Fig. 3. SEM photomicrographs of PLLA, PCLA, PCL scaffolds prepared with the addition of a gelatin nano-non-woven.
On the bottom surface of the scaffold obtained from PLLA with the addition of PVP and gelatin nano-non-wovens, rare small pores of a diameter of 5–10 µm were observed. On the upper surface, numerous, irregular pores of the size of 20–40 µm were also present. Between them pores of 5–15 µm in size were present. In the cross-section of the scaffold, large irregular, nearly oval pores 20–70 µm, and up to about 100 µm in size could be seen. Compared to the scaffold obtained by using only a gelatin nano-non-woven, pores were more linked, and their walls were thinner (1–2 µm). As in the previous case, significantly smaller round pores (ca. 1 µm) could be seen in the walls of larger pores.
Rare pores were having 5–10 µm, sometimes 20 µm in diameter were observed on the bottom surface of the scaffold prepared from PLLA with the addition of PVP, Pluronic®, and a gelatin nano-non-woven (Fig. 7). On the other hand, numerous irregular 20–40 µm pores could be seen on the upper surface. Irregular, nearly oval pores of the size of 20–80 µm are present in the cross-section of the scaffold. In contrast to the previous results, walls of these pores 5–10 µm thick, not only contained perforations but – first of all, their cross-section was distinctly divided into segments. It means that the inner walls of these pores did not have a solids structure.
Due to the promising results about the use of gelatin nano-non-woven in preparing scaffolds from poly-L-lactide, it was decided to test the effectiveness of the method for obtaining scaffolds from other biodegradable polymers: block copolymer poly(ε-caprolactone-b -lactide) and poly(ε-caprolactone).
Rare pores having less than 5 µm in diameter could be seen on the bottom surface of the scaffold prepared from block copolymer poly(ε-caprolactone-b -lactide) using gelatin nano-non-woven. Irregular, 20–50 µm pores are visible on the upper surface. Nearly oval pores of the size of 20–60 µm could be seen in the cross-section of the scaffold. Between them, there are smaller (10–15 µm) pores. These pores were also located in the inner 1–3 µm thick walls of larger pores.
Pores having 5–10 µm and 20 µm in diameter are present on the bottom surface of the scaffold prepared from PCLA with the addition of PVP and the gelatin nano-non-woven. Irregular 20–40 µm pores could be seen on the upper surface. In the cross-section of the scaffold oval, 50–80 µm pores are present in the cross-section of the scaffold. Additionally, the walls of these pores (3–5 µm thick) contained perforations.
Small pores (approx. 5–15 µm) could be seen on the bottom surface of the scaffold prepared from PCLA with the addition of PVP, Pluronic®, and the gelatin nano-non-woven. Irregular (20–40 µm) pores could be seen on the upper surface. Oval 40–80 µm pores could be seen in the cross-section of the scaffold. In the inner walls of these pores, smaller (1–2 µm) pores were present. Walls of these pores had 5–10 µm in thickness and were not stable – they consisted of some segments.
Another material tested was poly(ε-caprolactone). Unfortunately, scaffolds prepared from this polymer have shown severe contraction during a rinsing bath. Scaffolds were twisted, and their structure has wrinkles and discontinuities. The use of pressing roll to prevent contractions of the material failed to provide the desired effect. Although the scaffolds did not twist, numerous discontinuities of the material were seen in their structure. This effect could be caused by too low glass transition temperature of PCL, –60°C (for PLLA: +65°C), probably inadequate for the conditions used in this method (–18 and +40°C).
Small (less than 5 µm) and rarely distributed pores could be seen on the bottom surface of the scaffold prepared from PCL with the use of a gelatin nano-non-woven. On the upper surface, there were irregular 20–40 µm pores. Between them smaller (approx. 5 µm) pores were present. Oblong pores were having 40–80 µm in length were present in the cross-section. Walls of the pores were thick (5–15 µm) and twisted.
A number of pores of the size 5–10 µm could be seen on the bottom surface of the scaffold prepared from PCL with the addition of PVP and a gelatin nano-non-woven. Irregular pores of the size of 20–40 µm could be noted on the upper surface. Oblong (40–80 µm) pores could be seen in the cross-section of the scaffold. Walls of these pores were thick (5–15 µm) and twisted.
Few pores of the size of 5–15 µm could be seen on the bottom surface of the scaffold prepared from PCL with the addition of PVP, Pluronic®, and a gelatin nano-non-woven. Irregular pores of the size of 20–40 µm could be noted on the upper surface. Oblong pores of the size of 40–60 µm were present in the cross-section of the scaffold. As in the previous cases for this polymer, walls of pores were thick (5–15 µm) and twisted. Besides, their structure was not solid but divided into segments.
Table 2. Morphology of the membranes