Thiol-Organosilica Particles Internally Functionalized with Propidium Iodide as a Multicolor Fluorescence and X-ray Computed Tomography Probe and Application for Non-Invasive Functional Gastrointestinal Tract Imaging

Propidium iodide (PI) is a fluorescent nucleic acid dye that contains iodide molecules. Thiol-organosilica particles that were internally functionalized with PI (PI particles) were prepared for X-ray computed tomography (CT) and multicolor fluorescence imaging. PI particles of various sizes were synthesized in a one-pot process. The particles showed unique fluorescent signals and X-ray absorption, with enhancement of the fluorescence intensity of PI located inside organosilica particles. PI particles had multicolor fluorescence, including original fluorescence and near-infrared (NIR). Orally administered PI particles were observed in the gastrointestinal tract (GIT) using fluorescent imaging devices and X-ray CT. An in vivo fluorescence imaging system could detect the NIR fluorescence of PI particles in the GIT specifically. Multipurpose zoom fluorescence microscopy was used to noninvasively visualize the real-time passage of particles and the movement of the GIT. The passage and distribution of particles over time in the GIT were demonstrated using X-ray CT. A correlation analysis between the fluorescent and X-ray CT data demonstrated the characteristics, limitations, and novel potential for noninvasive functional GIT dual modal imaging.