The Amperometric Glucose Enzyme Electrode by Immobilized Glucose Oxidase in Glucose Oxidase/N-ethyl-Poly (4-vinyl)pyridine Multilayer

Enzylnebasedampcr()metricbiosensorsha\'eattractedincreasinginterestinthe1astt`xodecades.Inordertofabricate[heenzyn1elayer,considerahlceff()rtsha\,eheendcv()tcdt(1thedeveloprnent()fvari()ustechniquesf()rin1n1obilizingthcen/yn1c"2.Rcccntly.thcp()lyelectrolyte-proteincomplcx111ultilayerassen1blybyaIternateelectr()staticadsorptionhasbcenrep()rted',amullilaycrc()nsistingofalterl1atepolyethylenimineandglucoseoxidasclaycrswasassemb1edhyLv()veltl/>.ThesebioIllo1eculararthitecturesopenawaytoconstruct…     

Electrodeposition of Silver Nanoparticles on MWCNT Film Electrodes for Hydrogen Peroxide Sensing

Silver （Ag） nanoparticles were directly electrodeposited on multi-walled carbon nanotubes （MWCNT） in AgNO3/LiNO3 containing EDTA （ethylenediaminetetraacetic acid）. The structure and nature of the resulting Ag/MWNT composite were characterized by field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM） and X-ray diffraction （XRD）, and the distribution shape of Ag nanoparticles was found to be dependent on the presence of EDTA. The modified electrode showed excellent electrocatalytic activity to redox reaction of hydrogen peroxide and the mechanism of hydrogen peroxide was partly reversible procession with oxidation and reduction peaks at 0.77 and -0.83 V, respectively. The oxidation and reduction peak currents were linearly related to hydrogen peroxide concentration in the range of 1×10^-6-3×10^-4 and 1 ×10^-8-7× 10^-4 mol·L^-1 with correlation coefficients of 0.996 and 0.986, and 3s-detection limit of 9 × 10^-7 and 7 × 10^-9 mol·L^-1.     

Electrochemical Modified Electrodes Based on Metal‐Salen Complexes

Abstract

A general view of the electroanalytical applications of metal‐salen complexes is discussed in this review. The family of Schiff bases derived from ethylenediamine and ortho‐phenolic aldehydes (N,N′‐ethylenebis(salicylideneiminato)—salen) and their complexes of various transition metals, such as Al, Ce, Co, Cu, Cr, Fe, Ga, Hg, Mn, Mo, Ni, and V have been used in many fields of chemical research for a wide range of applications such as catalysts for the oxygenation of organic molecules, epoxidation of alkenes, oxidation of hydrocarbons and many other catalyzed reactions; as electrocatalyst for novel sensors development; and mimicking the catalytic functions of enzymes. A brief history of the synthesis and reactivity of metal‐salen complexes will be presented. The potentialities and possibilities of metal‐Salen complexes modified electrodes in the development of electrochemical sensors as well as other types of sensors, their construction and methods of fabrication, and the potential application of these modified electrodes will be illustrated and discussed.     

Colorimetric Detection of Mercury（Ⅱ） Based on Silver Nanoparticles

通过一步法制备了稳定、分散的聚多巴胺包被的银纳米粒子（AgNPs）.基于Hg2＋与聚多巴胺的吸附作用使AgNPs发生聚集,导致体系吸收信号发生变化,同时溶液颜色也发生相应改变,建立了Hg2＋的紫外-可见分光光度法及色度法.线性范围为0.5～5.0μmol/L,检出限为50 nmol/L.表征了紫外-可见光谱、红外光谱及扫描电镜显微成像（SEM）,优化了实验条件,并探讨了反应机理.该方法用于实际样品中Hg2＋的测定,RSD≤4.4%.     

Optical Determination of Glucose with Glucose Oxidase Immobilized in PVC together with Fluorescent Oxazol‐5‐One Derivatives

Abstract

Fully reversible biosensors for glucose monitoring based on solid polyvinylchloride (PVC) films where the enzyme glucose oxidase (GOx) was incorporated together with 2‐phenyl‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐1), 2‐(3,5‐dinitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐2), 2‐(4‐nitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐3) and 2‐(4‐tolyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐4) derivatives have been developed. The limit of detection (LOD) values for glucose were found to be 1.47×10^?5 M, 2.01×10^?5 M, 0.89×10^?5 M, and 0.12×10^?5 M for CPO‐1, CPO‐2, CPO‐3, and CPO‐4, respectively (n=7). Sensor films were found to have excellent photostability.     

