Sensitive detection of multiple blood biomarkers via immunomagnetic exosomal PCR for the diagnosis of Alzheimer's disease.

Blood exosomes are emerging as potential biomarkers for diagnosing brain diseases such as Alzheimer's disease (AD). There is currently a lack of an ultrasensitive technology for identifying core AD biomarkers in blood exosomes to optimize the utility of biomarkers in clinical practice. Here, an immunomagnetic exosomal polymerase chain reaction (iMEP) platform was developed using DNA-conjugated antibodies for the rapid detection of amyloid-β (Aβ 1-40 and Aβ 1-42 ) and phosphorylated tau (p-tau 396,404 and p-tau 181 ) in clinical blood exosomes. The toehold shift-mediated DNA affinity pulldown eliminates the high detection background, which allows the detection of biomarkers at concentrations down to 10 femtograms per milliliter. With the iMEP assay, exosomal Aβ 1-42 was more accurate in differentiating patients with AD from healthy individuals compared with exosomal p-tau 181 and p-tau 396,404 , with a sensitivity of 95.0% and a specificity of 95.0%. The iMEP technique is also adept at quantifying the levels of different exosomal biomarkers associated with disease pathogenesis.