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Quantum dot biomarkers for tracking endothelial progenitor cells and activated endothelium
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of new visualization techniques is essential in the field of bioimaging to gain deeper knowledge about various medical and biological events at the cellular and molecular levels. Quantum dots (QDs) are semiconductor nanocrystals which are opening new perspectives in biotechnology due to their powerful optical properties and high stability.  Utilization of QDs instead of commonly used organic dyes in labeling techniques adds several advantages, such as longer signal observation time of the biological samples; convenient multicolor labeling; deep tissue and organ tracking. Furthermore, more information can be obtained about the environment where QDs are located by characterizing the optical behavior of the QDs.

In this thesis work carboxyl coated QDs were used to label endothelial progenitor cells (EPCs). EPCs play an important role in cardiovascular diseases and the repair of the damaged endothelium, therefore an efficient in vivo tracking method is essential to understand the therapeutic potential of these cells. Our findings show an effective, cytoplasmic labeling of EPCs. Cell viability assay shows that QDs are not toxic to the cells in the concentration and incubation time tested in the study and QDs does not change the cell functions.

Furthermore commercially available QDs were functionalized with VCAM-1 binding peptide (VCAM-1BP) to specifically detect activated endothelial cells and activated endothelial wall in the aorta. Endothelial wall of the arteries are activated with VCAM-1 in the early stages of atherosclerosis, therefore early detection of this chronic disease may be performed with VCAM-1BP functionalized QDs. We found that VCAM-1BP functionalized QDs were able to detect the activated endothelium specifically.

The optical behavior of the QDs in different conditions and bio-systems were also characterized. It was found that several circumstances like different coating ligands can modify the fluorescence of the QDs. We observed that QD fluorescence intensity changes with different concentrations of Na+ and K+. We also found that significant blue-shift in QD peak emission occurs when QDs are internalized by cells and when functionalized QDs interact with cell surface molecule.

This thesis work provides efficient labeling techniques for cells and tissues with QDs and important knowledge about the optical behavior of QDs in bio-systems. These results give further perspectives to the future application of QD biomarkers as tracking agent and optical sensors for the different environmental changes in bio-systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 52 p.
Series
Trita-BIO-Report, ISSN 1654-2312
Keyword [en]
quantum dots, bioimaging, endothelium, adult stem cells, confocal microscopy
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-33295ISBN: 978-91-7415-929-5 (print)OAI: oai:DiVA.org:kth-33295DiVA: diva2:414273
Public defence
2011-05-25, FA 51, Roslagstullsbacken, AlbaNova, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20110505Available from: 2011-05-05 Created: 2011-05-02 Last updated: 2011-05-12Bibliographically approved
List of papers
1. Optical characterization of colloidal CdSe quantum dots in endothelial progenitor cells
Open this publication in new window or tab >>Optical characterization of colloidal CdSe quantum dots in endothelial progenitor cells
2010 (English)In: Journal of nanobiotechnology, ISSN 1477-3155, Vol. 8, no 1, 2- p.Article in journal (Refereed) Published
Abstract [en]

ABSTRACT: We have quantitatively analyzed the confocal spectra of colloidal quantum dots (QDs) in rat endothelial progenitor cells (EPCs) by using Leica TCS SP5 Confocal Microscopy System. Comparison of the confocal spectra of QDs located inside and outside EPCs revealed that the interaction between the QDs and EPCs effectively reduces the radius of the exciton confinement inside the QDs so that the excitonic energy increases and the QD fluorescence peak blueshifts. Furthermore, the EPC environment surrounding the QDs shields the QDs so that the excitation of the QDs inside the cells is relatively weak, whereas the QDs outside the cells can be highly excited. At high excitations, the occupation of the ground excitonic state in the QD outside the cells becomes saturated and high-energy states excited, resulting in a large relaxation energy and a broad fluorescence peak. This permits, in concept, to use QD biomarkers to monitor EPCs by characterizing QD fluorescence spectra.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-33376 (URN)10.1186/1477-3155-8-2 (DOI)20205887 (PubMedID)2-s2.0-77249151840 (Scopus ID)
Note
QC 20110505Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2011-05-05Bibliographically approved
2. Effects of Quantum Dot Labeling on Endothelial Progenitor Cell Function and Viability
Open this publication in new window or tab >>Effects of Quantum Dot Labeling on Endothelial Progenitor Cell Function and Viability
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2010 (English)In: Cell Medicine, ISSN 2155-1790, E-ISSN 2155-1790, Vol. 1, no 2, 105-112 p.Article in journal (Refereed) Published
Abstract [en]

