中国生物工程杂志

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.