Results and discussion
The major problem in obtaining polyester cellular scaffolds is their appropriate porosity and morphology of their pores. In the inversion phase method, it is not possible to obtain correct porous surfaces and large, interconnected pores inside the scaffold, without using pore precursors. Classic pore precursors, i.e. polymers (polyvinylpyrrolidone, polyethylene glycol) or crystals of salt that are being added into the polymer’s solution and then washed away from coagulated scaffolds – do not give the desired effect.[56] The pores which are formed this way are usually not large enough (over a dozen µm), unevenly distributed, and poorly interconnected.[57]
The scaffold for the culture of chondrocytes should have large (at least 30–40 µm) interconnected pores, distributed within the entire volume of the structure.[58] One of the scaffold surfaces must have high porosity, allowing for penetration of cultured cells inside the scaffold. On the other hand, the other surface should contain small, rare pores to prevent the cells from ”falling out” from the polymeric scaffold.[59]
In the presented examinations, the scaffolds of poly-L-lactide were obtained without using any pore precursors and with the PVP or both PVP and Pluronic® as the classic pore precursors.
If no pore precursors have been used, then small and round pores having a diameter of 3–6 µm were observed (Fig. 1) on the bottom surface of the scaffold prepared from PLLA, from the side of glass base. The upper surface was more porous than the bottom one. Moreover, there were larger, round pores 5–10 µm in diameter, and the rest of the pores were covered with a thin covering layer preventing the cells from penetrating inside the scaffold. In the cross-section of the scaffold, there were some oval pores 5–15 µm in size and the wall thickness of 1–2 µm.