Formulation and Evaluation of Chitosan‐Gellan Based Methotrexate Implants

An implant controlled‐release system for methotrexate delivery based on a polyion complex composed of chitosan and gellan was investigated. Multi‐layered implant was prepared by using poly(vinyl alcohol), gellan and chitosan. Two chitosan layers sandwiched the poly(vinyl alcohol)‐gellan layer, which acted as a methotrexate reservoir. The prepared implant was evaluated for swellability, in vitro and in vivo release and biodegradation studies. The equilibrium swelling and methotrexate release was found to depend on a concentration of calcium chloride, which was used as a crosslinking agent for gellan. Drug‐loaded implants were subcutaneously implanted in the back of Wistar rats. The in vivo studies showed that methotrexate was released slowly for a period over 30 days and also there was no fibrous capsule formation around the implant indicating the biocompatibility of the implant.     

Nanoparticles prepared by self-assembly of Chitosan and poly-γ-glutamic acid

The present paper describes the preparation and characterization of novel biodegradable nanoparticles based on self-assembly of poly-gamma-glutamic acid (γ-PGA) and chitosan (CH). The nanosystems were stable in aqueous media at low pH conditions. Solubility of the systems was determined by turbidity measurements. Surface charge and mobility were measured electrophoretically. The particle size and the size distribution of the polyelectrolyte complexes were identified by dynamic light scattering and transmission electron microscopy (TEM). It was found that the size and size distribution of the nanosystems depends on the concentrations of γ-PGA and CH solutions and their ratio as well as on the pH of the mixture and the order of addition. The diameter of individual particles was in the range of 20–285 nm measured by TEM, and the average hydrodynamic diameters were between 150 and 330 nm. These biodegradable, self-assembling stable nanocomplexes might be useful for several biomedical applications.     

Development of Lactose Biosensor Based on β‐Galactosidase and Glucose Oxidase Immobilized into Gelatin

In this article, we describe the preparation of a new lactose biosensor based on electrode coating with β‐galactosidase and glucose oxidase immobilized gelatin. For this purpose, β‐galactosidase and glucose oxidase enzymes were immobilized onto gelatin by crosslinking with glutaraldehyde. Properties of the immobilized β‐galactosidase and glucose oxidase enzymes electrode have been studied. The effects of glutaraldehyde concentration, temperature and pH variations and reusability were among the subjects analyzed. Lactose biosensors were subjected to continuous repeated use in order to observe reusability and shelf life; where standard lactose and milk samples were used as substrate solutions. Continuous reuse experiments showed that most of the lactose biosensors activities were retained even after the 10th use in a period of 30 days.     

Multianalyte Biosensor for Simultaneous Determination of Glucose and Galactose Based on Micromachined Chamber-type Electrodes

An amperometric multianalyte biosensor for the simultaneous determination of glucose and galactose was developed based on chamber-type electrodes, which were fabricated by micromachining technology. The dual cham-ber-type enzyme electrode with glucose and galactose sensor elements was integrated onto one microchip. The experimental parameters of this biosensor were optimized. The biosensor exhibited a linearity of up to 4.0 mol/L for glucose and 4.5 mol/L for galactose, and the response time was about 30 s for glucose and 40 s for galactose. No cross-talking behavior was investigated in the course of simultaneous measurement of the two analytes. Interference from electroactive species, such as ascorbic acid and uric acid, was minimized due to the permselectivity of Nation film. In addition, the biosensor displayed a storage stability of longer than one month.     

Biosensor for Hydrogen Peroxide Based on Chitosan and Nanoparticle Complex Film–Modified Glassy-Carbon Electrodes

Abstract

A biosensor for hydrogen peroxide was fabricated by co-immobilizing cadmium telluride (CdTe) nanoparticles, chitosan, and hemoglobin (Hb) matrix. There was a pair of nearly reversible redox peaks around ?0.360 V, and the electrochemical behavior of Hb was a surface-controlled process, with an electron-transfer rate constant of 1.36 s^?1 and surface coverage of 2.62 × 10^?10 mol cm^?2. Fourier transform infrared (FT-IR) spectra and ultraviolet–visible (UV-vis) spectra indicated that Hb sustained its natural conformation. It was demonstrated that Hb in the matrix kept its bioactivity and exhibited catalytic ability toward H₂O₂, with a response ranging from 7.44 × 10^?6 to 6.95 × 10^?4 M and a detection limit of 2.23 × 10^?6 M.     

