Songqin Liu

Reagentless glucose biosensor based on direct electron transfer of glucose oxidase immobilized on colloidal gold modified carbon paste electrode

The direct electrochemistry of glucose oxidase (GOD) adsorbed on a colloidal gold modified carbon paste electrode was investigated. The adsorbed GOD displayed a pair of redox peaks with a formal potential of -(449+/-1) mV in 0.1 M pH 5.0 phosphate buffer solution. The response showed a surface-controlled electrode process with an electron transfer rate constant of (38.9+/-5.3)/s determined in the scan rate range from 10 to 100 mV/s. GOD adsorbed on gold colloid nanoparticles maintained its bioactivity and stability. The immobilized GOD could electrocatalyze the reduction of dissolved oxygen and resulted in a great increase of the reduction peak current. Upon the addition of glucose, the reduction peak current decreased, which could be used for glucose detection with a high sensitivity (8.4 microA/mM), a linear range from 0.04 to 0.28 mM and a detection limit of 0.01 mM at a signal-to-noise ratio of 3sigma. The sensor could exclude the interference of commonly coexisted uric and ascorbic acid.

Renewable reagentless hydrogen peroxide sensor based on direct electron transfer of horseradish peroxidase immobilized on colloidal gold-modified electrode.

A novel renewable reagentless hydrogen peroxide (H(2)O(2)) sensor based on the direct electron transfer of horseradish peroxidase (HRP) is proposed. The direct electrochemistry of HRP immobilized on a colloidal gold-modified carbon paste electrode (Au-CPE) was investigated using electrochemical methods. The immobilized HRP displayed a pair of redox peaks in 0.1M phosphate buffer (PB), pH 7.0, with a formal potential of -0.346 V. The response showed a surface-controlled electrode process with an electron transfer rate constant of 6.04+/-0.18s(-1) determined in the scan rate range from 120 to 500 mV/s. The biosensor displayed an excellent electrocatalytic response to the reduction of H(2)O(2) without the aid of an electron mediator. The sensor surface could be renewed quickly and reproducibly by a simple polish step. The calibration range of H(2)O(2) was 0-0.3mM with linear relation from 0.48 to 50 microM and a detection limit of 0.21 microM at 3 sigma. The response showed Michaelis-Menten behavior at higher H(2)O(2) concentrations. The K(app)(M) value of HRP at HRP-Au-CPE was determined to be 3.69+/-0.71 mM.

Glucose sensor for flow injection analysis of serum glucose based on immobilization of glucose oxidase in titania sol-gel membrane

A novel amperometric glucose sensor was constructed by immobilizing glucose oxidase (GOD) in a titania sol-gel film, which was prepared with a vapor deposition method. The sol-gel film was uniform, porous and showed a very low mass transport barrier and a regular dense distribution of GOD. Titania sol-gel matrix retained the native structure and activity of entrapped enzyme and prevented the cracking of conventional sol-gel glasses and the leaking of enzyme out of the film. With ferrocenium as a mediator the glucose sensor exhibited a fast response, a wide linear range from 0.07 to 15 mM. It showed a good accuracy and high sensitivity as 7.2 microA cm(-2) mM(-1). The general interferences coexisted in blood except ascorbic acid did not affect glucose determination, and coating Nafion film on the sol-gel film could eliminate the interference from ascorbic acid. The serum glucose determination results obtained with a flow injection analysis (FIA) system showed an acceptable accuracy, a good reproducibility and stability and indicated the sensor could be used in FIA determination of glucose. The vapor deposition method could fabricate glucose sensor in batches with a very small amount of enzyme.

Electrochemistry of Cytochrome c Immobilized on Colloidal Gold Modified Carbon Paste Electrodes and Its Electrocatalytic Activity

Colloidal gold modified carbon paste electrodes were prepared by mixing 24-nm-diameter colloidal Au particles with carbon paste. The modified electrodes displayed a low charging current and a favorable electrochemical response of hexacyanoferrate (III). The direct electrochemical behavior of a horse-heart cytochrome c (cyt.c) adsorbed on this electrode surface is described. It showed a surface-controlled electrode process with the electron transfer rate constant of (1.21±0.08) s−1 and α of 0.67. Cyclic voltammograms showed small peak-to-peak separations at low scan rates. The adsorbed cyt.c maintained its activity and could also electrocatalyze the reduction of hydrogen peroxide. Since this behavior was quite pronounced the electrode was used for H2O2 detection. The KMapp value for this sensor was found to be 2.28±0.17 mM, allowing measurements down to 0.01 mM H2O2.

