Xanthan hydrogel films: molecular conformation, charge density and protein carriers.

In this article the molecular conformation of xanthan chains in hydrogel films was investigated by means of circular dichroism, showing substantial differences between xanthan hydrogel prepared in the absence (XNT) and in the presence of citric acid (XCA). The xanthan chains in XNT hydrogels films presented ordered conformation (helixes), while in XCA they were in the disordered conformation (coils), exposing a larger number of carboxylate groups than XNT. The large charge density in XCA hydrogels was evidenced by their behavior under variable ionic strength. Studies about the application of XNT and XCA for loading and delivering of bovine serum albumin (BSA) and lysozyme (LYZ) showed that both events are controlled by hydrogels and proteins net charge, which can be triggered by pH. The preservation of LYZ native conformation after hydrogel loading explained the substantial bactericidal activity of LYZ loaded hydrogels and enables their use as active wound dressings.