A microfluidic immunoassay system on a centrifugal platform.

A lab-on-a-CD immunoassay system was designed, fabricated, and tested. The actuator for the centrifugal platform consists of a flyball governor and a group of spring plungers. The microfluidic structures were fabricated using replica processes with poly-dimethylsiloxane (PDMS) as structural material. For better control, the valves in the microfluidic system were designed to be mechanical-pinch ones and actuated. The burst frequencies of the micro-valves can be tuned independently by adjusting the heights and pre-stresses of corresponding spring plungers. For the research work reported in this paper, four sequential valves and one inward pump were integrated on a centrifugal microfluidic system to develop an automated immunoassay system. Mouse IgG was used as a model analyte to test the feasibility of using the proposed device for immunoassay applications. Sample solution of goat anti-mouse IgG conjugated with magnetic nanoparticles was used for magnetic trapping mechanism to eliminate the blocking process. Rabbit anti-mouse IgG labeled with fluorescent molecules was used as the signal reporter. The entire microfluidic assay process, including beads trapping, immunoassay reaction, washing and pumping was completed in a centrifugal platform. The detection sensitivity may also be improved by using higher quality monoclonal antibodies. This new immunoassay platform offers some significant advantages over those reported in the field: simple fabrication, robust control, easy integration, and lower cost. The system may also be modified for detection of multiple targets. The technology has great potential for applications in complex fluid handling needed in biological, chemical and medical application in Lab-on-a-CD systems. [ABSTRACT FROM AUTHOR]