One-step electropolymeric co-immobilization of glucose oxidase and heparin for amperometric biosensing of glucose

Electropolymerization was used for the co-deposition of glucose oxidase and heparin onto metal electrode transducers. Such electropolymeric co-entrapment within a non-conducting poly(1,2-phenylenediamine) (PPD) film imparts both biocatalytic and anticoagulation activities onto the transducer, and greatly improves the performance of the sensor after exposure to whole blood. Essentially identical glucose signals are observed before and after exposure to blood samples. Scanning electron micrographs after such exposure reveal no platelet deposition or formation of a fibrin "clot". The effect of the heparin co-immobilization on the glucose response is examined. Improved biocompatibility is reported also in connection with a needle-type carbon paste biosensor configuration. The simultaneous localization of the enzyme and heparin offers great promise for simplifying the preparation of enzyme electrodes and designing biocompatible implantable glucose biosensors.     

Tin disulfide nanoflakes decorated with gold nanoparticles for direct electrochemistry of glucose oxidase and glucose biosensing

Previously, we have prepared nanoflake-like tin disulfide (SnS2) and used for the immobilization of proteins and biosensing. We have now modified an electrode with a composite consisting of nanoflake-like SnS2 decorated with gold nanoparticles (Au-NPs) and have immobilized glucose oxidase (GOx) on its surface in order to study its direct electrochemistry. Scanning electron microscopy, electrochemical impedance spectroscopy, Fourier transform IR spectroscopy and cyclic voltammetry were used to examine the interaction between GOx and the AuNP-SnS2 film. It is shown that the composite film has a larger surface area and offers a microenvironment that facilitates the direct electron transfer between enzyme and electrode surface. The immobilized enzyme retains its bioactivity and undergoes a surface-controlled, reversible 2-proton and 2-electron transfer reaction, with an apparent electron transfer rate constant of 3.87 s ^-1. Compared to the nanoflake-like SnS2-based glucose sensor, the GOx-based biosensor exhibits a lower detection limit (1.0 :M), a better sensitivity (21.8 mA?M ^-1 ?cm ^-2), and a wider linear range (from 0.02 to 1.3 mM). The sensor displays excellent selectivity, good reproducibility, and acceptable stability. It was successfully applied to reagentless sensing of glucose at ?0.43 V.

ITO electrode modified with Pt nanodendrites-decorated ZnO nanorods for enzymatic glucose sensor

Journal of Solid State Electrochemistry - This work demonstrated the property enhancement of Pt nanodendrite (PtNDs)-decorated ZnO nanorods (ZnONRs) modified indium tin oxide (ITO) electrode for an...     

Facile preparation of nitrogen-doped graphene scrolls via acoustic cavitation as electrocatalyst for glucose biosensing

Nitrogen doping is considered as a promising strategy to tailor and develop the intrinsic properties of graphene. In this work, we report a facile method for preparation of nitrogen-doped graphene scrolls (N-GSS) through acoustic cavitation, which can not only realize graphene nitrogen doping but also simultaneously result in its scrolled topological structure and improvement of reduction degree. As a metal-free electrocatalyst, the prepared N-GSS showed good electrocatalytic activity towards oxidation of hydrogen peroxide with the sensitivity of 87.8 μA mM^?1 cm^?2. Then N-GSS was employed as a matrix for glucose oxidase (GOD) loading, and the fabricated biosensor also exhibited excellent analytical characteristics, such as a high sensitivity (55.2 μA mM^?1 cm^?2), wide linear range (2 μM to 3.56 mM, R = 0.999) and low detection limit (1 μM).     

Fluorescence properties of gold nanorods and their application for DNA biosensing

This communication reveals new and unique optical properties with respect to enhanced fluorescence of gold nanorods as they elongate; a novel strategy for DNA hybridization studies based on monitoring the fluorescence intensity of gold nanorods has been demonstrated.     

