Bacterial biofilm found on a catheter. (www.cdc.gov)

Certain types of bacteria regulate gene expression through quorum-sensing, the detection of extracellular levels of signaling compounds produced by bacteria of the same species.  Once bacteria such as E. coli sense their population is sufficiently large to overwhelm a host’s immune system, they will aggregate and form a pathogenic matrix of bacteria, or biofilm.

While previous research already has provided insight into the mechanisms of bacterial quorum-sensing, it is of interest to evaluate drugs targeting biosynthesis of quorum-sensing molecules, such as AI-2 in E. coli.  The next step in this work is to evaluate the effect of biosynthetic pathway products formed in the microfluidic system on bacterial colonies.  A successful drug targeting quorum-sensing molecule biosynthesis will yield products that inhibit biofilm formation.  A MEMS (micro-electromechanical systems) biosensor designed for integrated biofilm detection is thus required for full evaluation of such drugs. 

 Schematic of proposed sensor I am working on developing an integrated,optical-absorbance based sensor to detect and monitor bacterial biofilm growth. The proposed sensor would be functionalized with spatial selectivity using hydrophobic interactions with a protein-antibody conjugate. Once bacteria are selectively deposited on the sensor surface, they will form a biofilm over a period of days. As the biofilm increases in thickness, it becomes less permissive to light. This feature is measured by illuminating the sensor with a laser, and measuring the electrical output of a photodiode integrated into the substrate underneath the biofilm.

Integrated into a microfluidic system, this device not only can be used by researchers as a tool to study biofilms, but it can also be applied toward pharmaceutical development. Operating in parallel, these devices’ sensitivity and speed could reduce the normal drug evaluation period from months to days.