Transport of Molecular Iodine From Antiseptic Iodophors across Hydrophilic-lipophilic Interfaces: Influence of Phospholipids.

The release and transport of molecular iodine (I2) from antiseptic iodophors across hydrophilic-lipophilic interfaces were studied to understand the impact of carrier polymers and phospholipids on release and transport of molecular iodine across biologically relevant interfaces. Five commercial povidone-iodine formulations and one modified dextrin-iodine complex, each standardized to 1% thiosulfate titratable iodine, were tested using a heptane-water interface model. Iodine release was quantified by both UV-vis spectroscopy and thiosulfate titration with and without phospholipid-rich lipophilic phase. Dilution significantly increased I2 release, with dextrin-iodine achieving near-complete transfer at higher dilutions due to reduced polymer-iodine binding. Phospholipids enhanced iodine transport via charge-transfer interactions, with release kinetics well-fitted by Weibull and Michaelis-Menten models (R 2 > 0.988). For aqueous iodophors, a dilution ratio of 8-10 fold is optimal, enabling dextrin-iodine to attain rapid 100% iodine release while povidone-iodine formulations released 40.3-68.1% of their iodine content in the presence of phospholipids. The active biocide in iodophors is molecular iodine and these findings highlight the critical role of iodophor carrier/composition and lipid interactions in maximizing iodine delivery, offering insight for developing next-generation antiseptic formulations.