Dual-mode biosensor for monoamine oxidase B activity detection based on electrochemistry and surface-enhanced Raman...

Alzheimer's disease (AD) is a neurodegenerative disease that threatens the physical health of elderly people. As a potential biomarker for AD, the assessment of monoamine oxidase B (MAO-B) activity is essential for the early diagnosis of AD. Prussian blue nanoparticles (PB NPs) are metal-organic framework materials that can react with hydrogen peroxide (H₂O₂) at low overpotential to produce a reduction current. Meanwhile, PB NPs are ideal Raman reporters with a sharp single vibrational peak at about 2150 cm^-1 in the Raman biological silence region.

In this work, a dual-mode biosensor (ITO/Au/PB NPs) was developed to detect MAO-B activity based on the dual responses of PB NPs utilizing electrochemistry and surface-enhanced Raman scattering (SERS) technology. PB NPs were linked on the surface of indium tin oxide (ITO) electrodes to react with H₂O₂, one of the products generated from the MAO-B catalyzed oxidation of phenylethylamine, resulting in a measurable reduction current at -50 mV. Concurrently, as the concentration of MAO-B increased, the Raman signal of PB NPs decreased due to its consumption. Notably, the electrodeposited AuNPs not only improved conductivity for electrochemistry detection but also provided numerous "hot spots" to enhance SERS intensity, ultimately achieving highly sensitive detection. The detection limits were calculated to be 17.13 ng mL^-1 for electrochemical detection and 4.81 ng mL^-1 for SERS detection, respectively.

Due to the excellent properties of PB NPs, this biosensor combines electrochemistry and SERS technology. Compared with traditional detection methods, this dual-mode strategy has two output signals that can be mutually verified, improving credibility and accuracy for MAO-B activity detection. Additionally, satisfactory recoveries in human serum of this PB NPs-based biosensor demonstrate considerable promising application for early diagnosis of AD.