同轴打印小直径组织工程血管*

随着人口老龄化问题的日益严重以及心血管疾病患病的增加,临床上对血管移植物的需求量也逐渐增大。利用涤纶和聚四氟乙烯制备大直径血管(>6mm)在临床上得到了广泛的应用,而小直径(< 6 mm)血管常因血栓和感染导致移植的失败,因此构建内皮细胞贴附的组织工程血管就显得至关重要。通过合成RGD修饰的海藻酸钠(RGD-alginate, RGD-ALG)以及甲基丙烯酸化的明胶(methacrylated gelatin,GelMA),利用氯化钙溶液溶解的普朗尼克F127作为牺牲材料,利用同轴打印制备出组织工程血管。通过选择不同直径的同轴打印喷嘴以及调节打印参数,可以制备出不同直径的组织工程血管。制备出的组织工程血管可以承受人生理状态下的血管压力,可以进行稳定的灌流培养,并且人脐静脉血管内皮细胞在通入组织工程血管中后可以稳定贴附在管壁上。

Construction of Small Diameter Tissue Engineering Blood Vessels by Coaxial Printing

Currently, with the severity of population aging, cardiovascular disease(CVD) brings about health problems and unbearable economic burdens. In ischemic illnesses caused by the damage of small-diameter blood vessels, blood vessel transplantation has become an effective solution to tackle this challenge. However, small-diameter blood vessels are currently in high demand. Therefore, it is pretty crucial to construct small-diameter tissue-engineered blood vessels (TEBV) using tissue engineering methods. With the advancement of tissue engineering and 3D printing technology, the research of vascular grafts has developed rapidly. At present, most of the vascular graft materials used for large-diameter vascular grafts are polyester and polytetrafluoroethylene (PTFE). However, it is not applicable for the fabrication of small-diameter TEBV, in which case a myriad of unavoidable problems may come alone, such as inflammation and thrombosis. At the same time, current TEBV has such limitations as insufficient mechanical properties, which seriously hinder the clinical translation of TEBV. Therefore, in this experiment, we independently synthesized methacrylated gelatin (GelMA) and RGD-modified sodium alginate (RGD-Alginate) combined to form a double cross-linking system. By adding xanthan gum, the printability of the system is guaranteed. We used coaxial printing to fabricate a tube-like structure. Hybrid material system was characterized by a low vacuum cryo-scanning electron microscope. We found honeycomb-like forms appear on the surface, indicating that oxygen and nutrients could be provided to the cells in the tube through penetration. As for the selection of materials, the sacrificial material in the inner layer is 25% Pluronic F127 dissolved in 2% calcium chloride (CaCl₂), and the outer material is 4% RGD-Alginate+5% GelMA+2% Xanthan Gum. During the printing process, the extrusion pressure of the printer is related to the diameter of the selected coaxial nozzles. When the 18G/14G coaxial nozzle is applied, the printing pressure is 55 kPa, and the printing speed is 5 mm/s. The syringe pump is utilized to extrude the material of the outer layer, whose speed is 264 μL/min. In the printing procedure, we selected two nozzles with different diameters to effectively fabricate a tube matching the nozzle diameter. In addition, a device for detecting burst pressure was established, which uses constant extrusion of the syringe pump to provide stable pressure to the tested tube. It has been demonstrated that the burst pressure is 328 mmHg±14 mmHg, which is quite different from the burst pressure of natural blood vessels in vivo. At the same time, it is sufficient to bear the vascular pressure in the physiological state of the human body. Human umbilical vein endothelial cells (HUVECs) were perfused into the tube-like structure (cell concentration was 1×10⁷/mL). Through the imaging characterization of the cell state in the tube-like structure, it was found that HUVECs can be stably attached to the inner wall of a fabricated tube-like structure.