Microencapsulation of Uncharged Low Molecular Weight Organic Materials by Polyelectrolyte Multilayer Self-Assembly

Abstract

Two uncharged microcrystalline substances, pyrene (PYR) and fluorescein diacetate (FDA), were rendered water dispersible by treatment with various amphiphilic substances and subsequently encapsulated by exposure to an alternating sequence of cationic and anionic polyelectrolytes. The amphiphilic compounds employed to charge the microcrystals were ionic surfactants, phospholipids, and polyelectrolytes with an amphiphilic nature. Polyelectrolyte layers were self-assembled onto the pre-charged microcrystalline templates by means of electrostatic layer-by-layer deposition, thus forming a multilayered polymeric shell around the crystalline cores. The semipermeable nature of the polymer multilayer shell was thereafter exploited to remove the templated core by exposure to a mild organic solvent. The release behavior of solubilized PYR and FDA from the crystalline core was examined by monitoring their fluorescence after dissolution with ethanol. Complete removal of the core yielded hollow polymer capsules of micr...