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Dielectrophoretic manipulation of particles for use in microfluidic devices

Description: Amplification and hybridization of DNA are commonly used techniques to verify the presence of a specific DNA sequence in a test sample. Automatic sample handling to concentrate and purify sample prior to amplification is desirable both from the cost standpoint and from the standpoint of reducing the possibility of sample contamination. This paper explores the use of the dielectrophoretic force to manipulate DNA, Bacillus globigii spores, and Erwinia herbicola bacteria to provide concentration and purification as part of the sample handling functions in biological monitoring equipment. It was found that for what would be considered a typical microfabricated structure with electrode gaps at 30 {micro}m operating at 5V, that concentration of the particles is very effective.
Date: June 23, 1999
Creator: Belgrader, P; Bettencourt, K; Hamilton, J; Miles, R & Nasarabadi, S
Partner: UNT Libraries Government Documents Department

Autonomous system for pathogen detection and identification

Description: This purpose of this project is to build a prototype instrument that will, running unattended, detect, identify, and quantify BW agents. In order to accomplish this, we have chosen to start with the world´┐Ż s leading, proven, assays for pathogens: surface-molecular recognition assays, such as antibody-based assays, implemented on a high-performance, identification (ID)-capable flow cytometer, and the polymerase chain reaction (PCR) for nucleic-acid based assays. With these assays, we must integrate the capability to: l collect samples from aerosols, water, or surfaces; l perform sample preparation prior to the assays; l incubate the prepared samples, if necessary, for a period of time; l transport the prepared, incubated samples to the assays; l perform the assays; l interpret and report the results of the assays. Issues such as reliability, sensitivity and accuracy, quantity of consumables, maintenance schedule, etc. must be addressed satisfactorily to the end user. The highest possible sensitivity and specificity of the assay must be combined with no false alarms. Today, we have assays that can, in under 30 minutes, detect and identify simulants for BW agents at concentrations of a few hundred colony-forming units per ml of solution. If the bio-aerosol sampler of this system collects 1000 Ymin and concentrates the respirable particles into 1 ml of solution with 70% processing efficiency over a period of 5 minutes, then this translates to a detection/ID capability of under 0.1 agent-containing particle/liter of air.
Date: September 24, 1998
Creator: Belgrader, P; Benett, W; Langlois, R; Long, G; Mariella, R; Milanovich, F et al.
Partner: UNT Libraries Government Documents Department

Manipulation of DNA for use in microfluidic devices

Description: MEMS microfluidic systems are becoming increasingly popular as a way to integrate sample preparation and biological assays on a single substrate. The resulting reduction in manual operations and reduced reagent use can lead to significant cost savings in performing biological tests. The authors have explored the use of small scale dielectrophoresis and electrophoresis as a way to manipulate DNA for sample preparation in DNA-based assays. The use of electric fields to manipulate DNA is readily achieved in MEMS devices using standard photolithography techniques to add electrodes to etched flow channels. Dielectrophoresis allows for manipulation of cells and DNA independently of the liquid. This ability is useful in small, valveless fluidic microchips. An advantage of the use of the dielectrophoretic force over an electrophoretic force is that dielectrophoresis works equally well using an AC field, thus reducing trapping of small ions and mitigating electrochemical effects at the electrodes. However, the dielectrophoretic force on the DNA is a function of the volume of the particle; thus, there is a lower practical limit to use of the dielectrophoretic force. Consequently they have also explored methods of manipulating smaller DNA fragments using what they refer to as a stepped electrophoresis method.
Date: November 18, 1998
Creator: Belgrader, P; Bettencourt, K; Davidson, J C; Mariella, R P; Miles, R; Nasarabadi, NS et al.
Partner: UNT Libraries Government Documents Department