Antibodies with infinite affinity were developed with the aim of improving targeted delivery of metal complexes to sites of disease. This is part of a series of chemical technology developments for biomedical imaging and therapy. Using a combination of genetics and chemical synthesis, it addresses challenges in developing proteins that specifically bind synthetic molecules and do not release them. The result is a set of reagents that promise to capture any of a large variety of metallic elements under physiological conditions and hold them for long periods of time.