Nanodiamond for biolabelling and toxicity evaluation in the zebrafish embryo in vivo

Nanodiamond (ND) has been proposed for various biomedical applications, including bioimaging, biosensing and drug delivery, owing to its physical‐chemical properties and biocompatibility. Particularly, ND has been demonstrated as fluorescence‐ and Raman‐detectable labels in many cellular models. Different surface functionalization methods have been developed, varying the ND's surface properties and rendering the possibility to attach biomolecules to provide interaction with biological targets. For this, toxicity is of major concern in animal models. Aside from cellular models, a cost‐effective animal test will greatly facilitate the development of applications. In this study, we use the rapid, sensitive and reproducible zebrafish embryo model for in vivo nanotoxicity test. We optimize the conditions for using this animal model and analyze the zebrafish embryonic development in the presence of ND. ND is observed in the embryo in vivo using laser confocal fluorescence microscopy and fluorescence lifetime imaging. Using the zebrafish model for a safety evaluation of ND‐based nanolabel is discussed. The defects originated color centers of nanodiamond emit visible fluorescence upon laser illumination. With nanodiamond's low toxicity, it can be used as a biocompatible biolabel in the zebrafish model. When injected with nanodiamond, the green fluorescence from nanodiamond at the head of the larval zebrafish is brightly visible; and the nanodiamond can be traced in the zebrafish in vivo.