关键词: 同轴打印, 组织工程, 双交联水凝胶, 海藻酸钠, 丙烯酰胺, 离子交联, 支架

Abstract: BACKGROUND: When cultivating cells with high demand for structure and oxygen, it is necessary to construct a three-dimensional biological scaffold with hollow pipe structure to make sure the cells get enough nutrients and oxygen. In recent years, hydrogel tissue engineering scaffolds with hollow pipe structure have been paid more and more attention. 
OBJECTIVE: The biological scaffold material based on sodium alginate was combined with coaxial printing technology to prepare a tissue engineering scaffold with a hollow pipe structure, and the cells were inoculated by perfusion to verify its biological properties.
METHODS: The sodium alginate-acrylamide mixed printing solution was prepared, and the parameters such as the printing speed of the inner and outer layers in the coaxial printing process, sodium alginate concentration, and calcium chloride concentration in the receiving dish were controlled to realize the printing of the tissue engineering scaffold with a hollow pipe — sodium alginate-polyacrylamide double-crosslinked hydrogel. The microstructure and elastic modulus of the scaffold were characterized. Mouse fibroblasts were injected into hollow pipes of tissue engineering scaffolds. Cell compatibility was observed by living/dead cell staining.
RESULTS AND CONCLUSION: (1) By exploring the printing parameters in the printing process, when the inner printing speed was constant, the outer diameter of the hollow pipe increased with the increase of the flow rate of the outer printing solution, and the inner diameter increased slightly. When the flow rate of the outer layer printing solution was constant, and the flow rate of the inner layer solution was increased, the outer diameter of the hollow pipe was basically unchanged, and the inner diameter was significantly improved. (2) Experimental results showed that the concentration of sodium alginate was 2.5%. Excessive concentration was not conducive to the fusion of multi-layer structure layers, and the mechanical properties of hydrogels prepared at too low concentration were insufficient. (3) The elastic modulus of the double-crosslinked hydrogel was higher, generally higher than 200 kPa, and increased with the increase of the concentration of calcium chloride, and reached the maximum value of 375 kPa when the concentration of calcium chloride in the inner layer was 2% and the concentration of calcium chloride in the receiving dish was 0.3%. (4) The staining of live and dead cells after the tissue engineering scaffold perfusion cells in vitro showed that the cells were distributed along the axis of the hollow pipe and had a higher survival rate, but the cell concentration was lower than that during perfusion. (5) The results show that the sodium alginate-polyacrylamide double-crosslinked hydrogel has strong mechanical properties while retaining good biocompatibility, and can be used in the construction of tissue engineering scaffolds with hollow pipes, and the method of “first preparing the scaffold, then inoculating the cells” also avoids the traditional “cells and printing solution are mixed and then prepared” method to limit the scaffold material and processing method.

Key words: coaxial printing, tissue engineering, double-crosslinked hydrogel, sodium alginate, acrylamide, ion crosslinking, scaffold