Fabrication and characterization of luminescent Pr3+ doped fluorapatite nanocrystals as bioimaging contrast agents
Silvestre, Oscar F.
Janjić, Goran V.
Mutavdzić, Dragosav R.
Nieder, Jana B.
Article (Published version)
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Fluorapatite doped with rare-earth elements has a wide-range of biomedical applications. Here, a new type of fluorapatite nanocrystals doped with praseodymium (FAP-Pr) with excitation-emission profiles in visible part of the spectrum is fabricated. Energy levels of Pr3+ activator ion contain metastable multiples states that offer the possibility of efficient multicolor emission lines in FAP nanocrystals. Three types of FAP-Pr nanocrystals with 0.1%, 0.5% and 1% atomic percent of Pr3+ (along with the undoped FAP control sample) are studied. Their novel chemical production method is described, the FAP-Pr nanocrystals structure, biocompatibility and the suitability for cell imaging are analyzed. Physicochemical characterization confirms crystals down to nanometer size. In addition, quantum-chemical calculation predicts that Pr3+ ions are incorporated into the FAP crystal lattice at Ca2 (6 h) sites. In vitro viability results shows that FAP-Pr nanocrystals are nontoxic to live cells. Addit...ionally, the cell uptake of the FAP-Pr nanocrystals is studied using fluorescence-based widefield and confocal microscopy. The nanocrystals show characteristic green emission at 545 nm (P-3(0)-> H-3(5) transition of Pr3+ ion) and orange emission at 600 nm (D-1(2)-> H-3(4)), which we use to discriminate from cell autofluorescence background. Orthogonal projections across 3D confocal stacks show that the nanocrystals are able to enter the cells positioning themselves within the cytoplasm. Overall, the new FAP-Pr nanocrystals are biocompatible and of the tested types, the 0.5% Pr3+ doped nanocrystals show the highest promise as a tracking nanoparticle probe for bioimaging applications.
Keywords:Praseodymium / Fluorapatite nanocrystals / Cancer cells / Bioimaging
Source:Journal of Luminescence, 2020, 217
- Elsevier, Amsterdam
Funding / projects:
- European Cooperation in Science and Technology through COST Action [MP1302]
- CCDR-N [NORTE-01-0145-FEDER-000019]
- Marie Curie fellowship, EU-EC, COFUND programme "NanoTRAINforGrowth" 
- Advanced technologies for monitoring and environmental protection from chemical pollutants and radiation burden (RS-43009)
- Synthesis of nanopowders and processing of ceramics and nanocomposites with specific electric and magnetic properties for application in integrated passive components (RS-45021)
- Studies of enzyme interactions with toxic and pharmacologically active molecules (RS-172023)
- Study of structure-function relationships in the plant cell wall and modifications of the wall structure by enzyme engineering (RS-173017)