Patent ID: 8440468

Claim:
A method for detecting a biomolecule in a sample by detecting a change of an electric signal comprising: applying the sample and protein tagged with a metal particle to a piezoelectric biosensor; wherein the piezoelectric biosensor comprises a probe fixed to a substrate of the piezoelectric biosensor; washing the piezoelectric biosensor with a buffer solution which does not contain salt capable of producing a precipitate and then with a low-concentration salt solution subsequently; applying a solution containing a metal enhancer to the piezoelectric biosensor; wherein a biomolecule in the sample binds to the probe, the protein binds to the biomolecule in the sample, and the metal enhancer binds to the metal particle; detecting the change between the electric signal prior to the biomolecule bonding to the probe, and the electric signal after the biomolecule bonds to the probe, the protein bonds to the biomolecule, and the metal enhancer bonds to the metal particle; and detecting quantitatively or qualitatively the biomolecule based on the change in the electic signal.