Emission-tunable probes using terbium(III)-doped self-activated luminescent hydroxyapatite for in vitro bioimaging

Lanthanide ion (Ln(3+))-doped nanoscale hydroxyapatites (nHAp) with tunable luminescence have attracted increasing attention due to their potential applications as useful biomedical tools (e.g., imaging and clinical therapy). In this study, we reported that doping Terbium (III) ions (Tb3+) in self-activated luminescent nHAp via a facile hydrothermal reaction, using trisodium citrate (Cit(3+)), generates unique emission-tunable probes known as Cit/Tb-nHAp. The morphology, crystal phase, and luminescence properties of these Cit/Tb-nHAp probes are studied in detail. Moreover, the results demonstrate that the luminescence of self-activated nHAp originates from the carbon dots trapped within the nHAp crystals, in which partial energy transfer occurs from carbon dots (CDs) to Tb3+. The color tunability is successfully achieved by regulating the addition of Cit(3+). Biocompatibility study indicates that when co-cultured with C6 glioma cells in vitro for 3 days, <= 800 ppm Cit/Tb-nHAp is not cytotoxic for C6 glioma cells. We also present in vitro data showing efficient cytoplasmic localization of transferrin conjugated Cit/Tb-nHAp into C6 glioma cells by fluorescence cell imaging. We have successfully engineered Cit/Tb-nHAp, a promising biocompatible agent for future in vitro and in vivo fluorescence bioimaging. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

In this study, Tb3+-doped luminescent nHAp probes known as Cit/Tb-nHAp were synthesized and characterized for their morphology, crystal phase, and luminescence properties. The color tunability was achieved by regulating the addition of Cit(3+). Biocompatibility study showed that <= 800 ppm Cit/Tb-nHAp was not cytotoxic for C6 glioma cells, and efficient cytoplasmic localization of transferrin conjugated Cit/Tb-nHAp into C6 glioma cells was demonstrated by fluorescence cell imaging, making it a promising agent for future in vitro and in vivo fluorescence bioimaging.