Harnessing Effective Molarity to Design an Electrochemical DNA‐based Platform for Clinically Relevant Antibody Detection

Easy‐to‐use platforms for rapid antibody detection are likely to improve molecular diagnostics and immunotherapy monitoring. However, current technologies require multi‐step, time‐consuming procedures that limit their applicability in these fields. Herein, we demonstrate effective molarity‐driven electrochemical DNA‐based detection of target antibodies. We show a highly selective, signal‐on DNA‐based sensor that takes advantage of antibody‐binding‐induced increase of local concentration to detect clinically relevant antibodies in blood serum. The sensing platform is modular, rapid, and versatile and allows the detection of both IgG and IgE antibodies. We also demonstrate the possible use of this strategy for the monitoring of therapeutic monoclonal antibodies in body fluids. Our approach highlights the potential of harnessing effective molarity for the design of electrochemical sensing strategies.     

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.     

Stretchable Electrochemical Sensor for Real‐Time Monitoring of Cells and Tissues

Stretchable electrochemical sensors are conceivably a powerful technique that provides important chemical information to unravel elastic and curvilinear living body. However, no breakthrough was made in stretchable electrochemical device for biological detection. Herein, we synthesized Au nanotubes (NTs) with large aspect ratio to construct an effective stretchable electrochemical sensor. Interlacing network of Au NTs endows the sensor with desirable stability against mechanical deformation, and Au nanostructure provides excellent electrochemical performance and biocompatibility. This allows for the first time, real‐time electrochemical monitoring of mechanically sensitive cells on the sensor both in their stretching‐free and stretching states as well as sensing of the inner lining of blood vessels. The results demonstrate the great potential of this sensor in electrochemical detection of living body, opening a new window for stretchable electrochemical sensor in biological exploration.     

Immobilized DNA switches as electronic sensors for picomolar detection of plasma proteins

The sensing principle of a new class of DNA conformational switches (deoxyribosensors) is based on the incorporation of an aptamer as the receptor, whose altered conformation upon analyte binding switches on the conductivity of an adjacent helical conduction path, leading to an increase in the measured electrical signal through the sensor. We report herein the rational design and biochemical testing of candidate deoxyribosensors for the detection and quantitation of a plasma protein, thrombin, followed by surface immobilization of the optimized sensor and its electrochemical testing in both a near-physiological buffer solution and in diluted blood serum. The very high detection sensitivity (in the picomolar range) and specificity, as well as the adaptability of deoxyribosensors for the detection of diverse molecular analytes both small and macromolecular, make this novel sensing methodology an extremely promising one. Such synthetic and robust DNA-based electronic sensors should find broad application in the rapid, miniaturized, and automated on-chip detection of many biomedically relevant substances (such as metabolites, toxins, and disease and tumor markers) as well as of environmental contaminants.     

Metallic Free Carbon Nanotube Cluster Modified Screen Printed Electrodes for the Sensing of Nicotine in Artificial Saliva

We demonstrate that metallic free carbon nanotube cluster modified screen printed electrodes provide an advantageous sensing methodology for nicotine. The electrochemical oxidation of nicotine is possible at low potentials compared to other commercially available carbon electrodes. Using the carbon nanotube cluster modified screen printed electrodes a detection range of 10 to 1000 μM is possible with a limit of detection of 2 μM. The sensing protocol is shown to be viable in artificial saliva and is promising as a portable and rapid sensor for nicotine in oral fluid (saliva) in areas such as health/life insurance, instances where smoking is banned and also as a point of care test to help improve smoking quit rates.     

Opto-fluidic micro-ring resonator for sensitive label-free viral detection

We have demonstrated sensitive label-free virus detection using the opto-fluidic ring resonator (OFRR) sensor. The OFRR is a novel sensing platform that integrates the microfluidics and photonic sensing technology with a low detection limit and small volume. In our experiment, filamentous bacteriophage M13 was used as a safe model system. Virus samples were flowed through the OFRR whose surface was coated with M13-specific antibodies. We studied the sensor performance by monitoring in real-time the virus and antibody interaction. It is shown that OFRR can detect M13 with high specificity and sensitivity. The detection limit is approximately 2.3 x 10(3) pfu mL(-1) and the detection dynamic range spanned seven orders of magnitude. Theoretical analysis was also carried out to confirm the experimental results. Our study will lead to development of novel OFRR-based, sensitive, rapid, and low-cost micro total analysis devices for virus detection.     

Task specific ionic liquid for direct electrochemistry of metal oxides

We present the first report on task specific ionic liquid (TSIL) for direct electrochemical detection of heavy metal oxides including cadmium oxide, copper oxide and lead oxide at room temperature. This TSIL based electrochemical sensor demonstrated a high sensitivity and selectivity towards the online monitoring of these trace metal oxide particulates, along with short detection time, low cost and high accuracy. This novel sensor platform opens new pathways for in-situ monitoring of metal oxide particulates for environmental sensing and decontamination applications.     

