Development of a screen-printed cholesterol biosensor: Comparing the performance of gold and platinum as the working electrode material and fabrication using a self-assembly approach

Gold (Au) and platinum (Pt) were used as the working electrode material to detect cholesterol in solution through enzymatically generated hydrogen peroxide (H₂O₂). Both gold and platinum were capable of detecting cholesterol through the electrochemical oxidation of H₂O₂, and could be used as the working electrode material. By comparison, however, Au was preferable over Pt in terms of higher response current and better sensitivity. Therefore, Au was chosen as the working electrode material for the fabrication of a thick-film screen-printed cholesterol biosensor consisting of three electrodes on an alumina substrate (working: Au, reference: Ag/AgCl, and counter: Au). The immobilization of the enzyme cholesterol oxidase (ChOx, E.C. 1.1.3.6) on the Au working electrode was achieved using a self-assembly approach. A thiol, 3-mercaptopropionic acid (MPA), was self-assembled onto the gold working electrode forming a thin organic layer that served as the anchor for the enzyme immobilization. 1-Ethyl-3(3-dimethylamino propyl)carbodiimide methiodide (EDC) was then used to immobilize the enzyme ChOx covalently on the gold working electrode through the carbodiimide coupling between the carboxyl (–COOH) groups of the self-assembled MPA layer and the amino (–NH₂) groups of the enzyme. Electrochemical measurements showed that this biosensor responded well to cholesterol, confirming that the self-assembly immobilization method was effective. The reproducibility, the interference, and the storage stability of the biosensor were studied and assessed.     

高检测灵敏度的DNA生物传感器

基于磁珠带标记DNA电化学传感器、磁珠标记的GMR(TMR)DNA生物传感器和纳米线场效应DNA生物传感器都具有高检测灵敏度的特点,是极具发展前途的研究方向。主要介绍了以上三种高检测灵敏度DNA生物传感器的基本检测原理,并对比分析了这三种传感器的优缺点。     

表面横波生物传感器的灵敏度分析

分析了延迟线型表面横波(STW)生物传感器的灵敏度与栅阵材料、厚度的关系。给出了计算栅阵对表面横波束缚能力的方法,由STW的束缚能力可以直接得到传感器的灵敏度。从Auld微扰理论出发推导出表面横波传感器灵敏度的表达式。根据上述理论分析,以AT切割压电石英基片为例,分别计算金、银、铝三种栅阵材料在不同厚度时的传感器灵敏度,并给出对比分析结果。结果表明,在相同栅阵厚度时,采用金栅阵的传感器灵敏度最高,银次之,铝最小;传感器的灵敏度随着栅阵厚度的增加而增加。     

Proteins from extremophiles as stable tools for advanced biotechnological applications of high social interest

Extremophiles are micro-organisms adapted to survive in ecological niches defined as 'extreme' for humans and characterized by the presence of adverse environmental conditions, such as high or low temperatures, extreme values of pH, high salt concentrations or high pressure. Biomolecules isolated from extremophiles possess extraordinary properties and, in particular, proteins isolated from extremophiles represent unique biomolecules that function under severe conditions, comparable to those prevailing in various industrial processes. In this article, we will review some examples of recent applications of thermophilic proteins for the development of a new class of fluorescence non-consuming substrate biosensors for monitoring the levels of two analytes of high social interest, such as glucose and sodium.     

心肌搏动细胞传感器及其在药物分析中的应用

针对产品全生命周期管理的特点，将元数据建模技术与本体相结合建立基于元数据的产品数据本体,提出基于元数据的产品概念模型和面向产品全生命周期的产品数据模型；通过分析元数据建模的元层次，提出了基于元数据的产品数据本体建模体系结构以及通用描述，并给出了某汽轮机产品数据模型实例.实例表明,在产品全生命周期管理中采用基于元数据的产品数据本体，能够有效地保证数据的安全性和一致性，可方便地进行模型集成和信息共享，满足实际产品设计和生产过程中出现的所有可能的情况.     

Self-powered photoelectrochemical biosensing platform based on Au NPs@ZnO nanorods array

Photoanodes, which are used in photoelectrochemical (PEC) water splitting, have been shown to be applicable in the construction of a PEC biosensing platform. This was realized by replacing water oxidization with oxidation of an appropriate test molecule. Here, we have demonstrated the feasibility of adopting photoanodes consisting of zinc oxide nanorods arrays decorated with plasmonic gold nanoparticles (Au NPs@ZnO NRs) for the self-powered PEC bioanalysis of glutathione (GSH) in phosphate-buffered saline (PBS) at an applied bias potential of 0 V vs. Ag/AgCl. This heterostructure exhibited enhanced PEC properties because of the introduction of the Au/ZnO interface. Under visible light illumination, hot electrons from surface-plasmon resonance (SPR) at the Au NP surface were injected into the adjacent ZnO and subsequently driven to the photocathode. Under ultraviolet (UV) light illumination, the photogenerated electrons in ZnO tended to transfer to the fluorine-doped tin oxide due to the step-wise energy band structure and the upward energy band bending at the ZnO/ electrolyte interface. These results indicate that plasmonic metal/semiconductor heterostructure photoanodes have great potential for self-powered PEC bioanalysis applications and extended field of other photovoltaic beacons.

