MicrospheresPolyglycolic AcidAbsorbable ImplantsDelayed-Action PreparationsLactic AcidDrug CarriersPolymersDrug Delivery SystemsBiodegradation, EnvironmentalParticle SizeDrug CompoundingChitosanChemistry, PharmaceuticalHolmiumMicroscopy, Electron, ScanningTechnology, PharmaceuticalGelatinHexuronic AcidsGlucuronic AcidPolyvinyl AlcoholPolystyrenes