Microwave-assisted Production of Solid Lipid Nanoparticles Rohan Shah A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy February 2016 Department of Chemistry and Biotechnology Faculty of Science, Engineering and Technology Swinburne University of Technology Melbourne, Australia Abstract Abstract The oral route is the first choice for drug administration, except in very specific situations such as when an immediate, systemic or local effect is intended. The oral route is also the most convenient and safest route of drug administration due to its easy and non- invasive nature, which also provides higher patient compliance and fewer complications. Despite these positive attributes, therapeutic efficacy of drug delivery systems can be problematic and can often be obscured due to physicochemical properties of the drugs and/or physiological constraints. Poor water solubility and/or poor permeability, the risk of degradation in the stomach and liver and poor hepatic first-pass metabolism are the major causes that not only affect oral bioavailability but also encumber the development of delivery systems. Industry estimates suggest that approximately 70 - 75% of new drug candidates and 40% of currently marketed drugs fail due to solubility and/or stability issues, prompting significant need for research in advanced lipophilic drug delivery systems. Solid lipid nanoparticles (SLNs) present a promising technology for lipophilic drug delivery. Their unique combination of small particle size, large specific surface area, solid nature, particle shape and surface chemistry has generated enormous enthusiasm and anticipation regarding pharmaceutical applications. SLNs can combine the advantages of other traditional colloidal carriers such as liposomes, emulsions, polymeric nanoparticles and micelles, and at the same time reduce their associated shortcomings. Some of the potential attractive features of SLNs include protection of incorporated drug molecules from the external biological environment, physicochemical stability, controlled drug release and target specificity. Their development, however, is still in its early stages and more research is required around their manufacture, characterisation and drug loading capacity. The SLNs generated in this thesis were prepared using a novel microwave-assisted microemulsion technology, and were compared with SLNs prepared by more conventional thermal heating. Stearic acid was used as the lipid with Tween® 20 as the surfactant. Various drugs were tested for their uptake and stability using these SLNs. Tetracycline-loaded SLNs were smaller, with lower polydispersity, physically more stable and had higher encapsulation efficiencies than conventionally produced drug- laden SLNs. iii Abstract An aim of the thesis was to provide potential drug delivery systems for lipophilic drugs belonging to the Biopharmaceutical Classification System (BCS) Class II and Class IV. For this purpose, drugs from different categories (and different chemistries) were selected, including antifungal drugs (clotrimazole, miconazole nitrate and econazole nitrate) and non-steroidal anti-inflammatory drugs (NSAIDs) (indomethacin, ketoprofen and nimesulide). These studies were aimed at evaluating the physicochemical and biological properties of the drug-loaded SLNs. The drug-loaded SLNs had a small size (200-300 nm), low polydispersity (0.1-0.3) and a moderate negative zeta potential (with the exception of miconazole nitrate and econazole nitrate). The crystallinity of the stearic acid was reduced, as evidenced by differential scanning calorimetry (DSC) and X-ray diffraction (XRD), when fabricated into SLNs - suggesting increased drug payload. The encapsulation efficiency of the drug- loaded SLNs was between 70% and 92% depending on the physicochemical properties of the drugs. The stability and encapsulation efficiency of drug-loaded SLNs were found to be influenced by the pH and electrolytes in the dispersion medium. Electron microscopy suggested that the SLNs were spherical to ellipsoidal in shape. The SLNs loaded with drugs exhibited biphasic drug release behaviours. The release mechanisms were, however, different for both drug categories. The SLNs loaded with NSAIDs exhibited a high initial “burst” followed by a sustained-release of drugs. The release mechanism was governed by Fickian diffusion. In contrast, the SLNs loaded with antifungal drugs (different drug chemistry) exhibited a slow, controlled and incomplete release of drugs, and was governed by non-Fickian release mechanisms. The viability of A549 epithelial cells when exposed to SLNs was found to be concentration-dependent. The small size (<300 nm) of SLNs produced by microwave- assisted microemulsion technique was suitable for