"We have created microfluidic devices for concentration and lysis of bacterial cells in a continuous mode based on applying microspheres."

Rapid, quantitative, and reusable immunosensors for bacteria detection on a microfluidic platform

Investigator: Chang Lu (Department of Agricultural and Biological Engineering)

Project Report 2006 - 2007

» Download Project Report 2006 - 2007

Project Rationale

The development of portable, rapid and sensitive biosensors for food safety applications enables point-of-care contamination detection and immediate interpretation of results. In this research project, our multi-disciplinary team is developing an integrated biosensor system on a microfluidic chip for detecting bacteria using immunoassay-based reactions. The device will offer a sensitivity to detect 102 to 103 bacterial cells and an assay time of less than 20 minutes per test. Our system will yield quantitative data for estimating the number of the target bacterium in a food sample. The microfluidic system under development consists of individual devices for cell lysis, lysate purification, and immunoassays. We will use an intracellular antigen, alcohol acetaldehyde dehydrogenase (Aad), and its antibody MAb-H7 to detect Listeria monocytogenes. In order to concentrate L. monocytogenes cells from food samples, we will fabricate magnetic nanobars with different sizes and geometries and develop protocols for immobilizing antibodies specific to L. monocytogenes on the surface.

A portable, reusable, and low-cost device will be useful for bacterial testing in food manufacturing laboratories. Carrying out bacteria detection tests within the food manufacturing lab will decrease turnaround time for the results and avoid potential growth/decrease/contamination of bacteria during transit. Large, expensive equipment is often needed to perform conventional analytical methods. Lab-on-a-chip approaches, however, allow sophisticated functions of analytical techniques to be miniaturized on a microchip. With this technology, it will be possible to perform bacteria detection on a microchip using only basic laboratory equipment. This technology can significantly benefit the food industry by enhancing the food safety testing capability for food manufacturers, food testing laboratories, and public health and governmental agencies.

Project Objectives

  • Fabricate magnetic nanobars with different sizes and geometries and develop protocols for immobilizing antibodies specific to L. monocytogenes on the surface. The amount of bacterial cells bound to the surface will be characterized under different conditions.
  • Develop electrophoresis-based immunoassay coupled with laser-induced fluorescence on a microfluidic chip. We will use this tool to quantitatively detect L. monocytogenes based on cell lysate, via the interaction between alcohol acetaldehyde dehydrogenase (Aad) and its monoclonal antibody (MAb-H7).
  • Demonstrate a prototype-integrated microfluidic system that incorporates different steps such as manipulation of magnetic nanobars, cell lysis, lysate purification, and immunoassay.

Project Highlights

We have created microfluidic devices for concentration and lysis of bacterial cells in a continuous mode based on applying microspheres. Microspheres are accumulated in a microfluidic channel, and the gaps between the microspheres retain bacterial cells. The electrical lysis can be carried out by applying an electrical pulse after cell concentration. This technology will allow incorporation of solid phase-based detection assays (e.g. ELISA) for bacterial identification by functionalizing the microsphere surface. With concentration, lysis, and detection capabilities contained in one miniaturized device, we can produce a biosensor system that is both robust and low cost.