Recent development in chitosan nanocomposites for surface‐based biosensor applications

Recent years have witnessed ever expanding use of biosensors in the fields of environmental monitoring, homeland security, pharmaceutical, food and bioprocessing, and agricultural industries. To produce effective and reliable biosensors, good quality immobilization of biological recognition elements is critical. Chitosan and its nanocomposites emerge as an excellent immobilization matrix on biosensor surface. As a natural polysaccharide, chitosan has many useful characteristics, such as high permeability and mechanical strength, biocompatibility and non‐toxicity, availability, and low cost. Due to the presence of amino and hydroxyl groups on chitosan, chitosan can easily crosslink with a variety of nanomaterials. This investigation of chitosan nanocomposite‐based biosensors presents recent development and innovations in the preparation of chitosan nanocomposites in coordination with biosensors for various bio‐detection applications, including chitosan nanocomposites formed with carbon nanomaterials, various inorganic and biological complexes. These chitosan nanocomposite based biosensors have demonstrated good sensitivity selectivity and stability for the detection of different types of targets ranging from glucose, proteins, DNAs, small biomolecules to bacteria. It is in our hope that this review will offer guidance for the development of novel biosensors and open up opportunities in the field of biosensor research.     

生物传感器在POCT中的应用研究

即时检测（POCT）是在病人旁边或现场进行的检测,因其简单、快速、便携且不受场所限制已成为目前体外分子诊断技术发展的一支风向标。而生物传感器以其快速、灵敏、高效、便携及易于自动化、微型化等优点在发展现场即时检测技术中具有非常大的潜力。近年来,随着生物传感技术、互联网技术的发展及各种新技术、新方法的兴起和融合,POCT技术和方法得到了实质性发展。本文简要介绍了生物传感器的分类和生物传感器在POCT中的应用现状,综述了近年来各类生物传感器在面向POCT检测应用的研究进展。生物传感器根据类型主要分为基于微流控芯片的生物传感器、基于纸的生物传感器、基于纳米材料的生物传感器、基于手机检测平台的生物传感器及集成的生物传感器等,并对这些传感器平台在POCT检测方面的应用做了阐述,最后对生物传感器在POCT应用中存在的问题进行了讨论,并对其发展趋势及前景做了展望。     

石墨烯纳米复合材料在电化学生物传感器中的应用

将石墨烯与其他纳米材料复合,是一种拓展或增强其应用的有效方法。借助不同组分间的协同作用,可以改善石墨烯的电学、化学和电化学性质,拓展和增强石墨烯的电化学效应,为固定氧化还原酶,实现直接电化学提供新型、高效的平台,应用于第三代电化学生物传感器的设计和制备,对葡萄糖、胆固醇、血红蛋白、DNA、H₂O₂、O₂、小生物分子等的检测显示出了优异的灵敏度和选择性。本文综述了基于石墨烯构筑的纳米复合材料在电化学生物传感器中的应用研究,包括石墨烯与贵金属、金属氧化物/半导体纳米粒子、高分子、染料分子、离子液体、生物分子等的纳米复合材料,并对石墨烯材料在电化学领域的发展方向和应用前景进行了展望。     

硅纳米线阵列电极作为细胞色素c传感器的研究

利用化学刻蚀法由p型硅片制备了硅纳米线阵列,经过表面去氧化层处理后,制备了检测蛋白质细胞色素c的电化学传感器.实验表明,硅纳米线阵列电极对细胞色素c有良好的电化学响应,并且在低浓度条件下具备线性响应的特点.根据与未经表面处理的硅纳米线阵列电极的实验结果相对比,提出了细胞色素c所具备的羧基末端与硅纳米线阵列电极表面的Si-H相互作用从而改善传感性能的检测机理.     

Organophosphorus insecticides extraction and heterogeneous oxidation on column for analysis with an acetylcholinesterase (AChE) biosensor

This paper presents an analysis method for organophosphorus insecticides based on AChE biosensors coupled with a preconcentration and oxidation on a solid phase column. Three organic solvents, acetonitrile (ACN), ethanol and methanol were tested for their influence on AChE activity, insecticide inhibition and their ability to elute the adsorbed insecticides. Our results showed that ACN in a concentration of 5% (v/v) had the less negative effect on biosensor analysis and was the most appropriate organic solvent for the column elution. The presence of the organic solvent in the incubation media of the biosensor was found to induce a reduction of the inhibition percentages. The inhibition of the biosensors was performed in phosphate buffer with 5% (v/v) ACN, while the initial and remaining response of the biosensors were measured in PBS. In these conditions, the LODs of paraoxon and dichlorvos were measured with or without a preconcentration step. The LODs of the AChE biosensor without sample preconcentration were 8 × 10⁻⁸ M for paraoxon and 1 × 10⁻⁷ M dichlorvos and the LOD obtained after the preconcentration step were 2.5 × 10⁻⁸ M for paraoxon and 2.5 × 10⁻⁸ M for dichlorvos. Moreover, the use of the column allowed the heterogeneous oxidation of organophosphorus insecticides for improved LOD.     

