Biomedical subjects

A J Gawron

Publications and source records attributed to A J Gawron.

6 recordsLinked to original sources

PubMed2001

Fabrication and evaluation of a carbon-based dual-electrode detector for poly(dimethylsiloxane) electrophoresis chips.

The first carbon-based dual-electrode detector for microchip capillary electrophoresis (CE) is described. The poly(dimethylsiloxane) (PDMS)-based microchip CE devices were constructed by reversibly sealing a PDMS layer containing separation and injection channels to another PDMS layer containing carbon fiber working electrodes. End-channel amperometric detection was employed and the performance of the chip was evaluated using catechol. The response was found to be linear between 1 and 600 microM with an experimentally determined limit of detection (LOD) of 500 nM and a sensitivity of 30 pA/microM. Collection efficiencies for catechol ranged from 36.0 to 43.7% at field strengths of 260-615 V/cm. The selectivity that can be gained with these devices is demonstrated by the first CE-based dual-electrode detection of a Cu(II) peptide complex. These devices illustrate the potential for a rugged and easily constructed microchip CE system with an integrated carbon-based detector of similar scale.

Carbon↗

PubMed2001

Microchip electrophoretic separation systems for biomedical and pharmaceutical analysis.

The application of microchip capillary electrophoresis (CE) systems to biomedical and pharmaceutical analysis is described and reviewed. Fabrication, instrumentation, and operation of the systems are discussed. An overview of applications is presented, covering four main areas: DNA sequencing, genetic analysis, immunoassays, and protein and peptide analysis. These systems have the potential to dramatically change the way that biochemical analyses are performed.

Animals↗

PubMed2001

Carbon paste-based electrochemical detectors for microchip capillary electrophoresis/electrochemistry.

The first reported use of a carbon paste electrochemical detector for microchip capillary electrophoresis (CE) is described. Poly(dimethylsiloxane) (PDMS)-based microchip CE devices were constructed by reversibly sealing a PDMS layer containing separation and injection channels to a separate PDMS layer that contained carbon paste working electrodes. End-channel amperometric detection with a single electrode was used to detect amino acids derivatized with naphthalene dicarboxaldehyde. Two electrodes were placed in series for dual electrode detection. This approach was demonstrated for the detection of copper(II) peptide complexes. A major advantage of carbon paste is that catalysts can be easily incorporated into the electrode. Carbon paste that was chemically modified with cobalt phthalocyanine was used for the detection of thiols following a CE separation. These devices illustrate the potential for an easily constructed microchip CE system with a carbon-based detector that exhibits adjustable selectivity.

Carbon↗

PubMed2000

Dual-electrode electrochemical detection for poly(dimethylsiloxane)-fabricated capillary electrophoresis microchips.

The development of a poly(dimethylsiloxane)-based (PDMS-based) microchip electrophoresis system employing dual-electrode electrochemical detection is described. This is the first report of dual-electrode electrochemical detection in a microchip format and of electrochemical detection on chips fabricated from PDMS. The device described in this paper consists of a top layer of PDMS containing the separation and injection channels and a bottom glass layer onto which gold detection electrodes have been deposited. The two layers form a tight reversible seal, eliminating the need for high-temperature bonding, which can be detrimental to electrode stability. The channels can also be temporarily removed for cleaning, significantly extending the lifetime of the chip. The performance of the chip was evaluated using catechol as a test compound. The response was linear from 10 to 500 microM with an LOD (S/N = 3) of 4 microM and a sensitivity of 45.9 pA/microM. Collection efficiencies for catechol ranged from 28.7 to 25.9% at field strengths between 200 and 400 V/cm. Dual-electrode detection in the series configuration was shown to be useful for the selective monitoring of species undergoing chemically reversible redox reactions and for peak identification in the electropherogram of an unresolved mixture.

Dimethylpolysiloxanes↗

PubMed2000

Optimization of the conditions for biuret complex formation for the determination of peptides by capillary electrophoresis with ultraviolet detection.

Capillary electrophoresis with UV detection was utilized to optimize copper complexation conditions for the analysis of neuropeptides. Complexation was confirmed by monitoring the response at a visible wavelength. Four complexation strategies were used to compare the UV response of native peptides and their respective copper complexes. All four strategies resulted in complete complexation, but on-capillary complexation provided significant advantages over precapillary and pre-/on-capillary. An increase in UV absorbance along with peak stacking resulted in a significantly greater response using the on-capillary technique. Also, on-capillary complexation does not require dilution of the sample. The effects of temperature and copper concentration were also investigated. The utility of this method for the separation of an enkephalin peptide mixture is presented.

Angiotensin II↗

PubMed2000

Detection of neuropeptides using on-capillary copper complexation and capillary electrophoresis with electrochemical detection.

Capillary electrophoresis with electrochemical detection using a carbon fiber electrode in conjunction with on-capillary copper complexation was evaluated for the determination of peptides in standard and biological matrices. Peptides composed of 2-10 amino acids were investigated. A comparison was made between the responses obtained for peptides containing the oxidizable residue tyrosine and those obtained for their respective copper complexes. Electrochemical detection of non-tyrosine-containing peptides and a cyclic peptide was also demonstrated. A separation of leucine (Leu)-enkephalin and five metabolites was developed and then used for the investigation of Leu-enkephalin metabolism in plasma. The appearance of the des-tyrosine (des-Tyr) Leu-enkephalin, which cannot be detected directly at a carbon electrode, was monitored using the on-capillary complexation technique. Direct injection of the plasma sample was possible using this methodology.

Angiotensins↗