a composite membrane structure for immobilizing biologically active materials , such as enzymes , is formed by coating a microporous polymeric membrane with a thin layer of an inert proteinaceous material , such as zein or collagen , so that the resultant coated membrane retains intercommunicating capillary pores that extend through its structure . immobilization of a biologically active material is carried out by contacting the coated membrane with the biologically active material in solution and drying . biologically active materials immobilized on the membrane can be used to perform biochemical reactions and are useful in carrying out tests for glucose and uric acid .