MEMS sample preparation stages for a point-of-care testing (POCT) device.

摘要

Growing demand for quick analytical information has driven successful Point-of-care-testing (POCT) device development, and immunosensors have been in the main stream of the development. Complex biological matrices that POCT device must analyze cause non-specific bindings and detection interference in sensors; these issues pose a significant bottleneck to commercializing POCT devices because immunosensors cannot have high selectivity as well as sensitivity. Our goal is to develop ways to relax the stringent requirements of immunosensor selectivity in portable POCT devices and miniaturize a Size Exclusion Chromatography (SEC) column using Micro-Electro-Mechanical System (MEMS) technology.;This dissertation focuses on prototyping and developing an SEC mini-column that could be used as the sample preparation stage on a POCT device, relaxing immunosensor selectivity requirements. Our research began in earnest with the original prototype, an SEC mini-column miniaturized on a flexible and biocompatible Polydimethylsiloxzne (PDMS) enclosure for potential use in medical implants to monitor health conditions.;In addition to the potential medical implants application, we explored the use of the mini-column toward portable hand-held POCT devices. The SEC mini-column separated a cancer biomarker from abundant proteins in human plasma evaluated by external fluorescent detection. From this success, we continued to explore the miniaturized separator's performance parameters by connecting an SEC mini-column and affinity mini-column containing Protein A/G agarose beads to deplete left-over abundant protein, Immunoglobulin G (IgG), in series.;Since medical diagnostics often extend to fluids besides plasma, we expanded our research to include technology for separating urine samples. Escherichia. coli (E. coli) in urine, for instance, causes Urinary Tract Infections (UTIs), and the current standard practice (culturing E. coli directly sampled from patient's urine) takes 24 to 48 hours to provide viable results. That time delay suggests why a quick, reliable, portable, hand-held POCT device for detecting E. coli directly from urine would greatly benefit patients and researchers. We implemented an E. coli separator integrated with Electrochemical Impedance Spectrometry (EIS) to connect two chambers in series---a concentration and sensing chamber---to reduce the false-positive effect from non-specific absorption coming from co-existing proteins or chemical in UTI infected urine.;The separation results of both the SEC mini-column and the E. coli separator showed great potential for making POCT devices more practical and commercially viable. Our prototype research has now established a baseline for these miniaturized separation mechanisms. In ongoing research, they will' need to be fully characterized and improved.