The antioxidant and antimicrobial activities of cornsilk extract encapsulated in polysaccharide nanoparticles
Above all, I owe my deepest gratitude Allah and to, after him, my supervisor Professor Dr. Wael Mamdouh whose guidance paved the way to make this thesis work possible. He supported me throughout my academic, and lab work. He provided me with immense knowledge and advised me to keep developing this research work. I really appreciate having the opportunity to work under his supervision, especially under the hard circumstances of COVID 19. Thanks to all the professors from whom I learned a lot throughout the courses of the nanotechnology program, Dr. Hassan El-Fawal, Dr. Adham Ramadan, Dr. Nageh Allam, Dr. Hanadi Salem, Dr. Mayyada El-Sayed, and Dr. Tarek Madkour. Also, it was an honor to work with Amro Shetta, Wessam Delann, Sara Omar, Nouran Sharaf, Jailan Essam, Omar Zidan, Haidy Yehia, Khadiga Sadek, Yasmine El-Kashef, Fatma El-Shishiny, Hend Amr, and Israa Ali, who helped, encouraged, and supported me. Special thanks to my colleague, James Kegere, who helped me in the SEM imaging and antibacterial tests. Thanks to The supportive staff of the chemistry department at AUC; Mr. Mahmoud Abdel Moez and Ali Reda who helped me with FTIR experiments. I am indebted to my mother and my uncle without their support and prayers, I would have not been able to get where I am. They encouraged me as they witnessed my hard work through this journey, I would like to dedicate my success to them. Last but not least, all the credits go to my partner during the journey of the master's degree, my husband who was very patient and understanding to support me through my thesis work and kept pushing me forward until I reached this point. To my sister, who has never let me down and always had an extraordinary power to cheer me up in the hardest time. I would also like to thank all, unnamed, people who provided me with corn that helped me as the sample of my research. I cannot neglect the role of The American University in Cairo, which was as a second home to me. I got all the support, needed equipment, and materials in addition to a welcoming atmosphere that made me able to academically improve myself. I would like to thank my committee members, Dr. Anwar Abd ElNaser and Dr. Medhat Al-Ghobashy. Thank you for giving me your time and patience to evaluate my thesis.
Abstract
Corn silk possess antibacterial and antioxidant activities due to its phenolic compounds but they are of low bioavailability that requires some innovative techniques to develop such active ingredients in a safe and less toxic manner. Accordingly, silk extract SE was encapsulated in chitosan nanoparticles CS NPs, which is a natural and abundant polymer derived from chitin. Among 15 experimental trials via design expert software, the optimum formula of SE x\CS NPs was prepared at 800 rpm, 5hrs. on magnetic stirrer, and by CS: TPP ratio was 2.5:1. Then SEM showed the majority of particles size diameter in the range of 25, 37, 39, and 55 and 77 nm were confirmatory for DLS particle size measurements of SE 0.5\CS NPs, SE 1\CS NPs, SE 1.5\CS NPs, and SE 2\CS NPs. FTIR results were confirmed the successful encapsulation and of SE in CS NPs by the appearance of the aromatic group bands at the wavenumber 1577.9 and 1417.5 cm-1. The cumulative extract release percentage was compared in two PH media showing no difference in their release profile. The release behavior of SE from CS NPs in those PH was indicative for using SE x\CS NPs as a topical preparation. SE x\CS NPs were tested for their antioxidant activities where % inhibition (free radical scavenging activity) of the four preparations SE 0.5\CS NPs, SE 1\CS NPs, SE 1.5\CS NPs, and SE 2\CS NPs showed 83.7, 84.7, 87.4, and 95.4% respectively higher than their corresponding amounts of free extract 31.5, 61.1, 74, and 87.4%. The TPC assay showed much lesser results for the four preparations of SE x\CS NPs ranged from 2.6 to 3.7 mg GAE\gm sample than that of their corresponding amounts of free extract which ranged from 16.5 to 35.7 mg GAE\gm sample. Also, the decreased values of TPC was indicative for the successful encapsulation of SE. The antibacterial test against S.auerus showed 100% BGI. In contrary, the antibacterial test against E.coli for the four preparations SE 0.5\CS NPs, SE 1\CS NPs, SE 1.5\CS NPs, and SE 2\CS NPs showed 70.44, 76.10, 82.51, and 98.27% BGI which was higher than that of their corresponding amounts of free extract 40.11, 59.30, 73.40, and 84.01% BGI.