Enhanced direct electron transfer of glucose oxidase based on a protic ionic liquid modified electrode and its biosensing application

A novel glucose oxidase (GOD) biosensor was fabricated with a protic ionic liquid (PIL) N-ethylimidazolium trifluoromethanesulfonate ([EIm][TfO]) as the modifier of a carbon electrode. Due to the excellent conductivity and the conformational changes of the microenvironment around the GOD, the electrochemical and biocatalytic properties of GOD immobilized on the PIL-based electrode were dramatically enhanced. A couple of well-defined redox peaks could be observed, with a formal potential of −0.476 V. The GOD biosensor presented good catalytic activity to the oxidation of glucose in oxygen-saturated phosphate buffer solutions. The cathodic peak currents of GOD decreased along with glucose concentrations. A linear response in the range 0.005–2.8 mM was obtained with a detection limit of 2.5 μM. The sensitivity and the apparent Michaelis–Menten constant (K _m) were estimated to be 14.96 μA mM⁻¹ and 1.53 μM, respectively. In addition, the biosensor remained stable over 30 days, indicating its good chemical and mechanical stability. The glucose content of several serum samples was determined by using the newly developed biosensor, and the results were in good agreement with those obtained by hospital measurements. All results suggested that PILs were a good media for supporting biocatalytic processes on the bioelectrode.     

Direct electrochemistry of glucose oxidase on sulfonated graphene/gold nanoparticle hybrid and its application to glucose biosensing

Sulfonated graphene nanosheet/gold nanoparticle (SGN/Au) hybrid was synthesized by electrostatic self-assembly of anionic SGN and positively charged gold nanoparticles. Due to the well-dispersivity of SGN in aqueous solution and its adequate negative charge, Au nanoparticles were assembled uniformly on graphene surface with high distribution. With the advantages of both graphene and Au nanoparticles, SGN/Au hybrid showed enhanced electrocatalytic activity towards O₂ reduction. Furthermore, it provided a conductive and favorable microenvironment for the glucose oxidase (GOD) immobilization and thus promoted its direct electron transfer at the glassy carbon electrode. Based on the consumption of O₂ caused by glucose at the interface of GOD electrode modified with SGN/Au hybrid, the modified electrode displayed satisfactory analytical performance, including high sensitivity (14.55 μA mM^?1 cm^?2), low detection limit (0.2 mM), an acceptable linear range from 2 to 16 mM, and also the prevention from the interference of some species. These results indicated that the prepared SGN/Au hybrid is a promising candidate material for high-performance glucose biosensor.     

Facile and controllable preparation of glucose biosensor based on Prussian blue nanoparticles hybrid composites

A glucose biosensor based on polyvinylpyrrolidone (PVP) protected Prussian blue nanoparticles (PBNPs)-polyaniline/multi-walled carbon nanotubes hybrid composites was fabricated by electrochemical method. A novel route for PBNPs preparation was applied in the fabrication with the help of PVP, and from scanning electron microscope images, Prussian blue particles on the electrode were found nanoscaled. The biosensor exhibits fast current response (<6 s) and a linearity in the range from 6.7x10(-6) to 1.9x10(-3) M with a high sensitivity of 6.28 microA mM(-1) and a detection limit of 6x10(-7) M (S/N=3) for the detection of glucose. The apparent activation energy of enzyme-catalyzed reaction and the apparent Michaelis-Menten constant are 23.9 kJ mol(-1) and 1.9 mM respectively, which suggests a high affinity of the enzyme-substrate. This easy and controllable construction method of glucose biosensor combines the characteristics of the components of the hybrid composites, which favors the fast and sensitive detection of glucose with improved analytical capabilities. In addition, the biosensor was examined in human serum samples for glucose determination with a recovery between 95.0 and 104.5%.     

Sulfonated polyaniline network grafted multi-wall carbon nanotubes for enzyme immobilization, direct electrochemistry and biosensing of glucose

A new nanomaterial was prepared by grafting a layer of sulfonated polyaniline network (SPAN-NW) on to the surface of multi-walled carbon nanotube (MWNT) and effectively utilized for immobilization of an enzyme and for the fabrication of a biosensor. SPAN-NW was formed on the surface of MWNT by polymerizing a mixture of diphenyl amine 4-sulfonic acid (DPASA), 4-vinyl aniline (VA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (APASA) in the presence of amine functionalized MWNT (MWNT-NH₂). The MWNT-g-SPAN-NW was immobilized with glucose oxidase (GOx) to fabricate the SPAN-NW/GOx biosensor. MWNT-g-SPAN-NW/GOx electrode showed direct electron transfer (DET) for GOx with a fast heterogeneous electron transfer rate constant (k_s) of 4.11 s^− 1. The amperometric current response of MWNT-g-SPAN-NW/GOx biosensor shows linearity up to 9 mM of glucose, with a correlation coefficient of 0.99 and a detection limit of 0.11 μM (S/N = 3). At a low applied potential of − 0.1 V, MWNT-g-SPAN-NW/GOx electrode possesses high sensitivity (4.34 μA mM^− 1) and reproducibility towards glucose.     

