Fundamentals on Scaffold-Protein-Cells Interactions
Ubiquity of Protein Adsorption in vitro and in vivo
Protein adsorption is essentially important for cell fate both in vitro and in vivo. For in vitro cell culture, serum-containing medium is generally indispensable for desirable cell adhesion, morphology and proliferation. Serum was initially intended to provide cells with nutrients such as amino acids or growth factors. In fact, however, the proteins in serum are equally or even more important. It was found that proteins in serum such as albumin and fibronectin preferentially adsorb onto the surface of a material before a cell attaches to the material. The adsorbed proteins act as a bridge between the cell and the material and the status of the “bridge” determines the interactions between the cells and the material. In other word, whether the information from the material could be transmitted to cells or what information the cells could perceive is determined by the adsorbed protein layer. In cases of serum-free culture, pre-adsorbed proteins are commonly required for appropriate cellular responses, though it is believed that the cells may rapidly secret sufficient extracellular matrix proteins to coat the material surface. In vivo, proteins are also present in blood or interstitial fluid and may immediately coat the foreign material introduced into the body. In brief, the actual surface perceived by cells, no matter in vitro or in vivo, is the protein-modified surface.