An integrated microelectronic device for biomolecular amplification and detection

Abstract

The extraordinarily high sensitivity, large dynamic range and reproducibility of polymerase chain reaction (PCR) have made it one of the most widely used techniques for analyzing nucleic acids. As a result, considerable effort has been directed towards developing miniaturized systems for PCR, but most rely on off-chip optical detection modules that are difficult to miniaturize into a compact analytical system and fluorescent product markers that can require extensive effort to optimize. This thesis presents a robust and simple method for direct label-free PCR product quantification using a microelectronic sensor. The thesis covers the design, fabrication, and characterization of the sensing technique and its integration with PCR microfluidics into a monolithic detection platform. The sensor used in this thesis study is an electrolyte-insulator-silicon (EIS) device fabricated on planar silicon substrates. Based on electronic detection of layer-by-layer assembly of polyelectrolytes, the sensing technique can specifically quantify double-stranded DNA product in unprocessed samples and monitor the product concentration at various stages of PCR to generate readout analogous to that of a real-time fluorescent measurement.

(cont.) Amplification is achieved with integrated metal resistive heaters, temperature sensors, and microfluidic valves. Direct electronic quantification of the product on-chip yields analog surface potential signals that can be converted to a digital true/false readout. A silicon field-effect sensor for direct detection of heparin by its intrinsic negative charge has also been developed. Detection of heparin and heparin-based drugs in buffer and serum has been studied, and a study demonstrating strong correlation between electronic heparin sensing measurements and those from a colorimetric assay for heparin-mediated anti-Xa activity has been performed.