You can freely build on How to Detect Disease Markers Using Colored Proteins

What this patent covers

This patent describes a way to find specific substances (antigens) in blood or cells by using a special 'tag.' The process involves creating a reagent by chemically bonding an antibody—which naturally seeks out a specific target—to a 'chromoprotein' like ferritin or cytochrome c. Because these chromoproteins have a natural color, they absorb specific wavelengths of light. When the tagged antibody binds to the target in a sample, the resulting mixture can be measured using a standard light-measuring device (colorimeter) to determine exactly how much of the target substance is present.

What is now free to use

All 1 claims of US 4302536 are in the public domain. Specifically:

The 1 dependent claim add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover methods using radioactive labels for detection

• Does not cover fluorescent markers or labels that require excitation light

• Does not cover detection methods that rely on enzymatic color changes rather than the inherent color of the protein

• Does not cover the use of synthetic dyes or artificial chromophores

Who is building on this today

Modern diagnostic companies continue to refine immunoassay techniques, though the industry has largely shifted toward more sensitive fluorescent and chemiluminescent methods. The core principle of linking a detection molecule to an antibody remains the foundation of ELISA and other common lab tests.

Products built on expired version of this technology

How to cite this patent in your documentation

Individual. US Patent 4302536. Colorimetric immunoassay process. Granted 1981, expired 1998. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.