However, nanoparticles could be precursors to microscopic machines that could potentially do a variety of tasks for a much longer period of time, ultimately replacing our blood.It’s also possible that enhanced blood will be genetically engineered rather than synthetically made.“One of the biggest advantages of this approach is that you would not have to worry about your body rejecting your new blood, because it will still come from you,” says Oxford University’s Sandberg.Regardless of how it is made, one obvious role for enhanced or “smart” blood would be to increase the amount of oxygen our hemoglobin can carry.“In principle, the way our blood stores oxygen is very limited,” Sandberg says.“So we could dramatically enhance our physical selves if we could increase the carrying capacity of hemoglobin.”

According to Sandberg and others, substantially more oxygen in the blood could have many uses beyond the obvious benefits for athletes.For example, he says, “it might prevent you from having a heart attack, since the heart doesn’t need to work as hard, or it might be that you wouldn’t have to breathe for 45 minutes.” In general, Sandberg says, this super blood “might give you a lot more energy, which would be a kind of cognitive enhancement.”

(For data on whether Americans say they would want to use potential synthetic blood substitutes to improve their own physical abilities, see the accompanying survey, U.S. Public Wary of Biomedical Technologies to ‘Enhance’ Human Abilities.)