Experimental studies X-ray induced cytotoxicity of aqueous colloidal solutions of UV-C luminescent La_1−x Pr_x PO₄ nanoparticles

The use of UV-C radiation for the treatment of tumors is a stand-alone therapeutic intervention that can induce cellular apoptosis and is independent of photosensitizer or oxygen concentration in tumor. To explore the potential of using X-ray excited UV-C luminescent nanoparticles as a basis for creating drugs to improve radiation therapy, two colloidal solutions of monoclinic La_1–x Pr_x PO₄ nanoparticles with different morphologies of large nanofibers (x = 0.02) or small nanorods (x = 0.05) were prepared using a microwave-assisted hydrothermal method. Comparison of X-ray excited UV-C luminescence of colloidal solutions showed approximately 6.3 times higher brightness for larger nanoparticles. The intrinsic and X-ray-induced cytotoxicity of the prepared colloidal solutions on the viability of cancerous Mh22a and healthy L929 cell cultures were studied using MTT assay and fluorescence microscopy. Fluorescence microscopy showed differences in the types of cell death (apoptosis or necrosis) after incubation with nanofiber or nanorod samples. X-ray irradiation was performed in two modes with different voltage on the X-ray tube (50 and 80 kV) and the same radiation dose (8 Gy). Groups of cells incubated with nanoparticles and irradiated with 50 kV mode showed greater death rate. According to MTT analysis, irradiation of cells incubated with La_0.98 Pr_0.02 PO₄ nanofibers at a concentration of 2 mg/mL reduced survival by 20-30%, and at the same time, according to fluorescence microscopy data, the number of cells undergoing apoptosis exceeded the number of cells that died through necrosis and reached 50-70%. Quantitative analysis of the relative number of dead cells caused by X-ray-induced cytotoxicity of La_0.95 Pr_0.05 PO₄ nanorods did not reveal statistically significant results in reducing cell viability.

1. Miwa S., Yano S., Hiroshima Y., Tome Y., Uehara F., Mii S., Efimova E.V., Kimura H., Hayashi K., Tsuchiya H., Hoffman R.M. Imaging UVC-induced DNA damage response in models of minimal cancer // J. Cell. Biochem. – 2013. – Vol. 114(11). – P. 2493-2499.

2. Müller M., Espinoza S., Jüstel T., Held K.D., Anderson R.R., Purschke M. UVC-Emitting LuPO4 :Pr3+ Nanoparticles Decrease Radiation Resistance of Hypoxic Cancer Cells // Radiat. Res. – 2020. – Vol. 193(1). – P. 82-87.

3. Squillante M. R., Jüstel T., Anderson R.R., Brecher C., Chartier D., Christian J.F., Cicchetti N., Espinoza S., McAdams D.R., Müller M., Tornifoglio B., Wang Y., Purschke M. Fabrication and characterization of UV-emitting nanoparticles as novel radiation sensitizers targeting hypoxic tumor cells // Opt. Mater. – 2018. – Vol. 80. – P. 197-202.

4. Espinoza S., Müller M., Jenneboer H., Peulen L., Bradley T., Purschke M., Haase M., Rahmanzadeh R., Jüstel T. Characterization of Micro- and Nanoscale LuPO4 :Pr3+, Nd3+ with Strong UV-C Emission to Reduce X-Ray Doses in Radiation Therapy // Part. Part. Syst. Charact. – 2019. – Vol. 36(10). – P. 1900280.

5. Espinoza S., Volhard M.-F., Kätker H., Jenneboer H., Uckelmann A., Haase M., Müller M., Purschke M., Jüstel T. Deep Ultraviolet Emitting Scintillators for Biomedical Applications: The Hard Way of Downsizing LuPO4 :Pr3+ // Part. Part. Syst. Charact. – 2018. – Vol. 35(12). – P. 1800282.

6. Tran T. A., Kappelhoff J., Jüstel T., Anderson R.R., Purschke M.U. V emitting nanoparticles enhance the effect of ionizing radiation in 3D lung cancer spheroids // Int. J. Radiat. Biol. – 2022. – Vol. 98(9). – P. 1484-1494.

7. Malyy T.S., Vistovskyy V.V., Khapko Z.A., Pushak A.S., Mitina N.E., Zaichenko A.S., Gektin A.V., Voloshinovskii A.S. Recombination luminescence of LaPO4-Eu and LaPO4-Pr nanoparticles // J. Appl. Phys. – 2013. – Vol. 113(22). – P. 224305.

8. Srivastava A.M., Setlur A.A., Comanzo H.A., Beers W.W., Happek U., Schmidt P. The influence of the Pr3+ 4f15d1 configuration on the 1S0 emission efficiency and lifetime in LaPO4 // Opt. Mater. – 2011. – Vol. 33(3). – P. 292-298.

9. Okamoto S., Uchino R., Kobayashi K., Yamamoto H. Luminescent properties of Pr3+ -sensitized LaPO4 :Gd3+ ultraviolet-B phosphor under vacuum-ultraviolet light excitation // J. Appl. Phys. – 2009. – Vol. 106(1). – Р. 013522.

10. Srivastava A.M. Aspects of Pr3+ luminescence in solids // J. Lumin. – 2016. – 169(B). – P. 445–449.

11. Bagatur’yants A.A., Iskandarova I.M., Knizhnik A.A., Mironov V.S., Potapkin B.V., Srivastava A.M., Sommerer T.J. Energy level structure of 4f5d states and the Stokes shift In LaPO4 :Pr3+: A theoretical study // Phys. Rev. B. – 2008. – Vol. 78(16). – P. 165125.

12. Hilario E.G., Rodrigues L.C.V., Caiut J.M.A. Spectroscopic study of the 4f5d transitions of LaPO4 doped with Pr3+ or co-doped with Pr3+ and Gd3+ in the vacuum ultra violet region // Nanotechnology. – 2022. – Vol. 33. – P. 305703.

13. McGahon A.J., Martin S.J., Bissonnette R.P., Mahboubi A., Shi Y., Mogil R.J., Nishioka W.K., Green D.R. The end of the (cell) line: methods for the study of apoptosis in vitro // Methods Cell Biol. – 1995. – Vol. 46. – P. 153-185.

14. Kusuzaki K., Murata H., Matsubara T., Satonaka H., Wakabayashi T., Matsumine A., Uchida A. Review. Acridine orange could be an innovative anticancer agent under photon energy // In Vivo. – 2007. – Vol. 21(2). – P. 205-214.

15. Qian H., Chao X., Williams J., Fulte S., Li T., Yang L., Ding W. X. Autophagy in liver diseases: A review // Mol Aspects Med. – 2021. – Vol. 82. – P. 100973.

16. Xu C. and Qu X. Cerium oxide nanoparticle: a remarkably versatile rare earth nanomaterial for biological applications // NPG Asia Mater. – 2014. – Vol. 6(3). – P. e90-e90.

17. Goodman C. M., McCusker C. D., Yilmaz T., Rotello V.M. Toxicity of gold nanoparticles functionalized with cationic and anionic side chains // Bioconjugate Chem. – 2004. – Vol. 15(4). – P. 897-900.

18. Schaeublin N.M., Braydich-Stolle L.K., Schrand A.M., Miller J.M., Hutchison J., Schlager J.J., Hussain S.M. Surface charge of gold nanoparticles mediates mechanism of toxicity // Nanoscale. – 2011. – Vol. 3(2). – P. 410-420.