Abstract
Near-infrared (NIR) fluorescent imaging is a powerful tool for the non-invasive visualization of the inner structure of living organisms. Recently, NIR fluorescence imaging at 1000–1400 nm (second optical window) has been shown to offer better spatial resolution compared with conventional NIR fluorescence imaging at 700–900 nm (first optical window). Here we report lead sulfide (PbS) quantum dots (QDs) and their use for in vivo NIR fluorescence imaging of cerebral venous thrombosis in septic mice. Highly fluorescent PbS QDs with a 1100 nm emission peak (QD1100) were prepared from lead acetate and hexamethyldisilathiane, and the surface of QD1100 was coated with mercaptoundecanoic acid so as to be soluble in water. NIR fluorescence imaging of the cerebral vessels of living mice was performed after intravascular injection (200–300 μL) of QD1100 (3 μM) from a caudal vein. By detecting the NIR fluorescence of QD1100, we achieved non-invasive NIR fluorescence imaging of cerebral blood vessels through the scalp and skull. We also achieved NIR fluorescence imaging of cerebral venous thrombosis in septic mice induced by the administration of lipopolysaccharide (LPS). From the NIR fluorescence imaging, we found that the number of thrombi in septic mice was significantly increased by the administration of LPS. The formation of thrombi in cerebral blood vessels in septic mice was confirmed by enzyme-linked immunosorbent assay (ELISA). We also found that the number of thrombi significantly decreased after the administration of heparin, an inhibitor of blood coagulation. These results show that NIR fluorescence imaging with QD1100 is useful for the evaluation of the pathological state of cerebral blood vessels in septic mice.
Highlights
For the past decade, a variety of quantum dots (QDs) that that emit from the visible to near-infrared (NIR) region have been developed for bioimaging probes [1]
Single-walled carbon nanotubes, silver sulfide (Ag2 S) QDs, and rare earth-doped nanoparticles emit at the second optical window, their fluorescence quantum yields (QY) are much less than that of PbS QDs [9]
We demonstrate that QDs with a 1100 nm emission peak (QD1100) can be used as a NIR fluorescent probe for the non-invasive visualization of cerebral blood vessels in living mice
Summary
A variety of quantum dots (QDs) that that emit from the visible to near-infrared (NIR) region have been developed for bioimaging probes [1]. The main advantages of QDs used for fluorescence imaging are their high brightness with emission tunability, multiplexed excitation, and their stability for long-term observation. Owing to these superior properties, QD probes are widely used for bioimaging in vitro and in vivo [1,2,3,4,5]. We have demonstrated that highly fluorescent NIR QDs that emit at the second optical window (1000–1400 nm). Among the several types of NIR fluorescent probes that have been reported, such as single-walled carbon nanotubes [10,11,12,13,14] and rare earth nanoparticles [15], lead sulfide (PbS)
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