Improving the biocompatibility of carbon nanodots for cell imaging

In the practice of in vivo imaging with carbon nanodots (CNDs) as probe, the volume of CNDs solution introduced into living body should be kept at minimum, and a higher concentration is needed to ensure sufficient quantity of the probe for obtaining bright image. Therefore, the improvement on biocompatibility of the CNDs is among the most important and critical issues. We report herein the improvement on the biocompatibility of CNDs with modification by ionic liquid. Amide group functionalization of carbon nanodots is first conducted through microwave irradiation, followed by coupling the ionic liquid 1-carboxymethyl-3-methyl imidazolium bromide on the surface of the Amide-CNDs via covalent conjunction to produce the modified carbon nanodots (IL-CNDs). This modification process significantly improved the biocompatibility of CNDs, as demonstrated by cell imaging at a higher concentration of CNDs. Both Amide-CNDs and IL-CNDs exhibit abundant surface functional groups, resulting in tunable fluorescent emission feature and potential applications in two-color cell imaging.