Enzyme-Linked DNA Displacement (ELIDIS) Assay for Ultrasensitive Electrochemical Detection of Antibodies**

Here we report the development of a method for the electrochemical ultrasensitive detection of antibodies that couples the programmability and versatility of DNA-based systems with the sensitivity provided by enzymatic amplification. The platform, termed Enzyme-Linked DNA Displacement (ELIDIS), is based on the use of antigen-DNA conjugates that, upon the bivalent binding of a specific target antibody, induce the release of an enzyme-DNA hybrid strand from a preformed duplex. Such enzyme-DNA hybrid strand can then be electrochemically detected with a disposable electrode with high sensitivity. We applied ELIDIS to demonstrate the sensitive (limit of detection in the picomolar range), specific and multiplexed detection of five different antibodies including three clinically relevant ones. ELIDIS is also rapid (it only requires two reaction steps), works well in complex media (serum) and is cost-effective. A direct comparison with a commercial ELISA kit for the detection of Cetuximab demonstrates the promising features of ELIDIS as a point-of-care platform for antibodies detection.     

Electrochemical Biosensors for Cancer Biomarkers Detection: Recent Advances and Challenges

Biomarkers are described as characteristics that provide information about biological conditions whether normal or pathological. Detection of biomarkers at the earliest stage of the cancer is of utmost importance for clinical diagnosis. Electrochemical biosensors allow detecting the low levels of specific analytes in blood, urine or saliva and providing a sensitive approach for direct measurement for cancer biomarker detection. Moreover, the integration of electrochemical devices with nanomaterials, such as carbon nanotubes, gold and magnetic particles offer amplification and multiplexing capabilities for simultaneous measurements of cancer biomarkers very sensitively. This review summarizes the recent developments of electrochemical biosensors systems for the detection of cancer biomarkers with emphasis on voltammetric, amperometric and impedimetric biosensors. A special attention is paid to aptamers and miRNAs that are very promising for the ultra‐sensitive and specific cancer biomarker detection.     

Recent Advances on Nanozyme-based Electrochemical Biosensors

Nanozymes are nanomaterials with enzyme-like catalytic activities. The unique features of nanozymes (such as high stability, low cost, large surface area for bioconjugation, ease of storage, and multi-functionalities) offer unprecedented opportunities for designing electrochemical biosensors. Recent years have witnessed the rapid development of nanozyme-based electrochemical biosensors. To highlight these achievements, this review first discusses the representative nanozymes including peroxidase mimics, oxidase mimics, hydrolase mimics, and superoxide dismutase mimics used in electrochemical biosensors. Then, it summarizes the bioanalytical applications for the detection of various analytes. Finally, current challenges and future research directions are summarized.     

Electrochemical Nucleic Acid Biosensors for the Detection of Interaction Between Peroxynitrite and DNA

We studied the reactivity of peroxynitrite and different nucleic acid molecules using DNA electrochemical biosensors. SIN‐1 (3‐morpholinosydnonimine) has been used for the simultaneous generation of NO?and superoxide, i.e., as a peroxynitrite (ONOO^?) donor. Double strand DNA (dsDNA), single strand DNA (ssDNA) and 15 guanine bases oligonucleotide (Oligo(dG)₁₅) were immobilized on a carbon paste electrode to generate the biosensor and DPV was selected as the electroanalytical technique. Results showed that electrochemical biosensors were very sensitive for detecting interaction between ONOO^? and DNA. A down/up effect was observed, i.e., at low ONOO^? concentrations the guanine oxidation signal decreased while at high ONOO^? concentrations the guanine oxidation current increased. Oligo(dG)₁₅ exhibited greater interaction at low ONOO^? concentrations than the other DNA molecules. The reactivity between ONOO^? and DNA was also evaluated in solution phase, showing the same down/up effect. Finally, the capacity of DNA to hybridize was prevented after interaction with ONOO^?.     

