Surface plasmon resonance biosensor for the detection of tau-amyloid β complex

•New biosensor for the prospective AD biomarker - the complex of protein tau and Aβ.•The method enables the detection of the tau-Aβ complex in CSF down to sub-pM levels.•First reported sensor-based measurement of the levels of tau-Aβ complex in CSF samples. The development of methods advancing the understanding of molecular processes related to Alzheimer’s disease (AD) and detection of biomarkers of AD presents an important research goal. We present a new biosensor-based method for the detection of a prospective biomarker of AD, the complex of protein tau and amyloid β (tau-Aβ). The detection method combines a new sandwich assay incorporating functionalized gold nanoparticles (AuNPs) with a surface plasmon resonance (SPR) biosensor. We optimize the assay with respect to the functionalization of the sensor surface and the choice of AuNPs and show that the sensor allows for the detection of the tau-Aβ complex in cerebrospinal fluid (CSF) with the limit of detection of 1 pM. We also present the results of a preliminary study in which we use the method to detect tau-Aβ complex in CSF samples.