title: A microfluidic-based electrochemical biochip for label-free DNA hybridization analysis.
abstract: Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration of pre-processing steps. Utilizing these devices towards the analysis of DNA hybridization events is important because it offers a technology for real time assessment of biomarkers at the point-of-care for various diseases. However, when the device footprint decreases the dominance of various physical phenomena increases. These phenomena influence the fabrication precision and operation reliability of the device. Therefore, there is a great need to accurately fabricate and operate these devices in a reproducible manner in order to improve the overall performance. Here, we describe the protocols and the methods used for the fabrication and the operation of a microfluidic-based electrochemical biochip for accurate analysis of DNA hybridization events. The biochip is composed of two parts: a microfluidic chip with three parallel micro-channels made of polydimethylsiloxane (PDMS), and a 3 x 3 arrayed electrochemical micro-chip. The DNA hybridization events are detected using electrochemical impedance spectroscopy (EIS) analysis. The EIS analysis enables monitoring variations of the properties of the electrochemical system that are dominant at these length scales. With the ability to monitor changes of both charge transfer and diffusional resistance with the biosensor, we demonstrate the selectivity to complementary ssDNA targets, a calculated detection limit of 3.8 nM, and a 13% cross-reactivity with other non-complementary ssDNA following 20 min of incubation. This methodology can improve the performance of miniaturized devices by elucidating on the behavior of diffusion at the micro-scale regime and by enabling the study of DNA hybridization events.
authors.affiliation: MEMS Sensors and Actuators Laboratory (MSAL), Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland; benyoav@umd.edu.
authors.forename: Hadar
authors.initials: H
authors.lastname: Ben-Yoav
authors.affiliation: MEMS Sensors and Actuators Laboratory (MSAL), Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Dykstra
authors.affiliation: Institute for Bioscience and Biotechnology Research, Fischell Department of Bioengineering, University of Maryland.
authors.forename: Tanya
authors.initials: T
authors.lastname: Gordonov
authors.affiliation: Institute for Bioscience and Biotechnology Research, Fischell Department of Bioengineering, University of Maryland.
authors.forename: William E
authors.initials: WE
authors.lastname: Bentley
authors.affiliation: MEMS Sensors and Actuators Laboratory (MSAL), Department of Electrical and Computer Engineering, Institute for Systems Research, University of Maryland.
authors.forename: Reza
authors.initials: R
authors.lastname: Ghodssi
mesh_terms: D004247:DNA / Q000032:analysis* / Q000235:genetics; D015342:DNA Probes / Q000737:chemistry / Q000235:genetics; D004277:DNA, Single-Stranded / Q000032:analysis / Q000235:genetics; D056656:Lab-On-A-Chip Devices; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D055616:Microtechnology / Q000379:methods; D009693:Nucleic Acid Hybridization / Q000379:methods*
chemical_list: D015342:DNA Probes; D004277:DNA, Single-Stranded; D004247:DNA