Preparation And Properties Of High Strength Double Network Hydrogels Based On Collagen And PEG

The double network hydrogel(DN gel) attracts much attention due to its water store capability(> 90%) and high mechanical properties. Nowadays, the research focus of DN gels is to improve biocompatibility for the application in the field of biomaterials. This study aims to prepare a series of DN gels with superior mechanical properties(compression modulus and fracture stress) and favorable biocompatibility for bone or cartilage tissue repair.(1) Preparation and characterization of CP DN gel.Polyethylene glycol diacrylate(PEGDA), an artificial polymer, was irradiated under UV light(365 nm) to form 1st soft network. A natural polymer collagen(Col) was crosslinked by chemical agent to obtain 2nd brittle network. By incorporation of these two networks together, the CP DN gel with superior mechanical strength was gained. When the content of Col increased from 8 to 14 wt%, the porosity of the hydrogel increased, and the average pore size was about 200~300 μm. When Col was 8 wt%, the fracture stress of the CP gel was 783.3 k Pa, which was 12.6- and 49.6-folds of Col and PEGDA gels, respectively. Moreover, the compression modulus increased 2~3 folds and 4.7~14.2 folds of Col and PEGDA gels. Therefore, the CP gel had significantly improved fracture strength and compression modulus.(2) Preparation and characterization of CHP and CHP-Lys gels.Hyaluronic acid(HA) and L-lysine(Lys) were introduced to obtain CHP and CHP-Lys gels for adjusting the structure and mechanical properties. The morphology study showed the CHP gel had uniform cellular structure with the pore size ranging from 80 μm to180 μm. The fracture strain of CHP gels reached 79.5% showing more ductile and flexible nature as compared with CP gel, but its strength was backward. Meanwhile, the architecture of CHP-Lys was more thick and solid leading to increased brittleness. Its comperssion modulus was 414 k Pa(19-folds of CHP gel and 1.7-folds of CP gel) and the fracture strain was above 50%. In this system, HA was to improve the ductibility and Lys was to increase the stiffness. These results showed that the mechanical properties of CHP-Lys gels were superior to CP and CHP gels with relatively high modulus and ductibility.(3) Cyto- and tissue compatibility evaluation of CHP-Lys gelsThe cytotoxicity and proliferation study showed that the hydrogel could safely serve as cell scaffold for MC 3T3-E1 in vitro. And the implantation experiment indicated the gel had mild tissue rejection and was biodegradable. Overall, these hybrid hydrogels had great potential in the application of bone and cartilage repair.