6.2.2.2　Polymer nano-spheres/capsules

Polymer nano-spheres（or nano-capsules）usually refer to solid or hollow zero-dimension NPs in range of tens to hundreds of nanometers formed by aggregating of hydrophobic polymers.PLA and PLGA are often used to prepare nano-spheres（or nano-capsules）to load drugs.Hydrophobic drugs can be loaded into the polymer matrix of polymer nano-spheres via hydrophobic interaction.In vivo，the drugs release slowly with gradual degradation of the polymers.Nano-capsules can be employed to encapsulate aqueous or oily solution of hydrophilic or hydrophobic drugs.(https://www.daowen.com)