Alzheimer's diagnosis beyond cerebrospinal fluid: Probe-Free Detection of Tau Proteins using MXene based redox systems and molecularly imprinted polymers.

Phosphorylated Tau proteins are promising biomarkers for the diagnosis and prognosis of Alzheimer's disease. This study presents a novel voltametric sensor using a vanadium MXene polydopamine (V(x)PDA) redox active composite and a Tau-441-specific polyaniline molecularly imprinted polymer (PANI MIP) for the sensitive detection of Tau-441 in interstitial fluid (ISF) and plasma. The V(x)PDA/PANI MIP sensor demonstrates a broad detection range of 5 fg/mL to 5 ng/mL (122 aM/L to 122 pM/L) in ISF without the use of redox mediators, with a lower limit of detection (LOD) of 2.3 fg/mL (60 aM/L). Furthermore, a handheld device utilizing this technology successfully detects Tau-441 in artificial serum with high sensitivity (5 fg/mL to 150 fg/mL (122 aM/L to 366 aM/L)) and specificity within a clinically relevant range. The rapid detection time (∼32 min) and low cost (∼£20/device) of this sensor highlight its potential for minimally invasive, early AD diagnosis in clinical settings. This advancement aims to facilitate a transition away from invasive cerebrospinal fluid (CSF)-based diagnostic techniques for AD.