Preparation Of Biosensor Research Articles

Graphene–polyamidoamine dendrimer–Pt nanoparticles hybrid nanomaterial for the preparation of mediatorless enzyme biosensor

A novel inorganic–organic hybrid nanomaterial was prepared by anchoring (3-glycidyloxypropyl)trimethoxysilane at the surface of graphene oxide, further cross-linking with polyamidoamine G-4 dendrimer, and final decoration with platinum nanoparticles. A glassy carbon electrode was coated with this hybrid nanomaterial and then used as support for the covalent immobilization of glucose oxidase. This enzyme electrode was employed to construct a mediatorless glucose amperometric biosensor. The resulting biosensor exhibited good electrocatalytical activity for the oxidation of the H2O2 produced by the enzyme catalyzed reaction, being able to detect glucose when poised at +400mV. The biosensor showed a wide linear response to glucose ranging from 10μM to 8.1mM, high sensitivity of 24.6mA/Mcm2 and low detection limit of 0.8μM. The biosensor was successfully tested for the quantification of glucose in samples of commercial soft drinks.

Development of a bienzymatic amperometric biosensor to determine uric acid in human serum, based on mesoporous silica (MCM-41) for enzyme immobilization

The aim of this work is the development of a biosensor to determine uric acid on serum. The biosensor has been developed through enzymatic immobilization of uricase from Candida spp. and peroxidase from horseradish on mesoporous silica with hexagonal symmetry (MCM-41). The mesoporous material was immobilized by Nafion assisted adsorption on a glassy carbon electrode, which was used as working electrode. Measurements were performed in a conventional three electrodes cell. The biosensor configuration allowed a fast, sensitive and stable electrochemical detection of hydrogen peroxide generated by the enzyme reaction. All experimental variables involved in the preparation and performance of the enzyme biosensor were optimized. Amperometry in stirred solutions at −100mV provided a linear calibration plot for uric acid in the 2–10μM concentration range. Furthermore, the proposed biosensor showed excellent analytical performance with detection and quantification limits of 0.33μM and 2μM, respectively; analytical sensitivity of 3.908nAμM−1, repeatability <2.11% and a long-term stability of 14 days (daily measurements). The biosensor yielded good results in the determination of uric acid in spiked human serum samples.

Preparation of graphene oxide-based surface plasmon resonance biosensor with Au bipyramid nanoparticles as sensitivity enhancer

A sensitive and selective wavelength-modulation surface plasmon resonance (SPR) biosensor based on graphene oxide (GO) and Au bipyramids (AuBPs) is reported for determination of bovine IgM. GO sheets with lengths of 100–300nm are synthesized and assembled on amine-modified Au film. The large surface area and abundant functional groups of GO allow the efficient immobilization of antibody. AuBPs are nanoparticles with a penta-twinned crystal structure, which have a sharp localized surface plasmon resonance (LSPR) band because of their high monodispersity. In the optimal conditions, the GO-based biosensor with AuBPs as sensitivity enhancers shows a satisfactory response to bovine IgM in the concentration range of 0.03–32μgmL−1. For contrast, traditional biosensor, GO-based biosensor and GO-based biosensor with Au nanorods (AuNRs) as sensitivity enhancers for antigen detection were also investigated. Consequently, the as-prepared GO sheets function as promising support for antibody and GO-based SPR biosensor using AuBPs as enhancers has the highest sensitivity among the four types of biosensors.

Electrochemical Biosensing Platform Using Hydrogel Prepared from Ferrocene Modified Amino Acid as Highly Efficient Immobilization Matrix

