Facile preparation of fluorescent nanodiamond based polymer nanoparticles via ring-opening polymerization and their biological imaging.

Fluorescent nanodiamond (ND) has been regarded as one of the most promising fluorescent nanoprobes owing to their chemical inert, biocompatibility, optical properties, and rich surface chemistry. The fluorescent ND has been mainly fabricated through high-energy ion beam irradiation of type Ib diamonds and subsequent thermal annealing. The generation of nitrogen-vacancy centers is the reason for the fluorescence. However, the physical method is relatively complicated and it need to expensive equipment as well as high cost. On the other hand, the resultant fluorescent ND particles are lack of functional groups and difficult to be dispersed in aqueous solution. Therefore, the development of facile methods to direct preparation of fluorescent ND and surface modification with functional polymers is of great research interest for expanding the biomedical applications of fluorescent ND. In this report, a facile strategy was reported for the first time to prepare hydrophilic polymers functionalized fluorescent ND (named as ND-PhE-PETOx) composites through the ring-opening polymerization and simultaneous simple nucleophilic substitution reaction using the non-fluorescent detonation ND as the raw material. The obtained fluorescent ND composites were characterized by various characterization techniques in details. The as-obtained ND-PhE-PETOx composites exhibit high water dispersibility, low toxicity and strong fluorescence intensity. Cell uptake results indicating that the fluorescent ND based composites can be effectively internalized by cells. Taken together, we have developed a novel and simple method for the preparation of fluorescent ND based composites, which show excellent physicochemical properties and great potential for biomedical applications.