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Rational design of nanoparticles for biomedical imaging and photovoltaic applications
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis aims to rationally design nanoparticles and promote their applications in biomedical imaging and photovoltaic cells.

Quantum dots (QDs) are promising fluorescent probes for biomedical imaging. We have fabricated two types of MSA capped QDs: CdTe/ZnSe core/shell QDs synthesized via an aqueous method and CdTe QDs via a hydrothermal method. They present high quantum yields (QYs), narrow emission band widths, high photo- and pH-stability, and low cytotoxicity. QD-IgG probes were produced and applied for labeling breast cancer marker HER2 proteins on MCF-7 cells.

For the purpose of single molecule tracking using QDs as fluorescent probes, we use small affibodies instead of antibodies to produce QD-affibody probes. Smaller QD-target protein complexes are obtained using a direct immunofluorescence approach. These QD-affibody probes are developed to study the dynamic motion of single HER2 proteins on A431 cell membranes.

Fluorescence blinking in single QDs is harmful for dynamic tracking due to information loss. We have experimentally studied the blinking phenomenon and the mechanism behind. We have discovered an emission bunching effect that two nearby QDs tend to emit light synchronously. The long-range Coulomb potential induced by the negative charge on the QD surface is found to be the major cause for the single QD blinking and the emission bunching in QD pairs.

We have studied the in vitro cytotoxicity of CdTe QDs to human umbilical vein endothelial cells (HUVECs). The QDs treatment increases the intracellular reactive oxygen species (ROS) level and disrupts the mitochondrial membrane potential. The protein expression levels indicate that the mitochondria apoptosis is the main cause of HUVCEs apoptosis induced by CdTe QDs.

Gold nanorods (GNRs) are scattering probes due to their tunable surface plasmon resonance (SPR) enhanced scattering spectrum. In order to control the yield and morphology of GNRs, we have systematically studied the effects of composition and concentration in the growth solution on the quality of the GNRs produced via a seed-mediated method. The aspect ratios of GNRs were found to be linearly depended on the concentration ratio of silver ions and CTAB. The high quality GNRs obtained were adsorbed to COS-7 cell membranes for dark field imaging.

We have rationally designed two types of QDs by wave function engineering so as to improve the efficiency of QD-sensitized solar cells. A reversed type-I CdS/CdSe QD confines excitons in the shell region, whereas a type-II ZnSe/CdS QD separates electrons in the shell and holes in the core. Their absorbed photon-to-current efficiencies (APCE) are as high as 40% and 60% respectively.

In conclusion, rationally designed nanoparticles are proven a high potential for applications as probes in biomedical labeling, imaging and molecule tracking, and as sensitizers for photovoltaic cells.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011.
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-33346ISBN: 978-91-7415-973-8OAI: oai:DiVA.org:kth-33346DiVA: diva2:414548
Public defence
2011-05-24, FB52, AlbaNova, Roslagstullsbacken, Stockholm, 14:00 (English)
Opponent
Supervisors
Note
QC 20110511Available from: 2011-05-11 Created: 2011-05-03 Last updated: 2011-05-11Bibliographically approved
List of papers
1. Aqueous Synthesis and Fluorescence-Imaging Application of CdTe/ZnSe Core/Shell Quantum Dots with High Stability and Low Cytotoxicity
Open this publication in new window or tab >>Aqueous Synthesis and Fluorescence-Imaging Application of CdTe/ZnSe Core/Shell Quantum Dots with High Stability and Low Cytotoxicity
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2010 (English)In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, Vol. 10, no 3, 1741-1746 p.Article in journal (Refereed) Published
Abstract [en]

CdTe/ZnSe core/shell quantum dots were directly synthesized in an aqueous condition by heating a mixed solution of ZnCl2, NaHSe and CdTe QDs in the presence of mercaptosuccinic acid as a stabilizer. By controlling the size and composition, the CdTe/ZnSe QDs with emission wavelength ranging from 540 to 630 nm, high quantum yield (44%) and narrow full width at half maximum (FWHM) could be obtained. Characterization results with HRTEM, XRD and EDX have shown that the synthesized CdTe/ZnSe ON have good monodispersity and a nice crystal structure, and exhibited better stability and less cytotoxicity as compared with CdTe QDs. Furthermore, luminescent QD-IgG bioprobes were produced to detect the breast cancer marker Her2 on the surface of fixed MCF-7 cancer cells for their optical imaging.