Electrochemical Biosensors for Cancer Biomarker Detection

Cancer is still one of the leading causes of death in the world. There are over 200 types of cancers currently known according to the National Cancer Institute. However, early diagnosis continues to be an important integral part of cancer treatment even though many advances in therapeutics have been made in the past decade. Quick diagnosis and early prevention are critical for the control of the disease status. Biomarkers are commonly indicative of a particular disease process and the cancer biomarkers are also widely used in oncology to help detecting the presence of various carcinomas. The detection of cancer biomarkers plays an important role in clinical diagnoses and evaluation of treatment for patients. Many immunoassay methods are developed for detection of cancer biomarkers. As the detection devices are normally viewed with high sensitivity, simple preparation and rapid response, electrochemical biosensors are increasingly used for the detection of cancer markers. This review describes the status, the latest research and trends of electrochemical sensors in the quantitation of cancer markers in recent years. In particular, the strategy to improve the sensitivities of the electrochemical biosensors by the aid of enzymatic amplification, nanoparticle amplification, ultilization of magnetic microspheres etc. is described herein. At last, we discuss some special features and limitations associated with the described systems that summarize the application and the development prospects of electrochemical immunoassay technology.     

PAMAM Dendrimers‐Based DNA Biosensors for Electrochemical Detection of DNA Hybridization

Gold electrodes were modified with submonolayers of mercaptoacetic acid (RSH) and further reacted with poly(amidoamine) (PAMAM) dendrimers (generation 4.0) to obtain thin films, on which DNA probe was later immobilized to afford a stable recognition layers. The characterization of the PAMAM/RSH‐modified electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance measurement. Differential pulse voltammogram (DPV) measurement was used to monitor DNA hybridization with daunomycin (DNR) as indicator. Experiments carried out with these novel materials not only showed an improved DNA attachment quantity on the dendrimers‐modified electrodes compared to DNA sensors with oligonucleotides directly immobilized on Au electrodes, but also exhibited a high selectivity, sensitivity and stability for the measurement of DNA hybridization.     

Electrochemical Biosensors for Detection of Biological Warfare Agents

This review discusses current development in electrochemical biosensors for detection of biological warfare agents. This could include bacteria, viruses and toxins that are aerosoled deliberately in air, food or water to spread terrorism and cause disease or death to humans, animals or plants. The rapid and unequivocal detection and identification of biological warfare agents is a major challenge for any government including military, health and other government agents. Reliable, specific characterization and identification of the microorganism from sampling location, either air, water, soil or others is required. This review will survey different types of electrochemical biosensors has been developed based on the following: i) Immunosensors ii) PCR (DNA base Sensor) iii) Bacteria or whole cell sensor and iv) Enzyme sensor. This article gives an overview of electrochemical biosensor for detection of biological warfare agents. Electrochemical biosensors have the advantages of sensitivity, selectivity, to operate in turbid media, and amenable to miniaturization. Recent developments in immunofiltration, flow injection, and flow‐through electrochemical biosensors for bacteria, viruses, and toxin detection are reviewed. The current research and development in biosensors for biological warfare agents detection is of interest to the public as well as to the defense is also discussed.     

Graphene Based Electrochemical Sensors and Biosensors: A Review

Graphene, emerging as a true 2‐dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production). This article selectively reviews recent advances in graphene‐based electrochemical sensors and biosensors. In particular, graphene for direct electrochemistry of enzyme, its electrocatalytic activity toward small biomolecules (hydrogen peroxide, NADH, dopamine, etc.), and graphene‐based enzyme biosensors have been summarized in more detail; Graphene‐based DNA sensing and environmental analysis have been discussed. Future perspectives in this rapidly developing field are also discussed.     

Electrochemical Aptasensors for Biological and Chemical Analyte Detection

Aptamers are short length, single-stranded DNA or RNA affinity molecules which interact with any desired targets such as biomarkers, cells, biological molecules, drugs or chemicals with high sensitivity. They have been extensively employed for medical applications due to having more advantages than the antibodies such as easier preparation and modification, higher stability, lower batch-to-batch variability and cost. Moreover, aptamers can be easily integrated efficiently with sensors, biosensors, actuators and other devices. In this review article, different applications of aptamers for biological and chemical molecules detection within the scope of electrochemical methods were presented with recent studies. In addition, the present status and future perspectives for highly-effective aptasensors for specific and selective analyte detection were discussed. As in stated throughout the review, combining of extraordinary properties of aptamers with the electrochemical-based biosensors could have improved the sensitivity of the assay and reduced limit of detection.     

