Facilitating Low-Energy Activation in the Near-Infrared Persistent Luminescent Phosphor Zn1+xGa2–2xSnxO4:Cr3+ via Crystal Field Strength Modulations (original) (raw)
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Theranostics, 2014
In vivo fluorescence imaging suffers from suboptimal signal-to-noise ratio and shallow detection depth, which is caused by the strong tissue autofluorescence under constant external excitation and the scattering and absorption of short-wavelength light in tissues. Here we address these limitations by using a novel type of optical nanoprobes, photostimulable LiGa5O8:Cr(3+) near-infrared (NIR) persistent luminescence nanoparticles, which, with very-long-lasting NIR persistent luminescence and unique photo-stimulated persistent luminescence (PSPL) capability, allow optical imaging to be performed in an excitation-free and hence, autofluorescence-free manner. LiGa5O8:Cr(3+) nanoparticles pre-charged by ultraviolet light can be repeatedly (>20 times) stimulated in vivo, even in deep tissues, by short-illumination (~15 seconds) with a white light-emitting-diode flashlight, giving rise to multiple NIR PSPL that expands the tracking window from several hours to more than 10 days. Our stu...
Long term in vivo imaging with Cr3+ doped spinel nanoparticles exhibiting persistent luminescence
Journal of Luminescence, 2016
Persistent luminescence is a singular property of some materials which are able to store the excitation or light irradiation energy at intrinsic traps or defects before slowly emitting lower energy photons within several hours. When such compounds are prepared as nanoparticles (NPs), when functionalization is realized to get colloidal materials well dispersed in aqueous medium, such nanoprobes open the use of the persistent luminescence for bioimaging applications. Recently, the numbers of in vivo applications increased with new modalities and new expectations. In this review, we focused our attention on the ZnGa 2 O 4 :Cr (ZGO:Cr) nanoparticles. When ZnGa 2 O 4 (ZGO), a normal spinel is doped with Cr 3+ ions, a high brightness persistent luminescence material with an emission spectrum perfectly matching the transparency window of living tissues is obtained. It allows in vivo mouse imaging with an excellent target-to-background ratio. One interesting characteristic of ZGO:Cr lies in the fact that its persistent luminescence can be excited with orange/red light, well below its band gap energy and in the transparency window of living tissues. This important property allows multiple re-excitations to perform long term bioimaging. Antisite defects of the direct spinel structure are assumed to provide shallow traps which store the excitation light. Charge release by room temperature thermal excitation and recombination center, here trivalent chromium, are responsible for the persistent luminescence. Following a primary excitation (UV or visible), one also observed that trapped charges can be released under 977 nm light stimulation for several spinel gallate materials, therefore increasing the modalities and the materials envisioned for in vivo excitation of these NPs.
Imaging and therapeutic applications of persistent luminescence nanomaterials
Advanced Drug Delivery Reviews, 2018
The development of probes for biomolecular imaging and diagnostics is a very active research area. Among the different imaging modalities, optics emerged since it is a noninvasive and cheap imaging technique allowing real time imaging. In vitro, this technique is very useful however in vivo, fluorescence suffers from low signal-to-noise ratio due to tissue autofluorescence under constant excitation. To address this limitation, novel types of optical nanoprobes are actually being developed and among them, persistent luminescence nanoparticles (PLNPs), with long lasting near-infrared (NIR) luminescence capability, allows doing optical imaging without constant excitation and so without autofluorescence. This review will begin by introducing the physical phenomenon associated to the long luminescence decay of such nanoprobes, from minutes to hours after ceasing the excitation. Then we will show how this property can be used to develop in vivo imaging probes and also more recently nanotheranostic agents. Finally, preliminary data on their biocompatibility will be mentioned and we will conclude by envisioning on the future applications and improvements of such nanomaterials.
