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Pullulan Ω-Carboxyalkanoates for Drug Nanodispersions Jameison T

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Pullulan Ω-Carboxyalkanoates for Drug Nanodispersions Jameison T Pullulan ω-carboxyalkanoates for Drug Nanodispersions Jameison Theophilus Rolle Thesis submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science In Macromolecular Science and Engineering Kevin J. Edgar, Committee Chair Richey Davis Lynne S. Taylor July 30th, 2015 Blacksburg, VA Keywords: pullulan, amorphous solid dispersions, carboxyalkanoates, drug delivery Copyright 2015, Jameison T. Rolle Pullulan ω-carboxyalkanoates for Drug Nanodispersions Jameison T. Rolle Abstract Pullulan is an exopolysaccharide secreted extracellularly by the black yeast-like fungi Aureobasidium pullulans. Due to an α-(1→6) linked maltotriose repeat unit, which interferes with hydrogen bonding and crystallization, pullulan is completely water soluble unlike cellulose. It has also been tested and shown to possess non-toxic, biodegradable, non-mutagenic and non- carcinogenic properties. Chemical modification of polysaccharides to increased hydrophobicity and increase functionality has shown great promise in drug delivery systems. Particularly in amorphous solid dispersion (ASD) formulations, hydrophobicity increases miscibility with hydrophobic, crystalline drugs and carboxy functionality provides stabilization with drug moieties and well as pH specific release. Successful synthesis of cellulose ω-carboxyalkanoates have been reported and showed great promise as ASD polymers based on their ability to retard the recrystallization of the HIV drug ritonavir and antibacterial clarithromycin. However, these cellulose derivatives have limitations due to their limited water solubility. Natural pullulan is water-soluble and modification with ω-carboxyalkanoate groups would provide a unique set of derivatives with increased solubility therefore stronger polymer-drug interactions in solution. We have successfully prepared novel pullulan ω-carboxyalkanoates, which exhibit good solubility in polar aprotic and polar protic solvents. All derivatives exhibit high thermal stability and most recorded high glass transition temperatures. Due to unknown impact of their three dimensional structure on miscibility and stabilization of drug against crystallization, each of these polymers possesses great potential for use in various drug delivery applications. Dedication This thesis is dedicated to my parents and family members who were always so supportive of my decisions and always encouraged me to continue to do my best. iii Acknowledgements I would first like to give thanks and praise to God, because without Him none of this would have been possible and it is because of Him, through stressful and doubtful times that I was able to get through. I would also like to thank my advisor Dr. Kevin Edgar for allowing me the opportunity to work with his group during my time here at Virginia Tech. He has always believed in me and always made me feel A LOT less stressed after our research update meetings. I am truly thankful for all the advice he has given over these past 2 ½ years and although I am not pursuing a PhD, I am grateful for him being so supportive with my decision to attend medical school. I will always cherish the moments that I have been blessed to work with him and I am thankful for all I have learned. I would also like to thank Dr. Richey Davis and Dr. Lynne Taylor for serving as members of my committee and for their support and guidance. I would like to that Dr. Judy Riffle and all of my classmates in the Fall 2013 MACR class. They made the transition from undergraduate to graduate life so smooth, I will cherish all of these friendships, and the memories made studying for those MACR exams. I would also like to thank all the members of the Edgar Research Group. We have had so much fun during my time here and I am deeply appreciative of the support of each of them. I am so happy to have been able to become such close friends and I hope that they all continue to strive for excellence. I thank them for all their guidance and direction and wish them the very best. Finally, I would like to that the Institute for Critical Technology and Applied Science (ICTAS), Macromolecules and Interfaces Institute (MII), the Department of Sustainable Biomaterials and the National Science Foundation (NSF) for all of their support during my time at Virginia Tech. Thank You Everyone!!! iv Table of Contents Abstract ................................................................................................................................ ii Dedication ............................................................................................................................ iii Acknowledgements .............................................................................................................. iv List of Figures ...................................................................................................................... vii List of Tables ........................................................................................................................ ix CHAPTER 1: Introduction ....................................................................................................... 1 CHAPTER 2: Review of Literature ........................................................................................... 4 2.1 History of Pullulan ......................................................................................................................... 4 2.2 Production of Pullulan .................................................................................................................. 5 2.3 Properties and Applications of Pullulan ........................................................................................ 9 2.4 Chemical Modification ................................................................................................................ 11 2.5 Drug Delivery............................................................................................................................... 22 2.6 Conclusion ................................................................................................................................... 26 2.7 References .................................................................................................................................. 27 CHAPTER 3: Synthesis of Pullulan ω-carboxyalkanoates for Drug Nanodispersions ............... 38 3.1 Abstract ....................................................................................................................................... 38 3.2 Introduction ................................................................................................................................ 38 3.3 Experimental ............................................................................................................................... 42 3.3.1 Materials ............................................................................................................................ 43 3.3.2 Measurements ................................................................................................................... 43 3.3.3 Synthesis ............................................................................................................................. 45 3.4 Results and Discussion ................................................................................................................ 50 3.4.1 Synthesis of pullulan ω-carboxyalkanoates ............................................................................... 50 3.4.2 Thermal properties .................................................................................................................... 57 3.4.3 Solubility ..................................................................................................................................... 60 3.4.4 Solubility parameters ................................................................................................................. 61 3.5. Conclusion ................................................................................................................................... 62 3.6 Acknowledgements ..................................................................................................................... 63 3.7 References .................................................................................................................................. 63 CHAPTER 4: Summary and Future Works ............................................................................. 67 4.1 Summary ..................................................................................................................................... 67 v 4.2 Future Works .............................................................................................................................. 68 4.2.1 Synthesis of pullulan ω-carboxyalkanoates by olefin cross-metathesis (OCM) ................. 68 4.2.2 Amorphous Solid Dispersions ............................................................................................. 69 4.2.3 Other Uses........................................................................................................................... 71 4.3 References .................................................................................................................................. 72 APPENDIX............................................................................................................................ 73 vi
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