Fabrication And Properties Of EMPLGA And Its Porous Scaffold Materials

Poly(lactic-co-glycolic acid)(PLGA) is one of important biomedical materials duo toits excellent biocompatibility and controllable degradation rate. However, the application inmedical field of PLGA is limited due to its lack of rich biological active groups, weakhydrophilicity and cell adhesion. The performances of PLGA material, such as thehydrophilicity, cell affinity, alleviating the accumulation of acid in degradation process canbe improved by copolymerized and grafted. After the modification, PLGA would have amore widely applications in the biomedical field.In this paper, D,L-Lactide and glycolide were prepared under high vacuum withstannous octoate (Sn(Oct)2) as the catalyst. The influence of different purification methodson the product yield and purity were investigated. The results showed that the productpurity of D,L-lactide is99.47%after six recrystallization by using watering-recrystallization method. The yield and purity of product are low by using isopropylalcohol or ethyl acetate as solvent, however the purity of glycolide reached92.63%byusing combination of isopropyl alcohol and ethyl acetate.Using maleic anhydride, D,L-Lactide and glycolide as raws, MPLGA was synthesizedby ring-opening polymerization. FTIR and1HNMR analysis proved that maleic anhydridehas successfully accessed the polymer skeleton. The effect of catalyst dosage, reaction timeand reaction temperature on the molecular weight and molecular weight distribution wasstudied. The MPLGA, with weight average molecular mass of5.3×104and molecularweight distribution of1.51was obtained when the amounting catalyst0.03wt%, reactiontime36h and reaction temperature140℃. Ethanediamine modified MPLGA(EMPLGA)were obtained by using N-acylation reaction, the hydrophilicity and biocompatibilityperformance of the polymer would be improved. Furthermore, the contact angle ofEMPLGA was much lower than PLGA and MPLGA, this indicated that EMPLGA hasexcellent hydrophilic properties, and the hydrophilic of MPLGA was slightly weaker thanPLGA duo to the introduction of the anhydride bond. A series of porous scaffolds materials was fabricated by molding/particulatedissolution method at room temperature. The influences of particle size and amount ofporogen on the diameter size, porosity, morphology and mechanical properties of thescaffolds were studied. The results showed the porosity of scaffolds increased with theincrease of the porogen amount. When the porogen amount was90wt%, the porosity of thescaffold reached up to81.86%, but the mechanical properties of the scaffold decreasedwith the increase of the porogen amount. We found the pore size increased with theincrease of the particle size. Therefore, the pore size can be controlled with the masspercentage of porogen particles and size of particles.The degradation behavious of MPGLA and EMPLGA in PBS solution wereinvestigated. The results indicated that mass loss and water uptake of both the scaffolds aregradually increasing with increasing degradation time; however, pH value of PBS,mechanical strength and weight average molecular mass decreased. In addition, the massloss of MPLGA increased rapidly in the process of degradation. The introduction of aminogroup in EMPLGA alleviated the acid accumulation, and the environment of degradationremains in a near neutral condition, mass loss and mechanical properties are stabledecreased trend. What is more, the water uptake of EMPLGA is always higher thanMPLGA duo to the large number of hydrophilic groups in EMPLGA. The morphologies ofporous scaffolds changed little on5th day and there were some microspures in the wall ofpores on10th day. Large pores began to appeared on25th day, and scaffolds began tocontract and collapse.