Quantum Dots Targeted to VEGFR2 for Molecular Imaging of Colorectal Cancer

Persistent Link:
http://hdl.handle.net/10150/565917
Title:
Quantum Dots Targeted to VEGFR2 for Molecular Imaging of Colorectal Cancer
Author:
Carbary, Jordan Leslie
Issue Date:
2015
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Advances in optical imaging have provided methods for visualizing molecular expression in tumors in vivo, allowing the opportunity to study the complexity of the tumor microenvironment. The development of fluorescent contrast agents targeted to molecules expressed in cancer cells is critical for in vivo imaging of the tumors. Contrast agents emitting in the near infrared (NIR) allow for an increased depth of penetration in tissue due to decreased absorption and scattering. There is also significantly less autofluorescence from tissue in the NIR. Quantum dots are nanoscopic particles of semiconductors whose fluorescent emission wavelength is tunable by the size of the particle with desirable fluorescent qualities such as a wide range of excitation wavelengths, a narrow emission band, high quantum efficiency, high photostablility, and they can be produced to emit throughout the NIR imaging window. It has been shown that vascular endothelial growth factor receptor 2 (VEGFR2) is upregulated in many cancers, including colorectal, as it is important in tumor angiogenesis and is considered a predictor for clinical outcome and, in some instances, is used for targeted therapy with anti-angiogenic drugs. For these reasons, quantum dots bioconjugated to VEGFR2 antibodies have the potential to provide contrast between normal tissue and cancer, as well as a mechanism for evaluating the molecular changes associated with cancer in vivo. In this dissertation, we present on the design of two contrast agents using quantum dots targeted to VEGFR2 for use in the molecular imaging of colon cancer, both ex vivo and in vivo. First, as a preliminary ex vivo investigation into their efficacy, Qdot655® (655nm emission) were bioconjugated to anti-VEGFR2 antibodies through streptavidin/biotin linking. The resulting QD655-VEGFR2 contrast agent was used to label colon adenoma in vivo and imaged ex vivo with significant increase in contrast between diseased and undiseased tissue, allowing for fluorescence based visualization of the VEGFR2 expressing diseased areas of the colon with high sensitivity and specificity. Then, QD655-VEGFR2 was used in a longitudinal in vivo study to investigate ability to correlate fluorescence signal to tumor development over time using optical coherence tomography and laser induced fluorescence spectroscopy (OCT/LIF) dual-modality imaging. The contrast agent was able to target VGEFR2 expressing diseased areas of colon; however, challenges in fully flushing the unbound contrast agent from the colon before imaging arise when moving from ex vivo imaging to in vivo image. Lastly, lead sulfide (PbS) quantum dots were made by colloidal synthesis to emit at a 940 nm (QD940) and conjugated to anti-VEGFR2 primary antibodies through streptavidin/biotin linking. The resulting QD940-VEGFR2 contrast agent was then used to label cells in vitro. The QD940-VEGFR2 molecules were able to positively label VEGFR2 expressing cells and did not label VEGFR2 negative cells. Very low photoluminescence and large amounts of aggregation after conjugation of the quantum dot to streptavidin was detected. Improvements to the quantum dot stability through synthesis, capping and conjugation techniques must be made for this contrast agent to be effective as a contrast agent for cancer imaging.
Type:
text; Electronic Dissertation
Keywords:
Molecular imaging; Quantum dots; VEGFR2; Biomedical Engineering; Colorectal cancer
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Biomedical Engineering
Degree Grantor:
University of Arizona
Advisor:
Utzinger, Urs

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleQuantum Dots Targeted to VEGFR2 for Molecular Imaging of Colorectal Canceren_US
dc.creatorCarbary, Jordan Leslieen
dc.contributor.authorCarbary, Jordan Leslieen
dc.date.issued2015en
dc.publisherThe University of Arizona.en
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en
dc.description.abstractAdvances in optical imaging have provided methods for visualizing molecular expression in tumors in vivo, allowing the opportunity to study the complexity of the tumor microenvironment. The development of fluorescent contrast agents targeted to molecules expressed in cancer cells is critical for in vivo imaging of the tumors. Contrast agents emitting in the near infrared (NIR) allow for an increased depth of penetration in tissue due to decreased absorption and scattering. There is also significantly less autofluorescence from tissue in the NIR. Quantum dots are nanoscopic particles of semiconductors whose fluorescent emission wavelength is tunable by the size of the particle with desirable fluorescent qualities such as a wide range of excitation wavelengths, a narrow emission band, high quantum efficiency, high photostablility, and they can be produced to emit throughout the NIR imaging window. It has been shown that vascular endothelial growth factor receptor 2 (VEGFR2) is upregulated in many cancers, including colorectal, as it is important in tumor angiogenesis and is considered a predictor for clinical outcome and, in some instances, is used for targeted therapy with anti-angiogenic drugs. For these reasons, quantum dots bioconjugated to VEGFR2 antibodies have the potential to provide contrast between normal tissue and cancer, as well as a mechanism for evaluating the molecular changes associated with cancer in vivo. In this dissertation, we present on the design of two contrast agents using quantum dots targeted to VEGFR2 for use in the molecular imaging of colon cancer, both ex vivo and in vivo. First, as a preliminary ex vivo investigation into their efficacy, Qdot655® (655nm emission) were bioconjugated to anti-VEGFR2 antibodies through streptavidin/biotin linking. The resulting QD655-VEGFR2 contrast agent was used to label colon adenoma in vivo and imaged ex vivo with significant increase in contrast between diseased and undiseased tissue, allowing for fluorescence based visualization of the VEGFR2 expressing diseased areas of the colon with high sensitivity and specificity. Then, QD655-VEGFR2 was used in a longitudinal in vivo study to investigate ability to correlate fluorescence signal to tumor development over time using optical coherence tomography and laser induced fluorescence spectroscopy (OCT/LIF) dual-modality imaging. The contrast agent was able to target VGEFR2 expressing diseased areas of colon; however, challenges in fully flushing the unbound contrast agent from the colon before imaging arise when moving from ex vivo imaging to in vivo image. Lastly, lead sulfide (PbS) quantum dots were made by colloidal synthesis to emit at a 940 nm (QD940) and conjugated to anti-VEGFR2 primary antibodies through streptavidin/biotin linking. The resulting QD940-VEGFR2 contrast agent was then used to label cells in vitro. The QD940-VEGFR2 molecules were able to positively label VEGFR2 expressing cells and did not label VEGFR2 negative cells. Very low photoluminescence and large amounts of aggregation after conjugation of the quantum dot to streptavidin was detected. Improvements to the quantum dot stability through synthesis, capping and conjugation techniques must be made for this contrast agent to be effective as a contrast agent for cancer imaging.en
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectMolecular imagingen
dc.subjectQuantum dotsen
dc.subjectVEGFR2en
dc.subjectBiomedical Engineeringen
dc.subjectColorectal canceren
thesis.degree.namePh.D.en
thesis.degree.leveldoctoralen
thesis.degree.disciplineGraduate Collegeen
thesis.degree.disciplineBiomedical Engineeringen
thesis.degree.grantorUniversity of Arizonaen
dc.contributor.advisorUtzinger, Ursen
dc.contributor.committeememberUtzinger, Ursen
dc.contributor.committeememberBarton, Jennifer K.en
dc.contributor.committeememberRomanowski, Mareken
dc.contributor.committeememberLynch, Ronalden
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