Silk fibroin/poly(carbonate)-urethane as a substrate for cell growth: in vitro interactions with human cells

Silk fibroin (SF)-based or -coated biomaterials are likely to be endowed with structural and surface properties that render them particularly apt for biomedical applications. In this work we investigated the behavior of four different strains of normal human adult fibroblasts that had been seeded onto membranes made up of poly(carbonate) urethane (PCU), the surfaces of which had or had not been homogeneously coated with SF. Cell adhesion within 3 h to the SF-coated PCU films was 2.2-fold that to their uncoated homologues. After 30 days of incubation in vitro, 2.5-fold more cells had grown on the SF-coated specimens than on the uncoated ones. This enhanced cell adherence and hence growth on the SF-coated surfaces was coupled with higher cumulative rates of d-glucose (but not l-glutamine) uptake and of bothlactate and interleukin-6 (IL-6) cumulative secretion. Conversely, human fibroblasts cultured on either type of PCU scaffolds never secreted any ELISA-assayable amount of three main proinflammatory cytokines, namely interleukin-1b (IL-1b), tumor necrosis factor-a (TNF-a), and transforming growthfactor- b1 (TGF-b1). Finally, when the metabolic activities were compared on a per 105 cells basis, it became clear that the adhesion to SF favored an initially higher consumption of d-glucose, a late higher release of IL-6, and an at-first more intense, but declining, extracellular assembly of type I collagen fibers. Overall, these results show that SF-coated PCU membranes represent a novel type of biomaterial that favors the adhesion, the growth and performance of specific metabolic tasks by normal human adult fibroblasts without eliciting any concurrent secretion of some of the chief proinflammatory cytokines