The development of a nanoscale Coulter counter for rapid genetic sequence recognition

Abstract

The goal of this thesis is the development of a nanoscale Coulter counter for the direct electrical detection of specific genetic sequences of deoxyribonucleic acid (DNA); the general approach used to accomplish sequence recognition is a refinement of the resistive pulse technique. Commercial Coulter counters fabricated with sub-micrometer apertures can size particles with roughly twenty nanometers of resolution. The characterization of DNA, which is more than an order of magnitude smaller than this resolution limit, requires the development of a detection system with a two nanometer limiting aperture. To help develop the techniques and instrumentation explored in this thesis, the biological toxin, alpha hemolysin, was implemented as "prototype" limiting aperture. With the practical knowledge gained from using a toxin channel, a general model for the nanopore as a low-noise sensor was developed. With this model, two broad goals were achieved. The first achievement was the development of novel genetic recognition strategies that exploit the properties of the nanopore within the limitations imposed by DNA structure and existing channel geometries. The second achievement was the design and prototyping of novel interface picoammeter for the measurement of the current fluctuations associated with DNA translocation through a nanopore. Although the instrumentation and methods developed in this thesis are limited to genetic sequence recognition, the hope is that elements of this work will be integrated with the development of silicon nanopores to achieve rapid de novo DNA sequencing in the future.