碳纳米管与生物分子的相互作用*

碳纳米管是一种具有特殊结构和性质的新型一维纳米材料,在生物学和临床医学上已有许多应用研究。大量研究表明,碳纳米管在药物载体、医学成像、疾病检测等方面有广泛的应用前景,碳纳米管与生物分子相互作用的具体机理和形式也成为目前研究的热门方向。本文总结了近几年来碳纳米管与氨基酸、多肽、蛋白质、酶、DNA等多种生物分子之间的相互作用,并对碳纳米管的生物学效应进行了相关综述。     

High-affinity chelator thiols for switchable and oriented immobilization of histidine-tagged proteins: a generic platform for protein chip technologies

Protein micro-/nanoarrays are becoming increasingly important in systematic approaches for the exploration of protein-protein interactions and dynamic protein networks, so there is a high demand for specific, generic, stable, uniform, and locally addressable protein immobilization on solid supports. Here we present multivalent metal-chelating thiols that are suitable for stable binding of histidine-tagged proteins on biocompatible self-assembled monolayers (SAMs). The architectures and physicochemical properties of these SAMs have been probed by various surface-sensitive techniques such as contact angle goniometry, ellipsometry, and infrared reflection-absorption spectroscopy. The specific molecular organization of proteins and protein complexes was demonstrated by surface plasmon resonance, confocal laser scanning, and atomic force microscopy. In contrast to the mono-NTA/His6 tag interaction, which has major drawbacks because of its low affinity and fast dissociation, drastically improved stability of protein binding by these multivalent chelator surfaces was observed. The immobilized histidine-tagged proteins are uniformly oriented and retain their function. At the same time, proteins can be removed from the chip surface under mild conditions (switchability). This new platform for switchable and oriented immobilization should assist proteome-wide wide analyses of protein-protein interactions as well as structural and single-molecule studies.     

Coupling of Antibodies to β-Cyclodextrin-Coated Gold Surfaces via an Intermediate Adamantyl-Modified Carboxymethylated Dextran Layer

-cyclodextrin-coated sensors chips were obtained by grafting amino--cyclodextrin or amino-polymers of -cyclodextrin (poly--CD-NH₂) to functionalized gold surfaces. An additional carboxymethylated dextran bearing adamantyl groups (Ad-Dex-COOH) was then immobilized onto the surface by formation of inclusion complexes between -cyclodextrin cavities and adamantyl groups. Such multilayered structures were stable in aqueous media. However, the initial -cyclodextrin-coated surface could be recovered by using sodium dodecylsulfate solutions (SDS). After activation withN-hydoxysuccinimide, dextran-coated sensor chips were used to bind antibodies. The immunoreactivity of the resulting biosensors was examined. Moreover, conditions leading to the complete regeneration of the initial surface were investigated. Throughout this study, interfacial adsorption and desorption phenomena were followed in real time by an optical technique, Surface Plasmon Resonance (SPR).     

Protein-Based Biosensors for Diabetic Patients

In this article we show the recent progress in the field of glucose sensing based on the utilization of enzymes and proteins as probes for stable and non-consuming fluorescence biosensors. We developed a new methodology for glucose sensing using inactive forms of enzymes such as the glucose oxidase from Aspergillus niger, the glucose dehydrogenase from the thermophilic microorganism Thermoplasma acidophilum, and the glucokinase from the thermophilic eubacterium Bacillus stearothermophilus. Glucose oxidase was rendered inactive by removal of the FAD cofactor. The resulting apo-glucose oxidase still binds glucose as observed from a decrease in its intrinsic tryptophan fluorescence. 8-Anilino-1-naphthalene sulfonic acid was found to bind spontaneously to apo-glucose oxidase as seen from an enhancement of the ANS fluorescence. The steady state intensity of the bound ANS decreased 25% upon binding of glucose, and the mean lifetime of the bound ANS decreased about 40%. These spectral changes occurred with a midpoint from 10 to 20 mM glucose, which is comparable to the KD of holo-glucose oxidase. The ANS-labeled apo-glucose dehydrogenase from Thermoplasma acidophilum also displayed an approximate 25% decrease in emission intensity upon binding glucose. This decrease can be also used to measure the glucose concentration. The thermophilic apo-glucose dehydrogenase was also stable in the presence of organic solvents, allowing determination of glucose in the presence of acetone. The third enzyme used for glucose sensing was the glucokinase from Bacillus stearothermophilus. A fluorescence competitive assay for the determination of glucose was developed based on the utilization of this thermostable enzyme. Taken together, our results show that enzymes which use glucose as their substrate can be used as reversible and non-consuming glucose biosensors in the absence of required co-factors. Moreover, the possibility of using inactive apo-enzymes for a reversible sensor greatly expands the range of proteins which can be used as sensors, not only for glucose, but for a wide variety of biochemically relevant analytes.