Disclosed are crosslinked particles (e.g., microparticles) that are capable of storing and releasing drugs. The particles can be macroparticles, microparticles, or nanoparticles and can be composed of polyester backbones. The particles can be loaded with a drug. The particles can degrade in vivo to release the drug. The particles can be prepared by crosslinking functionalized polyester backbones and loaded with a given drug. The particles of the present disclosure can be injected with a syringe. In some embodiments, the particles of the present disclosure are administered in connection with a surgery and release the drug after the site of the surgery for a period of 1-6 months.