Date of Graduation

Summer 2022

Degree

Master of Science in Chemistry

Department

Chemistry and Biochemistry

Committee Chair

Reza Sedaghat-Herati

Abstract

Chitosan has been studied as a non-viral vector capable of efficient gene delivery due to its favorable properties such as biodegradability, biocompatibility, and is non-toxic to mammalian cells. Incorporating electrostatic interactions in non-viral vectors enhance the vector permeability. This work focuses on two parts. Firstly, cationic chitosan derivatives were synthesized using quarternary ammonium and phosphonium groups. This was achieved by coupling carboxylic acid ligands with these quarternary groups to chitosan through an amide bond. The carboxylic acid ligands were synthesized from 4-methylbenzoic acid and either triethyl phosphine or triethyl amine. The ligand was then attached to chitosan through an amide bond using hydroxybenzotriazole (HOBt) and 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC). These compounds were then analyzed with 1H NMR and FT-IR analyses to determine the extent of incorporation of triethylammonium and triethylphosphonium groups into the chitosan backbone. Electrostatic interactions between these compounds and pDNA were studied using agarose gel electrophoresis. At charge ratios of 4:1 N+:P- or P+:P-both triethyl ammonium and triethyl phosphonium compounds complex with DNA. The second part of the work focuses on previously synthesized derivatives N(1carboxybutyl-4-triethylammonium chloride) chitosan and N(1-carboxybutyl-4-triethylphosphonium chloride) chitosan. These compounds were also studied using dynamic light scattering, zeta potential, and circular dichroism. These compounds were also PEGylated to aid in stability in aqueous media. The size of DNA/polymer complexes were between 140-340 nm at varying concentrations. Zeta potentials showed complete complexation after a weight ratio of 3:1 of polymer to DNA was achieved. Circular dichroism measurements revealed that at weight ratios at 4:1 of polymer to DNA that conformational changes of the DNA would occur. This work aims to investigate the newly synthesized compounds as viable gene therapy candidates capable of enhanced affinity towards nucleotides as well as further studying previously synthesized compounds for their efficiency towards complexing with DNA.

Keywords

chitosan, ammonium, phosphonium, gene therapy, DNA, 1H NMR spectroscopy

Subject Categories

Organic Chemistry | Polymer Chemistry

Copyright

© Alex M. McMullen

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Open Access

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