Jigsaw-like mini-pillar platform for multi-mode biosensing

The multiple sensing provides booming options to eliminate interference and ensure the accuracy of detection by mutually coupling and validating multiple data sets. Here, we integrate the jigsaw-like multifunctional mini-pillar platform to perform multi-mode (electrochemical, fluorescence, surface-enhanced Raman scattering (SERS) and colorimetric) sensing in individual microdroplets. Each mini-pillar connector can parallelize together by specific concave-convex interface to form integrated jigsaw-like platform for multi-mode sensing, and each specific mini-pillar can be modified into the individual sensing unit to read the prescribed signals. We successfully implemented electrochemical, fluorescence, SERS and colorimetric detection by multiple signals coupling to reduce the false positive analysis. Such platform brings a promising clue of in-situ analysis and point-of-care testing for disease diagnosis and health monitoring.     

面向亚硝酸盐检测的电化学传感器

亚硝酸盐有毒并可致癌,是一种广泛存在于自然环境和人类的生活领域中的污染物。亚硝酸盐的快速灵敏检测成为十分必要且具有重要意义的研究工作。电化学方法由于具有反应速度快、灵敏度高、检测限低等优点而倍受青睐。本文从复合电极基底及负载不同活性物质的角度详细介绍了近年来针对亚硝酸盐电化学检测的纳米复合材料传感器的研究进展,重点详述了构建方法和检测结果。以期通过它们个性和共性的比较,对构建新型电化学传感器提供参考。     

A label-free electrochemical test for DNA-binding activities of tumor suppressor protein p53 using immunoprecipitation at magnetic beads

In this paper we extend the application area of the label-free structure-sensitive electrochemical DNA sensing with mercury-based electrodes which is for the first time used, in combination with immunoprecipitation at magnetic beads (MB), for the probing of DNA interactions with tumor suppressor protein p53. The technique relies on capture of the p53-DNA complexes at MB via anti-p53 antibodies, followed by salt-induced dissociation of linear DNA from the complex and its voltammetric detection. Competitive binding of p53 to various plasmid DNA substrates, including lin or scDNAs with or without a specific target site, can easily be followed by ex situ electrochemical analysis of DNA recovered from the immunoprecipitated complexes. Compared to gel electrophoresis which is usually applied to analyze different plasmid DNA forms and their complexes with proteins, the electrochemical detection is faster and allows simpler quantitation of DNA containing free ends at submicrogram levels. We demonstrate applicability of the proposed technique to monitor different DNA-binding activities of wild type and mutant p53 proteins.     

基于纳米材料的电化学免疫传感器在传染性病原体POCT中的应用

传染性病原体POCT对于及时有效控制传染病尤为关键。相比于传统检测方法,基于电化学免疫传感器的传染性病原体检测具有快速、灵敏、准确、易于小型化和集成化等优势,尤其适用于传染病POCT。新兴的纳米材料因其独特的理化性质可用于修饰传感器界面或作为生物分子的固载基质以及信号标记物等,有助于构建出高选择性和高灵敏度的电化学免疫传感器。在本文中,我们着重阐述了不同结构的纳米材料修饰的电化学免疫传感器在传染性病原体POCT检测中的应用,进一步介绍了基于纳米材料的电化学免疫传感器与不同检测技术联用在传染性病原体POCT中的应用,并对其发展前景做出了展望。     

A tutorial review for employing enzymes for the construction of G-quadruplex-based sensing platforms

With rapid advances in the field of DNA chemistry, nucleic acids and DNA-modifying enzymes have recently emerged as versatile components for the construction of oligonucleotide-based sensors. Meanwhile, the G-quadruplex motif has been widely employed for the development of DNA-based assays due to its diverse structural variety. In this tutorial, we introduce the principles of G-quadruplex-based sensing and the use of DNA-modifying enzymes for sensor platform development. We also highlight recent studies of the application of DNA-modifying enzymes for the development of G-quadruplex-based luminescent detection platforms with a view towards how those enzymes play an important role in sensitivity enhancement.     

酶聚合体电流信号放大多通道电化学免疫传感体系及蛋白肿瘤标志物检测

本文构建了一种基于酶聚合体信号放大的多通道电化学免疫传感体系,并用于肝癌肿瘤标记物甲胎蛋白（AFP）的定量检测. 该传感体系由固定了抗AFP鼠单克隆抗体的多通道丝网印刷电极组成,可捕获肿瘤标记物抗原AFP,进而与抗AFP兔多抗特异性结合形成夹心免疫复合物,然后利用辣根过氧化物酶聚合体偶联的羊抗兔二抗（IgG-polyHRP）与三明治夹心免疫复合物结合,实现电流信号放大. 该体系结合多通道丝网印刷电极及自主研发的多通道电化学检测仪,可同时满足多通道电流信号的检测. 在最优化条件下,该传感体系检测AFP浓度的动态范围为64 pg·mL^-1 ~ 250 ng·mL^-1,最低检测下限为56 pg·mL^-1,具有检测灵敏度高、特异性强、操作简便以及仪器便携等优点.     

