Three Dimensional Printing Of Double Network Hydrogel Scaffold:Preparation And Characterization

The cartilage has a special mechanical property, with its compression modulus following the gradient change, which increasing from the superficial layer of 0.079 MPa to Inferior articular cartilage of 5.7 GPa. The traditional cartilage scaffold preparation method, such as particle leaching or phase separation, can’t accurately control external and internal structure of scaffolds, and the three-dimensional scaffold with uniform pore size can be obtained. What’s more, mechanical property of these scaffolds are unable to match natural cartilage. Therefore, it is promising to study to obtain scaffold with excellent mechanical properties, controllability of precise control of internal and external structure and outstanding cell viability.To try to solve these problems, this paper used sodium alginate and acrylamide as monomer materials to prepare the slurry with excellent printability by adjusting the proportion of the formula and feeding sequence. We utilized the rheological theory to analysis viscoelastic behavior of slurry, and combined it with 3D printing process parameters and scaffold design. To optimize printing process, we studied the influence factors of the printing property and stability of slurry, as a result, we have successfully prepared DNG scaffold with controllability of external and internal structure. The whole achievements includes the following aspects.Firstly, by optimizing the proportion of raw materials and feeding sequence to synthesize the sodium alginate/acrylamide double network hydrogels, whose swelling equilibrium and gel fraction were 14 and 93%, respectively, and the compression and tensile modulus were 0.19 MPa and 0.1MPa, the elongation at break was even 14 times.Secondly, with the rheology theory and printing tests, we verified and explained that calcium content was the key factor for viscosity and printing property of the gel slurry. On this basis we further derived that if the mass ratio of CaCl2 and SA was 0.05 to 0.07, slurry was printable. In addition, we added a certain amount of hydroxyapatite particles(<10μm) to the system to strength viscosity of the slurry to enhance the support of print lines for side hole. Through optimization, the quality ratio of hydroxyapatite and sodium alginate was set up from 0.7 to 1.Thirdly, after process exploration, we prepared double network hydrogel scaffolds with outstanding mechanical properties and uniform hole structure. The pore size of scaffolds was 350-550 μm, and the porosity reached 61%. The compression modulus and compressive strength of scaffolds after lyophilization were 2.24 MPa and 434 KPa, which reached the range of cartilage compression modulus. What’s more, respectively, both of them were inversely proportional to pore size.Lastly, we preliminarily explored the effect of the pore size of the double network hydrogel on cell proliferation. The results show that cells can proliferate on the scaffolds. After 3 days and 5 days, the measured OD value(which is proportional to cell number) was above 0.7 and 1.3. Cell proliferation effect was best when the pore size is 550 μm.