Title: “Design, Synthesis, Characterization, and Evaluation of a Cationic Poly-Amido-Saccharide towards Biocompatible Nucleic Acid Delivery”
Mark Grinstaff, PhD – BU BME (Advisor)
John Ngo, PhD – BU BME (Chair)
Béla Suki, PhD – BU BME
Arturo Vegas, PhD – BU Chemistry
Katrina Steiling, MD, M.Sc. – BUMC Pulmonary Division
Carbohydrates are central components of biological systems, with roles ranging from metabolism to immune signaling, and are utilized as antibiotics, anti-coagulants, and biomaterials. Carbohydrate polymers with ionic functionality, such as alginic acid and chitosan, are used in hydrogels, tissue engineering, drug delivery, and as nucleic acid vectors. The clinical translation of polysaccharide biomaterials is hindered by the poor chemical definition, poor batch-to-batch consistency, and demanding purification process of naturally-obtained material. Additionally, there are few synthetic methods yielding enantiopure, water-soluble carbohydrate polymers with high molecular weight. To address the need for translatable carbohydrate biomaterials, our group recently introduced bioinspired Poly-Amido-Saccharides (PASs) as enantiopure, water-soluble, and well defined carbohydrate polymers. These previously reported polymers, however, mimic polysaccharides with primarily metabolic roles due to the lack of charged functional groups important for biomaterial applications. In this thesis, I describe the synthetic methodology towards a regioselectively amine-functionalized β-lactam carbohydrate monomer, the subsequent synthesis of enantiopure, water-soluble amine-functional PASs (AmPAS), an evaluation of AmPAS biocompatibility and mucoadhesivity for pharmaceutical formulations, and the use of AmPAS for biocompatible nanoparticulate delivery of nucleic acids.
The results of a combined experimental and theoretical study indicate that bulky protecting groups enforce a 5H4 glycal conformation and favorable overlap of ring σC-O* with the allyloxocarbenium system that enhances negative hyperconjugation effects due to electron withdrawing protecting groups. These data inform the synthesis of amine-modified carbohydrate monomers, where bulky, electron-withdrawing groups are required for regioselective glycal functionalization and intermediate protecting group stability is necessary to obtain water-soluble polymers (AmPAS). AmPAS exhibit minimal cytotoxicity and immunogenicity, and, through single molecule force spectroscopy and ex vivo methods, significant mucoadhesivity important for pharmaceutical application. AmPAS are obtained with tunable molecular weight distributions to allow for nanoscale size- and charge-matched supramolecular assemblies with single stranded RNA and DNA oligonucleotides. These nanoparticles are stable in high serum conditions, exhibit high cell uptake, and are shown to successfully deliver anti-miR-21 oligonucleotides to mediate miR-21 knockdown in vitro. These promising results motivate the future application of AmPAS in small molecule and antisense oligonucleotide delivery formulations.