A Novel Glucose Biosensor Based on Palladium Nanoparticles and Its Application in Detection of Glucose Level in Urine

IntroductionThelevelofglucoseinbloodorurineindicateshyper andhypoglycaemia ,bothofwhichcanresultfromavarietyofendocrinedisorders .1 4 Therapidandreliabledetermi nationofglucoselevelisaroutineprojectinclinicchem istry.Urinesamplesaresaferandmoreconvenientthanbloodones .Meanwhile ,theconcentrationofglucoseinserumiscloselyassociatedwiththatinurine .2 4 Eventhoughglucoseelectrodeshavebeensuccessfullyusedinseruminclinicalapplication ,thequestionstillremainedofhowtodetecttheglucoselevelinurine ,wh…     

A New Bienzymatic Biosensor Based on Butyrylcholine Esterase‐Sulfhydryl Oxidase Enzymes

Abstract

Over the last decades, cholinesterase (ChE) biosensors have emerged as a sensitive and rapid technique for toxicity analysis in environmental monitoring, food, and quality control. These systems have the potential to complement or replace the classical analytical methods by simplifying or eliminating sample preparation protocols and making field testing easier and faster with significant decrease in costs per analysis. In this study, a new bienzymatic biosensor based on butyrylcholinesterase (BuChE) and sulfhydryl oxidase (SOX) enzymes was developed. This system makes use of the biocatalyzed hydrolysis of butyrylthiocholine to butyric acid and thiocholine that acts as a SOX substrate. Measurements were performed by following of the consumed oxygen level related to butyrylthiocholine concentration in the enzymatic reactions. Bienzymatic system was characterized and applied for detection of donepezil which is a reversible inhibitor of cholinesterase and belongs to a new class of cholinesterase inhibitors having an N‐benzylpiperidine and an indanone moiety, by following of the decrease in biosensor response as a result of competitive inhibition.     

Multianalyte Biosensors for the Simultaneous Determination of Glucose and Galactose Based on Thin Film Electrodes

A multianalyte biosensor for the simultaneous determination of glucose and galactose was developed by immobilizing glucose oxidase (GOD) and galactose oxidase (GAO) on Nation-modified thin film platinum disk electrodes. The dual Pt working electrodes with disk shape and the surrounding ring shaped counter electrode were fabricated by thin film technology,which were integrated onto the same microchip. The response of the designed biosensor for glucose and galactose were linear up to 6.0mmol/L and 3.5mmol/L with sensitivities of 0.3μA/mmol/L and 0.12μA/mmol/L, respectively. No cross-talking effect was observed.     

Determination of Silver by Stripping Voltammetry at Composite Pyrocarbon–Glass Ceramic Electrodes

Characteristic features of the process of Ag(I) discharge and ionization at a composite pyrocarbon–glass ceramic electrode were studied by stripping voltammetry. The optimal measurement conditions were selected, and n× 10^–6g/L Ag(I) was determined in drinking water (n= 4, RSD = 4%).     

A Novel DNA‐Enrichment Technology Based on Amino‐Modified Functionalized Silica Nanoparticles

Abstract

In this paper we report a novel DNA‐enrichment technology based on amino‐modified functionalized silica nanoparticles. The approach takes advantage of the amino‐modified silica nanoparticles that have been prepared in one step by the controlled synchronous hydrolysis of tetraethoxysilane and N‐(β‐amimoethyl)‐γ‐aminopropyltriethoxysilane in water nanodroplets of water‐in‐oil microemulsions. The functionalized silica nanoparticles display a positive surface charge at neutral pH due to the presence of amino groups on the surface of these nanoparticles. DNA‐enrichment has been realized in the form of nanoparticle–DNA complexes that is accomplished through electrostatic binding between the positive charge of the amino group and the negative charge of the phosphate groups of the nucleic acid. These nanoparticles have high affinity to bind DNA. The results show that 1 mg of nanoparticles can bind 97.2 µg of plasmid DNA with 4.3 kb. This novel DNA‐enrichment technology has been used successfully in gene delivery.     

Amperometric Biosensor for Hypoxanthine Based on Immobilized Xanthine Oxidase on Iron (III) Meso‐tetraphenylporphyrin Nanoparticles Modified Glassy Carbon Electrode

Abstract

The preparation and performance of hypoxanthine (Hx) electrochemical biosensor, which was based on iron (III) meso‐tetraphenylporphyrin (FeTPP) nanoparticles (NPs), is reported in this work. FeTPP NPs prepared by mixing solvent techniques with diameters ca. 25~45 nm and were used as a mediator. The XOD/FeTPPNP/GC electrode exhibited good amperometric signal for Hx. Based on the consumption of dissolved oxygen during the oxidation process of Hx catalyzed by the immobilized XOD, the biosensor could detect the concentration of Hx up to 0.34 mM with a detection limit of 1.0 µM. The usefulness of this biosensor for the analysis of real sample was also demonstrated by determining Hx in rat brain dialysate coupled with microdialysis.     

