Optical imaging for biological applications requires more sensitive tools. Near-infrared persistent luminescence nanoparticles enable highly sensitive in vivo optical detection and complete avoidance of tissue autofluorescence. However, the actual generation of persistent luminescence nanoparticles necessitates ex vivo activation before systemic administration, which prevents long-term imaging in living animals. Here, we introduce a new generation of optical nanoprobes, based on chromium-doped zinc gallate, whose persistent luminescence can be activated in vivo through living tissues using highly penetrating low-energy red photons. Surface functionalization of this photonic probe can be adjusted to favour multiple biomedical applications such as tumour targeting. Notably, we show that cells can endocytose these nanoparticles in vitro and that, after intravenous injection, we can track labelled cells in vivo and follow their biodistribution by a simple whole animal optical detection, opening new perspectives for cell therapy research and for a variety of diagnosis applications.
ZnGa2O4:Cr3+ is shown to be a new bright red UV excited long-lasting phosphor potentially suitable for in vivo imaging due to its 650 nm-750 nm emission range. Photoluminescence and X-ray excited radioluminescence show the 2E → 4A2 emission lines of both ideal Cr3+ and Cr3+ distorted by a neighboring antisite defect while long-lasting phosphorescence (LLP) and thermally stimulated luminescence (TSL) almost exclusively occur via distorted Cr3+. The most intense LLP is obtained with a nominal Zn deficiency and is related to a TSL peak at 335K. A mechanism for LLP and TSL is proposed, whereby the antisite defect responsible for the distortion at Cr3+ acts as a deep trap.
ZnGa2O4:Cr3+ presents near-infrared long-lasting phosphorescence (LLP) suitable for in vivo bioimaging. It is a bright LLP material showing a main thermally stimulated luminescence (TSL) peak around 318 K. The TSL peak can be excited virtually by all visible wavelengths from 1.8 eV (680 nm) via d–d excitation of Cr3+ to above ZnGa2O4 band gap (4.5 eV–275 nm). The mechanism of LLP induced by visible light excitation is entirely localized around CrN2 ion that is a Cr3+ ion with an antisite defect as first cationic neighbor. The charging process involves trapping of an electron–hole pair at antisite defects of opposite charges, one of them being first cationic neighbor to CrN2. We propose that the driving force for charge separation in the excited states of chromium is the local electric field created by the neighboring pair of antisite defects. The cluster of defects formed by CrN2 ion and the complementary antisite defects is therefore able to store visible light. This unique property enables repeated excitation of LLP through living tissues in ZnGa2O4:Cr3+ biomarkers used for in vivo imaging. Upon excitation of ZnGa2O4:Cr3+ above 3.1 eV, LLP efficiency is amplified by band-assistance because of the position of Cr3+4T1 (4F) state inside ZnGa2O4 conduction band. Additional TSL peaks emitted by all types of Cr3+ including defect-free CrR then appear at low temperature, showing that shallower trapping at defects located far away from Cr3+ occurs through band excitation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.