Synthesis and biological studies of a fullerene-Taxol conjugate and fullerene-based transfection vectors

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Title: Synthesis and biological studies of a fullerene-Taxol conjugate and fullerene-based transfection vectors
Author: Zakharyan, Tatiana Yurievna
Advisor: Wilson, Lon J.
Degree: Doctor of Philosophy thesis
Abstract: Fullerene (C60) derivatives have been extensively studied for a variety of medical applications, which include neuroprotective agents, HIV-1 protease inhibitors, photosensitizers for photodynamic therapy, MRI contrast agents, and radiopharmaceuticals. The first part of this work is dedicated to the development of a new application of C60 as a slow-release system for the liposome aerosol delivery of lipophilic chemotherapeutics to lung cancer. TaxolRTM (paclitaxel), one of the most active anticancer drugs in clinical use, has shown significant potential for treatment of lung cancer when delivered by the liposome aerosol method. However, rapid clearance of Taxol from the lungs (within 40 minutes after cessation of aerosol delivery) results in its reduced therapeutic efficacy. A C60-Taxol conjugate, a slow-release drug, has been designed and synthesized as a prospective solution to the problem. The conjugate was designed to have no intrinsic activity by modifying 2'-hydroxyl group of Taxol and to release the active drug via enzymatic hydrolysis of a 2'-ester bond. The conjugate synthesis involved the synthesis of Taxol-2'-succinate and a fullerene aminoderivative and then coupling them with EEDQ. Although very stable as a 10% DMSO solution at physiological pH, the C60-Taxol conjugate demonstrated the ability to release Taxol in the presence of bovine plasma with the hydrolysis half-life of about 80 minutes. The conjugate was also shown to form a stable liposome formulation using dilaurylphosphatidylcholine (DLPC), and as a DLPC suspension, demonstrated cytotoxic activity comparable to that of Taxol in human epithelial lung carcinoma A549 cells. With both clinically-relevant kinetics of hydrolysis and significant cytotoxicity in tissue culture, the conjugate holds promise for enhanced therapeutic efficacy of Taxol in vivo. The second part of this work is dedicated to the design and synthesis of C60-based transfection vectors in order to establish a structure-activity relationship (SAR) profile for this class of compounds. Several positively-charged derivatives of C60 were synthesized via Bingel and Prato chemistry and tested for transfection activity in HEK293 cells. Out of the three studied derivatives, only Bingel bisadducts permitted effective gene delivery. The maximum of protein expression was observed after 5 days of incubation which is consistent with the results reported for other known C60-based transfection vectors. The comparison of the structures of fullerene derivatives now known to permit effective gene delivery reveal similar structural features which can guide the design of potential C60-based transfection vectors.
Citation: Zakharyan, Tatiana Yurievna. (2006) "Synthesis and biological studies of a fullerene-Taxol conjugate and fullerene-based transfection vectors." Doctoral Thesis, Rice University.
Date: 2006

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