水分散性硫化镉纳米粒子的制备研究进展

表面修饰的硫化镉纳米粒子荧光性能优异而稳定,激发光谱宽,发射光谱窄而对称且发射波长可通过改变材料的粒径大小和组成来调控,因而在生物样本尤其是活组织的多色成像中极为有用,能有效避免因样本自身发光和光散射导致的信号干扰。硫化镉纳米粒子的研究已被许多科研工作者所青睐,是目前热点研究领域之一。近年来,水分散性硫化镉纳米粒子作生物荧光标记物的研究取得了长足的进展。本文综述了水分散性硫化镉纳米粒子的制备方法研究进展,分析了各种制备方法的优点与不足之处。     

Modification of electrodes with catalytic, size-exclusion films

The application of electroanalytical methodology to the study of liquid-phase samples can be complicated by the adsorption of sample components on the electrode surface. Macromolecules are particularly problematic in this regard. An early means of addressing this problem was to use a membrane permeable to the analyte as a barrier between the sample phase and the electrochemical cell. Amperometric determination of oxygen in biological fluids is a historically important example. This approach was refined by modifying electrodes with semi-permeable, conducting films applied directly to the surface of the working electrode. Cellulose acetate is an example of a conductive material that blocked adsorption of compounds in biological samples but was permeable to analytes such as hydrogen peroxide. Modification of electrodes with ion-exchange films and, more recently, porous sol?Cgel films was an expansion of this methodology. A complicating factor was that oxidation or reduction of most analytes requires a catalyst. The development of films that are size-exclusion barriers to interferents and incorporate an electron-transfer catalyst is described.     

Development and evaluation of a highly sensitive rapid response enzymatic nanointerfaced biosensor for detection of putrescine

Putrescine (1,4-diaminobutane) a biologically active diamine has been found to be a valuable analyte for several clinical and analytical purposes. The present work deals with diamine oxidase immobilized on iron oxide nanoparticles for quantifying the amount of putrescine produced, by the decarboxylation of ornithine, which is converted into hydrogen peroxide by the enzyme diamine oxidase (DAO). This reaction can be quantified using electrochemical techniques, which forms the basis of this work. Iron oxide (Fe(3)O(4)) nanoparticles, synthesized using thermal co-precipitation, were chosen for immobilization of DAO due to its simple preparation procedure, high surface area and cost-effectiveness. The size of the particles was in the range of 25-35 nm and the enzyme was linked covalently by carbodiimide activation and confirmed using FT-IR. For detecting the hydrogen peroxide released in the reaction, a glassy carbon-working electrode coated with enzyme linked iron oxide nanoparticles was poised at +0.4 V versus an Ag/AgCl reference electrode and a platinum wire was used as the counter electrode. A step-wise increase in current was observed and linearity was obtained in the range of 2-8 nM, with 0.65 nM as the minimum detection limit and the response time was found to be 0.3 seconds. Ascorbic acid, a common interfering molecule in biological samples, did not interfere with the measurements indicating the high degree of specificity of the diamine oxidase-based nano-interfaced biosensor.     

An overview of a sustainable approach to the biosynthesis of AgNPs for electrochemical sensors

Mother nature furnishes various sources to synthesize nanomaterial’s with different geometry, size, and functionality. In this outline, we aimed to discuss the biological source-mediated fabrication of Ag NPs because of their easy handling, yields, and economical and non-toxicity. The literature reveals that different plant species, fungi, and bacteria can employ biosynthesis, enabling the fabrication of nanoparticles with different features, notably size, geometry, and morphology. The exact mechanisms have not been understood well, even though it is trusted that bio-sourced is responsible for this process. The method of synthesis can be influenced by pH, concentration, time, and biomass. The optimized biosynthesized AgNPs can employ in various domains like sensors, nanomedicine, environmental pollution etc., The main objective of the paper is to elaborate on the biosynthesized AgNPS in electrochemical sensing and its surface modifications. Furthermore, these electroanalytical techniques are to be used for real-time sampling to allow the selective detection of the target analyte.     

