Photonic Lab-on-a-Chip for Rapid Cytokine Detection

A photonic lab-on-a-chip (PhLoC) was developed for rapid determination of interleukin-2 (IL-2) levels secreted by lymphocytes using measurement of optical absorbance. Optical and microfluidic components, including lenses, mirrors, and flow channels, were monolithically created using poly­(dimethylsiloxane) (PDMS). Sample and reagent solutions were processed in the form of liquid columns separated by air. A flow channel structure with an air bypass was used to release air between solution columns and to exchange solutions in the measuring chamber, avoiding the intrusion of air into the measuring chamber and the denaturation of the capture antibodies. The concentration of IL-2 was measured by enzyme-linked immunosorbent assay (ELISA) in the PhLoC. The total time required for the ELISA was less than 30 min. Clear concentration dependence was confirmed for IL-2 concentrations ranging from 50 to 1000 pg/mL. Thus, the concentration of IL-2 secreted by lymphocytes following activation by concanavalin A (Con A) could be measured using the PhLoC.