Rapid ELISA in Droplet on PDMS Dimple with Nanoliter Reagents Dispensed by Ink-jet Microchip

IgA ELISA was performed in a droplet using an ink-jet microchip for shortening the reaction time, saving the reaction reagents. Forty-five dimples (500-μm i.d., 100-μm depth) were prepared on a PDMS (polydimethylsiloxane) microchip plate (30×30 mm) for the reaction vessels. After the dimple was pored with nanoliter water containing glycerin, an antibody solution was firstly added for immobilization on the dimple, and then nanoliter reaction regents for ELISA (enzyme-linked immunosorbent assay) were added sequentially using an ink-jet chip. A good linear relationship between the fluorescence intensity of Ample®Red and concentration of IgA was obtained with each reaction time of 150 s.