Investigation of the emission spectra and cytotoxicity of TiO2 and Ti-MSN/PpIX nanoparticles to induce photodynamic effects using X-ray

Background: Photodynamic therapy (PDT) has been recognized as an effective method for cancer treatment; however, it suffers from limited tissue penetration depth. X-rays are ideal excitation sources for activating self-lighting nanoparticles that can penetrate through deep tumor tissues and convert the X-rays to visible light. In this study, Ti-MSN/PpIX nanoparticles for X-ray induced photodynamic therapy was synthesized. Preparation, characterization, and emission spectrum of Ti-MSN/PpIX nanoparticles as well as PDT activity and toxicity of the nanoparticles on HT-29 cell line were investigated. Methods: Firstly, mesoporous silica nanoparticles (MSN) were synthesized through sol-gel method. Then, TiO2 and PpIX were loaded in MSN. Next, the emission spectra of TiO2, Ti-MSN, and Ti-MSN/PpIX nanoparticles, while activated by X-ray (6 MVP), were recorded. In addition, viability of cells after treatment by Ti-MSN/PpIX nanoparticles and X-ray irradiation was studied. Results: SEM, TEM and FESEM images of the spherical composite nanoparticles showed that their dimensions were changed by incorporating Ti and organic compound of PpIX. Two-dimensional hexagonal structure with d i pp-spacing was about 3.5 nm with particle sizes of 70 -110 nm. The optical characteristics of TiO2 nanoparticles showed strong emission lines, which effectively overlapped with the absorption wavelengths of protoporphyrin IX (PpIX). Cellular experiments showed Ti-MSN/PpIX nanoparticles have proper biocompatibility, however, after X-ray irradiation, significant decrease of cell viability in the presence of the nanoparticles was observed. Conclusion: The presented X-PDT method could enhance RT efficacy and is enable that allows for reducing X-ray dose exposure to healthy tissues to overcome radio-resistant tumors.