1H NMR Self-Diffusion in Polymer-Surfactant Nanocapsules and Cryogels with Enzyme

The multicomponent self-diffusion in nanocapsules and cryogel biocatalytic systems containing alpha-chymotrypsin has been studied with the NMR-PGSE method at various temperatures and compared with the diffusion of such systems without enzyme. Unilamellar vesicles have been formed in water after "coating" with Brij-97 of the poly-(N,N-diallyl-N,N-didodecyl ammonium bromide), poly-DDAB, nanocapsules. The latter have been obtained by UV-irradiation of reversed hydrated micelles from DDAB in cyclohexane. Cryogels were made from poly(vinyl alcohol), PVA, aqueous solutions by a freezing-thawing cyclic process. Both compartmented systems were used as vehicles of the enzyme entrapped in inner aqueous cavities. The activation energies of self-diffusion for both these systems have been calculated. These data contain information concerning morphology and molecular packing. Encapsulation of alpha-chymotrypsin in the poly-DDAB/Brij-97 vesicles and the PVA cryogel lowers the Ds values for all molecules and shifts the cloud point toward the lower temperature. On the contrary, the syneresis point for the PVA cryogel is shifted for 8 degrees toward the higher temperature by the entrapment of the enzyme. Besides, entrapment of alpha-chymotrypsin in the cryogel promotes the increase of the Ea values for the PVA chain on 1.5 kJ/mol below the syneresis point. Such a difference indicates the influence of the H-bond system of PVA hydroxyl groups and water molecules on the interference of the protein globule. Entrapment of alpha-chymotrypsin leads to consolidation of this H-bond system. Copyright 1998 Academic Press.