Osteoblast behaviour on in situ photopolymerizable three-dimensional scaffolds based on D,L-lactide and epsilon-caprolactone: influence of pore volume, pore size and pore shape.

Bone marrow cells were cultured on in situ photopolymerizable scaffolds based on D,L-lactide and epsilon-caprolactone. The influence of pore volume, size and shape were evaluated. Bone formation was demonstrated by ALP activity, osteocalcin secretion and histological analysis. TEM at the polymer interface revealed osteoblasts which secreted an extracellular matrix containing matrix vesicles loaded with apatite. Cellular infiltration was possible for scaffolds with a porosity of 70 and gelatin particle size of 250-355 microm. Scaffolds with a porosity less than 70 had the tendency to form a polymer top layer. Although increasing the gelatin particle size to 355-500 microm, leads to infiltration even in scaffolds with a porosity of 60. No infiltration was possible in scaffolds with sodium chloride as porogen. On the contrary, sucrose and gelatin leads to better interconnected scaffolds at the same porosity. Hence, spherical gelatin particles are suitable to use as porogen in photopolymerizable scaffolds.

Encapsulation of osteoblast seeded microcarriers into injectable, photopolymerizable three-dimensional scaffolds based on d,l-lactide and epsilon-caprolactone.

UMR-106 seeded microcarriers were encapsulated into in situ, photopolymerizable three-dimensional scaffolds based on d,l-lactide and epsilon-caprolactone. UMR-106 and rat bone marrow cells proliferated and differentiated well on the microcarriers. The microcarriers were completely colonized after 14 days in culture. The viscous polymer paste allowed to mix the UMR-106 seeded microcarriers and gelatin (porosigen) properly. After the photopolymerization process, microcarriers and gelatin were evenly distributed throughout the scaffold. Gelatin was leached out within 7 h, and a porous scaffold was obtained. The microcarriers remained in the scaffold even after 7 days which demonstrates that they were well entrapped in the polymer. Increasing the amount of entrapped microcarriers (20-50%) leads to scaffolds with a reduced cross-linking. Hence, the microcarriers leached out. The encapsulated UMR-106 cells did not show pyknotic nuclei which demonstrates that the photopolymerization and handling the viscous polymer/gelatin/microcarrier paste is not detrimental for the cells.