X-ray-Induced Singlet Oxygen Activation with Nanoscintillator-Coupled Porphyrins

Abstract

Tb 2 O 3 coated with a polysiloxane layer is a biocompatible nanoscintillator that exhibits an appropriate pattern of biodistribution after injection. In this contribution, we combine this nanosystem with porphyrin molecules that are able to generate singlet oxygen, a major cytotoxic agent for photodynamic therapy application. Using time-resolved laser spectroscopy and singlet oxygen probes, we demonstrate this combination is suitable for singlet oxygen generation induced by X-ray and provide a physical study of the energy transfer observed between the nanoscintillator and the porphyrin. Combined with a radiotherapy protocol, the proposed nanohybrid system presents a combination of physical, chemical, and biological properties that make it a good candidate for photodynamic effects in deep tissues.

Scintillating Nanoparticles as Energy Mediators for Enhanced Photodynamic Therapy

“…Tb 2 O 3 coated with a polysiloxane layer (Tb 2 O 3 @SiO 2 ) is known to be a biocompatible nanoscintillator. 86 Gd-free Tb 2 O 3 has been found to have a higher density (8.230 g·cm −3 ) as compared to Gd 2 O 3 :Tb (7.901 g·cm −3 ), and it has also been found that luminescence quantum yield was preserved even if the NPs are small in size (inner core diameter ~3 nm). Since the biological and chemical properties of Tb 2 O 3 are well established, it was interesting to study the physical characteristics of this nanosystem when combined with a photosensitizer, 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin (TPP), in order to offer proof for the concept of X-ray activated PDT.…”

“…The Tb 2 O 3 @SiO 2 grafted TPP is more efficient in generating ROS that oxidize APF under X-ray irradiation than porphyrin solution. Reproduced with permission from [86]. Copyright 2013 American Chemical Society.…”

Photonanomedicine: a convergence of photodynamic therapy and nanotechnology

“…Forward-looking preclinical advances in inorganic PNM formulations, such as nanoscintillators 70 and upconversion nanoparticles 71 have enabled the conversion of deep-penetrating radiation, such as X-rays and NIR light, to visible wavelengths for deep-tissue PS excitation. However, these ambitious nanomaterials are hindered by the inherent toxicity of their components and dopants, such as heavy metal ions and rare-earth lanthanide ions.…”

Energy Transfer in Polystyrene Nanoparticles with Encapsulated 2,5-Diphenyloxazole

“…But despite of several advantages, the drawback of this method is the very small depth of the light penetration into the tissue [2]. Thus the idea of creating X-ray excited sensitizers composed of scintillating and photosensitizing parts with the electronic excitation energy transfer (EEET) from the first to the last one seems attractive [3].…”

“…Thus the idea of creating X-ray excited sensitizers composed of scintillating and photosensitizing parts with the electronic excitation energy transfer (EEET) from the first to the last one seems attractive [3]. Last years, several nanosystems based on this concept were described with various materials used as scintillators, various photosensitizer molecules and different ways of binding them to a system [2,[4][5][6][7]. In the frames of this concept, the X-ray stimulated luminescence of the porphyrin sensitizer was demonstrated for the nanoparticles containing polystyrene (PS), vinylpyridine, 2,5-diphenyloxazole (PPO) and hematoporphyrin [8].…”