A Sensitive SERS Sensor for Simultaneous Detection of Two Potential Biomarkers of Alzheimer's Disease: AChE and MAO-B

Monoamine oxidase B (MAO-B) and acetylcholinesterase (AChE) are potential biomarkers for Alzheimer's disease (AD). However, few methods exist to detect both AChE and MAO-B simultaneously. In this study, we developed a SERS sensor for the simultaneous detection of AChE and MAO-B based on the one-pot reaction system, which provided more valuable information for early AD diagnosis. Au NPs modified with Raman reporter 4-aminothiophenol (Au^PATP NPs) were attached to Cu-BTC via Schiff's base reaction (Au^PATP NPs@Cu-BTC), resulting in great Raman intensity. Phenethylamine (PEA), a substrate of MAO-B, competed with Au^PATP NPs for binding to Cu-BTC, reducing the intensity of the Raman signal. Additionally, two PATP molecules on free Au NPs coupled to DMAB due to the catalysis of Cu²⁺ in Cu-BTC, transforming Au^PATP NPs into Au^DMAB NPs and generating three new Raman peaks. TCh, the catalytic product of AChE, was chelated with Cu²⁺, so the coupling efficiency of PATP has been decreased, and the conversion of Au^PATP NPs to Au^DMAB NPs has been prevented. Based on the one-pot reaction system, both MAO-B and AChE can be detected by Raman signals from precipitated Au^PATP NPs@Cu-BTC and supernatant Au^DMAB NPs after centrifugation. The detection limits were 2.3 × 10^-3 μg mL^-1 for MAO-B and 1.6 × 10^-3 U L^-1 for AChE. We successfully detected MAO-B and AChE in serum with recoveries ranging from 100.0 to 113.7% for MAO-B and 93.6 to 120% for AChE. This manuscript presents a novel method for the simultaneous detection of MAO-B and AChE, showing great potential for early AD diagnosis.