Quantum dots-based "chemical tongue" for the discrimination of short-length A peptides

A "chemical tongue" is proposed based on thiomalic acid-capped quantum dots (QDs) with signal enrichment provided by excitation-emission matrix (EEM) fluorescence spectroscopy for the determination of close structural analogs-short-length amyloid beta (A beta) peptides related to Alzheimer's disease. Excellent discrimination is obtained by principal component analysis (PCA) for seven derivatives: A beta(1-16), A beta(4-16), A beta(4-9), A beta(5-16), A beta(5-12), A beta(5-9), A beta(12-16). Detection of A beta(4-16), A beta(4-16), and A beta(5-9) in binary and ternary mixtures performed by QDs-based chemical tongue using partial least squares-discriminant analysis (PLS-DA) provided perfect 100% accuracy for the two studied peptides (A beta(4-16) and A beta(4-16)), while for the third one (A beta(5-9)) it was slightly lower (97.9%). Successful detection of A beta(4-16) at 1 pmol/mL (1.6 ng/mL) suggests that the detection limit of the proposed method for short-length A beta peptides can span nanomolar concentrations. This result is highly promising for the development of simple and efficient methods for sequence recognition in short-length peptides and better understanding of mechanisms at the QD-analyte interface.