To increase the loading of glucose oxidase (GOx) and simplify glucose biosensor fabrication, hydrogel prepared from ferrocene (Fc) modified amino acid phenylalanine (Phe, F) was utilized for the incorporation of GOx. The synthesized hydrogel displays good biocompatibility and contains a significant number of Fc moieties, which can be considered as an ideal matrix to immobilize enzymes for the preparation of mediator-based biosensors. The hydrogel was studied by scanning electron microscopy, which indicated that it was composed of nanofibers with a diameter of around 50-100 nm and length extended to 1 mm. With the addition of GOx into the hydrogel and by directly dropping the resulting biocomposite onto the electrode surface, a glucose biosensor, that displays good performance due to improved enzyme loading and efficient electron transfer, can be simply constructed. The favorable network structure and good biocompatibility of the hydrogel could effectively avoid enzyme leakage and maintain the bioactivity of the enzymes, which resulted in good stability of the biosensor. The biosensor was utilized for the detection of glucose in blood samples with results comparable to those obtained from the hospital. The hydrogel as a functional component of an amperometric biosensor has implications for future development of biosensors and for clinical applications.

Development of an efficient immobilization matrix based on a conducting polymer and functionalized multiwall carbon nanotubes: synthesis and its application to ethanol biosensors.

Material modification is one of the hot topics recently. Hereby a novel functional monomer, 2-(4-nitrophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (BIPN), was synthesized for matrix generation through electrochemical polymerization. Its conducting polymer was successfully used for the biolayer construction in the biosensor preparation. The electrochemical and morphological properties were improved by the introduction of carboxylic acid functionalized multiwall carbon nanotubes (f-MWCNTs). Carboxylic acid functionalization of MWCNTs was carried out via acid treatment. The electrode surface was modified with the polymer and f-MWCNTs during electropolymerization to achieve a perfect immobilization matrix for alcohol oxidase. In order to prepare a new alcohol biosensor, alcohol oxidase (AOx) was immobilized onto the modified electrode. The modified electrode was characterized by scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques. Electrochemical responses of the enzyme electrodes were monitored at -0.7 V vs. Ag reference electrode by monitoring oxygen consumption in the presence of ethanol. Kinetic parameters, operational and storage stabilities were investigated. K, Imax, LOD and sensitivity were calculated as 16.946 mM, 3.31 μA, 0.806 mM and 476 μA mM-1 cm-2, respectively. Finally, this biosensor was applied to estimate the alcohol content in various beverages successfully.

Preparation of electrochemical biosensor for detection of organophosphorus pesticides.

Polyvinyl chloride (PVC) can be used to develop reaction beaker which acts as electrochemical cell for the measurement of OP pesticides. Being chemically inert, corrosion resistant, and easy in molding to various shapes and size, PVC can be used for the immobilization of enzyme. Organophosphorus hydrolase was immobilized covalently onto the chemically activated inner surface of PVC beaker by using glutaraldehyde as a coupling agent. The carbon nanotubes paste working electrode was constructed for amperometric measurement at a potential of +0.8 V. The biosensor showed optimum response at pH 8.0 with incubation temperature of 40°C. K m and I max for substrate (methyl parathion) were 322.58 µM and 1.1 µA, respectively. Evaluation study showed a correlation of 0.985, which was in agreement with the standard method. The OPH biosensor lost 50% of its initial activity after its regular use for 25 times over a period of 50 days when stored in 0.1 M sodium phosphate buffer, pH 8.0 at 4°C. No interference was observed by interfering species.

Correction: Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) on to a glassy carbon electrode (GCE) and subsequent casting of silica sol–gel (SiSG) entrapped laccase (Lac) enzyme on to the MWCNT/GCE. The catalytic activity of laccase biosensor was found to be good enough for sensitive determination of isoprenaline (ISP) with the aid of voltammetric techniques and we have also demonstrated the detailed electrochemical redox mechanism of ISP. From the effect of the pH, we have optimized the optimum pH as 6.5, and from effect of scan rate we have evaluated the kinetic parameters, heterogeneous rate constant, charge transfer coefficient and diffusion coefficient values. Furthermore the limit of detection (LOD) and limit of quantification (LOQ) values were found to be 1.8 × 10−7 M and 6.0 × 10−7 M, respectively. The simultaneous determination of ISP in the presence of uric acid (UA) and ascorbic acid (AA) was successfully carried out. The surface nature of the biosensor was characterized by using electrochemical impedance spectroscopy. Finally the validation of the proposed method was verified by the recovery of injection (ISP) in serum samples and their recoveries were found to be in a satisfactory range. The proposed method was found to have good repeatability, reproducibility and stability with low relative standard deviation (RSD) values.

