Self-Contained, Fully Integrated Biochips for Sample Preparation, PCR Amplification and DNA Microarray Analysis

Abstract

Rapid developments in back-end detection platforms (such as DNA microarrays, capillary electrophoresis, real-time polymerase chain reaction and mass spectroscopy) for genetic analysis have shifted the bottleneck to front-end sample preparation where the ‘real’ samples are used. In this chapter, we present a fully integrated biochip device that can perform on-chip sample preparation (including magnetic bead-based cell capture, cell preconcentration and purification and cell lysis) of complex biological sample solutions (such as whole blood), polymerase chain reaction, DNA hybridization and electrochemical detection. This fully automated and miniature device consists of microfluidic mixers, valves, pumps, channels, chambers, heaters and DNA microarray sensors. Cavitation microstreaming was implemented to enhance target cell capture from whole blood samples using immunomagnetic beads and accelerate DNA hybridization reaction. Thermally actuated paraffin-based microvalves were developed to regulate flows. Electrochemical pumps and thermopneumatic pumps were integrated on the chip to provide pumping of liquid solutions. The device is completely self-contained: no external pressure sources, fluid storage, mechanical pumps, or valves are necessary for fluid manipulation, thus eliminating possible sample contamination and simplifying device operation. Pathogenic bacteria detection from ≈ mL whole blood samples and single-nucleotide polymorphism analysis directly from diluted blood were demonstrated. The device provides a cost-effective solution to direct sample-to-answer genetic analysis and thus has a potential impact in the fields of point-of-care genetic analysis, environmental testing and biological warfare agent detection.