Tungsten disulphide nanosheet modulated fluorescent gold nanocluster immunoprobe for the detection of tau peptide: Alzheimer's disease biomarker

The neuronal tau peptide serves as a key biomarker for neurodegenerative diseases, specifically, Alzheimer's disease, a condition that currently has no cure or definitive diagnosis. The methodology to noninvasively detect tau levels from body fluids remains a major hurdle for a rapid and simple diagnostic approach. Thus, developing new detection methods for sensing tau protein levels is crucial. In this work, we report an immunoprobe based on anti-tau antibody (mAb-tau)-conjugated fluorescent gold nanoclusters (AuNCs) quenched with tungsten disulphide nanosheets (WS₂ NS) for the detection of tau protein in human serum samples. The mAb-tau conjugated probe is designed to provide a specific binding site for the tau peptide by strong antigen-antibody interface. The WS₂ NS surface quenches the fluorescence of mAb-tau@AuNCs, which is subsequently recovered by the addition of tau peptide in a linear concentration range (63.3-615.38 pg mL^-1). The enhancement in fluorescence of WS₂ NS@mAb-tau@AuNCs enables the quantification of tau peptide in concentrations pertinent to human serum tau levels in Alzheimer's patients. The developed probe achieves a limit of detection (LOD) and limit of quantification (LOQ) of 6.54 pg mL^-1 and 21.8 pg mL^-1 for tau peptide in PBS buffer. The study is further extended in spiked human serum samples, with satisfactory recovery percentages in the range of 94.37-117.53%. The technique holds promise as an immunoprobe for tau peptide detection and has potential in developing an economically viable probe for the clinical diagnosis of tau-related neurodegenerative disorders.