Novel fabrication of PCL porous beads for use as an injectable cell carrier system.

Injectable polycaprolactone (PCL) porous beads were fabricated for use as cell carriers by a novel isolated particle-melting method (for nonporous beads) and the following melt-molding particulate-leaching method (for porous beads). The prepared beads showed highly porous and uniform pore structures with almost the same surface and interior porosities (porosity, over 90%). The PCL porous beads (bead size, 400-550 microm) with different pore sizes (25-50 and 50-100 microm) were compared for their in vitro cell (human chondrocyte) growth behavior with the nonporous beads. The porous beads showed higher cell seeding density and growth than the nonporous beads. The pore size effect between the porous beads was not significant up to 7 days, but after that time the beads with pore sizes of 50-100 microm showed significantly higher cell growth than those of 25-50 microm. To evaluate the tissue compatibility of the PCL porous beads, the beads were dispersed, uniformly, in cold Pluronic F127 solution and injected into hairless mice, subcutaneously, in the gel state of Pluronic F127 at room temperature, leading to the homogeneous bead delivery. The histological findings confirmed that the PCL porous beads in Pluronic F127 gel are biocompatible: surrounding tissues gradually infiltrated into the porous beads for up to 4 weeks with little inflammatory response. The PCL porous beads with highly porous and uniform pore structures fabricated in this study can be widely applicable as cell carriers.