Biological Modification Of Polylactide Membrane Based On Polydopamine Adhesive Coating And The Study Of Cytocompatibility

Polylactic acid(PLA) is widely used in the field of bone tissue regeneration due to its excellent mechanical property, processability and biodegradability. However, there are still some limitations, such as: poor hydrophilicity, non-ideal cytocompatibility, lack of function of osteogenesis and vascularrization and so on. The above performances of PLA materials can be effectively improved via biological modification. As a key component of the mussel protein, dopamine(DOPA) can almost adhere to the surface of any materials, it can effectively improve the hydrophilicity and cytocompatibility of materials. Most importantly, it could serve as a reactive secondary platform, and bioactive molecules can be easily immobilized onto the surfaces of substrate materials via polydopamine(PDOPA) layer to make the substrate materials have excellent biological performances.Therefore, in this study, firstly PDLLA membranes were prepared by solution casting method and used as the substrate material, then they were modified based on the self-polymerization of DOPA in alkaline solution. A series of PDLLA/PDOPA-x composite membranes with different concentrations of DOPA was obtained. Scanning electronic microscopy(SEM), atomic force microscopy(AFM), contact angle and surface energy measurements were utilized to observe the surface morphologies, hydrophilicity and surface energy. Results suggested that obvious changes can be seen on the surfaces of PDLLA membranes after DOPA modification, and roughness remarkably increased. Meanwhile, the hydrophilicity was improved and the surface energy also increased accordingly. Finally, 2 g/L was identified as the suitable reactive concentration of DOPA.In view of the excellent biocompatibility, good osteogenetic activity and water solubility of chitooligosaccharide(COS), which was designed to be immobilized onto PDLLA membrane surface based on the intermediate layer of PDOPA, and a series of PDLLA/PDOPA-COS-y composite membranes immobilized with different concentrations of COS was obtained. SEM, AFM, contact angle, surface energy, Fourier transform infrared(ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy(XPS) were utilized to observe the surface morphologies, hydrophilicity, surface energy, chemical structure and surface elements. The results suggested that obvious rippled structure or a lot of ups and downs can be observed for the smooth PDLLA membrane after modification by DOPA and COS. Meanwhile, the hydrophilicity of PDLLA/PDOPA and PDLLA/PDOPA-COS composite membranes was improved and the surface energy also increased accordingly. FTIR and XPS results further confirmed the successful introduction of DOPA and COS to PDLLA surface, and the nitrogen content of PDLLA/PDOPA and PDLLA/PDOPA-COS composite membranes was determined and the suitable reactive concentration of COS was 4 g/L. The composite membranes prepared with appropriate concentration were used to evaluate cytocompatibility of MC3T3-E1 cells, and MC3T3-E1 cells were seed on the unmodified and modified materials for in vitro cell culture experiments. Osteoblast experiments suggested that PDLLA/PDOPA and PDLLA/PDOPA-COS surfaces showed a significant increase in adhesion, proliferation, osteogenic differentiation and alkaline phosphate activity(ALP) of MC3T3-E1 cells compared to the pristine PDLLA membrane. However, PDLLA/PDOPA-COS composite membrane was more effective in enhancing osteogenic differentiation and alkaline phosphate activity of MC3T3-E1 cells than PDLLA/PDOPA membrane.In view of deferoxamine(DFO) plays an important role in the process of angiogenesis, DFO was designed to be immobilized onto PDLLA membrane surface based on the intermediate layer of PDOPA, and a series of PDLLA/PDOPA-DFO-z composite membranes immobilized with different concentrations of DFO was prepared. SEM, AFM, contact angle, surface energy, ATR-FTIR and XPS were used to observe the surface morphologies, hydrophilicity, surface energy, chemical structure and surface elements. The results revealed that abundant ups and downs can be observed on the surface of PDLLA/PDOPA and PDLLA/PDOPA-DFO composite membranes compared with the smooth PDLLA membrane, and the surface roughness increased obviously. Meanwhile, due to the introduction of DOPA and DFO, the membrane hydrophilicity was significantly improved and the corresponding surface energy also increased. In addition, PDLLA/PDOPA-DFO composite membranes showed more obvious effect. FTIR and XPS results further confirmed the successful introduction of DOPA and DFO to PDLLA surfaces, and the nitrogen percentage of PDLLA/PDOPA and PDLLA/PDOPA-DFO composite membrane was determined and the appropriate reactive concentration of DFO was 2g/L. The composite membranes prepared with appropriate concentration were used to evaluate cytocomplibility and MC3T3-E1 and HUVECs were seed on the material surfaces before and after modification. In vitro cell experiments indicated that for MC3T3-E1 cells, both the PDLLA/PDOPA and PDLLA/PDOPA-DFO composite membranes were more beneficial to the attachment, proliferation and spreading of MC3T3-E1 cells compared to the original PDLLA membrane. Contrast to PDLLA/PDOPA and PDLLA/PDOPA-DFO membrane, it can be found that the PDLLA/PDOPA composite membrane was more beneficial to the attachment, proliferation and spreading of MC3T3-E1 cells. For HUVECs, both the PDLLA/PDOPA and PDLLA/PDOPA-DFO composite membranes were more beneficial to the attachment, proliferation and spreading of HUVECs compared to the original PDLLA membrane. Contrast to PDLLA/PDOPA and PDLLA/PDOPA-DFO membrane, it showed that the PDLLA/PDOPA-DFO composite membrane was more supportive for the attachment, proliferation and spreading of HUVECs.