HYALURONAN AS EFFECTIVE PLATFORMS FOR COMBINATORIAL CARBOHYDRATE DERIVATIVE GENERATION, AND FOR IMAGE-GUIDED SURGERY WITH SURFACE-ENHANCED RAMAN SPECTROSCOPY (SERS)

Summary

Hyaluronan (HA) is a polysaccharide consisting of repeating disaccharides of N-acetyl-D-glucosamine and D-glucuronic acid. HA plays important roles in a wide range of biological events. The principal endogenous receptor of HA, cluster of differentiation 44 (CD44), is overexpressed on many types of tumor cells as well as inflammatory cells in human bodies. HA-CD44 interactions are important in cell adhesion, cell migration, induction of hematopoietic differentiation, and signaling for cell... Show moreHyaluronan (HA) is a polysaccharide consisting of repeating disaccharides of N-acetyl-D-glucosamine and D-glucuronic acid. HA plays important roles in a wide range of biological events. The principal endogenous receptor of HA, cluster of differentiation 44 (CD44), is overexpressed on many types of tumor cells as well as inflammatory cells in human bodies. HA-CD44 interactions are important in cell adhesion, cell migration, induction of hematopoietic differentiation, and signaling for cell activation. Other HA receptors include lymphatic vessel endothelial HA receptor-1 (LYVE-1), and HA receptor for endocytosis (HARE). HA is versatile for chemical modification or conjugation by exploiting the reactivity of carboxyl group, hydroxyl group, or the reducing end of the HA chain. Through chemical modification of HA, various kinds of self-assembled HA nanoparticles (HA-NPs) can be generated. There are increasing interests in utilizing HA-NPs for targeted imaging and therapy. Active targeting from HA-CD44 mediated interaction could lead to selective accumulation of HA-NPs at targeted disease sites. Chapter 1 is a review focusing on the synthesis strategies of self-assembled HA-NPs, as well as their applications in therapy and biomedical imaging. With the recognition of the importance of HA-CD44 interactions, there have been substantial efforts to develop novel compounds capable of binding with CD44 to modulate CD44 biology. Chapter 2 reports a novel approach for generating HA derivatives with enhanced CD44 binding. By modifying the carboxyl group on HA with various amine, aldehyde, and isocyanide moieties through the Ugi reaction, 36 HA like polysaccharides were generated. Two lead compounds were identified with enhanced CD44 binding from the polysaccharide library compared to unmodified HA, which was confirmed by surface plasmon resonance and cellular studies. Ski-learn as a machine learning tool was utilized to analyze the library of binding data and yield prediction with an accuracy over 80%. In conclusion, modification of HA via the Ugi reaction can be a promising approach to develop novel binders toward CD44. While HA has been frequently employed as the targeting molecule in imaging via near infrared (NIR) or magnetic resonance (MRI) imaging, the potential of HA for surface-enhanced Raman spectroscopy (SERS) imaging has not yet been explored. SERS NPs are well-known for strong multiplexing capability, since different flavors of SERS NPs can be synthesized using different SERS dyes, resonant or non-resonant dye. SERS NPs are a promising tool for tumor margin removal in image-guided surgery. However, there are several challenges associated with SERS NPs for cancer imaging: 1) reproducible synthesis of SERS NPs; 2) ligand attachment for SERS NPs. Chapter 3 addresses these two issues by: 1) developing a reproducible protocol for 50 nm SERS NPs with low-femtomolar detection sensitivity; 2) employing liposome as the bridge for HA attachment to SERS NPs. The resulting HA-liposome SERS NPs have been successfully applied in imaging guided surgical removal of breast cancer in a spontaneous mouse breast cancer model. Show less