Fig. 1. SEM photomicrographs of PLLA, PCLA, PCL scaffolds obtained with classic pore precursor.
Round pores were having a diameter of 5–15 µm. It was observed on the bottom surface of the scaffold prepared from PLLA with the addition of PVP as the pore precursor. The upper surface was more porous than the bottom one. Pores at this surface were round and of a larger diameter (2–20 µm) and other pores were covered with a thin covering layer. Numerous oval pores of a size of 5–15 µm were seen in the cross-section of the scaffold. Between them were also larger pores of the size of 20–30 µm.
Moreover, smaller pores of the size under 5 µm were observed in the walls of these pores (1–2 µm thick). This is a critical feature of the culture of the cells as perforations of walls of inner pores allow for the migration of nutrients and metabolites. On the bottom scaffold surface obtained from PLLA with the PVP or Pluronic® addition round pores of a diameter of 10–15 µm was observed. Microscopic pores of the size less than 1 µm were observed between the bigger ones. The majority of pores were covered with a thin covering layer. Rare, irregularly distributed pores having 10–40 µm in diameter were seen on the upper surface. In the cross-section of the scaffold, there were oval pores of the size of 10–15 µm. Larger pores, having 30–50 µm in diameter were present between them. As in previous cases, the inner walls of pores had a thickness of 1–2 µm.
Considering that the addition of classic pore precursors didn’t allow for obtaining the scaffolds of a proper morphology, because pores were still too small and weakly interconnected – an unconventional approach has been adopted. The previous studies have shown that the use of polymeric non-wovens as non-classic pore precursors leads to the forming of scaffolds of a desirable morphology [58–62]. Cellulose-based non-wovens, despite their high efficiency, were characterized by irregular structure. Moreover, their removal from the structure of the scaffold required several weeks.