Development of hapten-linked microimmunoassays on polycarbonate discs

An amino-modified polycarbonate surface of compact discs is used to link haptens covalently and directly as an alternative to the classic protein-hapten conjugate adsorption coating strategy employed in immunoassays. The modified surface maintains its physical and optical properties, and a standard disk drive can then read the assay results. Advantages are evaluated, such as the use of a broader spectrum of coupling media including organic solvents that are inappropriate for proteins but necessary for some water-insoluble haptens and the bypassing of the synthesis and purification for protein conjugates. As proof of concept, competitive microimmunoassays were developed for chlorpyrifos, atrazine, and 2-(2,4,5-trichlorophenoxy)propionic acid (2,4,5-TP), in microarray format, obtaining detection limits of 37.2, 8.1, and 76 ng/L, respectively. The sensitivity was 1 order of magnitude better than that obtained for all the studied systems using hapten-protein conjugates adsorbed on polystyrene enzyme-linked immunosorbent assay (ELISA) plates and polycarbonate surfaces. Further, the influence of hapten structure and presentation on molecular recognition pattern is discussed. To our knowledge, this is the first time that microarray and compact disc technologies converge with this particular hapten immobilization mode. The great potential of the approach is demonstrated through the high-throughput capability of the disc in a range of analytical applications, as well as the inherent advantages of compact disc reading technology.