internalisation by epithelial cells. The SLN uptake by human epithelial cells (A549 and HeLa cells) was found to be energy- dependent. Confocal laser scanning microscopy (CLSM), fluorescence microscopy and flow-assisted cell sorting (FACS) techniques were used to ascertain that the SLN uptake by human epithelial cells was mediated by clathrin-dependent endocytosis. All these findings suggest that the SLNs produced by the novel microwave-assisted microemulsion technique can be used as potential drug delivery systems, and therefore, facilitate further development of the SLNs. iv Dedication Dedicated to my parents, Mr. Mahendra Shah and Mrs. Sangita Shah…! v Acknowledgements Acknowledgements Although I declare that this thesis is my own work, this thesis would not have the spirit that it has without the invaluable contributions provided by many people, and I am pleased to acknowledge their support, assistance and encouragement here. To my primary supervisor, advisor and guide Professor Ian Harding, this journey of PhD has been an incredible journey led by you. I sincerely thank you for believing in me and accepting me to pursue my PhD under you. I appreciate your generosity with reception of my postulations. Thanks most of all for the granting me complete freedom in conducting this research. Your enduring support and guidance have always motivated to give a little more. To my supervisor and mentor “Godfather” Professor Enzo Palombo, your guidance, support and constant encouragement have been, and continue to motivate me to think bigger and perform better. I will always be indebted to you for inventing opportunities for me that have served as a strong foundation for my career and establish myself as a researcher. You, like my father, have always inspired me to “earn” people. I will always be grateful for taking care of me during these five years. To my associate supervisor Dr. Daniel Eldridge, your enduring patience, backing and guidance have helped me navigate through the PhD journey. I appreciate all your time in correcting my writing despite your hectic teaching schedules. You have always enthused me with your extraordinary abilities of “striking-the right-cord” to inspire students to enjoy what they learn. This study was made possible through the financial support from the Department of State Development, Business and Innovation (State Government of Victoria). I am grateful to them, and to Australia India Institute, for providing the Victoria India Doctoral Scholarship. I would like to take this opportunity to thank Professor Amitabh Mattoo and the staff at the Institute for their constant support, assistance, encouragement and arranging the “cultural yatra” during these years. I am particularly grateful to a number of academic scholars for their educational insights and useful critiques: A/Professor Bob Laslett, Dr. Peter Mahon, Dr. Francois Malherbe, Dr. Tony Barton, Dr. Jitendra Mata, Professor Peter Kingshott, Professor Sarah Russell, vii Acknowledgements Dr. Mandy Ludford-Menting, Dr. Igor Sbarski, Dr. James Wang, Dr. De Ming Zhu, Dr. Pablo Juliano and A/Professor Shannon Notley. I truly appreciate the support of the Faculty of Science, Engineering and Technology at Swinburne University of Technology through the funding and resources provided to me. I am thankful to Chris Key, Soula Mougos, Ngan Nguyen, Dr. Huimei Wu, Andrea Chisholm, Angela McKellar, Katharine Adcroft, Dr. Rebecca Alfred, Chris Anthony, Antonina Gatt and Dr. Adrian Disdale for their support and assistance during my research work. I owe particular thanks to Savithri Galappathie for taking care of me all these years. To Neil Clifford, Glenda Runciman, Karin Grolimund, Stephen Morris, Adam Winterhalter, Gavin Robertson and Daniel Teis for providing the samples, technical advice and for their well wishes. The quality of work was enriched through the presence of awesome colleagues in laboratory and office; Matthew Quinn, Dr. Dhivya Rajasekaran, Gurvinder Kalra, Dr. Vi Truong Khanh, Yen, Vy Pham, Dr. Hayden Webb, Dr. Mohammad Al-Kobaisi, Tasnuva Tamanna, Dr. Elizabeth Ouwar, Eng Hooi Tay (Nelson), Dr. Kaylass Poorun and Dr. Abirami Ramalingam. I owe a particular thanks to my fellow “VIDS” colleagues for sharing this PhD journey with me. To my friends, Dr. Vandana Gulati, Dr. Pankaj Gulati, Dr. Avinash Karpe, Amol Ghodke, Mrudula Borse and Dr. Atul Kamboj and my niece Ryka, my housemates and friends in Australia, for their constant presence and unforgettable memories in Melbourne. I would also like extend my heartfelt thanks to Dr. Makarand Jawadekar, Mr. Vidyadhar Jawadekar and Mr. Amitabh Mehta for their appreciation of my progress and their constant encouragement to excel. I would like to thank Professor Rainer Müller, the pioneer