I am trying to determine why Nanoparticle based labels aren't more prevalent in Biological labs and Assays. Is it because the bio-conjugation reactions are (a) not consistent in their product yield and reproducibility (b) bioconjugation chemicals like EDC and Sulfo-NHs are difficult to handle (c) safety protocols in labs discourage the use of nanoparticle based labels or (d) other reasons which you can add on to this discussion.