Biomedical subjects

Jianbo Jia

Publications and source records attributed to Jianbo Jia.

9 recordsLinked to original sources

PubMed2007

Structure and electrochemical properties of carbon films prepared by a electron cyclotron resonance sputtering method.

This paper describes the characterization, electrochemical properties, and applications of carbon films prepared by the electron cyclotron resonance (ECR) sputtering method. The ECR-sputtered carbon film was deposited within several minutes at room temperature. The optimized sputtering conditions significantly change the film structure, which includes many more sp3 bonds (sp3/sp2 = 0.702) than previously reported film (sp3/sp2 = 0.274)1 with an extremely flat surface (0.7 A). The ECR-sputtered carbon films exhibit excellent electrochemical properties. For example, they have nearly the same potential window in the positive direction as that of high-quality, boron-doped diamond (moderately doped, 10(19)-10(20) boron atoms/cm3)2 and an even wider potential window in the negative direction with a low background current, high stability, and suppression of fouling by electroactive species without pretreatment. The electron-transfer rates at ECR-sputtered carbon films are similar to those of glassy carbon (GC) for Ru(NH3)(6)(2+)/(3+) and Fe(CN)(6)(3-)/(4-), whereas they are much slower than those of GC for Fe2+/3+, dopamine oxidation, and O2 reduction due to weak interactions between electroactive species and the ECR-sputtered carbon film surface. Such a response can be attributed to the ultraflat surface and low surface O/C ratios of ECR-sputtered carbon films. ECR-sputtered carbon film is advantageous for measuring biochemicals with high oxidation potentials because of its wide potential window and high stability. Highly reproducible and well-defined cyclic voltammograms were obtained for histamine and azide ions with a peak potential at 1.25 and 1.12 V vs Ag/AgCl, respectively. The film is very stable for continuous voltammetry measurements in 10 microM bisphenol A, which usually fouls the electrode surface with oxidation products.

Boron↗

PubMed2006

Electrochemically amplified detection for lipopolysaccharide using ferrocenylboronic acid.

A novel electrochemical technique for lipopolysaccharide (LPS) detection has been developed using a combination of ferrocenylboronic acid derivatives and an enzyme-modified electrode. The enzyme-modified electrode was constructed from a gold electrode modified with a bovine serum albumin membrane containing diaphorase. Ferrocenylboronic acid derivatives are oxidized on the electrode, and then regenerated by a diaphorase-catalyzed reaction in the presence of NADH. The consumption/regeneration cycle for ferrocenylboronic acid derivatives resulted in a chemically amplified current response. The current response for ferrocenylboronic acid derivatives decreased in association with its complexation with glycosyl units of LPS, and this current decrease caused by LPS was also amplified by the recycling process. On the other hand, the addition of a monosaccharide such as D-mannose or D-galactose induced no response at the same LPS concentration. The enzyme membrane immobilized on the electrode plays an important role in selectivity as well as chemical amplification. In addition, the enzyme-modified electrode exhibited a rapid response of 5 min for LPS, which is much faster than the currently used method. The detection limit of LPS from Escherichia coli O127:B8 was as low as 50 ng ml-1.

Biosensing Techniques↗

PubMed2006

Electrochemical performance of angstrom level flat sputtered carbon film consisting of sp2 and sp3 mixed bonds.

We have developed ultra-flat carbon film electrodes with a wide potential window and a low capacitive current by the electron cyclotron resonance (ECR) sputtering method. The film consists of sp2 and sp3 bonds (sp3/sp2 ratio = 0.702) and is sufficiently conductive for electrochemical measurements without doping. The film has average roughness of 0.7 A, which is much flatter than that of nanocrystalline diamond film. The potential limit of ECR sputtered carbon (current limit < +/-500 muA/cm2) in the positive direction is 2.0 V vs Ag/AgCl, which is slightly lower than that of boron-doped diamond (2.1 V) and much wider than that of a glassy carbon (GC) electrode (1.7 V). In contrast, a much wider potential window can be obtained in the negative direction. The capacitive current is also much lower than that of a GC electrode due to the ultra-flat surface and the low number of oxygen-containing groups at the film surface. ECR sputtered carbon film can be used to measure each base of oligonucleotides by electrochemical oxidation without any pretreatment. The ultra-flat surface and low surface oxygen concentration suppress fouling with electroactive species, such as oligonucleotides, NADH, and bisphenol A.

Biosensing Techniques↗

PubMed2004

Single-wall carbon nanotube-based voltammetric sensor and biosensor.

The pH-sensitive property of the single-wall carbon nanotube modified electrode based on the electroactive group on the single-wall carbon nanotube was explored by differential pulse voltammetry technique. In pH range 1-13 investigated in Britton-Robinson (B-R) buffer, the anodic peak shifted negatively along with the increase of pH exhibiting a reversible Nernstian response. Experiments were carried out to investigate the response of the single-wall carbon nanotube (SWNT) modified electrode to analytes associated with pH change. The response behavior of the modified electrode to ammonia was studied as an example. The potential response could reach equilibrium within 5 min. The modified electrode had good operational stability. Voltammetric urease and acetylcholinesterase biosensors were constructed by immobilizing the enzymes with sol-gel hybrid material. The maximum potential shift could reach 0.130 and 0.220 V for urea and acetylthiocholine, respectively. The methods for preparing sensor and biosensor were simple and reproducible and the range of analytes could be extended to substrates of other hydrolyases and esterases. This broadened the biosensor application of carbon nanotube in electrochemical area.

