Biosensor and application of the same

1. A biosensor, comprising:

a substrate, wherein the substrate comprises a first region and a second region adjoined to the first region, the second region is located on one side of the first region, a center of the substrate is concentrically surrounded by the first region and the second region in order from outside to inside, a bottom of the first region has a recessed cross section having a first depth, a bottom of the second region has a recessed cross section having an asymmetric U-shape and a second depth, the second depth is greater than the first depth, and a slope of a side wall of the recessed cross section of the second region near the center is greater than a slope of another other side wall of the recessed cross section of the second region near the first region;

a first polymer layer, disposed in the first region, wherein a plurality of composite antibodies are distributed in the first polymer layer, and each of the composite antibodies comprises a labelling molecule and a first antibody connected to the labelling molecule; and

a second polymer layer, disposed in the second region, wherein the second polymer layer has an inverse opal photonic crystal structure, the inverse opal photonic crystal structure comprises a plurality of holes, a plurality of gold nanoparticles and a plurality of second antibodies are disposed on a wall of each of the holes, and the first antibody and the second antibodies recognize the same antigen.

2. The biosensor of claim 1 , wherein the second region is located over the first region.

3. The biosensor of claim 1 , wherein the inverse opal photonic crystal structure is an inverted structure of a face-centered cubic structure of nanobeads, each of the nanobeads has a particle size in a range from 100 nm to 1000 nm, and the gold nanoparticles are distributed on a surface of each of the nanobeads.

4. The biosensor of claim 1 , wherein the labelling molecule comprises a fluorescent molecule, and a particle size of each of the gold nanoparticles is in a range from 5 nm to 80 nm.

5. The biosensor of claim 1 , further comprising a third polymer layer over the first polymer layer.

6. The biosensor of claim 1 , wherein the biosensor is a contact lens, the center of the substrate is an optical zone of the contact lens, the first region and the second region are located in a non-optical zone of the contact lens, at least the second polymer layer is exposed on one surface of the contact lens, and opposes a surface that is in direct contact with an eye.

7. A method of detecting an antigen concentration, comprising:

providing a biosensor described in claim 1 , wherein a substrate of the biosensor comprises a first region and a second region connected to the first region, and the second region is located on one side of the first region;

flowing a biological liquid sample containing an antigen from the second region to the first region of the biosensor, thereby releasing at least one of a plurality of composite antibodies comprising a first antibody and a labelling molecule, and reacting the at least one of the composite antibodies for a period of time with the antigen and at least one of a plurality of second antibodies to form a complex in the second region;

detecting an optical property of the complex in the second region of the biosensor by using a light source having a specific wavelength, wherein the optical property comprises a fluorescence intensity or a visual color; and

obtaining an antigen concentration according to the optical property.

8. The method of claim 7 , wherein the specific wavelength is in a range from 200 nm to 700 nm, and the fluorescence intensity is increased by at least two times based on an inverse opal photonic crystal structure in the second region.