Silk fibroin (SF) sponges are a promising scaffold material for tissue engineering due to their biocompatibility, mechanical properties, and ability to support calcium-phosphate formation in vitro. However, previous studies have shown that SF can mineralize spontaneously in the presence of culture media, which has a detrimental effect on experimental integrity when analyzing how cells deposit bone-like tissue in tissue engineering studies. In this study we analyzed the influence of four types of commercially available fetal bovine sera (FBS) supplied as either control or osteogenic media on mineralization of SF scaffolds seeded with human mesenchymal stem cells (hMSCs) or left acellular, respectively. Calcium assays (n=3) were performed at weeks three, five, and seven to assess the amount of mineralization per scaffold. By week seven there was no significant difference in calcium content between the cellularized osteogenic groups, which ranged from 581±118 to 648±63 μg per scaffold, nor between the cellularized control groups, which all remained below 15 μg. Though we expected calcium levels in the acellular scaffolds to remain low, by week seven the two most mineralized groups had calcium contents above 200 μg, nearly half the content of their cellularized counterparts. Furthermore, calcium contents were significantly different (P<0.01) between FBS varieties in both acellular osteogenic and control groups. While two osteogenic groups had average calcium contents higher than 200 μg per scaffold, the remaining two had <40 μg. A similar trend occurred in the control groups, with the same two groups having more than 300 μg per scaffold, while the others had <10 μg. These results demonstrate that understanding the role of cell media and the effects of FBS variation on scaffold mineralization is essential for optimizing osteogenic culture conditions, and maintaining experiment integrity by accounting for spontaneous mineralization in acellular scaffolds.
18 May 2013 - 22 May 2013