Method for early diagnosis of alzheimer'S disease using phototransistor
View Patent ↗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. Any difference between the first and second photocurrents indicates the presence of, and optionally amount of, labeled beta-amyloid in the cells.
1. A method for diagnosing Alzheimer's disease by detecting the presence of beta-amyloid in cells using a phototransistor device, comprising:
providing cells that potentially contain beta-amyloid;
labeling the cells 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 directly bound to the beta-amyloid if present, to provide labeled cells;
providing a phototransistor device for sensing a photocurrent level according to intensity of incident light, said phototransistor device including a channel layer;
illuminating the phototransistor and sensing a first photocurrent corresponding to the incident light;
selectively fixing said 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 layer;
illuminating the phototransistor and sensing a second photocurrent corresponding to said incident light after the labeled cells, if any, are fixed on the surface of the channel layer; and
detecting any difference between the first and second photocurrents so that the presence of, and optionally amount of, labeled beta-amyloid in said cells is indicated and Alzheimer's disease may be diagnosed.
2. The method as set forth in claim 1 , wherein a the magnetic bead has a diameter ranging between 50 nm and 5 μm.
3. The method as set forth in claim 1 , wherein the phototransistor device is composed of one or more phototransistors optionally arranged as an array.
4. The method as set forth in claim 1 , wherein the cells provided are selected from the group consisting of brain cells, olfactory cells, gustatory cells, visual cells and a combination thereof.
5. The method as set forth in claim 1 , wherein the channel layer comprises either amorphous silicon or polycrystalline silicon.
6. The method as set forth in claim 5 , wherein the phototransistor further comprises an insulation layer comprising SiO 2 , Si 3 N 4 , or PMMA deposited over the channel layer; source and drain electrodes; and a passivation layer.