1. College of Engineering, University of Georgia, Athens, GA 30602, USA;
2. Department of Chemistry, University of Georgia, Athens, GA 30602, USA;
3. Bio-Imaging Research Center, University of Georgia, Athens, GA 30602, USA;
4. National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health (NIH), Bethesda, MD 20852, USA;
5. Department of Physics and Astronomy, University of Georgia, Athens, GA 30602, USA;
6. Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA;
7. Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA.
* These authors contributed equally.
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:Cr3+ 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:Cr3+ 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 studies reveal promising potential of these nanoprobes in cell tracking and tumor targeting, exhibiting exceptional sensitivity and penetration that far exceed those afforded by conventional fluorescence imaging.
Keywords: LiGa5O8:Cr3+ nanoparticles, near-infrared, persistent luminescence, photostimulated persistent luminescence, in vivo imaging.