| Abstract: |
Metallic and magnetic nanoparticles provide versatile sensing platforms for biological and biomedical applications such as the detection and quantification of large biomolecules serving as diagnostic markers (biomarkers) in human medicine. Here, a new sandwich immuno-assay for surface-enhanced Raman scattering (SERS) based determination in combination with the isotope dilution (ID) approach of tau-protein, one of the established biomarkers for Alzheimer’s disease, will be shown.
The developed assay will be used to separate the target analyte from the matrix with the help of magnetic nanoparticles as well as to quantify of the tau-protein by utilisation of a sensitive SERS active marker coupled to gold nanoparticles. The linkage of both nanoparticles to the protein will be ensured by immunoreaction with specific antibodies (Fig. 1 left). Due to the high Raman cross section of the marker DTNB (5,5'-disulfanediylbis(2-nitrobenzoic acid)) this approach makes this method suitable for very small sample volumes and low analyte concentrations typically found in cerebrospinal fluid (CSF) samples for tau-protein on the order of >500 pg/mL while highest accuracy is achieved through the ID approach1. Therefore, an isotopic enriched form of the marker was used as perfect internal standard (spike). Due to the higher molecular weight of the spike a specific Raman shift can be observed and used for SI-traceable quantification. |
