"Nano" simply refers to scale — engineering particles far smaller than a single cell. In nutrition and nutraceutical research, this matters because many naturally occurring compounds (from turmeric to green tea extracts to various plant compounds) are poorly absorbed by the body in their normal form — most of what you eat or swallow as a supplement never actually reaches your bloodstream in a usable amount. Nano-scale delivery techniques are one active area of research into improving how much of a compound the body can actually use.
What This Is Not
This is one of the most common, least-explained questions in cancer care:
Scans detect disease above a certain size — not the small number of cells that can travel in the blood or settle elsewhere undetected. A real, well-recognized limitation of current technology, not a reason for alarm — but it's why "clear scan" and "cancer-free" aren't always the same thing.