Detection of ?-amyloid peptide aggregates by quartz crystal microbalance based on dual-aptamer assisted signal amplification

beta-amyloid peptide (A beta) aggregates are regarded as a typical neuropathology hallmark for the diagnosis of Alz-heimer's disease (AD). A beta 40 aggregates include soluble oligomers (A beta 40O) and insoluble fibrils (A beta 40F). Both of them can simultaneously bind to two different kinds of its aptamer (Apt1 and Apt2). As a mass-sensitive sensing platform, quartz crystal microbalance (QCM) converts changes in mass on the Au chip surface into frequency shift. Here, a dual-aptamer assisted A beta 40 aggregates assay was developed. Taking A beta 40O detection as an example, Apt2 was modified on the surface of Au chip by Au-S bond. Subsequently, the solution consisted of A beta 40O and gold nanoparticles-Apt1 (AuNPs-Apt1) were injected into the QCM chamber. As a result, A beta 40O was specifically recognized and captured by Apt2. AuNPs-Apt1 were also combined on the surface of the Au chip because A beta 40O can simultaneously bind to Apt1. Then, a significant frequency shift occurred because of the large weight of AuNPs. Similarly, this procedure can be used to detect A beta 40F. This QCM biosensor was able to detect A beta 40O with a range of 0.2-10 pM with a detection limit of 0.11 pM, while the linear range for A beta 40F was 0.1-10 pM with a detection limit of 0.02 pM. This QCM biosensor was simple and highly sensitive, which provided a new method for A beta 40 aggregates detection.

Automated summary

In this study, a dual-aptamer assisted A beta 40 aggregates assay was developed using quartz crystal microbalance. The assay can detect both A beta 40O and A beta 40F, and it is simple and highly sensitive.