Studies on the Interaction Mechanism of Morin-Co(II) with DNA and Preparation of Electrochemical DNA Biosensor

Studies on the Interaction Mechanism of Morin-Co(II) with DNA and Preparation of Electrochemical DNA Biosensor

Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) followed by sol–gel entrapment of laccase (Lac) enzyme on to the GCE.

Facile preparation of mesocellular graphene foam for direct glucose oxidase electrochemistry and sensitive glucose sensing

Biocompatible mesocellular graphene foam (MGF) was easily synthesized and conveniently used for the immobilization, direct electrochemistry, and biosensing of glucose oxidase (GOD). Detailed characterization revealed that the as-prepared MGF has high conductivity, ultra-large surface area (2581m2g−1) and pore volume (5.53cm3g−1) as well as high loading of GOD. When the pristine MGF served as a glucose biosensor, the direct and fast electron transfer with rate constant of 4.8s−1 was observed by cyclic voltammetry measurements. Based on the decrease of electrocatalytic currents, the prepared biosensor exhibited a wide linear range from 1.0 to 12mM with a detection limit of 0.25mM and a sensitivity of 2.87μAmM−1cm−2. Furthermore, the repeated and long-run test showed that the glucose biosensor was stable in both direct electrochemistry and sensitive glucose sensing. All these features besides the facile preparation, suggested that MGF would be a potential matrix for novel biosensor preparation.

Molecular simulations of myoglobin adsorbed on rutile (1 1 0) and (0 0 1) surfaces

The adsorption of myoglobin (Mb) on the surface of titanium dioxide is very important for the preparation of biosensors. Adsorption orientation and conformation of Mb on rutile (110) and (001) surfaces were investigated by combining Monte Carlo and molecular dynamics methods. The orientation, DSSP, superimposed structure, root-mean-square deviation and gyration radius of Mb were analyzed. Furthermore, the distribution of water molecules on rutile (110) and (001) surfaces and representative snapshots of water molecules at different rutile interfaces were also discussed in detail. Simulation results show that adsorbed Mb conformations are not influenced by surfaces obviously because of the strong hydrophilicity of both surfaces. Two layers of water molecules form on both rutile (110) and (001) surfaces. After 80ns molecular dynamics simulation, the heme of Mb is close to the rutile (001) surface and far away from the rutile (110) surface; this infers that electron transfer pathway of Mb is closer to the rutile (001) surface, which is favorable for faster electron transfer.

Glutamate sol-gel amperometric biosensor based on co-immobilised NADP+ and glutamate dehydrogenase

In this work the preparation and electrochemical characterisation of a new glutamate amperometric sol-gel biosensor is described. A carbon paste electrode was electrochemically modified with the phenothiazine dye methylene green (MG). The NADP+ and glutamate dehydrogenase were co-immobilised in a sol-gel matrix. When coupled to a flow injection system (FIA) the biosensor showed good electrocatalytic activity towards NADPH oxidation at the potential of + 0.3 V vs. Ag/AgCl; KCl sat., which represents a strong overpotential reduction. The biosensor yielded a linear response from 5.0 × 10−5 to 1.0 × 10−2 M glutamate concentration, with a detection limit of 5 × 10−6 M and reproducibility of results better than 2.3% (RSD). Moreover, the implemented biosensor showed to be still useful after 7 months, 500 determinations.

