A simple aptasensor for Aβ₄₀ oligomers based on tunable mismatched base pairs of dsDNA and graphene oxide

β-amyloid 1-40 oligomers (Aβ₄₀O) is considered to be one of the important biomarkers for the diagnosis and treatment of Alzheimer's disease (AD). To explore a method with excellent performance is favorable for measuring the low concentration of Aβ₄₀O in AD patients. Here, we developed a simple and fast method with a double stranded DNA (dsDNA)/graphene oxide (GO) based sensor, which was a fluorescent probe for a highly sensitive detection of Aβ₄₀O down to 0.1 nM with a linear detectable range from 0.1 nM to 40 nM. The proposed sensor effectively reduced non-specific adsorption and improved the specificity of detection because of the covalent conjugation of a binding DNA (bDNA) containing Aβ₄₀O-targeting aptamer (Apt_Aβ) onto GO surface, as well as the optimization of the number of mismatch base pairs of dsDNA. Moreover, AD patients and healthy persons were distinguished by this present method. All advantages of this method are exactly what the clinical detection of AD biomarkers need. This novel aptasensor might pave a way towards the early diagnosis of AD.