Properties of a liposomes-mediated thermo-sensitive alginate/alpha-tricalcium phosphate/collagen Ⅰ composite hydrogel / 中国组织工程研究

ABSTRACT

BACKGROUND: The thermo-sensitive composite hydrogels have gained increasing interest in bone regeneration domain due to their biomimetic extracellular matrix (ECM) structure, good biocompatibility, minimal invasive performance and in situ molding. OBJECTIVE:To prepare a thermo-sensitive injectable alginate/α-tricalcium phosphate (α-TCP)/collagen I (Alg/TCP/Col) composite hydrogel and explore its characterization. METHODS:Ca-carrying interdigitation-fusion vesicles (Ca-IFVs) were prepared. The liposomes carrying the optimal concentration of calcium ions were selected for the following experiments by investigating their encapsulation efficiency and drug loading rate. Alg/TCP/Col precursor solution (Alg or Alg/TCP precursor solution) was mixed with Ca-IFVs at 37℃ in different proportions (5, 10, 15, 20) to prepare thermosensitive hydrogels. The structure, rheology behavior, volume swelling ratio, and mechanical properties of the composite hydrogel were observed. MC3T3-E1 cells were co-cultured with Alg/TCP/Col, Alg, and Alg/TCP hydrogels, respectively. Then, morphology of the cells was observed by confocal microscopy at 1, 3, 7 days after co-culture. RESULTS AND CONCLUSION:(1) The pore size of the freeze-dried hydrogel was 50-100 μm, and TCP particles uniformly adhered to the surface of the Alg/TCP hydrogel surface. The Alg/TCP/Col hydrogel was a dense aggregate with collagen fibers in contrast to the Alg/TCP hydrogel. (2) The Alg/TCP/Col hydrogel exhibited a suitable phase transition temperature (Tm) between 35-39℃. (3) The volume swelling ratio of the hydrogel was increased with the increase of Ca-IFVs size. When the α-TCP complex was added into the Alg/TCP hydrogel, the swelling ratio decreased slightly. Alg/TCP/Col hydrogel exhibited a higher swelling ratio than the Alg/TCP hydrogel. (4) When the mixture ratio of precursor solution to liposome was 10, the compressive modulus of Alg/TCP/Col hydrogel and Alg/TCP hydrogel was significantly higher than that of the Alg hydrogel (P<0.05). (5) When the mixture ratio of precursor solution to liposome was 10, round MC3T3-E1 cells were observed on the Alg hydrogel; the cells on the surface of the Alg/TCP hydrogel were scattered and tended to extend; the cells on the surface of the Alg/TCP/Col hydrogel had a stress-extended morphology, and grew into the hydrogel, and meanwhile, the cell number increased significantly. To conclude, the liposome-mediated Alg/TCP/Col has good mechanical properties and cytocompatibility.