Active Hybridization and Electrical Detection in a DNA Chip for Portable Diagnostics

Active hybridization using the combined electrokinetic forces is proposed to accelerate in situ hybridization and enhance its sensitivity and specificity. Electrical detection of active hybridization is also investigated to miniaturize the device for demonstrating the point-of-care and on-site diagnostic applications. Currently, most of the existing DNA microarray chips are based on passive hybridization. Because of diffusion-limited reaction kinetics, passive hybridization normally takes a relatively long time (several hours to overnight) to complete. Also, the sensitivity may not be satisfied when the samples are in low concentration. Moreover, most of the state-of-the-art hybridization detections are based on fluorescent methods, which require dedicated optical equipment. The proposed techniques are suitable for developing portable devices and will be demonstrated on an avian influenza virus (AIV) diagnostic application. DNA hybridization enhanced by the combined electrokinetic forces will be investigated in a DNA chip (i.e., an array of electrodes fabricated on a substrate encapsulated with a microfluidic chamber). Capture strands are immobilized on the electrode surface and the target strands suspended in solution are injected into the DNA chip. The combination of AC electroosmosis and electrophoresis can induce circulating fluid motion and attractive force on electrodes to manipulate target strands. Therefore, efficient mixing and high concentration of DNA pairs could accelerate the hybridization reaction. The active hybridization conditions including applied electric field, hybridization time, salt concentration of the solution, etc., will be investigated and optimized. Electrical detection of active hybridization will be investigated for the device miniaturization. Therefore, electrodes in the DNA chip work for mixing, concentration, hybridization, and also detection. After active hybridization is completed on the electrodes, gold nanoparticles are injected to indicate the hybridized DNA. Then, gold enhancement is performed to form a conductive layer across the electrodes for signal amplification. Resistance value will be measured to determine the presence of hybridization and also the concentration of target strands quantitatively on the specific electrode. The proposed techniques can be potentially developed the portable diagnostic device and used in various field applications.

Project ID:PB10007-7223
External Project ID:NSC100-2221-E182-022