A mathematical model for the design of fibrin microcapsules with skin cells.

The use of fibrin in tissue engineering has greatly increased over the last 10 years. The aim of this research was to develop a mathematical model to relate the microcapsule-size and cell-load to growth and oxygen depletion. Keratinocytes were isolated from rat skins and microencapsulated dropping fibrinogen and thrombin solutions. The cell growth was measured with MTT-assay and confirmed using histochemical technique. The oxygen was evaluated using a Clark sensor. It was found that Fick-Monod model explained the cell growth for the first 48 h, but overestimated the same thereafter. It was necessary to add a logistic equation to reach valid results. In relation to the preferred implant alternative, when considering large initial cell loads, the possibility to implant small loads of fast-growing cells arises from the simulations. In relation to the microcapsule size, it was found that a critical diameter could be established from which cell growth velocity is about the same.