Gas foamed open porous biodegradable polymeric microspheres

Highly open porous biodegradable polymeric microspheres were fabricated for use as injectable scaffold microcarriers for cell delivery. A modified water-in-oil-in-water (W₁/O/W₂) double emulsion solvent evaporation method was employed for producing the microspheres. The incorporation of an effervescent salt, ammonium bicarbonate, in the primary W₁ droplets spontaneously produced carbon dioxide and ammonia gas bubbles during the solvent evaporation process, which not only stabilized the primary emulsion, but also created well inter-connected pores in the resultant microspheres. The porous microspheres fabricated under various gas foaming conditions were characterized. The surface pores became as large as 20 μm in diameter with increasing the concentration of ammonium bicarbonate, being sufficient enough for cell infiltration and seeding. These porous scaffold microspheres could be potentially utilized for cultivating cells in a suspension manner and for delivering the seeded cells to the tissue defect site in an injectable manner.