Chen, Dafeng
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Publication An integrated, self-contained microfluidic cassette for isolation, amplification, and detection of nucleic acids(2010-04-01) Chen, Dafeng; Mauk, Michale; Qiu, Xianbo; Liu, Changchun; Kim, Jitae; Ramprasad, Sudhir; Ongagna, Serge; Abrams, William; Malamud, Daniel; Bau, Haim H; Corstjens, PaulA self-contained, integrated, disposable, sample-to-answer, polycarbonate microfluidic cassette for nucleic acid-based detection of pathogens at the point of care was designed, constructed, and tested. The cassette comprises on-chip sample lysis, nucleic acid isolation, enzymatic amplification (polymerase chain reaction and, when needed, reverse transcription), amplicon labeling, and detection. On-chip pouches and valves facilitate fluid flow control. All the liquids and dry reagents needed for the various reactions are pre-stored in the cassette. The liquid reagents are stored in flexible pouches formed on the chip surface. Dry (RT-)PCR reagents are pre-stored in the thermal cycling, reaction chamber. The process operations include sample introduction; lysis of cells and viruses; solid-phase extraction, concentration, and purification of nucleic acids from the lysate; elution of the nucleic acids into a thermal cycling chamber and mixing with pre-stored (RT-)PCR dry reagents; thermal cycling; and detection. The PCR amplicons are labeled with digoxigenin and biotin and transmitted onto a lateral flow strip, where the target analytes bind to a test line consisting of immobilized avidin-D. The immobilized nucleic acids are labeled with up-converting phosphor (UCP) reporter particles. The operation of the cassette is automatically controlled by an analyzer that provides pouch and valve actuation with electrical motors and heating for the thermal cycling. The functionality of the device is demonstrated by detecting the presence of bacterial B.Cereus, viral armored RNA HIV, and HIV I virus in saliva samples. The cassette and actuator described here can be used to detect other diseases as well as the presence of bacterial and viral pathogens in the water supply and other fluids.Publication An Automated, Pre-Programmed, Multiplexed, Hydraulic Microvalve(2009-09-14) Chen, Dafeng; Kim, Jitae; Bau, Haim H.An automated, pre-programmed, multiplexed hydraulic valve actuator is described. The valve is membrane-based and normally open. In contrast to the membrane-based pneumatic valve, the hydraulic valve uses hydraulic liquid to exert the control pressure. The line pressure is controlled with a roller moving over a prefabricated topology. Multiple rollers, each traversing its own track, are assembled into a single carriage, which can be actuated either manually or with a single computer-controlled motor. A valve manifold and roller actuators are designed, fabricated, and tested to demonstrate three-way valve actuation in a pre-determined sequence. The performance of the valve is evaluated and the utility of the valve in the operation of a micro thermal cycler was demonstrated. Hydraulic controllers of the type described here can be operated either manually or under computer control and provide an inexpensive means of controlling flow in lab-on-a-chip devices.Publication A Timer-Actuated Immunoassay Cassette for Detecting Molecular Markers in Oral Fluids(2009-01-01) Changchun, Liu; Qiu, Xianbo; Chen, Dafeng; Ongagna, Serge; Chen, Zongyuan; Bau, Haim H.; Abrams, Williams R.; Malamud, Daniel; Corstjens, Paul L.A.M.An inexpensive, hand-held, point-of-care, disposable, self-contained immunoassay cassette comprised of air pouches for pumping, a metering chamber, reagents storage chambers, a mixer, and a lateral flow strip was designed, constructed, and tested. The assay was carried out in a consecutive flow format. The detection was facilitated with up-converting phosphor (UCP) reporter particles. The automated, timely pumping of the various reagents was driven by a spring-loaded timer. The utility of the cassette was demonstrated by detecting antibodies to HIV in saliva samples and further evaluated with a noncontagious, haptenized DNA assay. The cassette has several advantages over dip sticks such as sample preprocessing, integrated storage of reagents, and automated operation that reduces operator errors and training. The cassette and actuator described herein can readily be extended to detect biomarkers of other diseases in body fluids and other fluids at the point of care. The system is particularly suitable for resource-poor countries, where funds and trained personnel are in short supply.