Liquid chromatography/tandem mass spectrometry methods for quantitation of mevalonic acid in human plasma and urine: method validation,demonstration of using a surrogate analyte,and demonstration of unacceptable matrix effect in spite of use of a stable isotope analog internal standard

Selective, accurate, and reproducible liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods were developed and validated for the determination of mevalonic acid, an intermediate in the biosynthesis of cholesterol and therefore a useful biomarker in the development of cholesterol lowering drugs, in human plasma and urine. A hepta-deuterated analog of mevalonic acid was used as the internal standard. For both methods, calibration standards were prepared in water, instead of human plasma and urine, due to unacceptably high levels of endogenous mevalonic acid. The lower quality control (QC) samples were prepared in water while the higher QC samples were prepared in the biological matrices. For the isolation/purification of mevalonic acid from the plasma and urine matrices, the samples were first acidified to convert the acid analyte into its lactone form. For the plasma samples, the lactone analyte was retained on and then eluted off a polymeric solid-phase extraction (SPE) sorbent. For the urine method, the sample containing the lactone analyte was passed through a C-18 SPE column, which did not retain the analyte, with the subsequent analyte retention on and then elution off a polymeric SPE sorbent. Chromatographic separation was achieved isocratically on a polar-endcapped C-18 analytical column with a water/methanol mobile phase containing 0.5 mM formic acid. Detection was by negative-ion electrospray tandem mass spectrometry. The standard curve range was 0.500-20.0 ng/mL for the plasma method and 25.0-1,000 ng/mL for the urine method. Excellent accuracy and precision were obtained for both methods at all concentration levels tested. It was interesting to note that for certain batches of urine, when a larger sample volume was used for analysis, a high degree of matrix effect was observed which resulted not only in the attenuation of the absolute response, but also in a change of analyte/internal standard response ratio. This demonstrated that, under certain conditions, the use of a stable isotope analog internal standard does not, contrary to conventional thinking, guarantee the constancy of the analyte/internal response ratio, which is a prerequisite for a rugged bioanalytical method. On the other hand, under conditions where the sample matrix does not have such a deleterious effect, we have found that a stable isotope analog could serve as a surrogate (substitute) analyte. Thus, we have shown that using calibration standards prepared by spiking plasma with tri-deuterated or tetra-deuterated mevalonic acid, instead of mevalonic acid itself (the analyte), plasma QC samples that contain mevalonic acid can be successfully analyzed for the accurate and precise quantitation of mevalonic acid. The use of a surrogate analyte provides the opportunity to gauge the daily performance of the method for the low concentration levels prepared in the biological matrix, which otherwise is not achievable because of the endogenous concentrations of the analyte in the biological matrices.     

Recent advances in the direct electrochemical detection of drugs of abuse

In the last decade, the trafficking and use of illicit drugs showed a continuous incremental trend, remaining worldwide a challenging problem for the consequences on society, health, criminality, and environment. The introduction on the market of new products and of illicit synthetic compounds represents a new challenging task for analytical chemistry, looking for rapid and accurate methods for the detection of illicit substances in seized street samples, biological fluids, and wastewater. In this context, electrochemical sensors have shown promising results as an alternative to standard chromatographic and spectroscopic methods. This review aims at highlighting the most recent progresses in the use of electrochemistry for the detection of drugs of abuse, mainly including well consolidated substances like cannabinoids, cocaine, opioids, ecstasy, and methamphetamine as well as new psychoactive molecules widely diffused at the present time. Different strategies have been described particularly consisting in the direct electrochemical oxidation of the target analyte. The implementation of tailor-made portable instruments with electrochemical detection methods constitutes an added value to improve the effectiveness of electrochemical sensors for the identification of psychoactive substances when performing large-scale sampling tests.

