Synthesis And Drug Release Behaviors Of The Branched Polylactide

Because of a combination of excellent biocompatibility, suitable degradation profile in thebody, polylactide (PLA) had become the most popular candidate for diverse biomedical andpharmaceutical applications. Nevertheless PLA still bore some disadvantages, such as its highcrystallinity and the difficulty of controlled degradation rate. As introduction the branchpoints to the PLA backbone was an effective strategy to tailor the properties. In order tomodify the PLA, the star-branched, the hyperbranched and dendritic structures have beenwidely studied. Compared to its linear analogues, the three-dimention unsymmetrical globularstructure, better solubility, lower viscosity and the high number of modifiable surfacefunctional groups rendered the branched structure highly attractive. In this paper wesynthesized the different branched PLA copolymer and the branched copolymer microsphereswere developed to entrap the ibuprofen. The release profiles of the ibuprofen-loadingmicrospheres have been investigated in details.Firstly, the branched polylactic acid (PLAN) was synthesized by melt polycondensationfrom lactic acid and N, N-bi（2-hydroxyethyl）glycine and the ibuprofen-carried microsphereswere prepared by method of solvent evaporation. The obtained branched products werecharacterized by1H NMR spectrum and gel permeation chromatography (GPC). Thecontrolled-released properties of ibuprofen from this copolymer in vitro have also beeninvestigated. The experimental results indicated that the drug loading of PLAN increased to49.20%from28.67%of PLA and in vitro cumulative release of PLAN-ibuprofen loadedmicrospheres PLAN was63%after24h.Secondly, the star-branched polylactide (SPLA) was synthesized by ring-openingcopolymerization of lactide with different content hex(p-hydroxymethyphenoxy)cyclotriphosphazene as an initiator. The star-branched copolymer microspheres weredeveloped to entrap the ibuprofen, and the release profiles of the ibuprofen-loadingmicrospheres have been investigated. The results indicated that, as the arm length increased,the encapsulation efficiency of increased from67.73%to28.67%, and the release rate wasalso slower. Thirdly, the hyperbranched polylactide (HPLAB) was synthesized in a facile two-stepprotocol. The molecular structure of the corresponding polymer had been confirmed by13CNMR. The microspheres containing ibuprofen were fabricated by oil-in-water single emulsionsolvent evaporation approach. The controlled-released properties of ibuprofen from thiscopolymer in vitro have also been investigated. The experimental results indicated that, as thedrug loading amount was1:8, the encapsulation efficiency of HPLAB increased to66.15%from39.18%of PLA. The in vitro release behavior of the microspheres showed the ibuprofenreleases from HPLAB microspheres more slowly and smoothly than that from PLAmicrospheres. The DSC results suggested that ibuprofen incorporated in the HPLAB matrixevenly and there were more intermolecular force between the drug and HPLAB.