Potentiometric Biosensors Based on ISFETs and Immobilized Cholinesterases

This paper describes the authors' achievements in the development, investigation, and application of cholinesterase biosensors based on ISFETs. Various biosensors for determination of concentrations of different toxic substances (organophosphorous and carbamate pesticides, hypochlorite, glycoalkaloids) were designed on the basis of reversible and/or irreversible enzyme inhibition effects. The main analytical characteristics of the biosensors developed have been studied under different conditions and optimal experimental protocols for toxic substances determination have been proposed. Most of these biosensors show a high reproducibility and a good operational and storage stability. A quite good correlation with results obtained through routinely used standard methods as HPLC has been shown.     

A Novel Potentiometric Glucose Biosensor Based on Polyaniline Semiconductor Films

Abstract

Application of polyaniline semiconductor films to potentiometric biosensor development provides certain advantages comparing with the known systems. Using self-doped polyaniline instead of common polymer as pH transducer the stable potentiometric response of 70 mV/pH was obtained. Taking as an example glucose biosensor we showed that polyaniline based electrode possessed three-four fold increased potential shift than glucose-sensitive field-effect transistor did. One can increase the sensitivity of potentiometric biosensor using thick ion-exchange membranes (in our case Nafion) in order to concentrate product near electrode surface. Such sensor possessed higher response time.     

一种基于PVC膜电极的电位式葡萄糖传感器的研制

以三庚基十二烷基碘代季铵盐为电活性物质的PVC膜电极, 对过氧化氢和六价钼的络合物具有良好的电位响应. 将葡萄糖氧化酶固定到PVC膜电极表面, 制备成电位式葡萄糖传感器. 在优化的实验条件下, 该传感器在葡萄糖浓度为2×10^－4～5×10^－3 mol/L范围内有线性响应, 检测下限为5×10^－5 mol/L. 另外该传感器具有较高的稳定性和良好的选择性, 抗坏血酸、尿酸和一些氨基酸未对测定产生干扰.     

Potentiometric Cholesterol Biosensor Based on ZnO Nanowalls and Stabilized Polymerized Lipid Film

A novel potentiometric cholesterol biosensor was fabricated by immobilization of cholesterol oxidase into stabilized lipid films using zinc oxide (ZnO) nanowalls as measuring electrode. Cholesterol oxidase was incorporated into the lipid film prior polymerization on the surface of ZnO nanowalls resulting in a sensitive, selective, stable and reproducible cholesterol biosensor. The potentiometric response was 57 mV/ decade concentration. The sensor response had no interferences by normal concentrations of ascorbic acid, glucose, and urea, proteins and lipids. The present biosensor could be implanted in the human body because of the biocompatibility of the lipid film.     

纳米材料电化学与生物传感器——有机微污染物检测新途径

本文介绍了近年来纳米材料电化学与生物传感器在有机微污染物检测中的研究现状,分析了这些传感器中纳米材料修饰电极的特点,重点阐述了纳米材料在有机微污染物检测中的重要作用,列举了一些纳米材料电化学与生物传感器在有机微污染物检测中的应用。最后对纳米材料电化学与生物传感器用于有机微污染物的检测研究进行了简要评述和展望。     

A Fractal Analysis Approach for the Evaluation of Hybridization Kinetics in Biosensors

The diffusion-limited hybridization kinetics of analyte in solution to a receptor immobilized on a biosensor or immunosensor surface is analyzed within a fractal framework. The data may be analyzed by a single- or a dual-fractal analysis. This was indicated by the regression analysis provided by Sigmaplot (Sigmaplot, Scientific Graphing Software, User's Manual, Jandel Scientific, CA, 1993). It is of interest to note that the binding rate coefficient and the fractal dimension both exhibit changes, in general, in the same direction for both the single-fractal and the dual-fractal analysis examples presented. The binding rate coefficient expression developed as a function of the analyte concentration in solution and the fractal dimension is of particular value since it provides a means to better control biosensor or immunosensor performance. Copyright 2001 Academic Press.     