Acetylcholine↗

PubMed2003

Co-immobilized microbial biosensor for BOD estimation based on sol-gel derived composite material.

A novel type of biochemical oxygen demand (BOD) biosensor was developed for water monitor, based on co-immobilizing of Trichosporon cutaneum and Bacillus subtilis in the sol-gel derived composite material which is composed of silica and the grafting copolymer of poly (vinyl alcohol) and 4-vinylpyridine (PVA-g-P(4-VP)). Factors that influence the performance of the resulting biosensor were examined. The biodegradable substrate spectrum could be expanded by the co-immobilized microorganisms. The biosensor prepared also exhibited good reproducibility and long-term stability. Good agreement was obtained between the results of the sensor BOD measurement and those obtained from conventional BOD(5) method for water samples.

Bacillus subtilis↗

PubMed2003

Hydrogen peroxide biosensor based on microperoxidase-11 entrapped in lipid membrane.

A highly catalytic activity microperoxidase-11 (MP-11) biosensor for H(2)O(2) was developed to immobilizing the heme peptide in didodecyldimethylammonium bromide (DDAB) lipid membrane. The enzyme electrode thus obtained responded to H(2)O(2) without electron mediator or promoter, at a potential of +0.10 V versus Agmid R:AgCl. A linear calibration curve is obtained over the range from 2.0 x 10(-5) to 2.4 x 10(-3) M. The biosensor responds to hydrogen peroxide in 15 s and has a detection limit of 8 x 10(-7) M (S/N=3) Providing a natural environment with lipid membrane for protein immobilization and maintenance of protein functions is a suitable option for the design of biosensors.

Biosensing Techniques↗

PubMed2002

A method to construct a third-generation horseradish peroxidase biosensor: self-assembling gold nanoparticles to three-dimensional sol-gel network.

A novel method for fabrication of horseradish peroxidase biosensor has been developed by self-assembling gold nanoparticles to a thiol-containing sol-gel network. A cleaned gold electrode was first immersed in a hydrolyzed (3-mercaptopropyl)-trimethoxysilane (MPS) sol-gel solution to assemble three-dimensional silica gel, and then gold nanoparticles were chemisorbed onto the thiol groups of the sol-gel network. Finally, horseradish peroxidase (HRP) was adsorbed onto the surface of the gold nanoparticles. The distribution of gold nanoparticles and HRP was examined by atomic force microscopy (AFM). The immobilized horseradish peroxidase exhibited direct electrochemical behavior toward the reduction of hydrogen peroxide. The performance and factors influencing the performance of the resulting biosensor were studied in detail. The resulting biosensor exhibited fast amperometric response (2.5 s) to H2O2. The detection limit of the biosensor was 2.0 micromol L(-1), and the linear range was from 5.0 micromol L(-1) to 10.0 mmol L(-1). Moreover, the studied biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Biosensing Techniques↗

PubMed2002

Capillary electrophoresis with solid-state electrochemiluminescence detector.

We report capillary electrophoresis coupling to a solid-state electrochemiluminescence (ECL) detector for the first time. The solid-state ECL detector was fabricated by immobilizing the ECL reagent tris(2,2'-bipyridyl)ruthenium (TBR) in poly-(p-styrenesulfonate)-silica-poly(vinyl alcohol) grafting 4-vinylpyridine copolymer films. The excellent stability of the solid-state ECL detector in the phosphate solution satisfied application in CE. The CE with solid-state ECL detector system was characterized using tripropylamine (TPA) and proline. The influences of detection potential, the concentration of TBR in the film, and pH value of ECL buffer were investigated. The linear range for TPA and proline was 0.005-10 microM and 5-10 mM with correlation coefficients of 0.997 and 0.998, respectively. The detection limit (signal-to-noise ratio S/N = 3) was estimated to be 0.002 and 2.0 microM for TPA and proline, respectively. The relative standard deviations for 1.0 microM TPA and 1.0 mM proline were 8.7% and 7.5% with theoretical plate numbers of 70 000 and 16 000, respectively. Compared with the CE-ECL of TBR in aqueous solution, the CE coupling with solid-state ECL detector system gave the same sensitivity of analysis.

Electrophoresis, Capillary↗

PubMed2002

Direct electrochemistry of hemoglobin in egg-phosphatidylcholine films and its catalysis to H(2)O(2).

Direct electrochemistry of hemoglobin was observed in stable thin film composed of a natural lipid (egg-phosphatidylcholine) and hemoglobin on pyrolytic graphite (PG) electrode. Hemoglobin in lipid films shows thin layer electrochemistry behavior. The formal potential E degrees ' of hemoglobin in the lipid film was linearly varied with pH in the range from 3.5 to 7.0 with a slope of -46.4 mV pH(-1). Hemoglobin in the lipid film exhibited elegant catalytic activity for electrochemical reduction of H(2)O(2), based which a unmediated biosensor for H(2)O(2) was developed.

Animals↗