In this article, we describe the synthesis and solution properties of PEG-b-PTMC star block copolymers via ring-opening polymerization (ROP) of trimethylene carbonate (TMC) monomer initiated at the hydroxyl end group of the core PEG using HCl Et 2 O as a monomer activator. The ROP of TMC was performed to synthesize PEG-b-PTMC star block copolymers with one, two, four, and eight arms. The PEG-b-PTMC star block copolymers with same ratio of between hydrophobic PTMC and hydrophilic PEG segments were obtained in quantitative yield and exhibited monomodal GPC curves. The amphiphilic PEG-b-PTMC star block copolymers formed spherical micelles with a core-shell structure in an aqueous phase. The mean hydrodynamic diameters of the micelles increased from 17 to 194 nm with increasing arm number. As arm number increased, the critical micelle concentration (CMC) of the PEG-b-PTMC star block copolymers increased from 3.1 Â 10 À3 to 21.1 Â 10 À3 mg/mL but the partition equilibrium constant, which is an indicator of the hydrophobicity of the micelles of the PEG-b-PTMC star block copolymers in aqueous media, decreased from 4.44 Â 10 4 to 1.34 Â 10 4 .In conclusion, we confirmed that the PEG-b-PTMC star block copolymers form micelles and, hence, may be potential hydrophobic drug delivery vehicles.
The double-layered microspheres play an important role in controlling drug delivery for
pharmaceutical application, because of the low initial burst compared with single-layered spheres
and targetable delivery to specific organ. But it has drawback in loading drug and controlling size.
In this study, we developed double-layered spheres using relatively simple oil-in-water (O/W)
solvent evaporation method using bovine serum albumin (BSA) as water-soluble protein and
poly(D,L-lactide-co-glycolide) (PLGA). BSA/PLGA double-layered microspheres were fabricated
using O/W solvent evaporation method and investigated the specific character of double-layered
microspheres according to the kind of surfactants. In SEM observation, double layered microsphere
had spherical shape and smooth surface without pores. And the double layered microsphere using
O/W solvent evaporation method was transparency because of slow evaporation of solvent. In
fluorescent observation, we observed the fluorescent core in the double-walled spheres composed of
FITC-BSA and PLGA using fluorescent observation. In the case of polyvinylalcohol as emulsifier,
the yield was better than gelatin. As decreased concentration of PLGA, the size of double-layered
microspheres deceased.
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