In vitro colonization of stratified bioactive scaffolds by pre-osteoblast cells

Mesoporous bioactive glass-polycaprolactone (MBG-PCL) scaffolds have been prepared by robocasting, a layer by layer rapid prototyping method, by stacking of individual strati. Each stratus was independently analyzed during the cell culture tests with MC3T3-E1 preosteblast-like cells. The presence of MBG stimulates the colonization of the scaffolds by increasing the cell proliferation and differentiation. MBG-PCL composites not only enhanced pre-osteoblast functions but also allowed cell movement along its surface, reaching the upper stratus faster than in pure PCL scaffolds. The cells behavior on each individual stratus revealed that the scaffolds colonization depends on the chemical stimuli supplied by the MBG dissolution and surface changes associated to the apatite-like formation during the bioactive process. Finally, scanning electron and fluorescence microscopy revealed that the kinetic of cell migration strongly depends on the architectural features of the scaffolds, in such a way that layers interconnections are used as migration routes to reach the farther scaffolds locations from the initial cells source.

This manuscript provides new insights on cell behavior in bioceramic/polymer macroporous scaffolds prepared by rapid prototyping methods. The experiments proposed in this work have allowed the evaluation of cell behavior within the different levels of the scaffolds, i.e. from the initials source of cells towards the farther scaffold locations. We could demonstrate that the in vitro cell colonization is encouraged by the presence of a highly bioactive mesoporous glass (MBG). This bioceramic enhances the cell migration towards upper strati through the dissolution of chemical signals and the changes occurred on the scaffolds surface during the bioactive process. In addition the MBG promotes preosteblastic proliferation and differentiation respect to scaffolds made of pure polycaprolactone. Finally, this study reveals the significance of the architectural design to accelerate the cell colonization. These experiments put light on the factors that should be taken into account to accelerate the regeneration processes under in vivo conditions.