sFIDA automation yields sub-femtomolar limit of detection for Aβ aggregates in body fluids

Objectives: Alzheimer's disease (AD) is a neurodegenerative disorder with yet non-existent therapeutic and limited diagnostic options. Reliable biomarker-based AD diagnostics are of utmost importance for the development and application of therapeutic substances. We have previously introduced a platform technology designated 'sFIDA' for the quantitation of amyloid beta peptide (A beta) aggregates as AD biomarker. In this study we implemented the sFIDA assay on an automated platform to enhance robustness and performance of the assay. Design and methods: In sFIDA (surface-based fluorescence intensity distribution analysis) A beta species are immobilized by a capture antibody to a glass surface. A beta aggregates are then multiply loaded with fluorescent antibodies and quantitated by high resolution fluorescence microscopy. As a model system for A beta aggregates, we used A beta-conjugated silica nanoparticles (A beta-SiNaPs) diluted in PBS buffer and cerebrospinal fluid, respectively. Automation of the assay was realized on a liquid handling system in combination with a microplate washer. Results: The automation of the sFIDA assay results in improved intra-assay precision, linearity and sensitivity in comparison to the manual application, and achieved a limit of detection in the sub-femtomolar range. Conclusions: Automation improves the precision and sensitivity of the sFIDA assay, which is a prerequisite for high-throughput measurements and future application of the technology in routine AD diagnostics. (C) 2016 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.