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Characterization of VCAM-1-Binding Peptide-Functionalized Quantum Dots for Molecular Imaging of Inflamed Endothelium
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
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2013 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 8, no 12, e83805- p.Article in journal (Refereed) Published
Abstract [en]

Inflammation-induced activation of endothelium constitutes one of the earliest changes during atherogenesis. New imaging techniques that allow detecting activated endothelial cells can improve the identification of persons at high cardiovascular risk in early stages. Quantum dots (QDs) have attractive optical properties such as bright fluorescence and high photostability, and have been increasingly studied and developed for bio-imaging and bio-targeting applications. We report here the development of vascular cell adhesion molecule-1 binding peptide (VCAM-1 binding peptide) functionalized QDs (VQDs) from amino QDs. It was found that the QD fluorescence signal in tumor necrosis factor alpha (TNF-alpha) treated endothelial cells in vitro was significantly higher when these cells were labeled with VQDs than amino QDs. The VQD labeling of TNF-alpha-treated endothelial cells was VCAM-1 specific since pre-incubation with recombinant VCAM-1 blocked cells' uptake of VQDs. Our ex vivo and in vivo experiments showed that in the inflamed endothelium, QD fluorescence signal from VQDs was also much stronger than that of amino QDs. Moreover, we observed that the QD fluorescence peak was significantly blue-shifted after VQDs interacted with aortic endothelial cells in vivo and in vitro. A similar blue-shift was observed after VQDs were incubated with recombinant VCAM-1 in tube. We anticipate that the specific interaction between VQDs and VCAM-1 and the blue-shift of the QD fluorescence peak can be very useful for VCAM-1 detection in vivo.

Place, publisher, year, edition, pages
2013. Vol. 8, no 12, e83805- p.
National Category
Biological Sciences
URN: urn:nbn:se:kth:diva-141075DOI: 10.1371/journal.pone.0083805ISI: 000329325200127ScopusID: 2-s2.0-84896730935OAI: diva2:695328
Vinnova, P35914-1Swedish Foundation for Strategic Research Swedish Research Council, 621-2011-4381Science for Life Laboratory - a national resource center for high-throughput molecular bioscience

QC 20140210

Available from: 2014-02-10 Created: 2014-02-07 Last updated: 2015-03-06Bibliographically approved
In thesis
1. Time-Resolved Optical Properties of Colloidal CdSe-CdS/ZnS Core-Multishell Quantum Dots in Bioimaging
Open this publication in new window or tab >>Time-Resolved Optical Properties of Colloidal CdSe-CdS/ZnS Core-Multishell Quantum Dots in Bioimaging
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductor quantum dots (QDs) have attracted great attention as a novel fluorescent material in the last twenty years. Their superior optical properties such as high brightness and photostability, broad absorption spectrum, narrow and size-tunable emission spectrum, enable them great application in bioimaging.

However, the fluorescence from single QDs shows irregular on (bright) and off (dark) switches under continuous irradiation which is known as blinking. QD blinking may lead to information loss in single particle tracking and lower brightness in other bioimaging applications. We studied the blinking behavior and its mechanism by using CdSe-core QDs with different shell thicknesses under different excitations. We observed two types of fluorescence behavior, blinking with apparent on and off states and flickering without distinguishable on and off states under low (1.8 and 3.9 W/cm2) and high (12.1 and 25 W/cm2) excitations, respectively. The transfer of photoexcited electron or hole from CdSe core to the QD surface is responsible for QD blinking under low excitations. And further intraband excitation of photoexcited electron and hole is responsible for QD flickering under high excitations.

Ca2+ serves as the second messenger in signal transduction. Monitoring Ca2+ concentration in live cell is a key technique in biological research especially in neuroscience. Most of the commercial Ca2+ indicators are organic dyes which are easy to be photobleached. In order to develop QD-based Ca2+ indicator, we investigated the effect of Ca2+ on the QD fluorescence. We found that the fluorescence intensity, lifetime, and on-state ratio in single QD fluorescence were all decreased by Ca2+ ion. Theoretical study shows that one free Ca2+ could attach stably to the surface of one QD, attracting the photogenerated electron and repel the photogenerated hole, suppressing the radiative recombination between them, and resulting in the reduction of fluorescence intensity, lifetime and on-state ratio.

Overexpression of vascular adhesion molecule-1 (VCAM-1) in endothelial cells is a hallmark of inflammation-induced activation of endothelium and may serve as a target for evaluation atherogenesis in early stages. We conjugated VCAM-1 binding peptide to amino-coated QDs and employed the functionalized QDs (VQDs) to specifically image activated endothelial cells. Upon the interaction between VQDs and endothelial cells, a blue-shift of about 30 nm in the QD fluorescence peak was observed. We anticipate that the VQDs and the blue-shift phenomenon could be very useful for VCAM-1 detection in vitro and in vivo.

Furthermore, we studied the fluorescence of QDs embedded in a porous alumina membrane which is widely used as biomolecule and cell filter for biological research. We found that the fluorescence spectrum has small peaks superimposed on the principle curve. Theoretical study identifies that this modulation is due to the photonic band structure introduced by the membrane pores. This work could supply information about the interaction between QD fluorescence and porous membrane structure which would be useful when applying QDs to image biomolecules or cells filtered by the porous alumina membrane.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xvi, 69 p.
TRITA-FYS, ISSN 0280-316X ; 2015:11
National Category
Physical Sciences
Research subject
Biological Physics
urn:nbn:se:kth:diva-160939 (URN)978-91-7595-473-8 (ISBN)
Public defence
2015-03-27, Seminar room Air på SciLifeLab, Science for Life Laboratory, Tomtebodavägen 23A, Solna, 13:00 (English)

QC 20150306

Available from: 2015-03-06 Created: 2015-03-04 Last updated: 2015-03-06Bibliographically approved

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