| In this study, micelles encapsulated with or without naproxen were prepared via the self-assembly in aqueous medium with polyethylene glycol-graft-poly (lactic acid) (PPLA) as raw material. Their drug loading property were investigated.First,the self-assembly characteristics of PPLA was studied in water. Using stability as index, its potential application for drug delivery was investigated. The results show that the formation of micelles was effect by the organic solvent, preparation method, selective solvent, polymer concentration and stirring rate. The optimum preparation condition was as follows: acetone as organic solvent, water for the selective solvent, oil-water ratio of 1:10,PPLA micelle concentration of 1 mg - mL-1, stirring speed 400rpm and solvent evaporation method. The critical micelle concentration of PPLA-3, PPLA-4 were 3.0×10-4 g·L-1, 2.0×10-3 g·L-1 obtained by fluorospectrophotometer. The particle size and zeta potential tests by dynamic light scattering. The tests revealed that 1.0 mg mL-1 of PPLA-3, PPLA-4 micelles were 114.7nm and 86.5nm of the size; Zeta potentials were -27.84, 20.08 mV; uniform distribution and size dispersion coefficient (PDI) of less than 0.2.?The micelle presented certain stability when diluted and standing at room temperature, pH changes affect the stability of PPLA micelles. While the environment of micelles changed under alkaline and acidic, PPLA micelles appeared particle size and Zeta potential increased and coagulated.Secondly, rotary evaporation method was applied for reparation PPLA micelles which were characterized. With naproxen as the model drug, the effect of several factors including acetone volume, the ratio of solvent to water, the amount of naproxen, polymer concentratio, aqueous medium and addition sequence of material were investigated on entrapment efficiency by single-factorial experiments. two optimum preparation procedure were as follows: a. Naproxen 1.6mg, PPLA-3 20mg, acetone 1mL, water 10mL , solvent evaporation method.. b. Naproxen 2.4mg, PPLA-3 30mg, acetone 1mL, water 10mL , solvent evaporation method.. The morphology of PPLA load-micelles with a roughly spherical shape was analyzed by transmission electron microscopy (TEM). The particle size and zeta potential tests by dynamic light scattering revealed two results.Before and after drug-load ,one was the particle size of PPLA-3 micelle increased from 114.7 to 201.3nm, Zeta potential changes from -27.84 mV to -55.31 mV. The other one was the particle size of PPLA-4 micelle increased from 86.5 to 164.3nm, Zeta potential changes from -20.08 mV to -40.64 mV.In PBS, naproxen-loaded micelles duration release could be up to 5 days at 37℃. The factors such as material concentration and aqueous medium were no significant effect on drug release.Therefore, We concluded that PPLA, a novel applied polymer carriers, is a promising drug delivery system for hydrophobic drugs...
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