Conversion of d‐Galactose to d‐threo‐Hexos‐2,3‐diulose by Fungal Pyranose Oxidase

Pyranose oxidase (pyranose:O₂ 2‐oxidoreductase, EC 1.1.3.10) purified from mycelia of the basidiomycete fungi Trametes versicolor and Oudemansiella mucida catalyzed oxidation of d‐galactose successively at C‐2 and C‐3 to d‐threo‐hexos‐2,3‐diulose (2,3‐dehydro‐d‐galactose, 2,3‐diketo‐d‐galactose) in the yields up to 80%. The sites of oxidation were deduced from structures of the N,N‐diphenylhydrazone derivatives of the reaction products. Under the reaction conditions used, the diulose was susceptible to non‐enzymatic oxidative decarboxylation to d‐threo‐pentos‐2‐ulose (2‐dehydro‐d‐xylose, 2‐keto‐d‐xylose) in yields of 5–10%.     

Isocyanide‐Based Multicomponent Synthesis of Functionalized 2,6‐Dioxohexahydropyrimidines in 1 M Aqueous Glucose

An effective route to novel 2,6‐dioxohexahydropyrimidines is described. This involves reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates in the presence of N,N′‐dimethylurea in 1M aq. glucose.     

Activation‐Based Catalase Enzyme Electrode and its Usage for Glucose Determination

Abstract

In this study, a novel type amperometric biosensor, which is based on the activation of catalase enzyme by glucose, was developed and used for the sensitive determination of glucose. For the preparation of the biosensor catalase enzyme was immobilized in gelatin by using cross‐linking agent glutaraldehyde and fixed on a pretreated teflon membrane of a dissolved oxygen probe. Glucose was used as an activator for the catalase enzyme and determination of glucose is based on the assay of the differences on the catalase activity of the biosensor on the oxygenmeter in the absence and the presence of glucose in the reaction medium. The responses of the activation based catalase biosensor have a linear relation to glucose concentrations and good measurement correlation between 0.5 and 5.0 µM with 2 min response time. In the optimization studies of the biosensor the most suitable catalase amount were found as 1324 U cm^?2 and also phosphate buffer (pH: 7.0; 50 mM) and 35°C were obtained as the optimum working conditions. For the characterization studies of the biosensor some parameters such as activator and interference effects of some substances on the biosensor response, reproducibility and operational stability were performed.     

Amperometric Biosensors for Glucose Based on Layer‐by‐Layer Assembled Functionalized Carbon Nanotube and Poly (Neutral Red) Multilayer Film

Abstract

Multiwalled carbon nanotubes (MWNTs) were treated with a mixture of concentrated sulfuric and nitric acid to introduce carboxylic acid groups to the nanotubes. Conducting polymer film was prepared by electrochemical polymerization of neutral red (NR). By using a layer‐by‐layer method, homogeneous and stable MWNTs and poly (neutral red) (PNR) multilayer films were alternately assembled on glassy carbon (GC) electrodes. With the introduction of PNR, the MWNTs/PNR multilayer film system showed synergy between the MWNTs and PNR, with a significant improvement of redox activity due to the excellent electron‐transfer ability of carbon nanotubes (CNTs) and PNR. The electropolymerization is advantageous, providing both prolonged long‐term stability and improved catalytic activity of the resulting modified electrodes. The MWNTs/PNR multilayer film modified glassy carbon electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. As compared to MWNTs and PNR‐modified GC electrodes, the magnitude of the amperometric response of the MWNTs/PNR composite‐modified GC electrode is more than three‐fold greater than that of the MWNTs modified GC electrode, and nine‐fold greater than that of the PNR‐modified GC electrode. With the immobilization of glucose oxidase onto the electrode surface using glutaric dialdehyde, a biosensor that responds sensitively to glucose has been constructed. In pH 6.98 phosphate buffer, nearly interference‐free determination of glucose has been realized at ?0.2 V vs. SCE with a linear range from 50 µM to 10 mM and response time <10s. The detection limit was 10 µM glucose (S/N=3).