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Complexes That Are Potential Photoactivated Cisplatin

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Complexes That Are Potential Photoactivated Cisplatin Ru(II) COMPLEXES AS PHOTOACTIVATED CISPLATIN ANALOGS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Tanya N. Singh, M.S. * * * * * The Ohio State University 2006 Dissertation Committee: Approved by Professor Claudia Turro, Adviser Professor Malcolm Chisholm ________________________ Professor Yiying Wu Adviser Graduate Program in Chemistry ABSTRACT Cisplatin is an anticancer drug that is used in the treatment of various cancers; however, its toxicity towards healthy cells and its acquired resistance are problems that need to be overcome. Photodynamic therapy (PDT) is a treatment that combines the action of a light source and a photosensitizing agent to kill cancerous cells. Typical PDT methods require the photoreaction of singlet oxygen through energy transfer from an excited state, which results in oxidative damage to the cells. The need for molecular oxygen in the vicinity of the drug is a major drawback, since malignant and drug resistant cells are often hypoxic. Hence the design and DNA interactions of Ru(II) complexes that combines the mode of action of cisplatin with PDT will be investigated. 2+ 2+ Cis-[Ru(bpy)2(NH3)2] and cis-[Ru(bpy)2(CH3CN)2] were synthesized and their DNA binding to single stranded and double stranded DNA and to the DNA bases; 9- ethylyguanine and 9-methylguanine were investigated. Irradiating cis- 2+ [Ru(bpy)2(CH3CN)2] in water resulted in the formation of the bisaqua complex, cis- 2+ [Ru(bpy)2(OH)2] with quantum yields of φ350 = 0.377(3), φ400 = 0.207(1), φ450 = 2+ 0.222(18) whereas irradiation of cis-[Ru(bpy)2(NH3)2] in water resulted in quantum yields of φ350 = 0.024(2) and φ400 = 0.018. The higher quantum yield of photoaqaution 2+ observed upon irradiation of cis-[Ru(bpy)2(CH3CN)2] resulted in greater covalent DNA binding to both single and double stranded DNA. Binding of both complexes to 9- ii ethylguanine and 9-methyl guanine was also observed upon irradiation but not in the dark. + + The photolysis of cis-[Ru(phpy)(bpy)(CH3CN)2] and [Ru(phpy)CH3CN)4] in (II),(II) aqueous solution with λirr> 420 nm results in the formation of μ-oxo dimers of Ru of II II + molecular formula [(H2O)(bpy)(phpy)Ru ORu (phpy)(bpy)(OH2)]H .H2O and (II) (II) + [(CH3CN)(H2O)(phpy)Ru ORu (phpy)(H2O)(CH3CN)]H .H2O respectively. Cis- + + [Ru(phpy)(bpy)(CH3CN)2] and [Ru(phpy)CH3CN)4] bind to 9-ethylguanine and 9- + methylguanine upon irradiation. Binding of [Ru(phpy)CH3CN)4] to single stranded 15 mer DNA sequences was observed upon irradiation with λirr> 420 nm, however, no binding to single stranded DNA was observed upon irradiation of cis- + [Ru(phpy)(bpy)(CH3CN)2] . No binding to double stranded DNA was observed upon + + irradiation of cis-[Ru(phpy)(bpy)(CH3CN)2] and [Ru(phpy)(CH3CN)4] with λirr> 420 nm. Compound containing oxygen in the coordination sphere of ruthenium was studied as PDT agents. Cis-[Ru(quo)2(py)2] was observed to bind to 15-mer DNA sequences upon irradiation in aqueous solution with λirr > 345 nm. Binding to duplex DNA was observed upon irradiation of cis-[Ru(quo)2(py)2] with λirr> 345 nm. Irradiation of cis-[Ru(quo)2(py)2] with 395 nm < λirr < 420 nm also resulted in the metal complex binding to DNA, however, to a lesser extent. Theses results provide the way for the development of new metal complexes that can be better utilized to achieve the wavelength required for PDT. iii Dedicated to my Family, especially to my Loving Mother who passed away on June 30, 2003. iv ACKNOWLEDGMENTS The encouragement, advice and support from various people have this dissertation possible, without them there is no way that I would have been able to have made such an accomplishment. First and foremost, I want to express my greatest appreciation to my adviser, Dr. Claudia Turro, for her patience, guidance and support in making this dissertation possible and for spending her timeless effort in correcting and making suggestions to improve my scientific writing. She always instills in me and my group members to think independently and critically and to try and solve problems concerning our research, which are major components of attaining this level of confidence which is worthwhile for achieving this degree and for that I will always be thankful. I also want to thank Dr. Latif Chouai from Dr. Kim Dunbar’s group at Texas A & M University who synthesized some of the compounds that I worked with for my dissertation. I also want to thank Dr. Yoa Lui for intelligent discussions and for teaching and helping me to understand and do electrochemical measurements, low temperature emission and lifetime measurements. He was always willing to help me whenever I asked for help. v I have to say a big thank you