Biodegradable Microcapsules Prepared by Self-Healing of Porous Microspheres

A method is herein proposed to produce biodegradable microcapsules by a self-healing of porous microspheres, which were prepared from water-in-oil-in-water (W₁/O/W₂) double-emulsion templates. Methoxypoly(ethylene glycol)-b-poly-dl-lactide (PELA) was dissolved in ethyl acetate (EA) as the oil phase (O) of double emulsion, NaCl and poly(vinyl acetate) aqueous solutions serving as internal and external water phases (W₁ and W₂), respectively. Porous PELA microspheres were prepared by a two-step emulsification and solvent extraction method. Core materials, such as proteins or latex particles, could then be loaded by diffusion from the external water phase. Eventually, the pores in the surface could heal up triggered by a solvent swelling or infrared irradiation to form closed microcapsules. Compared with traditional encapsulations which are based on the two-step emulsification, the proposed posthealing approach could overcome some drawbacks, such as the shear destruction, solvent erosion to delicate core materials, or even their unexpected release during the emulsification. Besides PELA, poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) microcapsules were also proved feasible to fulfill such an approach.