The objective of this R21 proposal is to develop a multianalyte 2-D diffusion point-of-care assay (POC) for cardiac infarction. The 2-D diffusion assay consists of a "nonfouling" poly(oligoethyene glycol methacrylate (POEGMA) brush coated glass chip that contains two types of printed spots: "stable" spots of capture antibodies (Abc) and "soluble" spots of detection reagents that are printed with excipients so that they dissolve upon contact with blood. A finger stick of blood is applied to the surface, and the protein analytes in the blood diffuse across the nonfouling POEGMA brush and bind to immobile spots of the individual capture antibodies (Abc's) on the surface. Simultaneously, the blood dissolves the fluorescently labeled detection Ab's (Abd) from the labile spots, which then bind to their respective analyte-Abc spots, completing the sandwich. A final displacement step with buffer removes the blood components from the chip, revealing the formation of a fluorescent spot at the position where the unlabeled detection agent had been printed. This assay will require no sample preprocessing, will be multiplexed to detect cardiac troponin (cTnI) and the brain natriuretic pro-polypeptide (pro-BNP) on the same chip, and will provide quantitative read-out of analyte concentration, thereby providing a new dimension of capabilities to POC tests that are superior to the current gold standard - lateral-flow assays.
The proposed research will develop a new point-of-care clinical test -the 2-D diffusion assay- for cardiac infarction that requires no sample purification and minimal steps in testing. In this assay, adding a drop of blood to the surface of a thin polymer film allows a marker that is present in the patient's blood -and diagnostic of a disease- to bind to "stable" capture spots of capture antibodies, while simultaneously, the blood dissolves optically labeled detection antibodies that are printed as "soluble" spots, so that they migrate in solution to the stable spots of capture molecules bound to the marker, and complete the assay, resulting in a visible signal.