Erythrocyte containing cytosolic superparamagnetic nanoparticulate iron oxide, characterized in that the erythrocyte is viable, presenting a life comparable to that of untreated erythrocytes.Eritrocito que contiene óxido de hierro nanoparticulado superparamagnético citosólico, caracterizado por que el eritrocito es viable, presentando una vida comparable a la de eritrocitos sin tratar.