Size‐Dependent Blue Emission from Europium‐Doped Strontium Fluoride Nanoscintillators for X‐Ray‐Activated Photodynamic Therapy

Abstract

Successful implementation of X‐ray‐activated photodynamic therapy (X‐PDT) is challenging because most photosensitizers (PSs) absorb light in the blue region, but few nanoscintillators produce efficient blue scintillation. Here, we developed efficient blue‐emitting SrF2:Eu scintillating nanoparticles. Our optimized synthesis conditions resulted in cubic nanoparticles with 32 nm diameter and blue emission at 416 nm. Coating them with the porphyrin TMPyP in a core‐shell structure (SrF@TMPyP) resulted in maximum singlet oxygen (1O2) generation upon X‐ray irradiation for nanoparticles with 6 TMPyP depositions (SrF@6TMPyP). The 1O2 generation was directly proportional to the dose, did not vary in the low energy X‐ray range (48‐160 kVp), but was 21% higher when irradiated with low‐energy X‐rays than irradiations with higher energy gamma rays. In the clonogenic assay, cancer cells treated with SrF@6TMPyP and exposed to X‐rays presented a significantly reduced survival fraction compared to the controls. The SrF2:Eu Scintillating nanoparticles (ScNPs) and their conjugates stand out as tunable nanoplatforms for X‐PDT due to the efficient blue emission from the SrF2:Eu cores; the ability to adjust the scintillation emission in terms of color and intensity by controlling the nanoparticle size; the efficient 1O2 production when conjugated to a PS and, the efficacy of killing cancer cells.This article is protected by copyright. All rights reserved