(340c) Silica-Coated, Near-UV Activated YVO4:Eu3+,Bi3+ Nanophosphors for Dynamic Cell Imaging

Luminescent rare-earth-based inorganic nanoparticles (nanophosphors) are promising bioimaging agents due to their high photostability, sharp emission bands and relatively low toxicity ¹. Flame aerosol technology provides a scalable and highly reproducible process for production of such nanophosphors (e.g. Y₂O₃:Eu³⁺,Tb³⁺) with precise control of their composition and properties ^2,3. Nanophosphors that can be excited in the near-ultraviolet and visible region, such as YVO₄:Eu³⁺,Bi³⁺, provide a useful tool for bioimaging and in vitro dosimetry studies using conventional fluorescence microscopes.

Here, YVO₄:Eu³⁺,Bi³⁺ nanophosphors are made by flame spray pyrolysis and in-situ coated by a nanothin amorphous silica coating. The optimal Bi content for maximum red-shift of their excitation band edge towards the visible region is identified through systematic experiments. The nanophosphors with the optimal composition are highly crystalline and appear bright red under a conventional fluorescence microscope. Their photostability during dynamic imaging of HeLa cells in vitro is confirmed, contrary to commercial fluorescent (organic-dye labeled) SiO₂ nanoparticles that exhibit 50% photobleaching within 3.5 h [4]

The potential of these nanophosphors for dynamic cell imaging is demonstrated and compared to conventional organic dyes, demonstrating the nanophosphor superior performance/ We employed cell-bacterial co-cultures to identify how GFP-expressing S. pneumoniae bacteria interact with human epithelial lung cancer cells (A549). Furthermore, the nanoparticle interaction with these cells is further examined by employing upright and inverted cell culture orientations, and by the surface biofunctionalization of the nanoparticles with targeting antibodies compared with non-targeting bovine serum albumin. The amorphous silica coating here facilitates the biofunctionalization of the nanoparticle surface. The developed silica coated nanoprobes here will open up several avenues on dynamic nanoparticle-cell imaging.

REFERENCES

1. A. Escudero, C. Carrillo-Carrion, M. V. Zyuzin & W. J. Parak. Luminescent rare-earth-based nanoparticles: A summarized overview of their synthesis, functionalization, and applications. Topics Curr. Chem. 374, (2016).
2. G. A. Sotiriou, M. Schneider & S. E. Pratsinis. Color-tunable nanophosphors by codoping flame-made Y₂O₃ with Tb and Eu. J. Phys. Chem. C 115, 1084-1089 (2011).
3. G. A. Sotiriou, D. Franco, D. Poulikakos & A. Ferrari. Optically stable biocompatible flame-made SiO₂-coated Y₂O₃: Tb³⁺ nanophosphors for cell imaging. ACS Nano 6, 3888-3897 (2012).
4. A. Spyrogianni, P. Tiefenboeck, F. H. L. Starsich, K. Keevend, F. Krumeich, I. K. Herrmann, J.‐C. Leroux & G. A. Sotiriou. “Near‐UV Activated, Photostable Nanophosphors for in vitroDosimetry and Dynamic Bioimaging” AIChE J.in press, DOI: 10.1002/aic.16166 (2018).