Abstract: A method for diagnosing Alzheimer's disease by detecting the presence of beta-amyloid in cells using a phototransistor device. Cells that potentially contain beta-amyloid are provided and labeled with a multi-protein that selectively binds to beta-amyloid if present and that includes streptavidin, biotin and polyethylene glycol connected in sequence with the streptavidin being bound to a magnetic bead and the polyethylene glycol being bound to the beta-amyloid, to provide labeled cells. A phototransistor device including a channel layer is provided and a difference in photocurrent determined corresponding to incident light measured before and after selectively fixing the labeled cells on a surface of the channel layer by applying an external magnetic field effective to attract the magnetic bead to the phototransistor device through a permanent magnet positioned below the channel.

Abstract: Disclosed is a method for the early diagnosis of Alzheimer's disease. In the method, cells in which a biomarker characteristic of Alzheimer's disease, preferably beta-amyloid, is labeled with magnetic beads are selectively located in the channel region of a phototransistor, and a difference in photocurrent between normal cells and the cells comprising the protein biomarker labeled with magnetic beads is sensed to diagnose Alzheimer's disease at an early stage.

Abstract: Provided are a method of diagnosing Alzheimer's disease using a giant magnetoresistance sensor and a magnetic bead-polyprotein complex for diagnosing Alzheimer's disease. The method of diagnosing Alzheimer's disease using the giant magnetoresistance sensor may be applied to diagnose Alzheimer's disease more easily and simply using the giant magnetoresistance sensor than using conventional fluorescent materials or genetic analyses, and the magnetic bead-polyprotein complex may be mass-produced as a diagnostic biosensor for Alzheimer's disease, and thus to be useful to monitor and treat Alzheimer's disease.