Fe₃O₄/MXene Nanosphere-Based Microfluidic Chip for the Accurate Diagnosis of Alzheimer's Disease

Amyloid β protein oligomer (AβO) has been found to be a crucial biomarker of Alzheimer's disease (AD). Exploring an accurate detection method of AβO is of great significance for early AD diagnosis and treatment. Herein, a fluorescent biosensor for AβO detection is designed. It integrates fluorescence resonance energy transfer (FRET)-based fluorescence detection with a poly(dimethylsiloxane) (PDMS)-based microfluidic chip. The carboxyl fluorescein-modified AβO aptamers are employed as the fluorophore, and three-dimensional Fe₃O₄/MXene nanospheres are used as the fluorescence quencher for the first time. Moreover, the PDMS-based multichamber microfluidic chip serves as a fluorescence detection platform. The Fe₃O₄/MXene-based nanosphere-based biosensor shows an excellent linear relationship between the fluorescence intensity and the logarithm of the AβO concentration in the range of 0.10-200 nM. The detection limit is ∼0.05 nM at the ultralow sample volumes of ∼4.50 μL. These results strongly show that the fabricated high-performance biosensor can be widely used in smart healthcare including but not limited to medical diagnosis, health monitoring, and biological studies.