A New Approach to the Development of a Reusable Piezoelectric Crystal Biosensor

Abstract

A reusable piezoelectric crystal immunosensor for human albumin has been developed. The crystal was coated with protein a and then reacted with anti-human albumin antibody. Human albumin in the range 10^?4 mg/ml to 10^?1 mg/ml could be detected by the system. Crystals were regenerated by saturation with albumin and subsequent binding of a new anti-albumin antibody layer. The albumin assay could be repeated up to 5 times using the same crystal.     

Fabrication of Sensitive Potentiometric Cholesterol Biosensor Based on Co3O4 Interconnected Nanowires

Highly sensitive, selective, reliable and inexpensive cholesterol biosensors are highly demanded for the routine monitoring of cholesterol molecules in order to prevent heart failure incidents. In this study, Co₃O₄ nanostructures are synthesized using polyvinyl pyrrolidone surfactant as growth template by a low temperature aqueous chemical growth method. The morphology of nanostructures was investigated by scanning electron microscopy and X‐ray diffraction techniques. The nanostructures exhibit interconnected nanowires like morphology with interconnected network of nanowires. The nanostructures of Co₃O₄ are polycrystalline. The cholesterol oxidase was physically adsorbed on the interconnected nanowires of Co₃O₄ for the chemical sensing of cholesterol molecules. The sensor device detected a wide range of cholesterol from 1×10^?7 M to 1×10^?3 M concentrations with sensitivity of ?94.031 mV/decade. A detection limit of 0.035×10^?7 M cholesterol concentration was observed and a fast response time of 10 s was also noticed. The fabricated device is highly stable, selective, sensitive, reproducible and repeatable. All the collected information about presented cholesterol biosensor indicates its potential application for the monitoring of cholesterol concentrations from human blood serum and real‐life samples.     

Enzyme Urea Biosensor Based on a Modified Potentiometric PVC-Nonactin Membrane Electrode for Assay of Urea in Blood

Abstract

The developed potentiometric urea biosensor is based on a modified PVC-nonactin NH₃ -sensitive gas electrode. Membrane resistance has been optimised by incorporating lipophilic salt. The coefficient of variation for the standard urea solution is 2.45. The sensor performance has been compared with a photometric method for blood samples.     

Cholinesterases in Biorecognition and Biosensors Construction: A Review

Acetylcholinesterase and butyrylcholinesterase are the only two known cholinesterases. Acetylcholinesterase plays an important part in cholinergic system. It terminates neurotransmission by hydrolysis of transmitter acetylcholine. The role of butyrylcholinesterase is not well understood. It is able to detoxify several compounds such as cocaine, succinylcholine, and so forth. The current review is focused on the application of cholinesterases in biorecognition. Cholinesterases are important markers in the body. Butyrylcholinesterase activity in plasma can serve as a liver function test or specific marker for sensitivity to myorelaxants or liver carcinoma. Both cholinesterases can serve as markers of poisoning by some neurotoxic compounds. Nerve agents (sarin, soman, tabun, VX), some Alzheimer disease drugs (galantamine, huperzine, donepezil, rivastigmine), pesticides (carbofuran, trichlorfon, paraoxon, malaoxon), and natural toxins (aflatoxin, pyridostigmine) can act as inhibitors of butyrylcholinesterase and/or acetylcholinesterase. Devices filled with immobilized cholinesterases can be used for the assay of the aforementioned toxins. In this review, methods for examination of cholinesterases activity in the body and in analytical devices are described. Applications, types of diagnosis, and assays are described as well.     

Construction and Characterization of a Beet Stem Based Biosensor for Oxalate

Abstract

This report describes the construction and characterization of an oxalate-sensing electrode. The electrode is based on the incorporation of ground beet stem into the graphite paste of a graphite paste electrode. The hydrogen peroxide generated by enzymatic degradation of oxalate is monitored at a working voltage of 0.900 V vs SCE. All measurements were conducted in a succinic acid/EDTA buffer at pH 4.00. Under these conditions, the electrodes exhibit reproducible responses to oxalate. The lower limit of oxalate detection was less than 1.03 × 10^?4 M. The time to achieve a steady state response after exposure to a step change in oxalate concentration in solution is less than one minute. The magnitude of response to oxalate over the oxalate concentrations studied varies among several electrode tested as does the degree of linearity of response. An electrode studied still exhibited analytically useful responses to oxalate on the 15th day of its use. The beet stem-based electrodes display little response to glycolic acid, glucose, DL-valine, or pyruvate.     