A novel promising biomolecule immobilization matrix: Synthesis of functional benzimidazole containing conducting polymer and its biosensor applications

In order to construct a robust covalent binding between biomolecule and immobilization platform in biosensor preparation, a novel functional monomer 4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2-yl)benzaldehyde (BIBA) was designed and successfully synthesized. After electropolymerization of this monomer, electrochemical and spectroelectrochemical properties were investigated in detail. To fabricate the desired biosensor, glucose oxidase (GOx) was immobilized as a model enzyme on the polymer coated graphite electrode with the help of glutaraldehyde (GA). During the immobilization step, an imine bond was formed between the free amino groups of enzyme and aldehyde group of polymer. The surface characterization and morphology were investigated to confirm bioconjugation by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) at each step of biosensor fabrication. The optimized biosensor shows good linearity between 0.02mM and 1.20mM and a low limit of detection (LOD) of 2.29μM. Kinetic parameters Kmapp and Imax were determined as 0.94mM and 10.91μA, respectively. The biosensor was tested for human blood serum samples.

Creating Protein-Imprinted Self-Assembled Monolayers with Multiple Binding Sites and Biocompatible Imprinted Cavities

Imprinted monolayers have several advantages over bulk imprinted polymers such as excellent mass transfer of molecules into and out of imprinted sites and transduction of binding signals detected in real time. Protein-imprinted self-assembled monolayers (SAMs) were created with multiple binding sites and biocompatible imprinted cavities from functional thiols and novel disulfide compounds containing an oligoethylene glycol (OEG) terminal moiety and two amide groups incorporated in the chain (DHAP) in a biologically benign solution. DHAP played an important role in the formation of multiple binding sites and biocompatible cavities in addition to resisting nonspecific protein binding. The created protein-imprinted SAMs exhibited the excellent ability of specific binding of target proteins determined by multiple binding sites and imprinted cavities. The strategy generates tailor-made monolayer surfaces with specific protein binding and opens the possibility of controlled assembly of intellectual biomaterials and preparation of biosensors.

Hybridization of Bioelectrochemically Functional Infinite Coordination Polymer Nanoparticles with Carbon Nanotubes for Highly Sensitive and Selective In Vivo Electrochemical Monitoring

This study demonstrates the formation of a three-dimensional conducting framework through hybridization of bioelectrochemically active infinite coordination polymer (ICP) nanoparticles with single-walled carbon nanotubes (SWNTs) for highly sensitive and selective in vivo electrochemical monitoring with combination with in vivo microdialysis. The bioelectrochemically active ICP nanoparticles are synthesized through the self-assembly process of NAD(+) and Tb(3+), in which all biosensing elements including an electrocatalyst (i.e., methylene green, MG), cofactor (i.e., β-nicotinamide adenine dinucleotide, NAD(+)), and enzyme (i.e., glucose dehydrogenase, GDH) are adaptively encapsulated. The ICP/SWNT-based biosensors are simply prepared by drop-coating the as-formed ICP/SWNT nanocomposite onto a glassy carbon substrate. Electrochemical studies demonstrate that the simply prepared ICP/SWNT-based biosensors exhibit excellent biosensing properties with a higher sensitivity and stability than the ICP-based biosensors prepared only with ICP nanoparticles (i.e., without hybridization of SWNTs). By using a GDH-based electrochemical biosensor as an example, we demonstrate a technically simple yet effective online electroanalytical platform for continuously monitoring glucose in the brain of guinea pigs with the ICP/SWNT-based biosensor as an online detector in a continuous-flow system combined with in vivo microdialysis. Under the experimental conditions employed here, the dynamic linear range for glucose with the ICP/SWNT-biosensor is from 50 to 1000 μM. Moreover, in vivo selectivity investigations with the biosensors prepared by the GDH-free ICPs reveal that ICP/SWNT-based biosensors are very selective for the measurement of glucose in the cerebral system. The basal level of glucose in the microdialysates from the striatum of guinea pigs is determined to be 0.31 ± 0.03 mM (n = 3). The study offers a simple route to the preparation of electrochemical biosensors, which is envisaged to be particularly useful for probing the chemical events involved in some physiological and pathological processes.

