Determination of β-Amyloid Oligomer by Spectrophotometry Based on the Novel Colorimetric Probe

A novel and simple colorimetric probe (PEI-MSN/mAPOE-AuNPs), capable of efficiently determination of β-amyloid oligomer (Aβo) based on PEI functionalized mesoporous silica nanoparticles (PEI-MSN) loaded with glucose signaling molecules and mAPOE polypeptide-labeled gold nanoparticles (mAPOE-AuNPs), was constructed by combining competitive displacement reaction with colorimetric analysis together. Negatively charged mAPOE-AuNPs were electrostatically adsorbed on the surface of positive charge PEI-MSN to encapsulate glucose signaling molecules into mesoporous silica nanoparticles (MSN) pores. When Aβo was introduced to this system, mAPOE-AuNPs and PEI-MSN were separated owing to the larger specific force between Aβo and mAPOE polypeptide than the electrostatic interaction between mAPOE-AuNPs and PEI-MSN, causing the release of glucose molecules contained in PEI-MSN from the pores of MSN. Therefore, indirect colorimetric analysis for Aβo was developed by detecting the leaked glucose using the peroxidase activity of molybdenum disulfide nanosheets (MoS₂ NSs). Linear range of the standard curve for Aβo was 1.0-20 nmol·L^-1, with detection limit of 0.4 nmol·L^-1. Test for recovery was made by standard addition method, giving results in the range of 98.0%-110%, with RSDs (n=6) of the determined values in the range of 1.9%-2.7%.