Preparation And Properties Of Lithium Doped Photocrosslinkable Injectable Polyglyceride-Fumaric Chloride Composite

Objective:Insufficient bone mass in the edentulous ridge has always been a detrimental factor in clinical dental restoration.Bone augmentation techniques are commonly used to improve the height and the fullness of the alveolar ridge.Most frequently used bone grafting materials such as autologous bone,allogeneic bone and various biological materials are difficult to be widely used due to limited materials and immunologic rejection.Recent studies have shown that tissue engineering technology is an ideal method to solve this problem.However,though common bone tissue engineering scaffolds such as hydroxyapatite and decalcified bone matrix have good biocompatibility,but most of the repaired sites are the floor of maxillary sinus and the surface of alveolar bone,the shape of the defect is always irregular and bone resorption is serious,so the poor plasticity of common bone tissue engineering scaffolds limit their uses in the oral cavity.Injectable tissue engineering scaffolds have incomparable advantages in plasticity compared with traditional bone tissue engineering scaffolds and they have broad application prospects in oral prosthetics.In this study,poly glycerol sebacate、fumaric acid chloride and lithium ions were compounded in order to find a new bone tissue engineering scaffold with strong plasticity and osteoinductive activity.Methods:1.Synthesis of photocrosslinked poly glycerol sebacate-fumaroyl chloride(PGSF)compositesFour kinds of PGSF composites(1:0.8,1:0.9,1:1,1:1.1)were synthesized by crosslinking PGS with fumaric chloride at 50℃ for 24 h.The fluidity of materials was observed at room temperature.The composition of the scaffold was analyzed by Fourier transform infrared spectroscopy,tensile test and swelling test were applied to determine the optimal synthesis ratio of PGSF.IV2.Preparation and characterizations of lithium-doped injectable PGSF compositesThe scaffolds were divided into 3 groups,the PGSF-Li scaffold prepared by adding the lithium phosphate was used as experimental group,the PGS scaffold synthesized by the equal-purification of sebacic acid with glycerol and the PGSF scaffold synthesized by equal ratio of poly glycerol sebacate with fumaric acid chloride were synthesized as control groups.The structures of scaffolds in three groups were analyzed by fourier transform infrared spectroscope.The surface morphologies and the porosities and pore sizes of scaffolds in three groups were observed by scanning electron microscope.Thermogravimetric analyzer was used to detect the thermal stabilities of the three kinds of scaffolds.Contact angle measuring instrument was used to compare the hydrophilicities of three scaffolds,the swelling ratios of the three scaffolds were tested by swelling test,and the degradation behavior of three scaffolds was determined by in vitro weight loss experiments.Results:1.The specific absorption peaks detected in Fourier transform infrared spectroscopy proved that we had successfully synthesized PGSF scaffolds.When the synthesis ratio reaches 1:1.1,the obtained PGSF was solid at room temperature,while the other three kinds of PGSF had good fluidity and could fully cure after UV light irradiation.Nacl was used as porogen to obtain white sponge-like PGSF scaffold with good elasticity.Tensile test results showed that with the increase of the ratio of fumaryl chloride,the ultimate tensile stress of PGSF increaseed from 0.61 MPa to 0.98 MPa and the elongation at break also increased.The swelling test results showed that the swelling ratio of PGSF decreased with the increase of the proportion of fumaric chloride,there was statistical difference between groups(P<0.05).2.A specific absorption peak of phosphate was detected in the Fourier transform infrared spectroscopy of PGSF-Li scaffold.Three groups of scaffolds had random three-dimensional network structures under scanning electron microscopy.The pore sizes were 20-160μm,the porosity of PGS scaffold was(53.92±2.18)%,the porosity of PGSF scaffold was(53.89±2.22)%,and the porosity of PGSF-Li scaffold was(54.68±2.26)%,there was no significant difference between groups(P>0.05).The contact angle of PGS scaffold was 78.260±2.00°,the contact angle of PGSF scaffold was 91.33°±0.84°,and the contact angle of PGSF-Li scaffold was 85.35°±2.17°,there was statistical difference between groups(P<0.05).The thermogravimetric analysis results showed that PGSF-Li began to degrade at a higher temperature and ceased at a lower temperature compared to PGS and PGSF.In the swelling experiment,the swelling ratio of PGSF scaffold was the smallest,only 83.12±7.26%,followed by PGSF-Li scaffold.The swelling ratio of PGS scaffold was the largest,there was statistical difference between groups(P<0.05).In vitro degradation experiments showed that the degradation rate of PGSF-Li scaffold was faster than that of PGSF scaffold but slower than PGS scaffold.Conclusions:1.Three different kinds of photocrosslinkable injectable PGSF scaffold were successfully synthesized,the optimum synthesis ratio of poly glyceryl sebacate and fumaric acid was determined to be 1:1.2.PGSF scaffold has better performance in thermal stability and swelling ratio compared with PGS scaffold,but limited in hydrophilicity.Successfully introduced lithium phosphate into PGSF scaffold to synthesize PGSF-Li scaffold.PGSF-Li scaffold has superior performance in thermal stability and hydrophilicity compared with PGSF scaffold,which shows that the optimization of PGSF scaffold using lithium phosphate is a feasible choice.What’s more,the appropriate porosity and pore size also indicate that PGSF-Li has broad application prospects in tissue engineering.