Hyperbranched polyglycerol modified fluorescent nanodiamond for biomedical research

The aim of the present work was to functionalize fluorescent nanodiamond by covalent grafting with hyperbranched polyglycerol. Fluorescent nanodiamond, derived from high pressure high temperature micron-sized diamond, was oxidized and then thermally reacted with pure glycidol in the absence of catalyst. The results revealed that thermal polymerization of glycidol was notably faster on the nanodiamond surface as a result of a surface initiation of the isothermal ring opening polymerization. Interestingly, the aqueous dispersion of the resulting nanoparticles appeared stable at high ionic strength. Furthermore, the fluorescent nanodiamond grafted with hyperbranched polyglycerol displayed several hydroxyl end-groups which could be further derivatized by carboxylation or carbamatization and subsequently conjugated with protein linked via an amide bound. Notably, nanodiamonds retain their unique fluorescent characteristics. This work suggests that fluorescent nanodiamond coated with hyperbranched glycidol could be promising in biomedical research where aqueous dispersion of fluorescent nanoparticles stable in physiological medium is in high demand to label, track and quantify biomolecules.