     

Electrochemical methods for the determination of heparin

A review of studies on the determination of heparin in various samples (pharmaceuticals, biological fluids) by electrochemical methods of analysis in 1976–2014 is presented. Heparin is most often determined in pharmaceuticals by polarography using cationic dyes, and in biological samples, by differential pulse methods on non-stationary mercury electrodes. Works on the creation of heparin-selective electrodes coated with a polyvinylchloride membrane with quarternary ammonium salts are most promising; they can, probably, be used for the creation of portable devices for the determination of heparin.     

Molecularly Imprinted Polymers Combined with Electrochemical Sensors for Food Contaminants Analysis

Detection of relevant contaminants using screening approaches is a key issue to ensure food safety and respect for the regulatory limits established. Electrochemical sensors present several advantages such as rapidity; ease of use; possibility of on-site analysis and low cost. The lack of selectivity for electrochemical sensors working in complex samples as food may be overcome by coupling them with molecularly imprinted polymers (MIPs). MIPs are synthetic materials that mimic biological receptors and are produced by the polymerization of functional monomers in presence of a target analyte. This paper critically reviews and discusses the recent progress in MIP-based electrochemical sensors for food safety. A brief introduction on MIPs and electrochemical sensors is given; followed by a discussion of the recent achievements for various MIPs-based electrochemical sensors for food contaminants analysis. Both electropolymerization and chemical synthesis of MIP-based electrochemical sensing are discussed as well as the relevant applications of MIPs used in sample preparation and then coupled to electrochemical analysis. Future perspectives and challenges have been eventually given.     

Functional Magnetic Nanoparticles for Clinical Application: Electrochemical Immunoassay of Hepatitis B Surface Antigen and α-Fetoprotein

This work reports an efficient method to quantify the Hepatitis B surface antigen and α-fetoprotein in human serum using a functional magnetic nanoparticle-assisted sandwich-type electrochemical immunoassay. The Fe ₃ O ₄ magnetic nanoparticles were first modified with carboxyl functional groups to permit stable bioconjugation to the amine groups of most biological targets. The primary antibodies were then covalently stained on the surface of the functional magnetic nanoparticles, followed by the analyte and secondary antibodies, resulting in a sandwich-type (antibody-antigen-antibody/enzyme) immune complex. The secondary antibodies were labeled with horseradish peroxidase for the catalytic oxidation of 2-aminophenol to yield electrochemically reducible molecules. The separation using an external magnetic field guaranteed fast and reliable purification and enrichment of analytes. Quantitative analysis was performed upon representative clinical targets: Hepatitis B surface antigen and α-fetoprotein in human serum. The detection limits were 0.06 ng/mL for the former and 0.5 ng/mL for the latter, which were about 10 times lower than values obtained by conventional enzyme-linked immunosorbent assays. The reported method may be adopted as a general strategy for the sensitive and selective determination of additional proteins and biological molecules.     

High-Performance Nucleic Acid Sensors for Liquid Biopsy Applications

Circulating tumour nucleic acids (ctNAs) are released from tumours cells and can be detected in blood samples, providing a way to track tumors without requiring a tissue sample. This “liquid biopsy” approach has the potential to replace invasive, painful, and costly tissue biopsies in cancer diagnosis and management. However, a very sensitive and specific approach is required to detect relatively low amounts of mutant sequences linked to cancer because they are masked by the high levels of wild-type sequences. This review discusses high-performance nucleic acid biosensors for ctNA analysis in patient samples. We compare sequencing- and amplification-based methods to next-generation sensors for ctDNA and ctRNA (including microRNA) profiling, such as electrochemical methods, surface plasmon resonance, Raman spectroscopy, and microfluidics and dielectrophoresis-based assays. We present an overview of the analytical sensitivity and accuracy of these methods as well as the biological and technical challenges they present.     

