Assay method for biological target complexes on the surface of a biosensor

Claim 1

A method for detecting a target nucleic acid analyte by means of a piezoelectric sensor, wherein said target nucleic acid analyte is a DNA or RNA molecule, comprising: (a) coating a surface capture reagent consisting of streptavidin or avidin on the surface of a piezoelectric oscillator, wherein said streptavidin or avidin is directly adsorbed bonded to said oscillator surface by direct adsorption without the aid of an adhesion promoter and wherein said surface comprises a metallic gold film, to form a piezoelectric sensor; (b) contacting a liquid sample suspected of containing said target nucleic acid analyte with an enzyme reporter conjugate and a bifunctional binder conjugate to form a target complex, said complex comprising (i) the enzyme reporter conjugate further consisting of an enzyme and a polynucleotide recognition sequence which is selected to complex with a sequence within the target nucleic acid analyte, (ii) the suspected target nucleic acid analyte, and the bifunctional binder conjugate; (c) capturing the target complex with the surface capture reagent coated on the piezoelectric oscillator to form an assay system; (d) separating uncaptured target complex, enzyme reporter conjugate, and bifunctional binder conjugate from the assay system; (e) measuring the resonant frequency of the piezoelectric sensor; (f) contacting the assay system with a signal generating substrate specific for the enzyme of the target complex to the assay system; (g) allowing the accumulation on the surface of the piezoelectric oscillator of a signal generating product resulting from the conversion of the signal generating substrate by the enzyme; and (h) monitoring the resonant frequency of the piezoelectric oscillator caused by the accumulation of the signal generating product onto the piezoelectric sensor.

Claim 2

A method for detecting a target nucleic acid analyte by means of a piezoelectric sensor, wherein said target nucleic acid analyte is a DNA or RNA molecule, comprising: (a) coating a surface capture reagent consisting of streptavidin or avidin on the surface of a piezoelectric oscillator, wherein said streptavidin or avidin is directly adsorbed bonded to said oscillator surface by direct adsorption without the aid of an adhesion promoter and wherein said surface comprises a metallic gold film, to form a piezoelectric sensor; (b) contacting a liquid sample suspected of containing said target nucleic acid analyte with an enzyme reporter conjugate and a bifunctional binder conjugate to form a target complex, said complex comprising (i) the enzyme reporter conjugate further consisting of an enzyme and a polynucleotide recognition sequence which is selected to complex with a sequence within the target nucleic acid analyte, (ii) the suspected target nucleic acid analyte, and the bifunctional binder conjugate; (c) capturing the target complex with the surface capture reagent coated on the piezoelectric oscillator to form an assay system; (d) separating uncaptured target complex, enzyme reporter conjugate, and bifunctional binder conjugate from the assay system; (e) measuring the resonant frequency of the piezoelectric sensor; (f) contacting the assay system with a signal generating substrate specific for the enzyme of the target complex to the assay system; (g) allowing the accumulation on the surface of the piezoelectric oscillator of a signal generating product resulting from the conversion of the signal generating substrate by the enzyme; and (h) monitoring the resonant frequency of the piezoelectric oscillator caused by the accumulation of the signal generating product onto the piezoelectric sensor.