Nanostructured Gold for Immobilization of Thioaniline Functionalized Glucose Oxidase and Au Nanoparticles by Electropolymerization

Sensors are devices composed of an active sensing material with a signal transducer. Electrochemical sensors have more advantages over the others because the electrodes can sense the analyte that is present in the host without doing any damage to the host system. The immobilization of a protein on a metallic transducer can be a crucial step in the development of bionanodevices that find applications in the field of biomaterials, biocoatings, biofuel cells, etc. In the present study, we show the immobilization by electropolymerization of thioaniline functionalized glucose oxidase and Au nanoparticles on nanostructured gold films prepared by electrodeposition and compared to sputtered gold. This enzyme is employed in the preparation of biosensors of biomedical interest. The goodness of the Au film for enzyme binding is evaluated by comparison of the enzyme activity and of the interval of linearity for the determination of glucose concentration.

Electrochemical biosensing platform based on carboxymethyl cellulose functionalized reduced graphene oxide and hemoglobin hybrid nanocomposite film

A novel, biocompatible sensing strategy based on carboxymethyl cellulose (CMC) functionalized reduced grapheme oxide (rGO) nanocomposite film for immobilizing the hemoglobin (Hb) was first developed. The rGO-CMC/Hb film was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectra (EIS). The direct electrochemistry of rGO-CMC/Hb modified electrodes were investigated by cyclic voltammetry. The results indicated that Hb retained its bioactivity on the modified electrode and showed a couple of well-defined and quasi-reversible redox peaks. The immobilized Hb exhibited excellent bioelectrocatalytic activity toward the reduction of NO and H2O2. Two linear segments with different slopes for NO concentration were from 0.864μM to 19.8μM and from 19.8μM to 48.6μM, respectively. The detection limit is 0.37μM at 3σ. The developed biosensor exhibited excellent catalytic activity toward H2O2 over a wide linear range of 0.083–13.94μM with a detection limit of 0.08μM at 3σ. The facile and easy electrochemical approach used in this paper may open up a promising platform for protein immobilization and biosensor preparation.

Electrochemical biosensor for creatinine based on the immobilization of creatininase, creatinase and sarcosine oxidase onto a ferrocene/horseradish peroxidase/gold nanoparticles/multi-walled carbon nanotubes/Teflon composite electrode

A composite electrode consisted of gold nanoparticles (AuNPs), multi-walled carbon nanotubes (MWCNTs) and Teflon, to which peroxidase (HRP) and ferrocene (Fc) were incorporated as auxiliary enzyme and redox mediator, respectively, was constructed. The enzymes creatininase, creatinase and sarcosine oxidase were then co-immobilized onto the surface of the resulting HRP/Fc/AuNPs/MWCNTs/Teflon electrode for the preparation of a creatinine biosensor. Amperometry in stirred solutions using a detection potential of 0.0V vs Ag/AgCl allowed a linear calibration plot to be obtained in the 0.003–1.0mM creatinine concentration range with a limit of detection of 0.1μM (S/N=3). The apparent Michaelis-Menten constant for creatininase was KMap=4.1±0.4mM. The developed biosensor was validated with good results by determining creatinine in human serum and correlating with the spectrophotometric Jaffe's method.

Preparation of Enzyme-Immobilized Biosensor by the Combination of Electrodeposition and Electropolymerization

not Available.

Preparation of novel electrochemical glucose biosensors for whole blood based on antibiofouling polyurethane-heparin nanoparticles

In this paper, the novel polyurethane-heparin nanoparticles (PU-Hep NPs) were synthesized and used to establish an amperometric glucose biosensor that can be applied in whole blood directly, which was based on the antibiofouling property of PU-Hep NPs. More details of preparation of PU-Hep NPs, immobilizing glucose oxidase (GOx) on (PU-Hep)/glass carbon electrode (GCE) and its electrochemical behavior in whole blood were presented. The cyclic voltammetric results indicated that GOx immobilized on the PU-Hep NPs exhibited direct electron transfer reaction, and the cyclic voltammogram (CV) displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of −408mV. The biosensor had good electrocatalytic activity toward glucose with a low detection limit 1.4×10−5M in whole blood. The glucose biosensor did not respond to ascorbic acid (AA) and uric acid (UA) at their concentration normally encountered in blood. The development of materials science will bring a new momentum to electrical analysis.