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.
Polyzwitterions are employed as coating polymers for biomaterials to induce an antifouling property on the surface. Fine-tuning the betaine structure switches the antifouling property to be interactive with anionic tissue constituents in response to a tumorous pH gradient. The ethylenediamine moiety in the carboxybetaine enabled stepwise protonation and initiated the di-protonation process around tumorous pH (6.5). The net charge of the developed polyzwitterion (PGlu(DET-Car)) was thus neutral at pH 7.4 for antifouling, but was cationic at pH 6.5 for interaction with anionic constituents. Quantum dots coated with PGlu(DET-Car) exhibited comparable stealth and enhanced tumor accumulation relative to the PEG system. The present study provides a novel design of smart switchable polyzwitterion based on a precise control of the net charge.
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