Modified electrodes for electrochemical detection in flowing streams

Chemically modified electrodes exhibit unique behavior which can greatly benefit electrochemical detection in flowing streams. A review of the development and applications of modified electrodes in flow analysis is presented. Detailed discussions are given for different surface-modification strategies employed in flow analysis. Special attention is paid to electrocatalytic surfaces that allow the use of lower operating potentials, permselective coatings that offer controlled access at the detector surface or the incorporation of biological entities that specifically recognize the analyte. Future prospects are examined.     

Analytical Characteristics of Electrochemical Biosensor Using Pt‐Dispersed Graphene on Boron Doped Diamond Electrode

An electrochemical biosensor was developed using Pt‐nanoparticles (Pt‐NPs) dispersed graphene based on a boron‐doped diamond thin film electrode. To compare its performances with those of other biosensors, glucose was used as a target analyte. This biosensor exhibited a wide linear range, a low detection limit and a higher sensitivity compared to other amperometric biosensors using graphene‐based electrodes. In addition, the biosensor promotes a direct electron transfer between the redox enzymes and the electrode surface and detects low concentration analytes. The excellent performance of the biosensor is attributed to the synergistic effect of the Pt‐NPs, graphene sheet and the BDD thin film. Therefore, it can be a promising application for electrochemical detection of analytes.     

Combined Poly(alkyl cyanoacrylate)/Cyclodextrin Nanoparticles

The use of nanoparticles is of great interest for oral or parenteral administration. In fact, nanoparticles not only can protect the active ingredient, but they confer on it a large contact surface with biological membranes and a possible improvement in bioavailability. Biodegradability of nanoparticles, which can be considered as a pre-requisite in the case of parenteral administration     

High‐Performance Nucleic Acid Sensors for Liquid Biopsy Applications

Circulating tumour nucleic acids (ctNAs) are released from tumours cells and can be detected in blood samples, providing a way to track tumors without requiring a tissue sample. This “liquid biopsy” approach has the potential to replace invasive, painful, and costly tissue biopsies in cancer diagnosis and management. However, a very sensitive and specific approach is required to detect relatively low amounts of mutant sequences linked to cancer because they are masked by the high levels of wild‐type sequences. This review discusses high‐performance nucleic acid biosensors for ctNA analysis in patient samples. We compare sequencing‐ and amplification‐based methods to next‐generation sensors for ctDNA and ctRNA (including microRNA) profiling, such as electrochemical methods, surface plasmon resonance, Raman spectroscopy, and microfluidics and dielectrophoresis‐based assays. We present an overview of the analytical sensitivity and accuracy of these methods as well as the biological and technical challenges they present.     

Use of metal nanoparticles for preconcentration and analysis of biological thiols

Metal nanoparticles (NPs) exhibit several unique physicochemical properties, including redox activity, surface plasmon resonance, ability to quench fluorescence, biocompatibility, or a high surface-to-volume ratio. They are being increasingly used in analysis and preconcentration of thiol containing compounds, because they are able to spontaneously form a stable Au/Ag/Cu–S dative bond. They thus find wide application in environmental and particularly in medical science, especially in the analysis of biological thiols, the endogenous compounds that play a significant role in many biological systems. In this review article, we provide an overview of various types of NPs that have been applied in analysis and preconcentration of biological thiols, mainly in human biological fluids. We first discuss shortly the types of NPs and their synthesis, properties, and their ability to interact with thiol compounds. Then we outline the sample preconcentration and analysis methods that were used for this purpose with special emphasis on optical, electrochemical, and separation techniques.     

