Biologically active membrane material

A composite membrane structure for immobilizing biologically active proteinaceous materials comprising a thin microporous membrane having capillary pore sizes in the range from about 25 nanometers to 14 micrometers, said membrane being formed from a biologically inert synthetic polymer, said membrane having a thin, water-insoluble coating of an inert proteinaceous material on its surfaces, said coating being formed by (a), soaking the membrane with a solution of the proteinaceous material in an organic solvent, and (b), drying to form a thin layer of said inert proteinaceous material such that the coated membrane retains its intercommunicating capillary pores that extend through its structure, to permit fluid flow therethrough, and that provide a high surface-to-volume ratio, said coated membrane being capable of stably immobilizing a biologically active proteinaceous material thereon with retention of its activity upon contacting the coated membrane with a solution in which the biologically active material is dissolved, and drying.