Microfluidic DNA microarray analysis: a review

Microarray DNA hybridization techniques have been used widely from basic to applied molecular biology research. Generally, in a DNA microarray, different probe DNA molecules are immobilized on a solid support in groups and form an array of microspots. Then, hybridization to the microarray can be performed by applying sample DNA solutions in either the bulk or the microfluidic manner. Because the immobilized probe DNA binds and retains its complementary target DNA, detection is achieved through the read-out of the tagged markers on the sample target molecules. The recent microfluidic hybridization method shows the advantages of less sample usage and reduced incubation time. Here, sample solutions are confined in microfabricated channels and flow through the probe microarray area. The high surface-to-volume ratio in microchannels of nanolitre volume greatly enhanced the sensitivity as obtained with the bulk solution method. To generate nanolitre flows, different techniques have been developed, and this including electrokinetic control, vacuum suction and syringe pumping. The latter two are pressure-driven methods which are more flexible without the need of considering the physicochemical properties of solutions. Recently, centrifugal force is employed to drive liquid movement in microchannels. This method utilizes the body force from the liquid itself and there are no additional solution interface contacts such as from electrodes or syringes and tubing. Centrifugal force driven flow also features the ease of parallel hybridizations. In this review, we will summarize the recent advances in microfluidic microarray hybridization and compare the applications of various flow methods.