A drug carrier nanoparticle has been synthesized that can specifically target the proximal tubules of the kidneys. The nanoparticles accumulate in the kidneys to a greater extent than other organs (e.g., up to 3 or more times greater in the kidney than any other organ). They can encapsulate many classes of drug molecules. The nanoparticles are biodegradable and release the drug as they degrade. The particles can sustainably release a drug within the kidneys for up to two months. The nanoparticles are useful for the treatment of diseases that affect the proximal tubules, such as heart failure, liver cirrhosis, hypertension, and renal failure； the study of relative blood flow to the renal cortex and medulla； and delivery of agents to treat gout.
