On-chip microfluidic biosensor for bacterial detection and identification

In this paper, we have developed a simple and rapid method for the detection and identification of bacteria using a microfluidic lab-chip. The microfluidic chip utilizes impedance-based measurement to (1) detect cells and (2) identify them when used in conjunction with immobilized monoclonal antibodies. Bacteria in suspension passing through the microfluidic chamber are recognized by antibodies and selectively immobilized on the functionalized glass surface, thereby increasing the measured impedance within the chamber. Continuous perfusion of bacteria suspension through the derivatized chamber not only identifies specific bacteria but also enhances the chamber's detection sensitivity by accumulating bacteria on the chamber wall over time; this approach would be useful for detecting low concentrations of bacteria. To demonstrate this approach, we showed that the prototype sensor could detect 9 × 105 CFU mL−1E. coli (BL21(DE3)) in the solution by consecutive perfusions. The chip sensitivity with immobilized bacteria is governed by height of sensing chamber, and ∼104 CFU mL−1 of E. coli could easily be detected when a shallower chamber (2 μm high) was used. The selectivity of the sensor was tested using a suspension of two bacterial strains, E. coli and M. catarrhalis. The sensor chip is simple to use, requires minuscule samples, and eliminates extensive cell culture processes. Development of more advanced lab-chips with multiple chambers containing different antibodies that allow simultaneous detection of different bacteria strains will be a natural extension of this work.