A magnetoimpedance biosensor microfluidic platform for detection of glial fibrillary acidic protein in blood for acute stroke classification.

Acute stroke is the third leading cause of mortality and disability worldwide. Administration of appropriate therapy for acute stroke is critically dependent on timely classification into either ischemic or hemorrhagic subtypes, which have divergent treatment pathways. The current classification method is based on neuroimaging, which generally requires the transport of the patient to a hospital-based facility unless a mobile stroke unit is available. Plasma glial fibrillary acidic protein (GFAP) level has been identified as a useful blood-based biomarker to differentiate stroke subtypes. However, its conventional immunoassay methods are laboratory-based and time-consuming. Novel approaches for rapid stroke classification near the patients are urgently needed. Here, we report the development and testing of a microfluidic-based magnetoimpedance biosensor platform for measuring GFAP levels. The platform consists of a microfluidic chip for GFAP extraction from a blood sample and a magnetoimpedance (MI) biosensor that employs Dynabeads as a magnetic label to capture the GFAP molecules. We demonstrated the detection of recombinant GFAP protein in phosphate-buffered saline (PBS) and in mouse blood samples (detection limit 0.01 ng/mL) and of physiological GFAP in blood and plasma samples (detection limit 1.0 ng/mL) obtained from acute stroke patients. This detection level is within the range of cut-off levels required for clinical stroke subtype differentiation. This platform has the potential to be incorporated into a small device with further development to assist in the classification of acute stroke patients and clinical decision-making at the point-of-care.