Ultrasensitive detection of beta-amyloid 1–42 as a relevant biomarker for Alzheimer's disease in serum

Cognitive impairment is the only indicator of growing Alzheimer's disease (AD), which may cause dementia. There is no cure or effective treatment to prevent deep AD progression. Early diagnosis of AD will help healthcare professionals to implement the measures to slow down the AD progression, and the patient's family members will have time to make necessary modifications in their lifestyle. The amyloid-beta 1–42 (Aβ 1–42) is proposed to be a hallmark in AD diagnosis because its deposition in the human brain is the prime factor inducing AD. This work presents novel ultrasensitive optical biosensors for detecting Aβ 1–42 analyte. The dual prism and sensor cell were designed to separate sensing signals from the interface reflection and scattering noise. Additionally, assay conditions for Aβ 1–42 were optimized by characterizing their physical, optical, and immunochemical properties and probing wavelength. The dose-response curve shows linearity (R2 > 0.98) with a detection limit of 0.04 fg/mL in the defined buffer and 12.0 fg/mL in human serum. The proposed biosensing proved to be an effective tool enabling sensitive detection of target species in clinical diagnosis, environmental contamination, and food safety in real time.