Keyword
Optical Imaging, Quantum Dots, Aqueous Synthesis, Cytotoxicity, Stability, Fluorescence, Core-Shell Structure, cdte nanocrystals, in-vivo, room-temperature, size series, photoluminescence, photostability, nanoparticles, therapy, vitro
National Category
Chemical Sciences Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-19153 (URN)10.1166/jnn.2010.2049 (DOI)000273984800037 ()2-s2.0-77950955285 (ScopusID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-11-19Bibliographically approved
2. Highly stable and low toxic CdTe quantum dots synthesized via ahydrothermal method for cell imaging applications
Open this publication in new window or tab >>Highly stable and low toxic CdTe quantum dots synthesized via ahydrothermal method for cell imaging applications
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(English)Article in journal (Other academic) Submitted
Abstract [en]

Although biological applications of quantum dots (QDs) by now are widely recognized and reported, routine production of small-size water-soluble and stable QDs still remains a challenge. In the present work we highlight prospects offered by the hydrothermal method to synthesize water-soluble QDs. We illustrate the method by synthesizing CdTe QDs which process some outstanding properties like highly luminescent red emission and high stability over a wide pH range. Compared with those synthesized via the traditional aqueous method, we show that CdTe QDs synthesized via the hydrothermal method feature higher photostability and lower cytotoxicity. Based on such prepared CdTe QDs, luminescent QD-IgG bioprobes were produced to detect the breast cancer marker Her2 on the surface of MCF-7 cancer cells, indicating that such prepared QD systems are promising candidates for use as bioprobes.

National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-33344 (URN)
Note
QS 2011Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2013-11-19Bibliographically approved
3. Quantum dot-affibody fluorescence probes for single molecule tracking in living cell membranes
Open this publication in new window or tab >>Quantum dot-affibody fluorescence probes for single molecule tracking in living cell membranes
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-33314 (URN)
Note
QS 2011Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-05-11Bibliographically approved
4. Time correlation analysis of blinking from individual colloidalCdSe/CdS and CdSe/ZnS quantum dots
Open this publication in new window or tab >>Time correlation analysis of blinking from individual colloidalCdSe/CdS and CdSe/ZnS quantum dots
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(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-33315 (URN)
Note
QS 2011Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-05-11Bibliographically approved
5. An in vitro study of vascular endothelial toxicity of CdTe quantum dots
Open this publication in new window or tab >>An in vitro study of vascular endothelial toxicity of CdTe quantum dots
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2011 (English)In: Toxicology, ISSN 0300-483X, E-ISSN 1879-3185, Vol. 282, no 3, 94-103 p.Article in journal (Refereed) Published
Abstract [en]

Quantum dots (QDs), as novel bioimaging and drug delivery agents, are generally introduced into vascular system by injection, and thus directly exposed to vascular endothelial cells (ECs). However, the adverse effects of QDs on ECs are poorly understood. In this study, employing human umbilical vein ECs (HUVECs), we investigated the potential vascular endothelial toxicity of mercaptosuccinic acid (MSA)-capped CdTe QDs in vitro. In the experiment, water-soluble and pH stable CdTe QDs were synthesized; and the cell viability assays showed that CdTe QDs (0.1-100 mu g/mL) dose-dependently decreased the cell viability of HUVECs, indicating CdTe QDs induced significant endothelial toxicity. The flow cytometric and immunofluorescence results revealed that 10 mu g/mL CdTe QDs elicited significant oxidative stress, mitochondrial network fragmentation as well as disruption of mitochondrial membrane potential (Delta psi(m)); whereas ROS scavenger could protect HUVECs from QDs-induced mitochondrial dysfunction. Moreover, upon 24h exposure to 10 mu g/mL CdTe QDs, the apoptotic HUVECs dramatically increased by 402.01%, accompanied with alternative expression of apoptosis proteins, which were upregulation of Bax, down-regulation of Bcl-2, release of mitochondrial cytochrome c and cleavage of caspase-9/caspase-3. These results suggested that CdTe QDs could not only impair mitochondria but also exert endothelial toxicity through activation of mitochondrial death pathway and induction of endothelial apoptosis. Our results provide strong evidences of the direct toxic effects of QDs on human vascular ECs, and reveal that exposure to QDs is a significant risk for the development of cardiovascular diseases. These results also provide helpful guidance on the future safe use and manipulation of QDs to make them more suitable tools in nanomedicine.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
Quantum dots, Vascular endothelial cells, Apoptosi, s Mitochondrial dysfunction, Reactive oxygen species
National Category
Pharmacology and Toxicology
Identifiers
urn:nbn:se:kth:diva-33317 (URN)10.1016/j.tox.2011.01.015 (DOI)000289327500004 ()21291946 (PubMedID)2-s2.0-79952314659 (ScopusID)
Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2011-09-08Bibliographically approved
6. Controlling Yield and Morphology for GoldNanorods in a Seed-Mediated Synthesis Method forCell Imaging
Open this publication in new window or tab >>Controlling Yield and Morphology for GoldNanorods in a Seed-Mediated Synthesis Method forCell Imaging
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2010 (English)In: Advances in Optoelectronics and Micro/Nano-Optics (AOM), 2010 OSA-IEEE-COSArticle in journal (Refereed) Published
Abstract [en]

