Fig. 1.

Overview of the Proximity Extension Assay demonstrating the (a) immunoassay, (b) extension, (c) preamplification, (d) and detection steps used for proteomic analyses of protein biomarkers in this study. [12] Image courtesy of Olink Proteomics AB. (a) For this immunoassay, pairs of specific antibodies labeled with DNA oligonucleotides bind to their target-specific antigens (protein biomarkers) in a solution. Antigen binding, in turn, brings the PEA probes in close proximity. (b) Pair-wise binding of matching PEA probes occurs through hybridization and upon addition of a DNA polymerase results in extension of the two oligonucleotides to form DNA barcodes that will now serve as a reporter of the protein biomarkers. (c) The addition of primers results in preamplication of the new DNA sequences. (d) Microfluidic qPCR is used for amplification and quantification of these new DNA barcodes.