Fabrication of novel cyclodextrin-polyallylamine hydrochloride co-polymeric microcapsules by templating oil-in-water emulsions

Abstract

We report the fabrication of novel microcapsules with membranes of co-polymerised cyclodextrin (CD) and polyallylamine hydrochloride (PAH) which allows control of the membrane pore size depending on the type of CD used. The microcapsules were produced by interfacial cross-linking reaction of PAH and CDs with epichlorohydrin (EP) on the surface of oil-in-water emulsion templates. Our approach utilises the ability of the CD to form surface active inclusion complexes with inert linear oil molecules at the interface of the emulsion drops. The reaction was conducted with both CD and PAH adsorbing from the aqueous phase and the EP cross-linker coming from the oil phase, followed by the removal of the oil phase by solvent extraction. We demonstrated that the membrane properties can be tuned by choosing the type of oil used. We obtained hard and brittle CD-PAH co-polymeric shells by using silicone oil-in-water emulsions as sacrificial templates and soft deformable CD-PAH microcapsule membranes by templating tetradecane-in-water emulsions. The average microcapsule diameter reflected the emulsion drop size distribution and ranged between 20 and 65 micrometres. We also created CD-PAH Janus microcapsules containing both oil and void compartments which can be loaded simultaneously with both hydrophilic and hydrophobic payloads. We assessed the microcapsule morphology by optical microscopy and SEM and confirmed the inclusion of cyclodextrin into their membranes by FT-IR spectroscopy. We also studied the release kinetics of a model active component encapsulated in such CD-PAH microcapsules. Such microcapsules could find pharmaceutical and cosmetic applications as drug delivery vehicles and slow release formulations.