Document Type
Thesis - University Access Only
Award Date
2009
Degree Name
Doctor of Philosophy (PhD)
Department / School
Chemistry and Biochemistry
Abstract
Chitosan is a deacetylated product of chitin. Chitosan possesses positive charges, which give it the ability to bind negatively charged fats, proteins, molecules, etc. Chitosan has attained increasing interest as a biomaterial, due to its favorable properties including biocompatibility, biodegradability. The current research involves using N-(R)-succinamic acid to modify chitosan utilizing amide bond formation by diimide coupling reaction. Formation of this amide bond enhances hydrogen bonding to the collagen backbone in tum increasing the efficacy of chitosan in its diverse applications. The effects of molecular chain length, hydrophobicity, and aromaticity on the modification were investigated by using different amount of six N-(R)-succinamic acids reacted with native chitosan in aqueous solutions at room temperature. IR and NMR were used to determine the degree of deacetylation (ODA), an important parameter of chitosan that affects its physicochemical properties. The introduction of amide groups increased the hydroscopic nature of the samples. This additional moisture interfered with the quality of the IR spectra rendering IR ineffective for the determination of ODA. The NMR results showed the protons on the modified structure were seen at 2.8~3.3 ppm and 1.2~ 1.9 ppm. The integrations of protons on the deacetylated structure, the acetyl group, and the modified structure were compared to determine the ODA. The amine sites on the chitosan could be modified from 9% up to 23%. The results showed the efficiency of chitosan modification is dependent on the chemical nature of the modifying agent. An increase in the size and hydrophobic of modifying reagents results in more effective modification. Aromatic modifiers displayed better modification than aliphatic modifiers. SEC was used to study the molecular hydrodynamic behavior. Chitosan was incubated under room temperature (20 °C) at different time length. The hydrodynamic behavior was investigated by using different eluent pHs and column temperatures. The SEC results analysis demonstrated the modified chitosan molecular chain movement was highly temperature and solvent system dependent. The nature of the modifying reagent can be used to control the behavior of chitosan. The mobile phase pH=2.0 is the optimal condition to study the chitosan chain movement. As column temperature increased 10°C, it took one hour less for the chitosan to reach the solute-solvent interaction equilibrium. Native chitosan in 0.1 M HCl solvent inclines to dissociate when reached salvation equilibrium due to more compact molecular conformation. Chitosan with hydrophilic side chains and aromatic side chains tended to aggregate after reaching solvation equilibrium which indicated more extended conformation. Chitosan with hydrophobic side chains tends to dissociate after reached dissolution equilibrium which meant more compact molecular conformation. The 0.01 M NaH2PO.J0.25 M NaCl solvent system is a poor solvent for NCS and aromatic modified chitoan which caused the samples to aggregate as temperature increased due to poor solute-solvent interaction. Aliphatic modified chitosan dissociated as temperature increase because of the increasing solution entropy in good solvent. The bonding strength is a measurement of the bioadhesive nature. Ex vivo study was performed to measure the strength. The bonding was completed with fresh artery tissue in the presence of 0, 10 mM, 100 mM NaCl in the chitosan solution to determine the effect of ion concentration of the chitosan solution on bonding strength. The highest bonding strength recorded was 85.46 g/cm2 from modified chitosan with hydrophobic side chain in 10 mM NaCL The lowest bonding strength recorded was 42.06 g/cm2 from polymer with aromatic side chain in H20. Lower ionic strength solution resulted higher bonding strength due to more extended molecular conformation. The modified chitosan with aromatic side chains showed lower bonding strength because of the high electron density on the aromatic ring repelling the collagen molecules which made them having less chance to bond together. Chitosan with hydrophobic side chains showed lower bonding strength than chitosan with hydrophilic side chains. The steric hinderance prevented the interaction between chitosan with longer side chain and collagen molecules. The hydrophilic side chains attracted collagen molecules increased the bonding strength.
Library of Congress Subject Headings
Chitosan
Chitin
Collagen
Wounds and injuries -- Treatment
Format
application/pdf
Number of Pages
135
Publisher
South Dakota State University
Recommended Citation
Lin, Jia, "Modification, Characterization, and Application of N-(R)-Succinamic Acid Modified Chitosan" (2009). Electronic Theses and Dissertations. 1585.
https://openprairie.sdstate.edu/etd2/1585
