One-pot construction of mediatorless bi-enzymatic glucose biosensor based on organic-inorganic hybrid.

A new methodology for the fabrication of bienzymatic amperometric glucose biosensor based on the use of an organic-inorganic hybrid is presented. The fabrication involves a self-assembly directed one-pot electrochemical process. Bi-enzymes, horseradish peroxidase (HRP) and glucose oxidase (GOx) are immobilized into the porous and electroactive silica-polyaniline hybrid composite through electrochemical polymerization of N[3-(trimethoxysilyl)propyl]aniline in the presence of enzymes. The modified electrode is designated as PTMSPA/HRP-GOx. The direct electron transfer of HRP is achieved at the modified electrode. Also, the electrode exhibits excellent bio-electro-catalytic activity for the reduction of hydrogen peroxide. The response current at PTMSPA/HRP-GOx modified electrode revealed a good linear relationship with concentration of glucose range between 1 and 20mM with a response time of 7s. Thus, the modified electrode shows the combined advantages of polyaniline and silica networks through synergistic influence from the individual components. The PTMSPA assembly has shown the potential for a third generation amperometric biosensor.

Pd (core)-Au (shell) nanoparticles catalyzed conversion of NADH to NAD+ by UV-vis spectroscopy--a kinetic analysis.

Kinetics of Pd (core)-Au (shell) nanoparticles (NPs) catalyzed transformation of dihydronicotinamide adenine dinucleotide (NADH) to NAD(+) was monitored by UV-vis spectroscopy. Pd (core)-Au (shell) NPs were prepared by microwave irradiation method. High resolution transmission electron microscopy image reveals the core-shell morphology. X-ray diffraction pattern shows the presence of distinct crystalline domains for Pd and Au. The changes in absorbances at 340 nm were followed for various time intervals. Rates of conversion of NADH to NAD(+) were determined for different conditions. The conversion of NADH to NAD(+) was to be first order with respect to NADH at lower concentrations (upto 0.04 mM) and pseudo-first-order beyond 0.04 mM. Rate constants for the Pd (core) Au-(shell) NPs catalyzed transformation of NADH to NAD(+) were deduced.

Fabrication of enzymatic glucose biosensor based on palladium nanoparticles dispersed onto poly(3,4-ethylenedioxythiophene) nanofibers.

A new methodology involving the combination of a soft template (surfactant) and an ionic liquid (co-surfactant) is used to electrodeposit poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers. Electrochemical deposition of palladium nanoparticles and glucose oxidase (GOx) immobilization are done sequentially into nanofibrous PEDOT to fabricate the modified electrode (ME) (denoted as PEDOT-Pd/GOx-ME). The PEDOT-Pd/GOx-ME displays excellent performances for glucose at +0.4 V (vs. Ag/AgCl) with a high sensitivity (1.6 mA M(-)(1) cm(-2)) in a wider linear concentration range, 0.5 to 30 mM (correlation coefficient of 0.9985). Further, the electrode is insusceptible to the electroactive interfering species.

Hollow spherical nanostructured polydiphenylamine for direct electrochemistry and glucose biosensor.

Nanostructured, hollow spheres of polydiphenylamine (HS-PDPA) are prepared through a "soft template assisted self-assembly" approach. An enzymatic glucose biosensor is fabricated through immobilizing glucose oxidase (GOx) into HS-PDPA matrix. The HS-PDPA-GOx electrode exhibits a pair of well-defined reversible redox peaks with a fast heterogeneous electron transfer rate. At an applied potential of +0.65V, HS-PDPA-GOx electrode possesses high sensitivity (1.77 microAmM(-1)cm(-2)), stability and reproducibility towards glucose. The amperometric current response of HS-PDPA-GOx to glucose is linear in the concentration range between 1 and 28 mM with a detection limit of 0.05 mM (S/N=3). Also, HS-PDPA-GOx electrode shows high selectivity towards glucose in the presence of ascorbic acid, uric acid and acetaminophen at their maximum physiological concentrations.

Electrocatalytic oxidation of NADH at gold nanoparticles loaded poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) film modified electrode and integration of alcohol dehydrogenase for alcohol sensing.