Endothelial progenitor cells (EPC) play an important role in repairing damaged endothelium. An effective imaging method for in vivo tracking of EPCs is essential for understanding EPC-based cell therapy. Fluorescent quantum dots (QDs) have attractive optical characteristics such as extreme brightness and photostability. QDs are currently being investigated as probes for stem cell labeling; however, there is concern about whether QDs can be used safely. We investigated whether quantum dot (QD) labeling would influence EPC viability and function. Rat bone marrow-derived EPCs were cultured and characterized. The cells were labeled with near-infrared-emitting, carboxyl-coated QDs (8 nM) for 24 h. QD labeling efficiency was higher than 97%. Using WST-1 assay, we showed that the viability of the QD-labeled EPCs was not different from that of the control EPCs. Moreover, QD labeling did not influence the ability of EPCs to form capillary tubes on Matrigel and to migrate. The percentage of QD-positive cells decreased with time, probably due to the rapid division of EPCs. These data suggest that the carboxyl-coated QD705 can be useful for labeling EPCs without interrupting their viability and functions.

Keyword
Endothelial progenitor cells, Quantum dots; Cell labeling, Migration, Capillary tube formation
National Category
Biological Sciences
Identifiers
urn:nbn:se:kth:diva-33390 (URN)10.3727/215517910X451603 (DOI)
Note

QC 20110505

Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2017-01-10Bibliographically approved
3. Role of surface ligands in optical properties of colloidal CdSe/CdS quantum dots
Open this publication in new window or tab >>Role of surface ligands in optical properties of colloidal CdSe/CdS quantum dots
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2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 13, 5848-5854 p.Article in journal (Refereed) Published
Abstract [en]

In order to study the role of surface ligands in determining optical properties of colloidal quantum dots (QDs), we have selectively fabricated and studied CdSe/CdS core-shell QDs with strongly confined electron and hole states attached with commonly used surface ligands. Optical properties, viz. absorption and fluorescence of these QDs, are characterized from which salient changes have been observed for different ligand substitutions which, through theoretical analysis, can be associated with electronic structure properties of the QD-ligand composite systems, in particular localization of wave functions of electrons and holes in the QDs and the band matching of the HOMO-LUMO gap of the ligands. The findings can be utilized to facilitate the understanding and optimization of properties of QD biomarkers with functionalizing surface ligands for targeting cellular objects.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-33395 (URN)10.1039/c0cp02688c (DOI)000288447100043 ()2-s2.0-79952722232 (Scopus ID)
Funder
Swedish e‐Science Research Center
Note

QC 20110505

Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2017-03-01Bibliographically approved
4. Effects of K+ and Na+ ions on the fluorescence of colloidal CdSe/CdS and CdSe/ZnS quantum dots
Open this publication in new window or tab >>Effects of K+ and Na+ ions on the fluorescence of colloidal CdSe/CdS and CdSe/ZnS quantum dots
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2011 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 155, no 2, 823-830 p.Article in journal (Refereed) Published
Abstract [en]

In this work we studied the effects of K+ and Na+ ions on fluorescence properties of the colloidal quantum dots (QDs). It was found that the fluorescence intensity was enhanced when low concentration of ions was introduced to QD solutions, while it became weakened when ion concentrations reached their physiological levels in many bio environments. Such fluorescence changes can be attributed to interactions between QD surface ligands and ions as well as the Coulomb potential of ions that displaces the wave functions of the electron and hole confined inside the QD. These results are important for understanding the influence of different biological environments, such as extracellular and intracellular compartments, on optical properties of colloidal QDs.

Keyword
Colloidal quantum dots (QDs), Fluorescence properties of QDs, Electron and hole confinements in QDs, Effects of K+ and Na+ ions
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-33396 (URN)10.1016/j.snb.2011.01.055 (DOI)000291774100055 ()2-s2.0-79957805848 (Scopus ID)
Note

QC 20110705

Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2016-12-22Bibliographically approved
5. Significant blue-shift of luminescence peak from VCAM-1-binding peptide-functionalized quantum dots upon binding with VCAM-1
Open this publication in new window or tab >>Significant blue-shift of luminescence peak from VCAM-1-binding peptide-functionalized quantum dots upon binding with VCAM-1
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(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-33397 (URN)
Note
QS 2011Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2011-05-05Bibliographically approved
6. Molecular imaging of inflammation-activated endothelium using bio-conjugated quantum dots
Open this publication in new window or tab >>Molecular imaging of inflammation-activated endothelium using bio-conjugated quantum dots
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-33405 (URN)
Note
QS 2011Available from: 2011-05-05 Created: 2011-05-05 Last updated: 2011-05-05Bibliographically approved

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