Tandem Femto- and Nanomolar Analysis of Two Protein Biomarkers in Plasma on a Single Mixed Antibody Monolayer Surface Using Surface Plasmon Resonance

The multiplexed detection of protein biomarkers in plasma present over a range of clinically relevant concentrations continues to be difficult for surface-based bioaffinity detection platforms such as surface plasmon resonance (SPR). As well as nonspecific adsorption, challenges include quantitative comparison between targets whose concentrations differ by orders of magnitude, regenerating SPR chips after plasma exposure as well as the two or four channel limitation of many commercial SPR instruments limiting sample throughput. In this article, we explore an approach where two protein biomarkers alpha-1 antitrypsin (AAT) and Tau 381 are detected in tandem within a single SPR channel at micromolar and femtomolar concentrations respectively. This was achieved by creating a mixed antibody (antiAAT and antiTau) monolayer on the chip surface. Following the adsorption of AAT and/or Tau, further specificity was obtained via the adsorption of a DNA aptamer specific to each target. The detection range for each tar...