At the fundamental level, they are the same. But at the application level, they are not. Let me put this in an engineering way. If I let C = Chemical, B = Biomedical, and E = Electrical and electronic applications, then nano engineering is ~ C + E, whereas bionano engineering is ~ C + B. Note that I used the approximation symbol (~) instead of the definite one (=). Both tracks are multidisciplinary in nature.