子用量、反应时间确定了比色法测定的最优反应条件.结果表明:在弱酸溶液中,多西环素/土霉素分子中的氨基官能团(-NH_2)得到电子成为带电基团(-NH_3~+)并通过静电引力与纳米金粒子结合,使得纳米金粒子发生聚集,导致纳米金吸收光谱发生红移和展宽,颜色由酒红色变成蓝色;在盐酸-柠檬酸钠的缓冲溶液中加入2mL纳米金,反应时间为10min的条件下测得多西环素和土霉素的线性范围分别为0.06~0.66mg·L~(-1)和0.59~8.85 mg·L~(-1),检出限(3σ)分别为0.008 6、0.083 8mg·L~(-1).该方法前处理简单、灵敏、可靠,有望应用于食品分析和临床分析等领域.