Double porous poly (Ɛ-caprolactone)/chitosan membrane scaffolds as niches for human mesenchymal stem cells

In this paper, we developed membrane scaffolds to mimic the biochemical and biophysical properties of human mesenchymal stem cell (hMSC) niches to help direct self-renewal and proliferation providing to cells all necessary chemical, mechanical and topographical cues. The strategy was to create three-dimensional membrane scaffolds with double porosity, able to promote the mass transfer of nutrients and to entrap cells. We developed poly (Ɛ-caprolactone) (PCL)/chitosan (CHT) blend membranes consisting of double porous morphology: (i) surface macrovoids (big pores) which could be easily accessible for hMSCs invasion and proliferation; (ii) interconnected microporous network to transfer essential nutrients, oxygen, growth factors between the macrovoids and throughout the scaffolds. We varied the mean macrovoid size, effective surface area and surface morphology by varying the PCL/CHT blend composition (100/0, 90/10, 80/20, 70/30). Membranes exhibited macrovoids connected with each other through a microporous network; macrovoids size increased by increasing the CHT wt%. Cells adhered on the surfaces of PCL/CHT 100/0 and PCL/CHT 90/10 membranes, that are characterized by a high effective surface area and small macrovoids while PCL/CHT 80/20 and PCL/CHT 70/30 membranes with large macrovoids and low effective surface area entrapped cells inside macrovoids. The scaffolds were able to create a permissive environment for hMSC adhesion and invasion promoting viability and metabolism, which are important for the maintenance of cell integrity. We found a relationship between hMSCs proliferation and oxygen uptake rate with surface mean macrovoid size and effective surface area. The macrovoids enabled the cell invasion into the membrane and the microporosity ensured an adequate diffusive mass transfer of nutrients and metabolites, which are essential for the long-term maintenance of cell viability and functions.