Construction of a Highly Selective and Sensitive Dopamine Enzyme-free Biosensor Based on Carbon Nanomaterials

A selective and sensitive electrochemical enzyme-free sensor for dopamine (DA) was prepared, containing carbon nanomaterials, gold nanoparticles (GNPs) and room-temperature ionic liquid of 1-butyl-3-methylimidazolium tetrafluor (BmimBF₄). The peaks of DA, ascorbic acid (AA) and uric acid (UA) can be well separated by optimization of pH condition and carbon nanomaterials.Multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), single-walled carbon nanohorns (SWCNHs), carboxylated graphene (C-GR), were chosen to compare the affection to DA detection. The catalytic effect was SWCNTs>MWCNTs>C-GR≈SWCNHs. It showed carbon nanotube materials with electron acceleration channels play the key role in catalytic performance. The pH condition also influenced detection, all the redox peak potentials of DA, UA, and AA had a negative shift as the pH changed from low to high, but the amplitude of the shift was different. At pH 1, the three anodic peaks are separated ca.0.24 V and 0.20 V. Under optimum conditions linear calibration graphs were obtained over the DA concentration range 0.2 to 20 μM.The modified electrode was applied for the assay of spiked DA in blood serum and human urine.This work studied the influence of carbon nanomaterials on DA detection and provided a simple approach to selectively detect dopamine in the presence of AA and UA.     

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.     

A Chemometric Approach to the Indirect Potentiometric Determination of the Components of a Redox Couple

A chemometric approach to the determination of the components of a redox couple without their preseparation was proposed. The approach is based on the transformation of a potentiometric curve obtained by the multiple addition method to a direct regression line with a cotangent numerically equal to the analyte concentration. The approach was tested on simulated and experimental data for the reversible Fe(III)–Fe(II) system and applied to the determination of Cr(VI) in model solutions using excess solution of the Mohr's salt as an auxiliary reducing agent. In real determinations of Fe(III, II) and Cr(VI) in concentration ranges from 1 × 10^–3to n× 10^–5and from 2 × 10^–3to 5 × 10^–4M, RSD varied from 0.2 to 8% and from 3 to 12%, respectively.     

Comparison of Single Layer and Bilayer Biosensors Based on Crosslinking of Penicillinase for Potentiometric Detection of Penicillin in Milk and Antibiotics

The use of bilayers for fabrication of biosensors is advantageous for increasing enzyme loading. Substantial improvement in sensitivity is often achieved through immobilisation of the enzyme in both layers. In particular, the use of cross linking agents such as glutaraldehyde (GLA), bovine serum albumin (BSA) and polyvinyl alcohol (PVA) are beneficial for enhancing enzyme stability and, hence, for fabricating stable biosensors. The successful fabrication of a single layer BSA‐GLA‐P’nase biosensor for potentiometric detection of penicillin is described. Subsequently, the three crosslinking agents were employed with two polymers, polypyrrole (PPy) and polytyramine (PTy), together with penicillinase (P’nase) for fabrication of PPy‐NO₃‐P’nase/BSA‐PVA‐P’nase and PTy‐NO₃‐P’nase/BSA‐GLA‐P’nase bilayer biosensors. The analytical performances of the bilayer biosensors were then compared with the single layer BSA‐GLA‐P’nase biosensor for the determination of penicillin in milk and amoxycillin tablets. While the determination of penicillin in milk was somewhat problematic, its determination in amoxicillin tablets proved to be successful, with recoveries of 102±15 % obtained with the PPy‐NO₃‐P’nase/BSA‐PVA‐P’nase biosensor, 100±19 % with PTy‐NO₃‐P’nase/BSA‐GLA‐P’nase biosensor and 103±5 % with BSA‐GLA‐P’nase biosensor. Notably, the results of the latter agreed favourably with those obtained through a reference titrimetric method.     

