Research

Observation of individual biomolecules allows for characterization of real-time dynamics, molecular subpopulations, and heterogeneous biological behavior. This information, in turn, provides a molecular-based understanding of biological mechanisms and may elucidate the underlying causes of disease states. With these ideas in mind, the goal of our research is to develop and employ tools for the investigation of biological phenomena at the molecular and cellular level. We use fabrication technology to probe and measure biological systems in ways that are difficult or impossible to do using standard analytical techniques and instrumentation. Many conventional techniques are not sensitive enough to detect the signal from the small sample sizes that are used in miniaturized systems. As a result, there is a great need to develop new detection strategies specifically for these size scales. To address this need, we are investigating the advantages that miniaturized structures provide when combined with various detection modalities, such as electrochemistry and surface plasmon resonance.

We are developing electrochemical detection for lab-on-a-chip and chip-in-a-lab applications. Electrochemical detection is a very attractive scheme to employ as it is relatively simple to implement and integrate with portable systems. We are primarily interested in detecting quorum sensing molecules produced by bacteria. Each bacterial species produces a unique set of sensing molecules, which can be used as a fingerprint for identification of which bacteria are present in a sample. We are working with clinicians and veterinarians to translate into hospital settings for point-of-care identification of pathogens.

 

Sub-microfluidics for Bacterial Isolation and Cultivation

We are designing and fabricating fluidic devices that allow automated isolation and cultivation of bacterial cells in their native environment. Our devices can be used to characterize bacterial diversity in selected environments or to target isolation of species that have particular characteristics or functions.

By employing designed fluidic systems we are also investigating various parameters involved in quorum sensing in a controlled manner. Using microfluidics, we can localize discrete numbers of bacteria next to our fluidic electrochemical sensors that allow us to monitor the production of signaling molecules under various conditions. The fabricated structures allow us to precisely measure the effects of spatial and environmental changes on the bacteria.

Surface plasmons are optical waves trapped near a metal-dielectric interface that are caused by resonant interactions between the electromagnetic field and electrons oscillating near the surface of the metal. The fields decay exponentially away in both directions, extending only about 300 nm. Metals such as gold, silver, and copper create plasmons in the visible spectrum that can be easily monitored. SPR is often used in biosensor applications to probe interactions between analytes in solution and biomolecular recognition elements that are immobilized on the sensor surface. These sensors are of interest to the scientific community because they offer label-free real-time detection and employ relatively simple instrumentation that can potentially be integrated into portable lab-on-a-chip devices. We are utilizing this technology to visualize where bacterial cells accumulate on surfaces.

The newest instrument in the laboratory is a quartz crystal microbalance that we are using to evaluate biofilm formation and removal. The main advantage of QCM is that the sensor surface can be coated with any material of interest, allowing significant flexibility when evaluating new materials.