A novel solubilisation technique based on poly(y-glutamic acid) for the delivery of amphotericin B and anticancer agents Tan Dinh For the degree of Doctor of Philosophy Faculty of Science, The School of Pharmacy 29/39 Brunswick Square, London WCIN 1 AX ProQuest Number: 10104154 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10104154 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Plagiarism Statement This thesis describes the research conducted in the School of Pharmacy, University of London between March 2007 and March 2011 under the supervision of Dr Satyanarayana Somavarapu and Professor Steve Brocchini. I certify that the research described is original and that any parts of the work that have been conducted by collaboration are clearly indicated. I also certify that I have written all the text herein and have clearly indicated by suitable citation any part of this dissertation that has already appeared in publication. Signature 03 0 3 . tp \i^ Date Acknowledgements I would like to thank my supervisors Dr Satyanarayana Somavarapu and Professor Steve Brocchini for their guidance and support throughout the project. I would also like to express my gratitude to a number of important people who provided me with their technical expertise including Dr. Paul Stapleton for his assistance with the antifungal assays, Dr Ruchi Singh for her general advice and Dr Mohammad Owais and his research team for the animal studies of the AmB complexes. Last but not least, I would like to thank all my colleagues and staff with whom I shared four memorable years at SOP. Abstract Improving the water solubility of hydrophobic drugs still remains one of the foremost important issues in the formulation of a dmg. This thesis describes a novel complexation method based on biodegradable poly(y-glutamic acid) (PGA) for the effective solubilisation and delivery of the hydrophobic antifungal drug amphotericin B. Poly(y-glutamic acid) is a biosynthetic polymer derived from Bacillus anthracis and is known to be biocompatible and non-toxic towards humans and the environment; the sodium salt of which is highly water soluble. The preparation of an amphotericin B complex comprises of three steps: (i) initially the molecular weight reduction of PGA from 1500 kDa to 30-110 kDa by alkaline hydrolysis followed by (ii) hydrophobisation of PGA by activation with A-hydroxysuccinimide and then (iii) the complexation of amphotericin B with PGA to produce a highly water soluble PGA/amphotericin B complex. The complex shows attenuated toxicity compared with traditional amphotericin B deoxyeholate (Fungizone®) and comparable to the liposomal amphotericin B formulation (Ambisome®). The complex retains its broad- spectrum antifungal activity against Candida sp. In comparison to amphotericin B deoxyeholate, the Amphotericin B complexes show a marked reduction in the pro- inflammatory response which is thought to be responsible for infusion-related adverse effects. The complex shows enhanced uptake by macrophage which may further contribute towards the lower toxicity of the complex. In vivo studies demonstrate that AmB complexes to be more effective than Fungizone® with the complex constructed from the high molecular weight PGA the most efficacious. Analyses by Differential Scanning Calorimetry and X-Ray Powder Diffraction show that the complex is amorphous in nature although it proves to be stable for more than 6 months at 4^C and more than two months at 37®C. Finally, water solubility of chemotherapeutic agents such as SN-38, etoposide and resveratrol could also be improved using the same concept. Table of contents 1. CHAPTER I ..............................................................................................................15 General introduction..................................................................................................... 15 1.1. Solubilisation techniques for poorly water-soluble drugs............................ 15 1.2. Drug delivery systems.........................................................................................17 1.2.1. Micelles and polymeric micelles ..................................................................17 1.2.1.1. Micelles ................................................................................................... 17 1.2.1.2. Polymeric micelles ................................................................................. 18 1.2.2. Emulsions, Microemulsions and Nanoemulsions ........................................21 1.2.2.1. Emulsions ................................................................................................21 1.2.2.2. Microemulsions...................................................................................... 22 1.2.2.3. Nanoemulsions....................................................................................... 23 1.2.3. Complexes .....................................................................................................24 1.2.4. Solid dispersions ........................................................................................... 26 1.2.4.1. The amorphous form s ............................................................................27 1.2.5. Liposomes ......................................................................................................28 1.2.5.1. Mechanism of lipid bilayer formation ...................................................28 1.2.6. Solubilisation based on polymer technology ...............................................29 1.2.6.1. The applications of polymers in drug delivery .................................... 29 1.2.6.2. Advantages and disadvantages of drug delivery using polymers 31 1.3. PoIy(y-glutamic acid) (PGA).............................................................................34 1.3.1. Introduction to PGA ...................................................................................... 34 1.3.2. Production of PGA ........................................................................................ 35 1.3.3. Molecular weight of PGA .............................................................................36 1.3.4. Physicochemical and biological properties of PGA ................................... 38 1.3.5. Biological safety of PGA ..............................................................................41 1.3.6. Applications of PGA ..................................................................................... 42 1.3.6.1. PGA in the food industries.....................................................................42 1.3.6.2. PGA in the cosmetic industries............................................................. 43 1.3.6.3. PGA and environmental applications ...................................................43 1.3.6.4. Biomedical applications of PGA ........................................................... 44 1.3.7. PGA in drug delivery .................................................................................... 45 1.3.7.1. Protein delivery......................................................................................46 1.3.7.2. Gene delivery......................................................................................... 47 1.3.7.3. Vaccine delivery.....................................................................................48 1.3.7.4. Anticancer drug delivery........................................................................49 1.3.8. Applications of poly(a-glutamic acid) (PAGA) ....................................... 52 1.3.8.1. Ara-C conjugates ................................................................................... 52 1.3.8.2. Mitomycin C, daunomycin and adriamycin conjugates.......................53 1.3.8.3. Doxorubicin conjugate...........................................................................53 1.3.8.4. Camptothecin and SN38........................................................................55 1.3.8.5. Paclitaxel................................................................................................55 Hypothesis................................................................................................................... 57 Aims and objectives...................................................................................................58 2. CHAPTER II............................................................................................................59 Synthesis of low molecular weight activated poly(y-glutamic acid).......................59 2.1. Degradation of high molecular weight PG A..................................................62 2.1.1. Materials and methods ..................................................................................62 2.1.2. Characterisation of degraded PGA .............................................................. 63 2.1.2.1. Gel permeation chromatography (GPC) ..............................................63 2.1.2.2. Nuclear magnetic resonance spectroscopy (NMR) ..............................63