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A novel microbial BOD biosensor developed by the immobilization of P. Syringae in micro‐cellular polymers

BACKGROUND: A biochemical oxygen demand (BOD) sensor, based on an immobilized Pseudomonas syringae in highly porous micro‐cellular polymer (MCP) in combination with a dissolved oxygen electrode, has been developed for the analysis of biodegradable organic compounds in aqueous samples. Microorganisms were immobilized in a molded MCP disk and a wastewater sample was injected into the biocomposite disk by a flow injection system. Dissolved oxygen (DO) changes as a measure of soluble BOD was read with a DO probe placed into a flow cell carrying biocatalytically activated disk. RESULTS: Optimal response of the MCP BOD sensor was obtained at pH 6.8 and 25 °C with a typical response time of 3–5 min for a 2 mm thick molded polymeric disk. The sensor showed detection linearity over the range 5–100 mg L^?1 BOD₅ (r² > 0.99) at a flow rate of 0.6 mL min^?1. The repeatability and reproducibility of the sensor response were found to be 3.08% and 7.77%, respectively. BOD values produced with this biosensor for various municipal and industrial wastewaters correlated well with those determined by the conventional 5‐day BOD test. CONCLUSION: This new biosensor was different from present amperometric BOD biosensor configurations in which the biocatalyst (microbial/enzymatic) is placed between cellulose and Teflon membranes installed on a DO probe. The use of a molded MCP disk coniainng microbial activity offers better stability and lifetime for commercial use in environmental monitoring. Copyright © 2008 Society of Chemical Industry     

Grating coupled optical waveguide interferometer for label-free biosensing

A phase shifting optical waveguide interferometer is demonstrated for label-free evanescent wave biosensing in aqueous solutions. In the proposed configuration, the reference and measurement arms of the interferometer are combined inside an integrated optical Ta₂O₅ waveguide using an ion implanted grating. Biomolecules adsorbing on the waveguide surface shift the phase in the measurement arm, which is modulated at the same time by a periodically relaxing liquid crystal phase modulator. It is demonstrated that by analyzing the periodic intensity response at the end facet of the waveguide, the phase shifts in the measurement arm can be monitored in real-time with a precision of 10⁻⁴ rad. The high phase resolution allows the detection of surface adsorbed molecule densities below 1 pg/mm² without using any labeling or on-chip referencing. The instrument performance is demonstrated by monitoring in situ protein adsorption and affinity binding of low molecular weight pure biotin to an immobilized avidin layer.     

Nanocrystalline-diamond thin films with high pH and penicillin sensitivity prepared on a capacitive Si-SiO2 structure

A capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) sensor with improved pH and penicillin sensitivity has been realised using a nanocrystalline-diamond (NCD) film as sensitive gate material. The NCD growth process on SiO₂ as well as an additional surface treatment in oxidising medium have been optimised to provide high pH-sensitive, non-porous O-terminated films without damage of the underlying SiO₂ layer. The surface morphology of O-terminated NCD thin films and the layer structure of EDIS sensors have been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. To establish the relative coverage of the surface functional groups generated by the oxidation of NCD surfaces, X-ray photoelectron spectroscopy analysis was carried out. The hydrophilicity of NCD thin films has been studied by water contact-angle measurements. A nearly Nernstian pH sensitivity of 54-57 mV/pH has been observed for O-terminated NCD films treated in an oxidising boiling mixture for 80 min and in oxygen plasma. The high pH-sensitive properties of O-terminated NCD have been used to develop an EDIS-based penicillin biosensor. A freshly prepared penicillin biosensor possesses a high sensitivity of 85 mV/decade in the concentration range of 0.1-2.5 mM penicillin G. The lower detection limit is 5 μM.     

基于静电结合的电化学阻抗D-甘露糖生物传感器的研究

糖组学的研究已经成为后基因时代一个重要的研究领域.糖类物质与凝集素之间的特异性相互作用,能够用于制备糖生物传感器,文章设计了一种简便的D-甘露糖电化学阻抗生物传感器,以刀豆凝集素为分子识别物质,静电吸附法将刀豆凝集素固定到金圆盘电极的表面,用电化学阻抗法进行检测.实验结果表明,以[Fe（CN）6]3-4-氧化还原电对作为探针,电子转移阻抗变化值与D-甘露糖浓度的对数在5.0×10-8～1.0×10-5 mol/L之间呈良好的线性关系,检出限为0.02μmol/L.