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

β-amyloid peptide (Aβ) aggregates are regarded as a typical neuropathology hallmark for the diagnosis of Alzheimer's disease (AD). Aβ aggregates include soluble oligomers (AβO) and insoluble fibrils (AβF). 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 Aβ aggregates assay was developed. Taking AβO detection as an example, Apt2 was modified on the surface of Au chip by Au-S bond. Subsequently, the solution consisted of AβO and gold nanoparticles-Apt1 (AuNPs-Apt1) were injected into the QCM chamber. As a result, AβO was specifically recognized and captured by Apt2. AuNPs-Apt1 were also combined on the surface of the Au chip because AβO 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 AβF. This QCM biosensor was able to detect AβO with a range of 0.2-10 pM with a detection limit of 0.11 pM, while the linear range for AβF 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 Aβ aggregates detection.