Microtechnologies for nucleic acid analysis: from concept to commercialization

Abstract

Current commercial instruments for amplification of nucleic acids via the polymerase chain reaction (PCR) have provided the technical requirements to prove the viability and potential of this powerful biotechnological technique. However, there are significant opportunities to advance the instrumentation technology to allow for the extension of the PCR technique beyond the laboratory and make it low-cost, rapid, flexible, and automated. As well, similar improvement opportunities in sample purification and processing techniques exist. Speeding up the ramping rates between denature, extension, and anneal temperatures has been shown to augment the PCR process, and this concept has developed into a commercial product. As well, the ability to perform homogeneous assay with PCR has also been incorporated into commercial products. Thusly, some of the recent advances in the chemistry such as the Taqman or molecular beacons technique have been exploited with these new commercial thermal cycling products that contain fluorescence detection and product quantitation capabilities. In spite of these advances in instrument technologies, there are still limitations in functionality, and therefore opportunities for improvements. Some of these new commercial opportunities for technological improvements include: independent control of the thermal cycling and optical systems at each reaction site, rapid thermal cycling of the large volumes (100 /spl mu/L or greater) required for clinical analyses of infectious diseases, low power consumption, use of solid state optical components (which can lower cost), modularity, ease of serviceability, and portability. Although it has been shown that quantitative, homogeneous PCR assays can be performed in both large bench-top instruments and in a portable format, pre-PCR sample preparation remains the significant bottleneck in terms of the need for human intervention, complexity, and lack of automation. Sample preparation routines range from a simple dilution of inhibitors to complex filtering, centrifuging, lysing, mixing, solid phase extraction, etc. Automation of some of these procedures has typically taken the form of robots replacing human-mediated steps, and several solid phase extraction techniques. As with the analytical thermal cyclers for PCR, opportunities exist for improvements that will augment the distribution and applicability of the PCR technique. Specific examples of these technological improvements include replacing human mediated fluid handling steps with microfluidic devices that are self-contained and automated, combining process steps in a flow-through disposable cartridge format, and speeding up the steps with micromachined, electronically controlled "chips". In this presentation, I will describe the development of the concepts, history, and the commercialization of new instrument systems and devices that take advantage of the improvements afforded by implementing these technological advances.