Detection of DNA hybridization on chemically modified graphene platforms

The increasing demand for simple, low-cost, rapid, sensitive and label-free methods for the detection of DNA sequences and the presence of single nucleotide polymorphisms (SNPs) has become an important issue in biomedical research. In this work, we studied the performances of several chemically modified graphene nanomaterials as sensing platforms by using the electrochemical impedance spectroscopy technique for the detection. We employed a hairpin DNA as a highly selective probe for the detection of SNP correlated to Alzheimer's disease. We believe that our findings may present a foundation for further research and development in graphene-based impedimetric biosensing.     

Electrochemical Sensing of Explosives

This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field‐deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low‐cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low‐cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (‘Lab‐on‐Chip’) devices for on‐site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems.     

Topical advances in nanomaterials based electrochemical sensors for resorcinol detection

The ever-increasing environmental pollution is a severe threat to the ecosystem’s healthy sustainability, and therefore environmental monitoring of these pollutants has become a burning issue throughout the world. In recent years, cost-effective, selective, portable, sensitive, and rapid sensing devices must be developed in urgent need. Advancement in nanotechnology has urged the use of different types of nanomaterials as an excellent electrode material to amplify the electrochemical detection in terms of long-term stability and electrocatalytic activity of the electrochemical sensors in addition to fulfill the aforementioned desires. This review article intimates significant advancement in developing the enzymatic and non-enzymatic electrochemical sensors based on different nanomaterials for the detection of resorcinol (RS) in the absence or presence of other phenolic compounds. This also concludes the current associated challenges as well as future perspectives for the analysis of RS in the environment. There is plethora of reported articles on RS sensors, but this review mainly discusses the selective reports on the applications of RS sensors.     

A Highly Sensitive and Selective Label-free Electrochemical Biosensor with a Wide Range of Applications for Bisphenol A Detection

A label-free DNA-based electrochemical biosensor owning high sensitivity and selectivity has been established for detecting bisphenol A in a wide range of applications. Coupling the high electrochemical performance of graphene oxide-thionine-Au nanomaterial with the specific binding capacity of the aptamers to BPA, the monitoring of trace amount of BPA was realized, the detection limit was 3.3 pg ⋅ mL⁻¹ with strong anti-interference. Besides, using molecular docking, it was found that BPA binds to the bases DC-49, DC-51, DG-52, DG-53 and DA-63 on the aptamer via hydrogen bonding and π-π stacking interactions. Finally, the biosensor had been successfully applied in different real samples.     

Characterization of the GM1 pentasaccharide-Vibrio cholera toxin interaction using a carbohydrate-based electrochemical system

Antibody- or DNA-based electrochemical systems have been developed widely for several decades, while carbohydrate-based electrochemical systems have been rarely reported. Herein, we used an electrochemical detection system to understand the molecular relationships in carbohydrate-protein interactions that can provide useful information about biological processes in living organisms. This system was also helpful for the development of potent biomedical agents. Electrochemical detection was achieved through the observation of electrochemical response changes of ferrocyanide solution that resulted from the interaction of carbohydrate and protein using a modified GM1 pentasaccharide containing an anchoring thiol group that was directly immobilized on a gold electrode. As the concentration of the GM1 pentasaccharide increased, the current decreased gradually and saturated after 2 nM. We also found that the drop in current depended on the size of the carbohydrate (larger size of the carbohydrate denoted a higher slope of the current reduction), indicating that the current could be modulated by the molecular size of the carbohydrate as well as its concentration. This system was able to detect very low concentrations of carbohydrate (down to 20 fM), which highlighted the advantage of the electrochemical system. Interestingly, we found that a potential shift at the maximum current occurred upon interaction with cholera toxin proteins. By comparing results for different sizes of GM1 analogues, we surmise that the potential shift is closely associated with the specificity for the carbohydrate-protein interaction. Collectively, a carbohydrate-based electrochemical system can be leveraged for the facile and rapid analysis of carbohydrate-protein interactions.     

Optical and electrochemical responses of an anthrax biomarker based on single-walled carbon nanotubes covalently loaded with terbium complexes

An effective single-walled carbon nanotube (SWNT) covalently loaded with unsaturated terbium emissive material was designed for specific and rapid (2-3 s) detection of calcium dipicolinate (CaDPA) (detection limit 1 μM). The nanoprobe was successfully assembled onto electrodes and its sensing abilities were investigated through electrochemical measurement. Cyclic voltammetry curves were selectively responsive to calcium dipicolinate compared with benzoic acid, o-phthalic acid and m-phthalic acid. This novel material provides dual opto-electrochemical recognition of the anthrax biomarker CaDPA.