Quantitative-nanoliter immunoassay in capillary immune microreactor adopted inkjet technology†
A quantitatively controlled immunoassay at the nanoliter level based on inkjet technology was developed. The volumes of solutions/samples introduced were accurately controlled at the nanoliter level by using a four-channel inkjet microchip. Antibody/antigen recognition was performed in an amino modified capillary with a short diffusion distance. As a proof-of-concept, a sandwich immunoassay of human IgA was conducted using the developed method. The results demonstrated a low detection limit (0.03 ng mL−1) and a wide linear range (0.1–100 ng mL−1, R2 = 0.9959), comparable to currently used methods. For each capillary immunoassay, the volumes of the ejected solutions for human IgA, FITC conjugated anti-human IgA and the glycine–HCl dissociation solution were 52.15 ± 1.53 nL, 65.70 ± 2.06 nL and 37.51 ± 0.96 nL, respectively. This method, in which an inkjet functions as a novel “nanoliter pipette” in combination with a capillary for nanoliter immunoassays, has promising applications in areas of clinical diagnosis and drug screening.