Abstract
We report an ultrasensitive immunoassay for tau protein—a key marker of Alzheimer's disease. This sensing platform relies on graphene oxide (GO) surfaces conjugated with anti-human tau antibody to provide quantitative binding sites for the tau protein. The GO quenches standard fluorescein isothiocyanate labelled tau (tau-FITC) when tau protein and tau-FITC are both present and compete for the binding sites. This change in fluorescence signal can be used to quantitate tau protein. In contrast with traditional enzyme-linked immunosorbent assay (ELISA), our method does not require enzyme-linked secondary antibodies for protein recognition nor does it require an enzyme substrate for optical signal generation. This requires fewer reagents and has less systematic error than the antigen–antibody recognition steps in ELISA. Our method has a tau protein detection limit of 0.14 pmol ml−1 in buffer. This approach could be developed into a promising biosensor for the detection of tau protein and may be useful in the clinical diagnosis of tau-induced neurodegeneration syndromes.
Highlights
There will soon be at least 100 million people worldwide suffering from Alzheimer’s disease (AD) [1], which is a neurodegenerative disorder causing serious problems like memory loss, irritability, aggression, mood swings, etc. [2,3] Despite these huge problems, there is no definitive diagnosis for AD other than traditional neuropsychological, cognitive and neurological tests; the accuracy of these tests depends on the cooperation of both2018 The Authors
We report an ultrasensitive immunoassay for tau protein—a key marker of Alzheimer’s disease
We present a series of fluorescence spectra of different reaction mixtures for the characterization and optimization of assay parameters such as the quenching effect of tau-FITC on bare graphene oxide (GO), on antibodyconjugated GO and on bovine serum albumin (BSA)-blocked GO surface
Summary
There will soon be at least 100 million people worldwide suffering from Alzheimer’s disease (AD) [1], which is a neurodegenerative disorder causing serious problems like memory loss, irritability, aggression, mood swings, etc. [2,3] Despite these huge problems, there is no definitive diagnosis for AD other than traditional neuropsychological, cognitive and neurological tests; the accuracy of these tests depends on the cooperation of both2018 The Authors. [2,3] Despite these huge problems, there is no definitive diagnosis for AD other than traditional neuropsychological, cognitive and neurological tests; the accuracy of these tests depends on the cooperation of both. The accuracy of ELISA is affected by a set of problems intrinsic to the technique: the uncertainty of the recognition between secondary antibodies and antigens causing false signals [12,13,14]; lack of definitive chemical surface properties of the ELISA 96-well polystyrene plates for protein attachment [15]; and introduction of systematic and human errors in the procedures, such as plate washing
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