(314a) A Programmable Microfluidic System for Selective RNA or DNA Extraction From Various Raw Biological Samples

While the number and type of microfluidic analysis techniques has grown in recent years, the practical use of lab-on-a-chip systems to perform wide-ranging laboratory-type tests would be greatly benefited by the development of a sample preparation device that purifies genetic material from raw biological samples. The varied conditions of the sources of such material and the stringent requirements of analysis techniques force system-specific sample preparation operations, which often require time consuming and expensive manual handling. We present a system that promises to be a step towards universal sample preparation in its ability to take samples from various sources and selectively extract and purify nucleic acids (DNA or RNA).

The entire extraction system provides a compact, portable control platform with minimal inputs (electrical power, a usb connector, and an optional pressure supply). The polydimethylsiloxane (PDMS) microfluidic chip that performs the main fluid handling tasks of the system is fabricated in three layers: the fluidic channel layer, the functional flexible membrane layer, and the pneumatic control layer. The PDMS chip contains on-chip valves, channels, reservoirs, and pumps that are all pneumatically controlled via electrically actuated solenoid valves. A LabView computer program operates the solenoid valves in sequence to perform a variety of tasks such as sample input, lysis, incubation, mixing, extraction, cleaning, etc. The PDMS chip also has input ports for the reagents required to extract nucleic acid from a variety of samples.

The nucleic acid is purified on the chip using standard solid phase extraction on a disposable glass fiber filter. A cleaning/disinfectant step has been included to allow for multiple tests on a single PDMS chip, but the PDMS chip is also manifold-mounted for easy replacement for sensitive tests where disposable units are desired.

The extraction process operates by pumping the sample and various buffers and solutions through integrated pipetting/mixing reservoirs and past the extraction filter. Altering the amounts, types, and sequences of reagents used is easily accomplished by adjusting the control program, which allows selective adjustment of the protocol to handle different sample types and control the output as DNA, RNA or both. The ability of the system to handle different sample inputs is demonstrated by extracting DNA from both a stock DNA solution and whole blood, and by extracting RNA form a both a stock RNA solution and living E. coli cells with 429 ng of RNA being extracted from 70 million cells.

This system has proven capable of handling a variety of sample preparation tasks in an effort to make automated nucleic acid sample preparation more practical and available. Such work is a step towards a universal sample preparation unit that can handle many kinds of samples from viruses to tissue samples and provide rapid, meaningful results from a lab-on-a-chip platform.