Nanoprobes with near-infrared persistent luminescence for in vivo imaging
Proceedings of the National Academy of Sciences, 2007
Fluorescence is increasingly used for in vivo imaging and has provided remarkable results. Yet this technique presents several limitations, especially due to tissue autofluorescence under external illumination and weak tissue penetration of low wavelength excitation light. We have developed an alternative optical imaging technique by using persistent luminescent nanoparticles suitable for small animal imaging. These nanoparticles can be excited before injection, and their in vivo distribution can be followed in real-time for more than 1 h without the need for any external illumination source. Chemical modification of the nanoparticles' surface led to lung or liver targeting or to long-lasting blood circulation. Tumor mass could also be identified on a mouse model. biodistribution ͉ in vivo optical imaging ͉ nanoparticles ͉ phosphorescent nanoparticles
NIR-Persistent Luminescence Nanoparticles for Bioimaging, Principle and Perspectives
Near Infrared-Emitting Nanoparticles for Biomedical Applications, 2020
The development of nanoparticles for NIR imaging and diagnostics is an area of considerable interest. Among the different imaging modalities, optics emerged has an interesting technique since it is a non-invasive, cheap imaging technique allowing real time imaging. In-vitro, this technique is very useful, however in-vivo fluorescence imaging suffers from suboptimal signal-to-noise ratio, which is caused by the strong tissue autofluorescence under constant external excitation. To address this limitation, novel types of optical nanoprobes are actually being developed in the deep red/near infrared (NIR) range and among them, persistent luminescence nanoparticles (PLNPs), with long lasting near-infrared luminescence capability. These NPs allow optical imaging to be performed in an excitation-free and consequently autofluorescence-free manner. This chapter will first introduce the physical phenomenon associated to the long luminescence delay of such nanoprobes, from minutes to hours after ceasing the excitation, and will then highlight the tools used in physico-chemistry laboratories to characterize these nanoparticles with a focus on the ZnGa2O4 nanoparticles which are widely studied over the world. Then their biocompatibility will be mentioned and finally the evaluation in term of new advances for in-vivo bioimaging theranostics nanoprobes will be presented. We will conclude this chapter by envisioning perspectives for such nanomaterials.
Optical Materials, 2017
The analysis of the optical spectroscopy of the Cr 3þ doped spinel was initiated by Prof. Georges Boulon more than twenty years ago. More recently persistent luminescence nanoparticles of Cr doped zinc gallate have found interest for in vivo imaging of small animals. Here we evaluated near infra-red (NIR) excitation (or NIR photostimulation) via photo-transfer mechanism as an additional tool for in vivo optical imaging. Investigation of the persistent luminescence induced by NIR photostimulation is studied after either a primary UV (band-to-band excitation) or visible irradiation (direct Cr 3d-3d excitation). UV or visible pre-excited ZnGa 2 O 4 :Cr (ZGO:Cr) nanoparticles are kept active during several days thanks to deep traps (with depths 1 eVe1.2 eV) observed in these samples which can be probed through thermally stimulated luminescence (TSL) technique showing glow curve maximums at 470 K and 530 K upon visible light excitation. These deep traps are stable at room temperature but can be emptied by NIR light photostimulation. Experiments were carried out to study the photostimulation induced trappingdetrapping in the ZGO:Cr phosphor. Photostimulation was also tested in vivo for small animal optical imaging to offer new perspectives and modalities.
Persistent Luminescence Nanoparticles for Bioimaging
Advances in Intelligent and Soft Computing, 2012
Optical imaging is a rapidly developing field of research aimed at noninvasive monitoring of disease progression, evaluating the effects and pharmacokinetic of a drug, or identifying pathological biomarkers. To this end, it requires the development of targeting and highly specific contrast agents. In fluorescence imaging, an external light of appropriate wavelength is used to excite the fluorescent molecule, followed almost immediately by the release of longer wavelength, lower energy light for imaging. Fluorescence is increasingly used for imaging and has provided remarkable results. However this technique presents several limitations, especially due to tissue autofluorescence under external illumination and weak tissue penetration of low wavelength excitation light. To overcome these drawbacks, we have developed an innovative technique using persistent luminescence nanoparticles (PLNP) for optical imaging in small animal. Such nanoparticles can be excited before systemic injection, and their biodistribution monitored in real-time for dozen of minutes without the need for any external illumination source. This review article will focus on recent works undertaken in our laboratory on the synthesis of PLNP, their surface modifications and applications for bioimaging.