An antibody detection method, comprising: using a biosensor for detecting an antibody, wherein said biosensor comprises an enzyme covalently linked to an inhibitor protein via a peptide linker having two epitopes at the ends of said peptide linker, and wherein said biosensor is defined by two equilibrium constants, K closed-open,1 and K closed-open,2 that describe the equilibrium between a closed and an open state of said biosensor in the absence and presence, respectively, of said antibody according to: K closed − open, 1 = K d EI / C eff, EI, and K closed − open, 2 = 0.5 * K d EI / K d AP * C eff, AP / C eff, EI wherein: K d(Ap) is an intermolecular dissociation constant of a monovalent binding of said antibody and said epitope, K d is an intermolecular dissociation constant of the binding of said enzyme and said inhibitor protein, C eff is an effective concentration of said inhibitor protein in proximity of said enzyme, and C eff is an effective concentration of a free epitope in proximity of the remaining antigen-binding domain of said antibody; and wherein said K closed-open,1 is smaller than said K closed-open,2. using a biosensor for detecting an antibody, wherein said biosensor comprises an enzyme covalently linked to an inhibitor protein via a peptide linker having two epitopes at the ends of said peptide linker, and wherein said biosensor is defined by two equilibrium constants, K closed-open,1 and K closed-open,2 that describe the equilibrium between a closed and an open state of said biosensor in the absence and presence, respectively, of said antibody according to: K closed − open, 1 = K d EI / C eff, EI, and K closed − open, 2 = 0.5 * K d EI / K d AP * C eff, AP / C eff, EI wherein: K d(Ap) is an intermolecular dissociation constant of a monovalent binding of said antibody and said epitope, K d is an intermolecular dissociation constant of the binding of said enzyme and said inhibitor protein, C eff is an effective concentration of said inhibitor protein in proximity of said enzyme, and C eff is an effective concentration of a free epitope in proximity of the remaining antigen-binding domain of said antibody; and wherein said biosensor comprises an enzyme covalently linked to an inhibitor protein via a peptide linker having two epitopes at the ends of said peptide linker, and wherein said biosensor is defined by two equilibrium constants, K closed-open,1 and K closed-open,2 that describe the equilibrium between a closed and an open state of said biosensor in the absence and presence, respectively, of said antibody according to: K closed − open, 1 = K d EI / C eff, EI, and K closed − open, 2 = 0.5 * K d EI / K d AP * C eff, AP / C eff, EI wherein: K d(Ap) is an intermolecular dissociation constant of a monovalent binding of said antibody and said epitope, K d is an intermolecular dissociation constant of the binding of said enzyme and said inhibitor protein, C eff is an effective concentration of said inhibitor protein in proximity of said enzyme, and C eff is an effective concentration of a free epitope in proximity of the remaining antigen-binding domain of said antibody; and K d(Ap) is an intermolecular dissociation constant of a monovalent binding of said antibody and said epitope, K d is an intermolecular dissociation constant of the binding of said enzyme and said inhibitor protein, C eff is an effective concentration of said inhibitor protein in proximity of said enzyme, and C eff is an effective concentration of a free epitope in proximity of the remaining antigen-binding domain of said antibody; and wherein said K closed-open,1 is smaller than said K closed-open,2.