The present invention relates to a biosensor (1) which enables the concentration of a desired molecule inside a liquid in the medium, and essentially comprises at least one metallic plate (2) which functions as a ground plate, and which is preferably manufactured from aluminum, at least one dielectric substrate (3) which is located on top of the metallic plate (2), at least one split-ring resonator (4) which is realized on top of the dielectric substrate (3), and which is coated with a dielectric layer, at least two symmetrical antennas (5) which are realized on the same plane with the split-ring resonator (4) on the substrate (3), at least two ports (6) where a network analyzer is connected with the antennas (5) via SMA (SubMiniature Version A) connectors.