Surface functionalization of a microfluidic biosensor for bacteria detection and identification

Rapid identification and detection of bacteria is an important issue in environmental and food science. We have developed an impedance-based method to simultaneously identify and detect bacteria in a derivatized microfluidic chamber with monoclonal antibodies. The presence of bacteria in the solution can be selectively recognized and fixed on the chamber wall and detected via impedance change in real time. The optimum reaction time between antibody and bacteria has been estimated using a simple model and evaluated experimentally. Various concentrations of cultured E. coli cells ranging from 105 to 108 CFU/ml were tested using the biosensor. By taking the advantage of a microfluidic system, the bacteria can be concentrated and accumulated on the chamber wall by continuously perfusing the chamber with bacterial suspension, therefore, enhancing the detection limit of the sensor. Using this approach, the biosensor was able to detect 106 CFU/ml E. coli (BL21(DE3)) via five consecutive perfusions. The selectivity of the sensor is demonstrated by testing the antibody reaction for two bacteria stains, E. coli and M. catarrhalis. By derivatizing the chamber walls with specific antibodies, we can clearly identify the bacteria that are specific to the antibodies in the detection chamber. The simplicity of the technique also makes the device portable and ideal for clinical and field applications.