Designed experiments are carried out to systematically study the effects of silver ions on morphology and yield of gold nanorods synthesized via a seed-mediated method. Gold nanorods synthesized with different silver ions and CTAB concentrations were characterized by absorption spectroscopy and TEM. The shape and yield of gold nanorods were effectively controlled by adjusting the concentration ratio of CTAB and silver ions for synthesis. Dark field images of a glass slide sample with gold nanorods deposit and a sample with gold nanrods staining cells further confirmed that high quality gold nanorods were obtained.

Identifiers
urn:nbn:se:kth:diva-33345 (URN)10.1109/AOM.2010.5713561 (DOI)2-s2.0-79952836035 (ScopusID)
Note
QC 20110511Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2013-11-19Bibliographically approved
7. Wave-Function Engineering of CdSe/CdS Core/Shell Quantum Dots for Enhanced Electron Transfer to a TiO2 Substrate
Open this publication in new window or tab >>Wave-Function Engineering of CdSe/CdS Core/Shell Quantum Dots for Enhanced Electron Transfer to a TiO2 Substrate
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2010 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 35, 15184-15189 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we have synthesized a series of core/shell quantum dots (QDs) for the purpose of enhancing the electron transfer from the dots to a TiO2 substrate. We make use of the fact that CdSe is a small-bandgap material compared with CdS; therefore, in a common CdSe/CdS core/shell QD, the photo-excited electron is confined deeply in the CdSe core. By special construction of the CdS/CdSe core/shell QDs, referred as reversed type-I, the electron wave function will distribute largely in the shell region. This facilitates the transfer of the electron from the QD to the TiO2 substrate, resulting in significantly improved electron-injection efficiency. Such an enhanced electron-injection efficiency was confirmed by fluorescence lifetime decay measurements, showing the largest lifetime reduction after that the QDs were adsorbed on the TiO2 surface. The reversed type-I CdS/CdSe QDs show a much higher photon-to-current conversion efficiency than type-I CdSe/CdS and CdSe QDs without shell. Furthermore, by chemical-bath depositing of CdS on the QD-sensitized electrode to form a quantum-well structure, the electron recombination between the QDs and the redox couple was reduced, hence further enhancing the electron-injection efficiency. The absorbed-photon-to-current efficiency of the quantum well CdS/CdSe/CdS sensitized solar cells reaches a value as high as 60%.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-27683 (URN)10.1021/jp102978g (DOI)000284520100075 ()2-s2.0-77956966564 (ScopusID)
Funder
Swedish e‐Science Research Center
Note
QC 20101221Available from: 2010-12-21 Created: 2010-12-20 Last updated: 2012-05-22Bibliographically approved
8. Solar cells sensitized with type-II ZnSe-CdS core/shell colloidal quantum dots
Open this publication in new window or tab >>Solar cells sensitized with type-II ZnSe-CdS core/shell colloidal quantum dots
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2011 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 5, 1536-1538 p.Article in journal (Refereed) Published
Abstract [en]

Type-II quantum dots (QDs) were applied for QDs-sensitized solar cells for the first time and showed prominent absorbed photon to current conversion efficiency.

Keyword
SELF-ASSEMBLED LAYERS, SEMICONDUCTOR NANOCRYSTALS, TIO2 NANOSTRUCTURES, ELECTRON INJECTION, SHAPE CONTROL
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-30262 (URN)10.1039/c0cc03401k (DOI)000286389500042 ()2-s2.0-78751549134 (ScopusID)
Funder
Swedish e‐Science Research Center
Note
QC 20110222Available from: 2011-02-22 Created: 2011-02-21 Last updated: 2013-10-02Bibliographically approved

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