Abstract:
Glycosaminoglycans (GAGs) are key factors in various molecular and physiological processes. In particular, it has been shown that the modification of sulfation codes, or sulfation arrangements of GAGs affect developmental processes and numerous diseases in the brain and other tissues. Sulfation codes have been shown to be responsible for the differential binding to growth factors. However, few mechanisms that regulate the action of sulfated GAG molecules have been elucidated. In our lab, we chemically modified alginate with different sulfation densities and then biotinylated alginate sulfates to create hydrogels and nanofilms presenting various sulfation patterns. The build-up of the sulfated films and subsequent growth factor binding were assessed in situ using quartz crystal microbalance with dissipation monitoring (QCM-D). Basic fibroblast growth factor (FGF-2) and nerve growth factor (NGF) binding were validated quantitatively via enzyme-linked immunosorbent assay (ELISA) and qualitatively via immunostaining. Finally, the morphology and growth of adipose derived stem cells, cancer and normal cell lines were evaluated on the different substrates by cytoskeletal imaging, immunohistochemistry and real-time polymerase chain reaction (RT-PCR). Alginate sulfation caused drastic changes in cell behavior where increased sulfation inhibited cell spreading and promoted longer filopodia. Cell size analysis indicated that stem cells seeded on highly sulfated substrates could better maintain their stemness when compared to substrates with a lower sulfation density. The effects of the sulfated substrates were also studied on epidermal, neural, breast and lung cancer cell lines in 2D and 3D by cell imaging, immunostaining and activity assays. Epidermal and neural cell lines showed increased proliferation on highly sulfated substrates. On the other hand, treatment of lung and breast cancer cell lines with alginate sulfates added in solution inhibited cell growth while maintaining relevant differentiation markers for normal healthy cells. The ability to prepare sulfated substrates with controlled sulfation levels has strong implications in the biomedical field. In particular, it can be used to induce different levels of growth factor binding and subsequently result in differential effects on cells seeded on these substrates.

Bio:
Dr. Rami Mhanna received his BE in Computer and Communications Engineering from Notre Dame University (Zouk Mosbeh, Lebanon) in 2006 and his MSc in Biomedical Engineering from The University of Melbourne (Melbourne, Australia) in 2008. Dr. Mhanna pursued his Doctoral studies in the Biosensors and Bioelectronics and the Cartilage Engineering and Regeneration labs at the Swiss Federal Institute of Technology (ETH Zurich, Switzerland). He defended his PhD titled “Engineering Chondrogenic Micro-Environments for Tissue Engineering Applications” in 2013 and then completed a postdoctoral fellowship in the 3B’s research group (Biomaterials, Biodegradables and Biomimetics) in Portugal. In 2014, he joined the Biomedical Engineering Program at the American University of Beirut as an Assistant Professor. In September 2020, he was appointed as Coordinator of the Biomedical Engineering Program. He was promoted to Tenured Associate Professor in September 2022. His research is focused on the fields of tissue engineering, drug delivery and surface science where he utilizes biomimetic microenvironments for basic and applied investigations. Dr. Mhanna is strongly involved in translational research and worked under a number of schemes including the Middle East Partnership Initiative (MEPI) – Tomorrow’s Leaders Program (TLP), MSFEA industry initiative, the Joint USJ/AUB Healthcare Innovation and Technology Stimulus, the European Bank for Reconstruction and Development and the Lebanese Industrial Research Achievements program. His work was published in more than 35 peer-reviewed original research articles in reputable journals such as Small, Biomaterials, and Advanced Functional Materials. He also has two patents, two book chapters and more than 20 conference contributions. More details may be found at www.aub.edu.lb/pages/profile.aspx?memberId=rm136.