Chemical modification of polymers with physiologically active species using water-soluble carbodiimides

The covalent immobilization of some proteins (ovomucoid from duck egg white, human serum albumin, aldolase and thiroglobulin) on the surface of polyethylene grafted with polyacrylic acid has been studied. Water-soluble carbodiimide was (1-ethyl-3-(3-dimethylaminopropyl carbodiimide) used as a condensing agent. It was shown that three different reactions can occur in the reaction mixture during immobilization: the reaction between carboxy groups of graft copolymer and amino groups of protein (the immobilization reaction itself) and reactions between carboxy and amino groups of protein molecules (reactions of intra- and intermolecular cross-linking). The reaction of intramolecular cross-linking leads to a decrease in the physiological activity of the immobilized substance, while other reactions do not affect it. The preliminary activation of this surface by carbodiimide before the modification allows to maintain the activity after immobilization on the insoluble surfaces.