Renewable phenol biosensor based on a tyrosinase-colloidal gold modified carbon paste electrode

Abstract A novel renewable tyrosinase-based biosensor was developed for the detection of phenol by immobilizing tyrosinase on a colloidal gold modified carbon paste electrode. Anionic colloidal gold was beneficial to the immobilization of tyrosinase and to the retention of its bioactivity to a large extent. The biosensor showed a sensitive electrochemical response to the reduction of the oxidation product of phenol by dissolved O2 in the presence of immobilized tyrosinase. The effects of pH, operating potential and the volume of the colloidal gold solution for sensor preparation on the amperometric response were explored for optimum analytical performance. The best performing biosensor exhibited a fast response (less than 5 s), a high sensitivity (12.3 μA cm−2 μM−1) and good storage stability for monitoring phenol. The linear range spanned the concentration of phenol from 4 to 48 μM with a correlation coefficient of 0.9973 (n=12) and a detection limit of 6.1 nM at 3σ. The response showed Michaelis–Menten behavior at larger phenol concentrations. The KMapp value of immobilized tyrosinase on colloidal gold was calculated to be (53.6±3.2) μM using phenol as the substrate.

Application of Colloidal Gold in Protein Immobilization, Electron Transfer, and Biosensing

Abstract Direct electron transfer between redox proteins and electrodes is of practical and theoretical interest and can be improved by electrode or protein modification. The direct contact of protein with electrode surfaces can lead to a significant change of the protein structure and/or function. Immobilized colloidal gold on electrode surfaces provides a microenvironment similar to that of the redox protein in native systems and gives the protein molecules more freedom in orientation, thus reducing the insulating property of the protein shell for the direct electron transfer and facilitating the electron transfer through the conducting tunnels of colloidal gold. This brief review focuses on the current state of the colloidal gold used for protein immobilization, electron transfer and biosensing, with emphasis on recent advances, challenges and trends.

Mediator-free phenol sensor based on titania sol/gel encapsulation matrix for immobilization of tyrosinase by a vapor deposition method

A novel amperometric phenol sensor was constructed by immobilizing tyrosinase in a titania sol-gel matrix. The tyrosinase entrapped sol-gel film was obtained with a vapor deposition method, which simplified the traditional sol-gel process and avoided the shrinkage and cracking of conventional sol-gel-derived glasses. This matrix provided a microenvironment for retaining the native structure and activity of the entrapped enzyme and a very low mass transport barrier to the enzyme substrates. Phenol could be oxidized by dissolving oxygen in presence of immobilized tyrosinase to form a detectable product, which was determined at -150 mV without any mediator. The phenol sensor exhibited a fast response (less than 5 s) and sensitivity as high as 103 microA/mM, which resulted from the porous structure and high enzyme loading of the sol-gel matrix. The linear range for phenol determination was from 1.2x10(-7) to 2.6x10(-4) M with a detection limit of 1.0x10(-7) M. The apparent Michaelis-Menten constant of the encapsulated tyrosinase was calculated to be (0.29+/-0.02) mM. The stability of the biosensor was also evaluated.

Disposable nitrite sensor based on hemoglobin-colloidal gold nanoparticle modified screen-printed electrode

Abstract An unmediated, disposable nitrite amperometric biosensor based on hemoglobin (Hb)-colloidal gold nanoparticle modified screen-printed carbon electrode (Hb-Au-SPCE) was proposed. The immobilized Hb showed a couple of quasi-reversible redox peak with a formal potential of −0.224 V (vs. SCE) in 0.2 mol dm−3 pH 5.5 NaAc-HAc buffer. The formal potential changed linearly between pH 4.0 to 9.0 with a slope of −46.4 mV pH−1. The Hb-Au-SPCE displayed a rapid amperometric response to the reduction of nitrite, which allowed to be used for the determination of nitrite with a linear range from 3.0 × 10−7 to 7.0 × 10−4 mol dm−3 and a detection limit of 1.0 × 10−7 mol dm−3 at 3σ. The amperometric sensor had a high sensitivity, good accuracy, and stability and is simple to use, lost-cost, rapid for the nitrite quantitative detection in practical applications.

Disposable biosensor based on a hemoglobin colloidal gold-modified screen-printed electrode for determination of hydrogen peroxide

A disposable reagentless hydrogen peroxide biosensor based on the direct electrochemistry of hemoglobin immobilized on a colloidal gold-modified screen-printed carbon electrode (Hb-Au-SPCE) was proposed. The electrochemical behavior of immobilized Hb at a SPCE was studied for the first time. The electrode reaction of immobilized Hb showed a surface-controlled process with an electron transfer rate constant of (0.40 /spl plusmn/ 0.02) s/sup -1/ determined in the scan rate range from 25 to 200 mV s/sup -1/. The Hb-Au-SPCE exhibited an electrocatalytic activity toward the reduction of hydrogen peroxide with a K/sub M//sup app/ value of 1.8 mM, which was allowed to be used as a disposable sensor for determination of hydrogen peroxide with a linear range from 1.0 /spl times/ 10/sup -5/ M to 3.2 /spl times/ 10/sup -4/ M, a detection limit of 5.5 /spl times/ 10/sup -6/ M at 3/spl sigma/, a high sensitivity, fast response, and good selectivity, accuracy, and reproducibility. The disposable reagentless sensor was stable, low cost, and simple to use for detection of hydrogen peroxide in real samples.