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Based on solid-in-oil-in-water emulsification, we fabricated biodegradable poly(ϵ-caprolactone) microspheres containing gentamicin using conventional homogenization and a fluidic device. The feasibility of the poly(ϵ-caprolactone) microspheres as drug carriers was evaluated in terms of encapsulation efficiency, release behavior of gentamicin, and antimicrobial activity. The poly(ϵ-caprolactone) microspheres prepared using a fluidic device (fluidic device microspheres) had a uniform diameter and a smooth surface, whereas the poly(ϵ-caprolactone) microspheres prepared using conventional homogenization (conventional homogenization microspheres) exhibited polydisperse and a porous structure. At 0.3 wt% of gentamicin concentration, the encapsulation efficiencies of the conventional homogenization and fluidic device microspheres were 39.5% and 72.0%, respectively. In addition, a significant amount of gentamicin was only released initially from the conventional homogenization microspheres, whereas the fluidic device microspheres released gentamicin in a sustained manner for 28 days. These results confirmed the superior performances of the uniform fluidic device microspheres for drug delivery system. We further proposed a model for microsphere formation to explain the difference in performance of the conventional homogenization and fluidic device microspheres.

Uniform poly(l‐lactic acid) (PLLA) microbeads with unimodal or bimodal porous structures are fabricated using a simple fluidic device based on a single oil‐in‐water emulsion method, where an alkane (octane, undecane, tridecane, and pentadecane) serves as the porogen. During the solvent evaporation, the alkanes spontaneously undergo a microphase separation, resulting in a highly porous structure. The size and size distribution of the pores in the PLLA microbeads can be easily controlled by changing the alkane type and concentration. When the undecane, tridecane, and pentadecane are used as the porogen at 6 wt%, the PLLA microbeads have the bimodal porous structure with a large hollow pore in the center and many small pores. In vitro and in vivo studies reveal that those PLLA microbeads with the bimodal porous structure readily facilitate the penetration and proliferation of cells and host tissues compared with the other PLLA microbeads. These results indicate that the superior properties of PLLA porous microbeads with a bimodal porous structure are suitable for diverse biomedical applications such as tissue engineering, cell delivery, and plastic surgery.

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