Study On Synthesis Of Dendronized Polylactide And Preparation Of Its Drug-loading Microsphere

The synthesis of dendronized polylactide (PLLA) and preparation of its drug-loading microshpere which was based on the four-generation polyester dendrons synthesized by divergent method were investigated. The dendronized PLLA is a well-defined dumbbell-shaped tri-block copolymer, consisting of hydrophobic PLLA and hydrophilic linear poly(ethylene glycol) (PEG) with narrow molecular weight distributions and varied PLLA arm lengths, which have been synthesized via the sequential preparation of terminal dendronized polyhydric PEG and ring-opening polymerization of L-lactide (LA). The terminal dendronized polyhydric PEG was prepared by the conjugation of amine-terminated fourth-generation polyester dendrons with NHS-activated PEG followed by the deprotection of acetonide groups at the surface of the dendrons. The dendrons and productions were characterized by FT-IR, NMR, GPC, DSC and TG. It was discovered that the dendrons were well-defined and the PLLA arms can be readily controlled by the feed ratio of LA monomer to the hydroxyl groups in PEG macro-initiator. The copolymer's glass transition temperature, melting point and crystallinity were declined. And the copolymer has high molecular weight with narrow molecular weight distributions and improved hydrophilicity with much terminal hydroxyl which could be chemical modificated. The copolymer microsphere was prepared by emulsion-solvent evaporation method, characterized by SEM and SL, which showed a range of 1.40μm to 3.17μm in mean diameter with narrow microsphere size distribution and regular smooth surface without gap. The drug loading efficiency of temozolomide-dendronized polylactide microsphere is 20.1%and the in vitro control release time is 48 hours.