Several towering intellects at the University of California, San Diego have devised a method of targeted drug delivery: nano-fish constructed of gold, silver and nickel. This on the heels of a recent announcement by an Israeli firm utilizing nano-bots to release medication in cockroaches (BOJ, 2016).
The fish do not operate autonomously, but may be compelled to motion via simple exposure to electromagnetic waves, an elegant alternative to the primitive syringe.
The precious metals the fish will persist indefinitely within the body if not removed, so reusability is on the table as well.
Source