Over-1000 nm Near-infrared Fluorescence and SPECT/CT Dual-modal in vivo Imaging Based on Rare-earth Doped Ceramic Nanophosphors

Abstract

In this study, we aimed to develop a dual-modal in vivo imaging based on over-1000 nm near-infrared (OTN-NIR) fluorescence and single photon emission computed tomography (SPECT)/computed tomography (CT). As an OTN-NIR nanophosphor material, Ytterbium and erbium ion co-doped yttrium phosphate nanoparticles (YPO₄ NPs) was synthesized by a hydrothermal synthesis method. Biocompatible poly(ethylene glycol) (PEG)/polycation block copolymer and radioactive ¹¹¹In were introduced on the YPO₄ NPs surface (PEG-¹¹¹In-YPO₄ NPs). The PEG-¹¹¹In-YPO₄ NPs showed high dispersion stability in physiological saline and excellent radioactivity in any of PBS and FBS solutions. Furthermore, in vivo OTN-NIR fluorescence and SPECT /CT imaging of live mice was performed. Strong OTN-NIR emission from the blood vessel and organs of live mice were observed. Moreover, SPECT/CT images clearly showed the three dimensional images of the live mice. Therefore, PEG-¹¹¹In-YPO₄ NPs is an attractive candidate for the OTN-NIR fluorescence and SPECT/CT dual-modal imaging probe, and the concept can be served as a novel platform for real-time imaging and three dimensional quantitative determinations.