Field-effect transistor-based biosensor
A sensor is provided. The sensor includes a field effect transistor comprising: an active region comprising a source region, a drain region, and a channel region between the source region and the drain region; a dielectric region on the channel region; an enzyme coupled to the dielectric region, the enzyme having an active site for interacting with a substrate; an electrolyte-screening layer coupled to the dielectric region, covering part of the enzyme while leaving the active site uncovered, thereby permitting interaction of the substrate with the active site, and a fluidic gate region to which the active site of the enzyme is exposed. A biosensing device including one or more of the sensors is also provided.
1. A sensor comprising a field effect transistor for sensing a substrate of an enzyme in a sample including electrolyte, the field effect transistor comprising:
an active region comprising a source region, a drain region, and a channel region between the source region and the drain region;
a dielectric region on the channel region;
a binding layer or a linker present on the dielectric region;
the enzyme coupled to the dielectric region by being bound to the binding layer or the linker, the enzyme having an active site for interacting with the substrate, wherein a portion of the enzyme closest to the dielectric region on the channel region is within 1 nm of the dielectric region;
an electrolyte-screening layer coupled to the dielectric region and covering part of the enzyme while leaving the active site uncovered, thereby permitting interaction of the substrate with the active site while reducing electrolyte screening by the electrolyte on the substrate; and
a fluidic gate region to which the active site of the enzyme is exposed.
2. The sensor according to claim 1 , wherein the binding layer is a self-assembled monolayer.
3. The sensor according to claim 2 , wherein the self-assembled monolayer is further bound to molecules forming the electrolyte-screening layer on the self-assembled monolayer.
4. The sensor according to claim 3 , wherein the molecules are polyalkylene glycol molecules.
5. The sensor according to claim 3 , wherein the molecules are selected from hydrocarbon molecules having zero or more hydrogen atoms substituted by halogen atoms.
6. The sensor according to claim 5 , wherein the halogen atoms are fluorine atoms.
7. The sensor according to claim 1 , wherein the electrolyte-screening layer comprises a lipid bilayer.
8. The sensor according to claim 7 , wherein the lipid bilayer is a cell membrane.
9. The sensor according to claim 1 , wherein a height (h) of the electrolyte-screening layer is such that from 2 to 10 nm of the enzyme is covered.
10. The sensor according to claim 1 , wherein the enzyme is selected from polymerases, peptidases, and proteases.
11. The sensor according to claim 1 , wherein the active site of the enzyme comprises a binding pocket for selectively binding the substrate.
12. The sensor according to claim 1 , wherein the sensor comprises a single enzyme and is for sensing a single substrate at a time.
13. The sensor according to claim 1 , wherein the enzyme is bound to the binding layer via the linker.
14. A biosensing device comprising one or more sensors according to claim 1 .
15. The biosensing device according to claim 14 , wherein the one or more sensors is a plurality of sensors.
16. The biosensing device according to claim 15 , wherein the plurality of sensors are in fluid communication with each other.
17. The biosensing device according to claim 15 , wherein each sensor of the plurality of sensors is associated with a different enzyme.
18. The sensor according to claim 1 , wherein only a single instance of the enzyme is coupled to the dielectric region on the channel region.
19. The sensor according to claim 1 , wherein the enzyme has been modified via site-specific modification of an N-terminal position or a C-terminal position of the enzyme to bind the enzyme to the linker at the N-terminal position or the C-terminal position of the enzyme.
20. The sensor according to claim 1 , wherein a positive charge of the substrate, when the substrate is bound to the enzyme within the active site of the enzyme, is located closer to the dielectric region than the height (h) of the electrolyte-screening layer.