Spectroscopic and Potentiometric Investigation of a Diprotic Acid: An Experimental Approach to Understanding Alpha Functions

A laboratory experiment suitable for second- or higher-year chemistry students uses thymol blue, an organic dye, for investigating the fraction of each colored species present as a function of pH. Visible color changes in the vivid, highly absorbing dye permit students to see relative amounts of acid, base, and ampholyte species during the titration, while potentiometric measurement of pH and spectroscopic determination of concentrations permit quantitation of the species present. A standard Beers law calibration curve is constructed for known concentrations of the pure forms of each species at a pH where that species is present as nearly 100% of the total analytical concentration of the dye. Using the molar absorptivities of the three species computed from the calibration curves, simultaneous determination of concentration by species is performed on a set of solutions having constant total concentration of dye such that each solution represents one point in the range pH 0 to pH 13. A mathematical software application is used to solve the simultaneous equations and determine the fraction of each species present. Students then use a spreadsheet application to plot the fractions as functions of pH (the alpha functions). The significance of the isosbestic points in the spectra is also explored.     

Antioxidant Activity Evaluation Assay Based on Peroxide Radicals Generation and Potentiometric Measurement

A new version of potentiometric evaluation of antioxidant activity in biological liquids, food, drinks, and so forth, based on the mediator system combined with the free radicals generation has been proposed. A radical initiator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH), and K₃[Fe(CN)₆]/K₄[Fe(CN)₆] as a mediator system were used. Interactions of the mediator system with radicals, radicals with antioxidants, and erythrocytes have been investigated. The correlation coefficient between the data obtained in the presence and the absence of AAPH equals 0.98. In addition, the possibility to determine a free radical generation rate by using the mediator system has been demonstrated.     

Potentiometric Biosensor System Based on Recombinant Urease and Creatinine Deiminase for Urea and Creatinine Determination in Blood Dialysate and Serum

A biosensor system for simultaneous determination of creatinine and urea in blood serum and dialysate samples was developed. It consisted of creatinine and urea biosensors based on a potentiometric transducers with two identical pH‐sensitive field‐effect transistors. In creatinine biosensor, creatinine deiminase immobilized via photopolymerization in PVA/SbQ polymer on one transistor served as a biorecognition element, while bovine serum albumin in PVA/SbQ polymer placed on the second transistor was used for reference. The urea biosensor was created in the same way but recombinant urease was used instead of creatinine deiminase. The linear ranges of creatinine and urea measurement were 0.02–2 mM and 0.5–15 mM, correspondingly, which allowed simultaneous determination of the metabolites. Response time of the biosensor system was 2–3 min; RSD of responses did not exceeded 5 %. The biosensors demonstrated absence of non‐selective response towards components of blood dialysate and serum. Urea and creatinine concentrations were determined in 20 samples of blood dialysate and serum. The results correlated well with traditional methods of analysis. Creatinine and urea biosensors were stable during five months of storage (during this time the responses decreased by about 10 %). The proposed biosensor system can be effectively used for analysis of serum samples and for hemodialysis control.     

A Practical Approach to the Synthesis of Dianhydro Sugars

Chiral tetrols derived from various carbohydrate precursors have been converted into the corresponding dianhydro sugar derivatives in a one pot procedure. The course of reaction very much depends upon the protecting groups used. In case of D-mannitol and sorbitol, it has been shown that when 3,4-hydroxy groups are protected as trans-acetonide group, the present methodology furnished exclusively 1,2: 5,6-dianhydro derivatives in excellent yield. However, if the 3,4-hydroxy groups are protected with benzyl group a mixture of products consisting of dianhydro sugar, a furan and a bicyclo[2.2.2]octane derivatives were obtained. This method has also been used to synthesize dianhydro sugars in which the two diol moieties are placed adjacent to each other or separated by one or more carbon atoms.