Detection of Listeria Monocytogenes by Electrochemical Impedance Spectroscopy

Listeria monocytogenes is detected by electrochemical impedance spectroscopy using a mouse monoclonal antibody immobilized onto an Au electrode. This yields sensitivities of 0.825 kΩ cm²/(CFU/mL) and 1.129 kΩ cm²/(CFU/mL) and detection limits of 5 CFU/mL and 4 CFU/mL for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non‐specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross‐reactivity to this food pathogen. Potential technological hurdles to development of a multiplexed impedance biosensor for food pathogens are also discussed.     

丙肝电化学免疫传感器在血清检测中的应用

丙型肝炎病毒(hepatitis C virus,HCV)是丙肝的致病因子,该病毒自70年代发现以来,就一直困扰着人类。丙肝已成为近年来最为严重的传染病之一。目前临床诊断丙肝的主要方法有血清学非特异性检测[1]和特异性检测(酶联免疫分析方法、重组免疫印迹、聚合酶链反应[2]等)。血清学非特     

Carbon‐Nanotube Based Electrochemical Biosensors: A Review

This review addresses recent advances in carbon‐nanotubes (CNT) based electrochemical biosensors. The unique chemical and physical properties of CNT have paved the way to new and improved sensing devices, in general, and electrochemical biosensors, in particular. CNT‐based electrochemical transducers offer substantial improvements in the performance of amperometric enzyme electrodes, immunosensors and nucleic‐acid sensing devices. The greatly enhanced electrochemical reactivity of hydrogen peroxide and NADH at CNT‐modified electrodes makes these nanomaterials extremely attractive for numerous oxidase‐ and dehydrogenase‐based amperometric biosensors. Aligned CNT “forests” can act as molecular wires to allow efficient electron transfer between the underlying electrode and the redox centers of enzymes. Bioaffinity devices utilizing enzyme tags can greatly benefit from the enhanced response of the biocatalytic‐reaction product at the CNT transducer and from CNT amplification platforms carrying multiple tags. Common designs of CNT‐based biosensors are discussed, along with practical examples of such devices. The successful realization of CNT‐based biosensors requires proper control of their chemical and physical properties, as well as their functionalization and surface immobilization.     

Substantial Influence of Temperature on Anchoring of Gold‐Nanoparticle Monolayer for Performance of DNA Biosensors

This paper presents a way of modification of crystalline gold surface with a high quality layer of gold nanoparticles (Au NPs) via self‐assembled dithiol. The application of additional Au NPs monolayer prepared at various temperatures was tested with three types of biosensors previously described in the literature. The examined DNA biosensors differed by the detection method and the way of the immobilization of DNA probe at the modified gold electrode surface. For the immobilization of DNA probe in the sensing layer either the formation of SAM or the affinity binding (biotin – sterptavidin) or covalent attachment were used. The necessary condition of successful preparation of a perfect such monolayer is the preparation temperature of 4 °C. The preparation of Au NPs layers at higher than 4 °C temperatures leads to poor repeatability and unsatisfactory precision of the measurements. The application of the perfect Au monolayer lowers the detection limit (circa by 10 to 100 times) for all tested DNA biosensors.     