Functionalized gold nanoparticle supported sensory mechanisms applied in detection of chemical and biological threat agents: A review

There is a great necessity for development of novel sensory concepts supportive of smart sensing capabilities in defense and homeland security applications for detection of chemical and biological threat agents. A smart sensor is a detection device that can exhibit important features such as speed, sensitivity, selectivity, portability, and more importantly, simplicity in identifying a target analyte. Emerging nanomaterial based sensors, particularly those developed by utilizing functionalized gold nanoparticles (GNPs) as a sensing component potentially offer many desirable features needed for threat agent detection. The sensitiveness of physical properties expressed by GNPs, e.g. color, surface plasmon resonance, electrical conductivity and binding affinity are significantly enhanced when they are subjected to functionalization with an appropriate metal, organic or biomolecular functional groups. This sensitive nature of functionalized GNPs can be potentially exploited in the design of threat agent detection devices with smart sensing capabilities. In the presence of a target analyte (i.e., a chemical or biological threat agent) a change proportional to concentration of the analyte is observed, which can be measured either by colorimetric, fluorimetric, electrochemical or spectroscopic means. This article provides a review of how functionally modified gold colloids are applied in the detection of a broad range of threat agents, including radioactive substances, explosive compounds, chemical warfare agents, biotoxins, and biothreat pathogens through any of the four sensory means mentioned previously.     

Electrochemical DNA nano-biosensor for the detection of genotoxins in water samples简

In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing DNA on Au nanoparticles and a self-assembled monolayer of cysteamine modified Au electrode. The assembly processes of cysteamine, Au nanoparticles and DNA were characterized by cyclic voltammetry （CV）. The Au nanoparticles enhanced DNA immobilization resulting in an increased guanine signal. The interaction of the analyte with the immobilized DNA was measured through the variation of the electrochemical signal of guanine by square wave voltammetry （SWV）. The biosensor was able to detect the known genotoxic compounds： 2-anthramine, acridine orange and 2- naphthylamine with detection limits of 2, 3 and 50 nmol/L, respectively. The biosensor was also used to test actual water samples to evaluate the contamination level. Additionally, the comparison of results from the classical genotoxiciw bioassay has confirmed the applicability of the method for real samoles.     

An Electrochemical Sensor Based on Gold Nanoparticles Incorporated in Mesoporous MFI Zeolite for Determination of Purine Bases in DNA

An electrochemical sensor was developed based on gold nanoparticles incorporated in mesoporous MFI zeolite for the determination of purine bases. Au nanoparticles (AuNPs) were incorporated into the mesoporous MFI zeolite (AuNPs/m‐MFI) by post‐grafting reaction. The composite materials were characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS) and electrochemical methods. Au nanoparticles with a size of 5‐20 nm are uniformly dispersed in the pores of mesoporous MFI zeolite. And the morphology of MFI zeolite can be perfectly kept after pore expansion and Au nanoparticles incorporation. The electrocatalytic oxidation of purine bases (guanine and adenine in DNA) is investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface‐confined Au nanoparticles provide the good catalytic activity for oxidation of purine bases. The simultaneous detection of guanine and adenine can be achieved at AuNPs/m‐MFI composites modified glassy carbon electrode (GCE). The electrochemical sensor based on AuNPs/m‐MFI exhibits wide linear range of 0.5–500 μM and 0.8–500 μM with detection limit of 0.25 and 0.29 μM for guanine and adenine, respectively. Moreover, the electrochemical sensor is applied to evaluation of guanine and adenine in herring sperm DNA samples with satisfactory results.     

On the applicability of nanodiamonds produced by detonation synthesis for phenol testing in aqueous media

It was found that the catalytic effect of modified nanodiamonds (MND) in the H₂O₂–4-aminoantipyrine–phenol oxidative azo coupling reaction is due to microimpurities of iron and copper ions on the surface of nanoparticles. The efficiency of MND as a catalyst is determined by the amount of surface impurities of these ions and can be doubled by their additional adsorption on nanoparticles. Using MND for phenol indication ensures a linear yield of the colored product of the azo coupling reaction over an analyte concentration range of 0.05–10 μg/mL. The possibility of reusing MND for phenol testing in aqueous samples was demonstrated.