Lab-on-a-chip technology for determination of protein isoform profiles

A novel lab-on-a-chip technique for rapid (<15 min) and quantitative isoform-profile determination is presented. Ion-exchange chromatographic separation of protein-isoforms and a sensitive immunoassay detection are combined in a porous monolith chip. Thin lines of immobilized antibodies are used for specific capturing of target molecules, which can be detected by the reaction with antibodies bound to carbon black nano-strings. The bound carbon black is quantified by the use of an image scanner. As demonstrated with transferrin isoforms, differing only by 0.1 pH unit in their pI, this technology can distinguish minor differences in protein carbohydrate structure and enable specific determination of proteins in a complex environment, requiring only a few picogram of isoform for detection.