Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
2000-12-13
2004-07-20
Diamond, Alan (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S461000, C204S400000, C204S403010, C435S287200, C435S287100, C436S806000
Reexamination Certificate
active
06764583
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the collection or concentration of particles in an electric field of fluidic device, particularly to detecting the presence of pathogens trapped in an electric field, and more particularly to the use of impedance measurements to detect the presence of pathogens trapped in an electric field.
Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized particles in non-uniform electrical fields and is currently an active area of research. Because most biological cells and macromolecules behave as dielectric particles in external AC electric fields, DEP has found many useful biotechnological applications including separation, levitation, and characterization of biological particles. The use of dielectrophoresis to collect particles is well known when operating under pressure driven flow. Currently efforts are being carried out involving concentrating bacterial biological sample for DNA analysis on sets of interdigitated electrodes using the dielectrophoretic force generated for a particle in the non-uniform field generated by applying a voltage to the electrodes.
There has been a need for a means for detecting the presence of pathogens at the electrodes to determine if sufficient pathogens have been collected to analyze further or potentially to identify the pathogen.
The present invention provides a solution to the above mentioned need by using impedance measurments between the electrodes to detect the presence of pathogens trapped in an electric field generated by the electrodes. Due to the change of impedance between the electrodes which is caused by trapped pathogens, the impedance change is used to determine the degree of particle trapping. Thus the invention provides an impedance sensor for detecting pathogens.
SUMMARY OF THE INVENTION
It is an object of the present invention to determine the presence of pathogens trapped in an electric field.
A further object of the invention is to use impedance measurements between electrodes to determine the degree of pathogen trapping in an electric field.
A further object of the invention is to provide a sensor to detect particles trapped in an electric field using the dielectrophoretic force.
Another object of the invention is to provide a method and apparatus for detecting pathogens trapped in a field using the dielectrophoretic force by measuring changes in the impedance between the electrodes caused by the trapped pathogens.
Another object of the invention is to provide a sensor used to detect the presence of pathogens on electrodes used to concentrate sample using the dielectrophoretic force or any other force on a surface by impedance measurements between the electrodes.
Other objects and advantages will become apparent from the following description and accompanying drawings. Basically the present invention involves an apparatus and method for detecting the presence of pathogens trapped on electrodes by impedance measurements. Since the presence of pathogens trapped on electrodes, such as by the electrophoretic force, the impedance between the electrodes changes as the number of trapped pathogens increases, and this change of impedance is utilized to determine if sufficient pathogen has been collected to analyze further or potentially to identify the pathogen. The apparatus merely involves interdigitated electrodes, for example, located on the inner surface of a fluidic channel through which sample is passed and pathogens are trapped by the dielectrophoretic force, as known in the art, and a means for measuring the impedance between the electrodes, which changes by the trapping of the pathogens. By determining the impendance change, the amount of trapped pathogen can be determined. Thus, the invention involves a sensor using impendance change to detect the presence of pathogens trapped in an electric field produced by the interdigitated electrodes, via an AC voltage applied across the interdigitaled electrodes. The sensor can effectively detect trapped pathogens when the sample is passed through the fluidic channel by pressure driven flow or by electrokinetic/electroosmotic flow, etc. Thus, any commercial assay such as clinical PCR or any biological research apparatus that is concentrating sample can utilize the sensor of the present invention to determine if sufficient DNA, pathogens, etc., have been collected to analyze some or to identify the pathogen.
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Milner et al, “Dielectrophoretic classification of bacteria using differential impedance measurements,” Electronics Letters, vol. 34, No. 1, Jan. 8, 1998.*
Fiedler, S., et al., “Dielectrophoretic Sorting of Particles and Cells in a Microsystem,” Anal. Chem, 1998, 70, American Chemical Society, pp. 1909-1915.
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Carnahan L. E.
Diamond Alan
Scott Eddie E.
The Regents of the University of California
Thompson Alan H.
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