介孔材料在电化学生物传感器中的应用进展

回顾了近年来有序介孔材料在电化学生物传感器中的应用及发展状况,简述了规则介孔材料的合成方法及特点、生物分子在介孔材料上的固定方法及其优缺点,通过总结近年几种介孔材料电化学生物传感器的研究进展,提出介孔材料在电化学生物传感器领域的应用前景(引用文献49篇)。     

Electrochemical DNA Biosensors Based on Palladium Nanoparticles Combined with Carbon Nanotubes

Palladium nanoparticles, in combination with multi‐walled carbon nanotubes (MWCNTs), were used to fabricate a sensitivity‐enhanced electrochemical DNA biosensor. MWCNTs and palladium nanoparticles were dispersed in Nafion, which were used to modify a glassy carbon electrode (GCE). Oligonucleotides with amino groups at the 5′ end were covalently linked onto carboxylic groups of MWCNTs on the electrode. The hybridization events were monitored by differential pulse voltammetry (DPV) measurement using methylene blue (MB) as an indicator. Due to the ability of carbon nanotubes to promote electron‐transfer and the high catalytic activities of palladium nanoparticles for electrochemical reaction of MB, the sensitivity of presented electrochemical DNA biosensors was remarkably improved. The detection limit of the method for target DNA was 1.2×10^?13 M.     

Electrochemical Sensors,a Bright Future in the Fabrication of Portable Kits in Analytical Systems

Analysis of food, pharmaceutical, and environmental compounds is an inevitable issue to evaluate quality of the compounds used in human life. Quality of drinking water, food products, and pharmaceutical compounds is directly associated with human health. Presence of forbidden additives in food products, toxic compounds in water samples and drugs with low quality lead to important problems for human health. Therefore, attention to analytical strategy for investigation of quality of food, pharmaceutical, and environmental compounds and monitoring presence of forbidden compounds in materials used by humans has increased in recent years. Analytical methods help to identify and quantify both permissible and unauthorized compounds present in the materials used in human daily life. Among analytical methods, electrochemical methods have been shown to have more advantages compared to other analytical methods due to their portability and low cost. Most of big companies have applied this type of analytical methods because of their fast and selective analysis. Due to simple operation and high diversity of electroanalytical sensors, these types of sensors are expected to be the future generation of analytical systems. Therefore, many scientists and researchers have focused on designing and fabrication of electroanalytical sensors with good selectivity and high sensitivity for different types of compounds such as drugs, food, and environmental pollutants. In this paper, we described the mechanism and different examples of DNA, enzymatic and electro‐catalytic methods for electroanalytical determination of drug, food and environmental compounds.     

Application of Nanoparticles in Electrochemical Sensors and Biosensors

The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle‐based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems.     

Design and Development of a Non-Enzymatic Electrochemical Biosensor for the Detection of Glutathione

Glutathione (GSH-reduced form) is a tripeptide that plays a vital role as an antioxidant to remove xenobiotics in the human body and changes in GSH levels are a marker for the progression of various diseases. In this context, a highly sensitive non-enzymatic electrochemical biosensor for the detection of GSH has been developed using reduced graphene oxide Manganese oxide (rGMnO) nanocomposite as the nano-interface. Initially, graphene oxide was synthesized by Hummer's method and then thermally reduced in the presence of MnO₂ in a blast furnace to obtain rGMnO nanocomposite. The nanocomposite was characterized to validate its structure and morphological properties via Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry and amperometry studies showed that upon the addition of GSH, the Pt/rGMnO modified working electrode exhibited a linear response in the range of 1–100 μM at an input voltage of −0.62 V. The developed sensor was found to have a sensitivity of 0.3256 μA μM⁻¹ and LOD of 970 nM with a recovery of 92–104 % in real blood serum samples.     

黄曲霉毒素电化学生物传感器

黄曲霉毒素（aflatoxin,AF）是一种具有强烈毒性和强致癌性的生物毒素,对其进行快速而准确的分析是减小和避免黄曲霉毒素危害的最有效手段之一。电化学生物传感器因其快速、灵敏、特异性强、易于微型化等优势在黄曲霉毒素分析受到国内外研究者的广泛关注。目前,应用于黄曲霉毒素分析的电化学生物传感器主要有免疫传感器、酶传感器和DNA传感器。本文综述了不同传感器的研究现状,特别介绍了新材料新技术在黄曲霉毒素免疫分析中发挥的重要作用,并对黄曲霉毒素的电化学生物传感分析存在的问题和发展前景进行了探讨及展望。