Nanocomposites and nanomaterials

Using HfO2 nanoparticles to enhance scintillation in polystyrene for efficient X-ray photodynamic therapy
Losytskyy M.Y.1, Vretik L.O.1, Nikolaeva O.A.1, Degoda V.Y.1, Shcherbakov O.B.2, Podust G.P.1, Samoilov O.M.3, Ohulchanskyy T.Y.4, Yashchuk V.M.1
1 Taras Shevchenko National University of Kyiv, Volodymyrs’ka Str., 64/13, Kyiv-01601, Ukraine. E-mail: mlosytskyy@gmail.com
2 Zabolotny Institute of Microbiology and Virology, NAS of Ukraine, Kyiv, Ukraine
3 Institute for Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
4 College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China.

Various nanosystems (NS) that generate toxic reactive oxygen species (ROS) upon X-ray excitation have recently been developed for use in X-ray induced photodynamic therapy (X-ray PDT). Usually, such NS consist of scintillator part (which absorbs high-energy X-ray quanta and transforms them into low-energy electronic excitations) and photosensitizer part (which generates ROS), with excitation energy transfer from the former to the latter. Herein, we report the effect of non-emitting HfO2 nanoparticles (NP) on the X-ray induced luminescence of recently designed and studied NS consisting of polystyrene NP with incorporated molecules of diphenyloxazole (PS-PPO NP) as scintillator and chlorin e6 as photosensitizer [1]. Excitation with the X-rays (about 15 keV) of the colloidal suspension of PS-PPO NP (about 8% by mass) in the presence of HfO2 NP (about 1.25% by mass) resulted in luminescence emission of PPO, its intensity was 15% higher than in the absence of HfO2. This could be explained by additional excitation of styrene matrix of PS-PPO NP with secondary electrons emitted by Hf atoms. In addition, differential scanning calorimetry studies revealed non-additive interaction (at high concentrations) of HfO2 NP, PS-PPO NP and chlorin e6 with the model phospholipid membrane, pointing to a good interaction not only of the complex with the membrane, but also that of individual components of the system.
The work is supported by the National Research Foundation of Ukraine (project 2020.02/0367)

1.	Losytskyy M.Yu., Vretik L.O., Nikolaeva O.A., Marynin A.I., Gamaleya N.F., Yashchuk V.M. Polystyrene-diphenyloxazole-chlorin e6 nanosystem for PDT: energy transfer study // Mol Cryst Liq Cryst.-2016.-639, N 1.-P.169-176.