Iodine-polyurethane matrices: antimicrobial activity vs method of preparation

Polyurethane matrices were prepared by incorporation of iodine during polyurethane polymerization and by immersion of the preformed polymer in iodine solutions. Examination of the IR spectrum has shown that treatment of the polymer with a concentrated solution of iodine produced structural changes in the polymer. Iodine caused a shift of the N-H stretching band to a lower frequency due to the formation of a complex within an intramolecular hydrogen bonding which takes place between the lone pair electrons of iodine and amine hydrogen. The antimicrobial activity was determined by antimicrobial assay according to the European Pharmacopoeia. The results have shown that, for the same concentration of iodine in the polyurethane matrix, a different antimicrobial activity is obtained by using the two different methods of preparation. In patches prepared by the incorporation method, the iodine was strongly bound to polyurethane. In this case, antimicrobial activity was lower than with patches prepared by the immersion method where all iodine was available for antimicrobial activity.