Cascade primer exchange reaction-based amplification strategy for sensitive and portable detection of amyloid β oligomer using personal glucose meters

Amyloid β oligomer (AβO) is an important biomarker for Almerzheimer's disease (AD) early diagnosis. In present study, cascade primer exchange reaction (PER) based amplification strategy was proposed for sensitive and portable detection of AβO using personal glucose meters (PGM). Two PER processes were employed here. In the primary PER, the hairpin template 1 (HT1) was designed with a primer binding domain, a primer extending domain and a blocking extending domain. The primers were designed to be modified on magbeads surface. Initially, the primer binding domain in HT1 was locked by AβO aptamer. When target AβO was present, aptamer bound with AβO and dissociated from HT1 to initiate the primary PER. The products acted as the primer of the secondary PER to hybridize with another hairpin template 2 (HT2), initiating the secondary PER and producing numerous ssDNA with repeated DNA-invertase binding sites. After binding with DNA-invertase, the obtained conjugates were magnetically separation to catalyze the conversion of sucrose to glucose, which were detected by a PGM. The strategy achieved a limit of detection of 0.22 pM with a linear ranged from 1 pM to 250 pM. Satisfactory reproducibility results were obtained in actual samples. This strategy provided a superior tool for sensitive and convenient detection of AβO, and showing a great potential in the early diagnosis of AD.