to my family and friends who have supported me in my decision to continue graduate school and for there encouragement and kind words when things got rough especially having to deal with the death of my Mom during my third year here at OSU and my Dad having a heart attack shortly after that. The one thing that my Mom had always longed for and hoped for was to be there when I graduate with my PhD. Today she is not here in flesh but I know that her spirit is here and will always be with me and she will forever hold a special place in my heart. I am so grateful to my sister, Nardia, and brother, Garry who always seems to be the stronger one emotionally even though they are the youngest and for helping me to deal with hard times and for my Dad who always puts on a brave face to put a smile on my face in difficult times. Lastly, I would like to thank Aaron Rachford for his patience and understanding in listening to my research frustrations and for his suggestions. He was always kind and very warm hearted and always takes the time to listen to me without any complaint even though I am sure he must have been dealing with his own research frustrations because being a graduate student himself, it is almost impossible to not have any research frustrations. Throughout all this, he always cares and supports me in my decisions. vi VITA March 21, 1977…………………………. Born - St. Elizabeth, Jamaica 1995-1999………………………………... B.S. Chemistry and Biochemistry, University of the West Indies (UWI) 1999-2000……………………………….... Organic Chemistry Graduate Student (UWI) 2000-2002 M.S. Chemistry, The Ohio State University 2000-Present………………………….…… Graduate Teaching and Research Associate, The Ohio State University PUBLICATIONS Research Publication 1. Photoinduced DNA Binding by a Ru(II) Complex: A Photo-Cisplatin Analog" Tanya N. Singh and Claudia Turro, Inorg. Chem., 2004, 43, 7260-7262. FIELDS OF STUDY Major Field: Chemistry vii TABLE OF CONTENTS Abstract............................................................................................................................... ii Acknowledgments................................................................................................................v Vita ............................................................................................................................... vii List of Tables ..................................................................................................................... xi List of Scheme ................................................................................................................. xiii List of Figures.................................................................................................................. xiv Chapters 1. Introduction..............................................................................................................1 1.1. Cisplatin ............................................................................................................1 1.2. Interaction of cisplatin with DNA.....................................................................2 1.3. Photodynamic Therapy .....................................................................................4 References.......................................................................................................10 2. Background............................................................................................................14 2.1. Photophysical Properties and Photochemistry of Ru(II) polypyridyl complexes ........................................................................................................14 2.2. Photochemistry of Ruthenium Ammine Complexes ......................................21 2.3. Covalent DNA Binding...................................................................................29 References..............................................................................................................34 3. Experimental Section.............................................................................................39 3.1. Materials.........................................................................................................39 3.2. Instrumentation ...............................................................................................44 3.3. Methods...........................................................................................................46 viii References..............................................................................................................50 2+ 2+ 4 Photoreactivity of cis-[Ru(bpy)2(CH3CN)2] and cis-[Ru(bpy)2(NH3)2] ……...51 4.1. Electronic Absorption and Emission………………………………………..51 4.2. Photochemistry in Solution.............................................................................52
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