A novel amperometric biosensor based on NiO hollow nanospheres for biosensing glucose

NiO hollow nanospheres were synthesized by controlled precipitation of metal ions with urea using carbon microspheres as templates, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized on the surface of hollow nanospheres through chitosan-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of NiO hollow nanospheres, the constructed glucose biosensors exhibited a high sensitivity of 3.43 μA/mM. The low detection limit was estimated to be 47 μM (S/N = 3), and the Michaelis-Menten constant was found to be 7.76 mM, indicating the high affinity of enzyme on NiO hollow nanospheres to glucose. These results show that the NiO hollow nanospheres are a promising material to construct enzyme biosensors.     

Biofunctionalization of aqueous dispersed, alumina membrane-templated polymer nanorods for use in enzymatic chemiluminescence assays

The noncovalent immobilization of alkaline phosphatase (ALP) onto aqueous dispersed nylon 6 nanorods ( approximately 310 nm mean diameter; approximately 6 microm mean length) prepared by anodic aluminum oxide (AAO) membrane templating was studied. Using multi-stacked layer-by-layer (LBL) assembly with the cationic quaternary ammonium polymer Sapphire II , the amount of ALP enzyme loaded onto the polymer nanostructures was found to be 115+/-7 microg mg(-1) nanorod. The biofunctionalized nanorods were also characterized for their chemiluminescent activity with the dioxetane substrate, CSPD . The results indicate that the kinetic parameters, K(m) and V(max), for the catalytic activity of the nanostructure-bound ALP enzyme are different from those of soluble ('free') ALP. While the K(m) value was measured to be 156 microM for free ALP, the apparent K(m) value determined for the LBL-immobilized ALP is approximately 20% lower (122 microM). Furthermore, despite the relatively high enzyme loading capacity of the nanorods, the specific activity of the bound ALP enzyme was found to be almost nine times lower than that measured for free ALP. Finally, additional experiments revealed that the catalytic activities of both free ALP and nanorod-conjugated ALP are affected similarly by changes in pH, with optimal performance levels occurring under conditions of pH 9.5. To the best of our knowledge, this study represents the first report examining the preparation of aqueous dispersed, AAO-templated polymer nanorods for potential application as enzyme scaffolds in chemiluminescent-based assay systems.     

Surfactant assisted solvothermal synthesis of LiFePO_4 nanorods for lithium-ion batteries

Well-shaped and uniformly dispersed LiFePO_4 nanorods with a length of 400–500 nm and a diameter of about 100 nm, are obtained with participation of a proper amount of anion surfactant sodium dodecyl sulfonate(SDS) without any further heating as a post-treatment. The surfactant acts as a self-assembling supermolecular template, which stimulated the crystallization of LiFePO_4 and directed the nanoparticles growing into nanorods between bilayers of surfactant(BOS). LiFePO_4 nanorods with the reducing crystal size along the b axis shorten the diffusion distance of Li~+ extraction/insertion, and thus improve the electrochemical properties of LiFePO_4 nanorods. Such prepared LiFePO_4 nanorods exhibited excellent specific capacity and high rate capability with discharge capacity of 151 mAh/g, 122 mAh/g and 95 mAh/g at 0.1C, 1 C and 5 C, respectively. Such excellent performance of LiFePO_4 nanorods is supposed to be ascribed to the fast Li~+ diffusion velocity from reduced crystal size along the b axis and the well electrochemical conductivity. The structure, morphology and electrochemical performance of the samples were characterized by XRD, FE-SEM, HRTEM, charge/discharge tests, and EIS(electrochemical impedance spectra).     

A novel amperometric biosensor based on gold nanoparticles-mesoporous silica composite for biosensing glucose

We report a novel bienzyme biosensor based on the assembly of the glucose oxidase (GOD) and horseradish peroxidase (HRP) onto the gold nanoparticles encapsulated mesoporous silica SBA-15 composite (AuNPs-SBA-15). Electrochemical behavior of the bienzyme bioconjugates biosensor is studied by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that the presence of mesoporous AuNPs-SBA-15 greatly enhanced the protein loadings, accelerated interfacial electron transfer of HRP and the electroconducting surface, resulting in the realization of direct electrochemistry of HRP. Owing to the electrocatalytic effect of AuNPs-SBA-15 composite, the biosensor exhibits a sensitive response to H₂O₂ generated from enzymatic reactions. Thus the bienzyme biosensor could be used for the detection of glucose without the addition of any mediator. The detection limit of glucose was 0.5 μM with a linear range from 1 to 48 μM. Supported by the National Natural Science Foundation of China (Grant Nos. 20635020 & 90606016)     

Gold nanorods and poly(amido amine) dendrimer thin film for biosensing

Journal of Solid State Electrochemistry - The use of gold nanomaterials in electrochemical biosensing has been proven to be effective either by modifying the electrodes’ surface or by...     

