EVIDENCE OF INTERACTION BETWEEN AGAROSE AND GUAR GUM FROM CHANGES IN NETWORK RESPONSE TO SOLVENT PERTUBATION

Comparative investigation has been carried out on the gel setting temp eratures and mechanical properties of agarose gels of several concentr ations and of 1:1 agarose-guar gum gels of 1% total polymer concentrat ion. In order to investigate the origin of the synergistic interaction s observed, the 1% gels were submitted to immersion tests in ethyl alc ohol and in dimethyl sulphoxide-water solutions. Weight changes were o bserved and the mechanical properties of the resulting gels revealed d istinguishing characteristics between the two systems. The solid state C-13 NMR spectrum of 1:1 agarose-guar gum gel after immersion in pure dimethyl sulphoxide corroborates the role of guar gum in retaining th e network, despite dissolution of a large quantity of agarose. Transmi ssion electron microscopy (TEM) was used to image the supramolecular s tructure of agarose, guar gum and agarose-guar gum systems. Artefacts were observed for pure agarose and guar gum as a result of the procedu re used for sample preparation. Nevertheless, the connectivity expecte d for a tridimensional network was observed in the agarose domains of the mixed gel and attributed to the stabilizing effect of guar gum. (C ) 1997 Elsevier Science Ltd.