Solid-phase assay for d-biotin on avidin-cellulose disks

Abstract Filter-paper disks of uniform size were chemically modified by the introduction of isonitrile functional groups. Avidin was then covalently linked to the disks in a four-component condensation reaction involving disk isonitrile groups and avidin carboxyl groups in the presence of a water-soluble aldehyde and an amine. Quantitative assay of unknown d -biotin solutions could be conveniently carried out with such avidin-cellulose disks by a two-step procedure: (i) immersion in the unknown sample, and (ii) exposure to an excess of radioactive biotin. Based on the known total capacity of the disks for biotin, the amount of unlabeled biotin extracted from solution by avidin-cellulose disks could be easily estimated.