Release Kinetics and Antimicrobial Properties of Iodinated Species Liberated from Physically and Chemically Modified Starch Granules

Herein, the preparation of iodine-loaded high amylose starch (HAS) granules and their utility as slow release reservoirs for the delivery of antimicrobial iodinated species are described. Several varieties of HAS granules are studied including those that are physically or chemically modified. Granules are impregnated with iodinated species, resulting in stained materials that are bench stable. Mass gain after staining with Lugol's solution range from 5 to 18 wt% depending on the type of starch granule. Release kinetics for both chemically and physically modified iodinated granules show an initial burst phase followed by a tapering of iodinated species release. A two-step granule pretreatment protocol is developed that significantly alters the release of iodinated species relative to granules that are untreated. Microbiological data indicate that even after 2 weeks, unmodified and lyophilized iodinated granules release sufficient quantities of antimicrobial iodine to completely kill planktonic Escherichia coli and Staphylococcus aureus. Pretreated lyophilized granules also show complete killing power at 3.5 weeks. Although increasing the temperature from 25 to 37 degrees C does not alter the release characteristics, the addition of salt significantly inhibits release.