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Biomedical subjects

J Christopher Ball

Publications and source records attributed to J Christopher Ball.

5 recordsLinked to original sources
PubMed2006

Microfabrication of screen-printed nanoliter vials with embedded surface-modified electrodes.

A self-contained ion-selective sensing system within a nanoliter-volume vial has been developed by integrating screen printing, laser ablation, and molecular imprinting techniques. Screen printing and laser ablation are used in tandem to fabricate nanoliter-volume vials with carbon and Ag/AgCl ring electrodes embedded in the sidewalls. Using multisweep cyclic voltammetry, the surface of the carbon electrode can be modified with a polypyrrole film. By polymerizing pyrrole in the presence of nitrate, pores complementary to the nitrate anion in size, shape, and charge distribution are formed in the resulting film. Electrochemical cells modified with this nitrate-imprinted polypyrrole film show a near-Nernstian response to nitrate, and excellent reproducibility. The integration of molecular recognition and electrochemical response in the nanoliter vials is demonstrated by the detection of as little as 0.36 ng nitrate in nanoliter-volume samples. The integration of tailored molecular recognition within nanoliter vials via established fabrication and imprinting protocols should result in a number of nanosensor devices with applications in BioMEMS and micro total analysis systems.

Electrochemistry↗
PubMed2004

Carbon nanotube aqueous sol-gel composites: enzyme-friendly platforms for the development of stable biosensors.

A new type of composite material based on carbon nanotubes and an aqueous sol-gel process has been developed. The electrochemical characteristics of these composites were investigated and compared to composites made with an alkoxy silane sol-gel process. The use of carbon nanotubes, as the conductive part of the composite, facilitated fast electron transfer rates. The feasibility of this type of composite for the development of biosensors was demonstrated using l-amino acid oxidase. The stability of the enzyme was increased when it was encapsulated in the aqueous sol-gel, and the sensor retained more that 50% of its response after 1 month of testing.

Biosensing Techniques↗
PubMed2003

Covalent immobilization of beta-galactosidase onto a gold-coated magnetoelastic transducer via a self-assembled monolayer: toward a magnetoelastic biosensor.

The enzyme beta-galactosidase has been covalently immobilized onto a gold-coated magnetoelastic film via a self-assembled monolayer (SAM) of omega-carboxylic acid alkylthiol. Use of magnetoelastic transduction allows for the wireless monitoring of enzymatic activity through the associated change in the frequency and amplitude of magnetic fields. The formations of SAMs of 3-mercaptopropanoic acid and thioctic acid were monitored by magnetoelastic transduction. After coupling of beta-galactosidase to the SAMs, the enzyme activity was monitored by using a substrate that forms an insoluble product upon action of the enzyme. Specifically, an indolyl galactopyranoside substrate was employed in conjunction with an azo dye as the precipitating system. The immobilized enzyme was evaluated and found to have an apparent Michaelis-Menten constant (KM) of 1.2 mM for the indolyl galactopyranoside. Calibration plots for both substrates and inhibitors were generated to establish the versatility of this sensing system. Kinetic parameters for nonprecipitating substrates were determined in conjunction with a precipitating enzymatic substrate by way of a competitive inhibition study using beta-galactosidase attached to magnetoelastic strips. The methods developed within this work allow for the fabrication of wireless enzyme sensing systems, which can also be used as another means of screening for enzyme inhibitors.

Biosensing Techniques↗
PubMed2002

Characterization of electrochemically deposited polypyrrole using magnetoelastic material transduction elements.

Magnetoelastic alloy films have been used as a working electrode in an electrochemical cell. This material allows magnetic interrogation of electrochemical deposition. This technique was used to monitor the electrochemical deposition of polypyrrole by multisweep (CV) and potentiostatic methods. Since the determination of the mass-sensitive magnetoelastic film's resonance frequency is based on magnetic transduction, an inherent advantage of this method is that it requires no electrical connections other than the working lead of the potentiostat. Increases in pyrrole deposition correlated with a decrease in the peak resonance frequency of the magnetoelastic alloy. This technique provides a novel approach by which one can monitor electrochemical processes.

Alloys↗