Abstract: A solution of an active protein substance and an inactive protein substance is reacted with a cross-linking agent, optionally in the presence of an inert carrier, under cross-linking conditions to produce articles comprising both active and inactive protein substances. The active protein substance comprises up to about 20 percent, e.g. from 1 to 20 percent by weight, based on the final weight of the total protein substance, whereas the cross-linking agent comprises from 0.5 to 8 percent by weight, based on the weight of the total treated mixture. The obtained articles are in the form of a solution or a suspension in aqueous medium, in the form of a film, in the form of a membrane, in the form of a fabric, in the form of a porous material, or in the form of a mass, such as granules, pills or tablets.