RadioisotopesMicrospheresIsotopesIsotope LabelingNitrogen IsotopesPolyglycolic AcidOxygen IsotopesCarbon IsotopesDelayed-Action PreparationsParticle SizeDrug CarriersDrug CompoundingLactic AcidZinc IsotopesPolymersSulfur IsotopesChitosanDeuteriumIron IsotopesChemistry, PharmaceuticalStrontium Isotopes