Aluminum oxide surfaces for diagnostic applications

A method of testing whether affinity binding has occurred to an analyte of interest, comprising:

• a) providing an aluminum oxide surface;
• b) providing a biomolecule specific for affinity binding to the analyte, the biomolecule including a histidine rich domain, a metal binding domain or a metal binding moiety to immobilize the biomolecule through physical adsorption on the aluminum oxide surface, wherein the histidine rich domain provides at least 4 consecutive histidine residues, and wherein the metal binding domain or the metal binding moiety is selected from phosvitin, porphyrin-containing proteins and macromolecules, and nitrogen-containing macrocyclic aminopolycarboxylic acids;
• c) either i) immobilizing the biomolecule on the aluminum oxide surface and then contacting with a sample for affinity binding to the analyte, or ii) contacting the biomolecule with a sample for affinity binding to the analyte and then immobilizing the biomolecule and any affinity bound analyte on the aluminum oxide surface;
• and
• d) detecting the presence of the analyte upon either i) binding of the analyte to the biomolecule immobilized on the aluminum oxide surface, or ii) immobilizing the biomolecule and any affinity bound analyte on the aluminum oxide surface.

A method of testing whether affinity binding has occurred to an analyte of interest, comprising:

• a) providing an aluminum oxide surface on a reflective metal capable of generating a colour when covered by a layer of aluminum oxide, the aluminum oxide surface being a porous anodized aluminum oxide surface having a refractive index in the range of 1.2 to 1.4 to provide a first eye visible interference colour;
• b) providing a biomolecule specific for affinity binding to the analyte, the biomolecule including a binding domain or binding moiety to immobilize the biomolecule on the porous anodized aluminum oxide surface;
• c) either i) immobilizing the biomolecule on the porous anodized aluminum oxide surface and then contacting with a sample for affinity binding to the analyte, or ii) contacting the biomolecule with a sample for affinity binding to the analyte and then immobilizing the biomolecule and any affinity bound analyte on the porous anodized aluminum oxide surface;
• and
• d) detecting a subsequent eye visible interference colour different from the first eye visible interference colour denoting the presence of the analyte upon either i) binding of the analyte to the biomolecule immobilized on the porous anodized aluminum oxide surface, or ii) immobilizing the biomolecule and any affinity bound analyte on the porous anodized aluminum oxide surface.

A method of testing whether affinity binding has occurred to an analyte of interest, comprising:

• a) providing an aluminum oxide surface on a reflective metal capable of generating a colour when covered by a layer of aluminum oxide, the aluminum oxide surface being a porous anodized aluminum oxide surface;
• b) providing a biomolecule specific for affinity binding to the analyte, the biomolecule including a binding domain or binding moiety to immobilize the biomolecule on the porous anodized aluminum oxide surface;
• c) either i) immobilizing the biomolecule on the porous anodized aluminum oxide surface and then contacting with a sample for affinity binding to the analyte, or ii) contacting the biomolecule with a sample for affinity binding to the analyte and then immobilizing the biomolecule and any affinity bound analyte on the porous anodized aluminum oxide surface;
• and
• d) detecting a subsequent eye visible interference colour different from the first eye visible interference colour denoting the presence of the analyte upon either i) binding of the analyte to the biomolecule immobilized on the porous anodized aluminum oxide surface, or ii) immobilizing the biomolecule and any affinity bound analyte on the porous anodized aluminum oxide surface;
• wherein a combined thickness of the biomolecule and one or more layers of the affinity bound analyte is maintained in a range below 42 nm such that the subsequent eye visible interference colour is a first or second order interference colour.