MicrospheresPolymersPolyglycolic AcidDrug CarriersDelayed-Action PreparationsParticle SizeDrug CompoundingLactic AcidChitosanChemistry, PharmaceuticalBiocompatible MaterialsDrug Delivery SystemsMicroscopy, Electron, ScanningPolystyrenesAbsorbable ImplantsTechnology, PharmaceuticalPolyvinyl AlcoholHexuronic AcidsSurface PropertiesPolyestersAlginates