One-step continuous synthesis of biocompatible gold nanorods for optical coherence tomography

We present a novel one-step flow process to synthesize biocompatible gold nanorods with tunable absorption and biocompatible surface ligands. Photothermal optical coherence tomography (OCT) of human breast tissue is successfully demonstrated using tailored gold nanorods designed to have strong absorption in the near-infrared range.     

Metal-alloy-dispersed carbon-paste enzyme electrodes for amperometric biosensing of glucose

The preferential electrocatalytic detection of hydrogen peroxide and the selective biosensing of glucose at carbon-paste enzyme electrodes dispersed with bimetallic (Ru–Pt) alloy particles are described. Unlike the marked acceleration of the redox reaction of the peroxide product (versus single metal catalysts), the signals of common interfering compounds shift to higher potentials. Such use of carbon-supported alloy particles thus results in a greatly enhanced sensitivity compared to the dispersion of pure metals, without compromising the remarkable selectivity inherent to metallized carbon biosensors.     

One-step preparation of sulfonated carbon and subsequent preparation of hybrid material with polyaniline salt: a promising supercapacitor electrode material

The present trend to increase the energy density of electrochemical supercapacitor is to hybrid the electrochemical double layer capacitance electrode materials of carbon with loading or encapsulation of transition metal oxide or conductive polymeric pseudocapacitor materials as the binary or ternary hybrid electrochemical active materials. In this work, we selected polyaniline salt-sulfonated carbon hybrid (PANI-SA?C _SA ) as a cheaper electrode material for supercapacitor electrode. Sulfonated carbon (C _SA ) was prepared from hydrothermal carbonization of furaldehyde and p-toluenesulfonic acid. Polyaniline-sulfate salt containing sulfonated carbon was prepared by chemical oxidative polymerization of aniline using ammonium persulfate in presence of sulfuric acid and sulfonated carbon via aqueous, emulsion and interfacial polymerization pathways. Formation of hybrid material was confirmed from scanning electron microscopy. Among the hybrid prepared with three different polymerization pathways, hybrid prepared by aqueous polymerization pathway showed better electrochemical performance. The specific capacitance of the hybrid prepared via aqueous polymerization was 600 F g^?1, which is higher than that of the pristine PANI-SA (350 F g^?1) and C _SA (30 F g^?1). Hybrid material was subjected for 8000 charge-discharge cycles and at 8000 cycles; it showed 88% retention of its original specific capacitance value of 485 F g^?1 with coulombic efficiency (97–100%). These results showed that C _SA micro spheres prevent the degradation of PANI-SA chains during charge/discharge cycles. Specific capacitance, cycle life, low solution resistance, low charge transfer resistance and high phase angle value of PANI-SA?C _SA supercapacitor cell indicates a higher performance supercapacitor system.

Open image in new window

Graphical abstract Synthesis of hybrid of sulfonated carbon with polyaniline sulfate salt and its supercapacitor performance Ravi Bolagam, Palaniappan Srinivasan,^* Rajender Boddula

     

Design, preparation and testing of suitable probe-receptors for RNA biosensing

Absolute measurements of a given RNA in a cheap, easy, rapid and reproducible manner using biosensors technology could overcome many of the operative and analytical limits of conventional molecular biology methods. To this end, an integrated approach for the design, synthesis, and connection of RNA probes to the transducing surface of a microgravimetric biosensor has been developed. Suitable probes to be used as the bioreceptors in RNA biosensor were successfully designed by using a purposely developed computational method whose selection criteria are based on the accessibility of target region to probe, on pairing stability of probe-target duplex and on the uniqueness of selected targets over all known expressed sequences from a genome data base. Automated chemical synthesis of selected probes was performed and the oligonucleotides produced were covalently conjugated to the sensing surface of a quartz microbalance. The microgravimetric sensor was tested in a flow chamber by measuring the variation of resonance frequency due to the binding of synthetic target substrates. Specific dose dependent binding was observed. Furthermore, the binding of a transcribed full-length mRNA substrate was successfully monitored under similar conditions.