A new modified electrode is fabricated by dispersing gold nanoparticles onto the matrix of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), PEDOT-PSS. The electrocatalytic activity of the PEDOT-PSS-Au(nano) electrode towards the oxidation of beta-nicotinamide adenine dinucleotide (NADH) is investigated. A substantial decrease in the overpotential (>0.7 V) has been observed for the oxidation of NADH at the PEDOT-PSS-Au(nano) electrode in comparison to the potential at PEDOT-PSS electrode. The Au nanoparticles dispersed in the PEDOT-PSS matrix prevents the fouling of electrode surface by the oxidation products of NADH and augments the oxidation of NADH at a less positive potential (+0.04V vs. SCE). The electrode shows high sensitivity to the electrocatalytic oxidation of NADH. Further, the presence of ascorbic acid and uric acid does not interfere during the detection of NADH. Important practical advantages such as stability of the electrode (retains approximately 95% of its original activity after 20 days), reproducibility of the measurements (R.S.D.: 2.8%; n=5), selectivity and wide linear dynamic range (1-80 microM; R(2)=0.996) are achieved at PEDOT-PSS-Au(nano) electrode. The ability of PEDOT-PSS-Au(nano) electrode to promote the electron transfer between NADH and the electrode makes us to fabricate a biocompatible dehydrogenase-based biosensor for the measurement of ethanol. The biosensor showed high sensitivity to ethanol with rapid detection, good reproducibility and excellent stability.

A novel glucose biosensor based on immobilization of glucose oxidase into multiwall carbon nanotubes-polyelectrolyte-loaded electrospun nanofibrous membrane.

Nanofibrous glucose electrodes were fabricated by the immobilization of glucose oxidase (GOx) into an electrospun composite membrane consisting of polymethylmethacrylate (PMMA) dispersed with multiwall carbon nanotubes (MWCNTs) wrapped by a cationic polymer (poly(diallyldimethylammonium chloride) (PDDA)) and this nanofibrous electrode (NFE) is abbreviated as PMMA-MWCNT(PDDA)/GOx-NFE. The NFE was characterized for morphology and electroactivity by using electron microscopy and cyclic voltammetry, respectively. Field emission transmission electron microscopy (FETEM) image reveals the dispersion of MWCNT(PDDA) within the matrix of PMMA. Cyclic voltammetry informs that NFE is suitable for performing surface-confined electrochemical reactions. PMMA-MWCNT(PDDA)/GOx-NFE exhibits excellent electrocatalytic activity towards hydrogen peroxide (H(2)O(2)) with a pronounced oxidation current at +100 mV. Glucose is amperometrically detected at +100 mV (vs. Ag/AgCl) in 0.1M phosphate buffer solution (PBS, pH 7). The linear response for glucose detection is in the range of 20 microM to 15 mM with a detection limit of 1 microM and a shorter response time of approximately 4 s. The superior performance of PMMA-MWCNT(PDDA)/GOx-NFE is due to the wrapping of PDDA over MWCNTs that binds GOx through electrostatic interactions. As a result, an effective electron mediation is achieved. A layer of nafion is made over PMMA-MWCNT(PDDA)/GOx-NFE that significantly suppressed the electrochemical interference from ascorbic acid or uric acid. In all, PMMA-MWCNT(PDDA)/GOx-nafion-NFE has exhibited excellent properties for the sensitive determination of glucose like high selectivity, good reproducibility, remarkable stability and without interference from other co-existing electroactive species.

Electrospun poly(vinylidene fluoride)/poly(aminophenylboronic acid) composite nanofibrous membrane as a novel glucose sensor.

Electrospinning was used to prepare the nanofibrous membrane (NFM) of the composite comprising poly(vinylidene fluoride) and poly(aminophenylboronic acid) (PVdF/PAPBA-NFM). The PVdF/PAPBA-NFM displayed an excellent linear response to the detection of glucose for the concentration range of 1 to 15mM with a response time of less than 6s. Further experiments on amperometric sensing of glucose were performed in the presence of interferents such as uric acid, ascorbic acid, acetaminophen, fructose, mannose, etc. using PVdF/PAPBA-NFM. The interferents did not give significant overlapping current signal during the determination of glucose. Also, PVdF/PAPBA-NFM possesses better reproducibility toward glucose detection and storage stability.

Fabrication of a new polyaniline grafted multi-wall carbon nanotube modified electrode and its application for electrochemical detection of hydrogen peroxide.

A modified electrode is fabricated by grafting polyaniline (PANI) chains onto multiwalled carbon nanotube (MWNT) for the detection of hydrogen peroxide (H2O2). PANI grafted MWNT modified electrode (PANI-g-MWNT-ME) displays excellent electrocatalytic response to the detection of H2O2 in a concentration range of (1.0-20) x 10(-8) M showing linear response to current, with an extended lower detection limit down to 1 nM. This modified electrode exhibits an accelerated electron transfer at the interface with minimized surface fouling and surface renewability. Further, electrochemical analysis of H2O2 performed in the presence of common interferents such as uric acid, ascorbic acid and acetaminophen with the modified electrode reveals that there is no overlapping signal from the interferents. The combined presence of MWNT and PANI in the modified electrode provides high sensitivity and selectivity.