Enhanced
angiography based on magnetic resonance imaging (MRI)
has emerged as a noninvasive, robust, and high-resolution imaging
technique for the clinical evaluation of vascular diseases. However,
the effects of clinical Gd-chelating contrast agents are unsatisfactory
for MRI contrast enhancement owing to their short blood half-life
caused by rapid vascular extravasation, especially in microvessels.
To address these issues, nanoprobes based on red blood cell membrane-coated
ultrasmall NaGdF4 nanoparticles that exhibit much higher
longitudinal molar relaxivity (r
1) than
the clinically used contrast agent gadolinium diethylenetriaminepentaacetic
acid have been developed. Furthermore, the appropriate hydrodynamic
diameter and stealth nature aid the nanoprobes to reside longer within
the blood vessels without extravasation, thereby increasing the contrast
between the blood vessels and surrounding tissues. Through probe-enhanced
three-dimensional (3D) dynamic contrast-enhanced MR angiography, the
main arteries and veins of the mouse were readily discernible, and
even tiny vessels with sub-millimeter diameters could be clearly depicted.
With this level of outstanding MR angiography performance, the embolization
and recanalization processes of the carotid artery can be serially
monitored with high imaging resolution using only a single injection.
Additionally, the results of clearance studies and the toxicity tests
further highlight the safety features of the nanoprobe. To summarize,
the nanoprobes used in this study exhibit less extravascular leakage
and a longer blood half-life, thus successfully overcoming the defects
of the conventional low-molecular-weight Gd-based contrast agents
and demonstrating their potential usefulness in enhanced MR angiography.
In this study, we find that silk fibroin as an antioxidant is capable of scavenging OH˙ and accelerating the degradation of water-soluble fullerene, which provides further insight into the application of WSF in intratracheal instillation and inhalation.
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