Development of a low cost biosensing platform for highly sensitive and specific on-site detection of pathogens and infections

A highly sensitive, specific, real time, and field-deployable surveillance tool is critical to the control of pathogens and infections, as well as ecological impact of chemicals exposure. This work investigates the development of a low cost biosensing platform that can be used for viral disease diagnosis and chemical detection. The sensing mechanism is known as AC electrokinetics (ACEK) capacitive sensing. By applying an inhomogeneous AC electric field on sensor electrodes, positive dielectrophoresis is induced to accelerate the travel of analytes. The same applied AC signal also directly measures the capture of target by the probe on sensor surface. The realized sensing platform is not only rapid but also highly sensitive and specific. Built on our initial proof-of-concept of ACEK capacitive sensing, this work studies in details the immobilization of probes on electrode surface, electrode design, the interactions between biomolecules such as nucleic acids and testing buffers, and the effect of dielectrophoresis and accompanying ACEK phenomena. Experimental comparisons are made between sensors with various probe immobilization, different electrode designs, testing buffer and detection protocols. As a result, much higher sensitivity and selectivity have been achieved. We are able to successfully detect virus particles in nasal swab samples, specific antibody in serum and whole genome nuclei acids in serum. To extend the application of this sensing method on other electrode platform, polyimide-based laser printed electrodes are also investigated and successfully demonstrated for small molecule detection. However, this type of sensor exhibits high internal resistance, making it only suitable for chemical or particle detection in highly resistive electrolyte, such as de-ionized water. With procedural and design improvements discussed in this work, it is expected that ACEK capacitive sensing will become a disruptive technology in on-site biochemical detection.