Electrospinning Equipment: Electrospun Membranes with High Resilience by In situ Crosslinking

In recent years, with the development of tissue engineering and regenerative medicine, the application of elastic biodegradable scaffolds in soft tissue regeneration and small - diameter vascular grafts (SDVGs) has received extensive attention. Small - diameter vascular grafts need to match the mechanical properties of native blood vessels to meet the requirements of complex physiological environments. However, existing elastic biomaterials (such as polycaprolactone, PCL) have good biocompatibility, but their semi - crystalline nature makes them relatively rigid, lacking sufficient flexibility and compliance, and it is difficult to meet the mechanical requirements of vascular grafts. In contrast, poly(glycerol sebacate) (PGS) has attracted much attention due to its flexibility and low tensile strength. However, when used alone, it has problems such as poor processability and too fast degradation rate.

Professor Yuan Xiaoyan's team from the School of Materials Science and Engineering, Tianjin University, successfully prepared electrospun membranes with high elasticity and excellent compliance through the blend electrospinning of PCL and PGS combined with in - situ photocrosslinking technology. In the process of blend electrospinning, an electrospinning machine was used. The study found that by adjusting the ratio of PCL to PGS, the mechanical properties of the electrospun membranes in the wet state were significantly improved, showing elastic characteristics close to those of the human saphenous vein. The research results were published in the journal Chem. Res. Chinese Universities. This achievement provides a new material solution for the development of small - diameter vascular grafts, especially in enhancing the flexibility and biocompatibility of vascular grafts. Figure 1A (Schematic illustration of PCL/PGS electrospun membranes) shows the preparation process of PCL/PGS electrospun membranes and in - situ crosslinking.

In the study of PCL/PGS electrospun membranes, as shown in Figure 2B, the crosslinked structure formed by the in - situ photocrosslinking reaction enables the PCL/PGS electrospun membranes to exhibit good elasticity. In the hemolysis rate test of tubular scaffolds, the results show that the hemolysis rates are all far lower than the safe threshold of 5%, confirming that the crosslinked structure can maintain a low hemolysis rate. In addition, through cell culture experiments, it was observed that cells can adhere and proliferate well on the scaffolds, reflecting suitable cytocompatibility. In addition, as can be seen from Figure 2B, as the PGS content increases from 8PCL/2PGS to 5PCL/5PGS, the slope of the stress - strain curve increases, indicating that the tensile strength of the membrane gradually increases. This is because the introduction of PGS improves the flexibility of the material, and it works synergistically with PCL to enhance the overall tensile performance under the crosslinked structure.

Figure 3 mainly shows the in vitro culture of human umbilical vein endothelial cells (ECs) and vascular smooth muscle cells (SMCs) on PCL/PGS electrospun membranes. From the proliferation curves of ECs and SMCs, it can be seen that cells can grow well on each sample membrane. ECs proliferated significantly from 3 to 6 days with no significant differences among samples, and SMCs showed an increasing trend from 3 to 5 days. However, the number of SMCs on the 5PCL/5PGS and 4PCL/6PGS membranes was relatively lower than that on PCL, which may be related to the increased hydrophilicity of the samples due to the addition of PEGDA. Through SEM and CLSM images, it can be seen that ECs spread and extend on the membrane, and SMCs spread in a spindle shape, indicating that the cell growth morphology is normal, which shows that the PCL/PGS electrospun membranes have good cytocompatibility and can provide a suitable growth environment for cells.

The stress - strain curves of PCL and PCL/PGS electrospun membranes in the dry and wet states are similar in shape. The cyclic tensile curves show that an increase in the PGS content can enhance the reversible recovery of the membranes and reduce irreversible deformation. For example, under a 50% strain in the dry state, the irreversible deformation of PCL is about 26.2%, and that of 4PCL/6PGS drops to 8.4%; in the wet state, the irreversible deformation of 4PCL/6PGS is only 7.5% and has a tendency to fully recover. As the PGS content changes, the Young's modulus and tensile strength also change. 8PCL/2PGS has higher Young's modulus and tensile strength, while 4PCL/6PGS significantly reduces the Young's modulus but maintains a tensile strength similar to that of PCL. The elongation at break of all PCL/PGS membranes is still relatively high compared to PCL. After stretching, the PCL membrane has obvious stretching marks, while the PCL/PGS membranes have inconspicuous marks, which benefits from the enhanced elasticity of the crosslinked structure and the recovery ability of the fibrous morphology (Figure 4).

In the evaluation of the tensile properties of PCL/PGS electrospun tubular scaffolds in the wet state (Figure 5), the stress - strain curves in the longitudinal and circumferential directions show that the addition of PGS significantly reduces the Young's modulus of the tubular scaffolds, making them softer; the tensile strength increases or decreases in the longitudinal direction due to crosslinking, and decreases with the increase of the PGS content in the circumferential direction, and the elongation at break decreases. The burst pressure of most experimental groups is higher than 3000 mmHg, and that of 4PCL/6PGS is about (1995±23) mmHg, which can meet the requirements of vascular grafts. The cyclic tensile curves show that the irreversible deformation of the 4PCL/6PGS tubular scaffold under a 20% strain is negligible. The compliance increases with the increase of the PGS content. The compliances of the 5PCL/5PGS and 4PCL/6PGS tubular scaffolds are 1.67%±0.37% and 2.28%±0.49% per 100 mmHg, respectively, which are comparable to that of the natural saphenous vein (1.5% per 100 mmHg). Moreover, the 4PCL/6PGS tubular scaffold can easily return to its original shape after compression and stretching, showing excellent elasticity and being more suitable for small - diameter vascular grafts.

In summary, in this study, electrospun membranes and tubular scaffolds with improved elasticity at different mass ratios of PCL/PGS were prepared through the in - situ photocrosslinking reaction of poly(glycerol sebacate) methacrylate (PGS - MA) and poly(ethylene glycol) diacrylate (PEGDA). The electrospinning device was used to fabricate these materials. The crosslinked structure not only endows the electrospun membranes and tubular scaffolds with elasticity but also maintains a low hemolysis rate and suitable cytocompatibility. Specifically, as the PGS content increases from 8PCL/2PGS to 5PCL/5PGS, the tensile strength of the PCL/PGS electrospun membranes increases. In addition, the resilience of the tubular scaffolds gradually increases. The compliance of the 5PCL/5PGS tubular scaffold is comparable to that of the natural saphenous vein, and the 4PCL/6PGS tubular scaffold has the highest compliance. Therefore, this feasible strategy for preparing PCL/PGS electrospun scaffolds is expected to be an application method for small - diameter vascular grafts used in vascular regeneration.

Article source: https://doi.org/10.1007/s40242-025-5026-8