Novel scaffolds fabricated from protein-loaded microspheres for tissue engineering

Biodegradable scaffolds play an important role in tissue engineering by providing physical and biochemical support for both differentiated and progenitor cells. Here, we describe a novel method for incorporating proteins in 3D biodegradable scaffolds by utilizing protein-loaded microspheres as the building blocks for scaffold formation. Poly(l,d-lactic-co-glycolic acid) (PLGA) microspheres containing bovine serum albumin (BSA) were fused into scaffolds using dichloromethane vapor for various time intervals. Microspheres containing 0, 0.4, 1.5, 4.3% BSA showed that increased protein loading required increased fusion time for scaffold fabrication. Protein release from the scaffolds was quantified in vitro over 20 days and compared to that of loose microspheres. Scaffolds had a slightly lower (up to 20%) release over the first 10 days, however, the cumulative release from both microspheres and scaffolds at the end of the study was not statistically different and the rate of release was the same, indicating that microsphere release can be predictive of scaffold kinetics. Scaffolds fused from larger (113.3±58.0 μm) rather than smaller (11.15±11.08 μm) microspheres, generated pores on the order of 200 μm as compared to 20 μm, respectively, showing control over pore size. In addition, four dyes (carbon black, acid green, red 27, and fast green FCF) were encapsulated in PLGA microspheres and fused into homogeneous and partitioned scaffolds, indicating control over spatial distribution within the scaffold. Finally, the scaffolds were seeded with fibroblast cells, which attached and were well spread over the polymer surface after 4 h of incubation. These results highlight the versatility of this simple scaffold fusion method for incorporating essentially any combination of loaded microspheres into a 3D structure, making this a powerful tool for tissue engineering and drug delivery applications.