When you look up articles on injectable nanotechnology you can see several projects in the works. The one I find most interesting is a type of microscopic injectable nano mosquito that carries a poisonous payload to inject into a cell such as a cancer cell. In that particular article they were trying to work out how to give it some form of intelligent propulsion to find its target. By the time they add 5G capabilities, they could just tell it to target the heart for remote suicide heart attacks.