Nanocomposites and nanomaterials

Nanosystems entrapping gold nanoparticles in polystyrene-based matrix for efficient X-ray photodynamic therapy
Losytskyy M.Y.1, Vretik L.O.1, Nikolaeva O.A.1, Degoda V.Y.1, Yakovliev A.2, Ohulchanskyy T.Y.2, Qu J.2, 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 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong Province, 518060, P. R. China.

Photodynamic therapy (PDT) comprises light, photosensitizer (PS), and oxygen to treat cancer and other diseases. X-ray PDT, which employs X-ray irradiation to generate excited PS producing reactive oxygen species, is suggested to overcome the main problem of PDT i.e. low depth of light penetration into biological tissues. As PSs cannot be directly activated by X-ray due to a big mismatch between energy of X-ray photon (~keV-MeV) and that of excited electronic state of PS (~eV), a conventional X-ray PDT involves scintillating nanoparticles (NPs), capable of converting high energy radiation into visible light through a scintillation process [1]. Scintillating materials absorb X-ray photons and generate secondary electrons, which then produce excited electronic states of the scintillator molecules or atoms. The X-ray PDT nanosystems contain scintillating NPs and PS, and the electronic excitation energy of the scintillator is transferred to PS and excites it [2]. However, as the energy of the secondary electrons remains high, their migration distance is of hundreds of nm, which strongly exceeds the NPs size, resulting in low efficiency of conversion of X-ray photons energy to that of electronic excited states of scintillator and PS and, finally, low efficiency of X-ray PDT. Herein, we present new design of the X-ray PDT nanosystem consisting of NPs of heavy element (e.g., gold), scintillating polymer matrix (polystyrene) and PS. A successful combination of these principal components is important for obtaining the nanoscaled agents for efficient X-ray PDT.

1.	Fan W., Huang P., Chen X. Overcoming the Achilles’ heel of photodynamic therapy // Chem Soc Rev.-2016.-45.-P. 6488-6519.
2.	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.-P. 169-176.