Effects of preparation conditions on the microstructure of porous microcapsule membranes with straight open pores

Preparation and characterisation of chitosan microcapsules loaded with Cortex Moutan

The process of preparation and characterisation of chitosan microcapsules loaded with Cortex Moutan was studied and the optimum condition for microcapsule preparation was investigated by orthogonal array analysis. Based on the yield percentage of microcapsule, the optimum condition for microcapsule preparation was (i) core-shell ratio=1:2; (ii) chitosan concentration=6% (w/v); (iii) agitation speed=1100 rpm; and (iv) cross-linking time=90 min. Meanwhile, relative importance of the preparation parameters was in the order: core-shell ratio, agitation speed, chitosan concentration and cross-linking time. The Fourier transform infrared spectroscopy analysis revealed that Cortex Moutan has been completely encapsulated into chitosan microcapsule. The release rate of Cortex Moutan from microcapsules in pH 5.4 phosphate buffered saline (PBS) was slightly better than that in pH 5.0 PBS after the initial 48 h and the release rate became steady after that.

Microcapsules with macroholes prepared by the competitive adsorption of surfactants on emulsion droplet surfaces

We demonstrate a simple, unique method for preparing microcapsules with holes in their shells. Cross-linked polymelamine microcapsules are prepared by the phase-separation method. The holey shell of each microcapsule is synthesized on the surface of an oil-in-water (O/W) emulsion droplet where a water-soluble polymeric surfactant and an oil-soluble surfactant are competitively adsorbed. The water-soluble polymeric surfactant provides a reaction site for shell formation. The oil-soluble surfactant molecules seem to self-assemble while the shells are being formed, so holes appear where they assemble. The critical degree of surface coverage of an emulsion droplet by the water-soluble polymeric surfactant needed to form the holey shells is determined to be 0.90 from theoretical calculations in which competitive adsorption is considered. Theoretical consideration suggests that the size and quantity of the holes in the microcapsule shells are controlled by the composition of the surfactants adsorbed on the surface of an emulsion droplet. This theoretical consideration is confirmed by experiments. The prepared microcapsule with controllable macroholes in its shell has the potential to be used for controlled release applications and can be used to fabricate a microcapsule that encapsulates hydrophilic compounds.