The core-shell structure of 5-FU/PEG-PBLG nanoparticles. (A) Morphology under SEM (× 80000). SEM showed 5-FU/PEG-PBLG nanoparticles have a core-shell structure, a spherical or elliptical shape, and a smooth surface. The hydrophobic central core is a non-gilt grizzly area, about 200 nm in diameter and the hydrophilic shell is a gilt white area, about 30 nm in thickness. (B) Morphology under TEM (× 50000). TEM showed that nanomicelles were round or oval particles of uniform size with fuzzy edges.