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TECHNICAL FIELD

The present invention relates to a novel molecular recognition element that can be used for biosensing technology such as an immunosensor.

BACKGROUND ART

In a conventional immunoassay such as ELISA using an antibody labeled with an enzyme, or the like, it is necessary to separate (Bound/Free (B/F) separation) an antibody not bound to an antigen by performing a washing operation such as lateral flow after a reaction between an antigen and an antibody in order to remove a nonspecific signal. However, such a B/F separation operation complicates the procedures and the efficiency of the B/F separation may affect the signal accuracy.

As the enzyme used for labeling an antibody, a peroxidase, and an alkali phosphatase are often used. In Non-Patent Literature 1, an electrochemical type immunoassay using an antibody labeled with a glucose oxidase (GOD) is disclosed.

CITATION LIST

[Non-Patent Literature 1] FEBS LETTERS, June 1977 DOI: 10.1016/0014-5793 (77) 80317-7

SUMMARY OF INVENTION

In the method disclosed in Non-Patent Literature 1, electrons generated by a reaction of the GOD and a substrate are converted to a hydrogen peroxide, and the hydrogen peroxide diffuses into the solution and is reduced on the surface of an electrode to generate a signal. Therefore, in the reaction system, a signal that would be generated by an antibody-GOD existing in the vicinity of the electrode due to nonspecific adsorption, etc. becomes a noise, and therefore it is required to undergo a careful cleaning step. In addition, when nonspecific adsorption is strong, or an antigen, which is the target molecule, has been adsorbed nonspecifically, it is difficult to completely remove the nonspecific signal. Further, depending on the environment between the GOD bound to the antibody and the electrode, there is a limitation on removing noise components by washing.

One aspect of the invention is to provide a novel molecular recognition element that can be used in biosensing technology such as an immunosensor.

According to an embodiment of the invention, a molecular recognition element comprising a target molecule-recognizing portion, and a direct electron transfer-type oxidoreductase linked to the target molecule-recognizing portion is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the target molecule-recognizing portion comprises a target molecule-recognizing protein, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein a target molecule is an antigen and the target molecule-recognizing portion is an antibody against the antigen, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the direct electron transfer-type oxidoreductase is an oxidoreductase comprising an electron-transferring domain, or an electron-transferring subunit, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the electron-transferring domain is a heme-containing domain, or the electron-transferring subunit is a heme-containing subunit, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the oxidoreductase is a glucose dehydrogenase, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the target molecule-recognizing portion and the direct electron transfer-type oxidoreductase are linked by a cross-linker, is provided.

According to another embodiment of the invention, the molecular recognition element, wherein the molecular recognition element comprises a fusion protein of the target molecule-recognizing portion and the direct electron transfer-type oxidoreductase, is provided.

According to another embodiment of the invention, a sensor comprising an electrode, and the aforedescribed molecular recognition element immobilized on the electrode, is provided.

According to another embodiment of the invention, the sensor wherein the molecular recognition element is immobilized on the electrode by means of a monolayer forming molecule, is provided.

According to another embodiment of the invention, a method for measuring a target molecule comprising introducing a sample containing a target molecule into the aforedescribed sensor; and detecting a signal based on the target molecule, is provided.

According to another embodiment of the invention, a reagent for measuring a target molecule comprising the aforedescribed molecular recognition element, is provided.

According to an embodiment of the present invention, a molecular recognition element capable of directly transferring electrons to an electrode can be constructed by linking a direct electron transfer-type oxidoreductase to a molecular recognition portion such as an antibody.

Since a direct electron transfer signal can be detected based on the occurrence of the specific antigen-antibody binding, a system of measurement that is not affected by nonspecific binding, and does not require a careful washing operation can be constructed.

From the above, construction of an electrochemical immunosensor free from the influence of nonspecific adsorption can be expected.

