# Modification of PLA Scaffold Surface for Medical Applications
## 3 Results and Discussion
### Analysis of the External Surface of the Membrane
#### 3.4.2 FTIR-ATR Spectroscopy  
The unmodified samples, as well as the samples shortly after modification, were tested by FTIR-ATR analysis. Due to the high similarity of the results obtained, only an example spectrum for the tested materials was presented. On the FTIR-ATR spectra of the membrane surface after modification, no significant changes in the surface layer were observed (Figure 8). This may have been because the material undergoing the modification had oxygen-containing groups in its composition. Subsequent functional groups introduced during the process had no significant effect on the appearance of the spectra. Figure 7: The morphology of Membrane II (MII) before and after plasma modification. The obtained results corresponded to those obtained by [PERSON], who studied the PLA surface after modification in a diffuse coplanar surface barrier discharge by FTIR spectroscopy. The results indicated that DBD plasma did not significantly affect the sample surface. Two sharp peaks were observed at a wavelength of 1748 cm\({}^{-1}\), corresponding to C = O stretching vibration in the group -O-C = O, and another at 1181 cm\({}^{-1}\), corresponding to -CH-O- stretching vibration. The triplet at wavelengths of 1128, 1081, and 1044 cm\({}^{-1}\) indicates the presence of C-O stretching vibrations in the -CO-O group. Low-intensity peaks at 2996 cm\({}^{-1}\) and 2945 cm\({}^{-1}\) were assigned to C-H stretching vibrations in the CH\({}_{3}\) group [10]. Based on the obtained results, it was found that the method using DBD plasma could be successfully used to modify the surfaces of polylactide membranes. Due to polylactide's special properties (biodegradability and biocompatibility), it is a good material for applications in tissue engineering. To conduct cell cultures on scaffolds, it is necessary to give appropriate surface properties, which can be obtained by plasma methods. Such modifications depend on many parameters (e.g., the type of gas in which the discharge was generated, the type of modified material, and the exposure time). The best results of the modification process were obtained for MII. The increase of the SFE, compared with the unmodified material, was about 34%, and the value of the polar component increased more than threefold. The material was modified in an Ar + CO\({}_{2}\) atmosphere with a discharge power of 20 W. Very favorable results were also obtained for MII when modified in carbon dioxide and an equimolar mixture of argon and air. For the scaffolds obtained by the dry method, it was observed that the plasma effect in an atmosphere containing CO\({}_{2}\) was more effective than in an atmosphere with a reduced content of oxygen or inert gas. As a result of the modification in the Ar + CO\({}_{2}\) atmosphere, the contact angle of the membrane surface with water was smaller than that of the material after modification in an atmosphere of CO\({}_{2}\) and the unmodified membrane. The high value of the polar component indicates the formation of new polar groups on the surface of the material, which is a positive phenomenon and proves that the conducted modification process is favorable for tissue engineering. These polar groups are mainly oxygen-based species [28]. The wettability of the material increases, and its hydrophilic character increases. For most of the studied MI surfaces, a significant increase in the SFE and polar component were observed when they were modified in argon and for a 60 s exposure time. It was found that the obtained membranes after modification showed higher hydrophilicity and were more wettable with polar liquids; however, their porous structures were not damaged. The highest values of the surface free energy and polar component were obtained when the process was conducted at a 20 W discharge power. A further increase of the discharge power did not have a positive effect on the wetting with polar liquids. Moreover,  
Figure 8: FTIR-ATR spectrum of the unmodified and modified samples.