Structure Design And Modification Of Mannitol-polylactide Tissue Engineering Materials

L-lactide was synthesized by L-lactic acid using ZnO/Sn(Oct)2 as catalyst under the pressure of 400Pa. Six-arm mannitol-polylactide(ML-PLLA ) that hassix side chains of polylactide was synthesized by polymerizing L-lactide in the presence of mannitol which has a characteristic of six hydroxyl. Coupling ML-PLLA/GA and glutamic acid capped ML-PLLA-GC were prepared by modifying with Glutaric anhydride and L-Glutamic acid, respectively. IR, 1H-NMR,UV,DSC and TGA were used for characterization and the effects of glutaric anhydride and L-Glutamic acid on the structure and properties of ML-PLLA was also investigated. The results showed that:The catalytic activity of ZnO/Sn(Oct)2 for the preparation of L-lactide is higher than that of ZnO or Sn(Oct)2. The optimized preparation conditions for L-lactide: m(ZnO):m(Sn(Oct)₂)=1: 2; the mass ratio of ZnO/Sn(Oct)₂ to reactant is 2.0%; the pressure of 400 Pa; reaction temperature of 180-210℃. Under these conditions, the yield of L-lactide reaches 45.2%.ML-PLLA was synthesized by ring-opening polymerization of L-lactide in the presence of mannitol, it has the characteristic of low melt viscosity. With the increase of the ratio of mannitol in the feed, the molecular weight, the melting point as well as Mw/Mn of ML-PLLA all decrease, indicating the molecular weight distribution is becoming narrow. In addition, the time required for the synthesis of ML-PLLA is shorter than that of PLLA.ML-PLLA/GA were prepared by coupling ML-PLLA with glutaric anhydride, then the hydroxyl group of the coupled ML-PLLA was converted to carboxyl group. Compared with ML-PLLA, ML-PLLA/GA has higher tensile-strength, lower melting point, better thermal stability and degradation performance, its water absorption character is also enhanced significantly. The length of the side chain of ML-PLLA greatly influences the water absorption of ML-PLLA/GA. The shorter side chain of ML-PLLA, the better water absorption character, and vice versa. Therefore, the water absorption character of product can be adjusted by controlling the length of side chainof ML-PLLA.Amino acid capped ML-PLLA-GC that can make ninhydrin to bring about color reaction was prepared by the reaction of activated L-Glutamic acid with ML-PLLA in DMSO solvent. L-Glutamic acid can specifically react with Ninhydrin and the reactive product shows bright blue and purple.