Over the past decade, different methods have been adopted for conjugating catechol with chitosan backbone and the resulting chitosan-catechol has been well characterized. Additionally, the crosslinking mechanisms of chitosan-catechol polymers have been explored in detail. However, the exact interfacial binding strategy of such crosslinked polymers with various tissue substrates is still not clear. For example, consider the bioadhesion of chitosan-catechol adhesive synthesized using the EDC/NHS carbodiimide chemistry to mucin-rich tissue surfaces. First, mucin is rich in the amino acid, cysteine, which contains carboxyl (-COOH) and amine (-NH<sub>2</sub>) sites as well as and thiolate groups (-SH). The chitosan itself has primary amine groups that can interact with the negatively charged carboxylic acid presented by mucin. However, in addition to such electrostatic interactions, chitosan and mucin both contain primary amine groups, and H-bonding between them at physiological pH could also contribute to adhesion and needs to be accounted for while predicting adhesion mechanisms. Second, physiological conditions cause the oxidation of catechol to quinone, which is expected to form irreversible covalent bonds with the amine moieties on the tissue surface through either Michael-type addition or Schiff’s base formation, or interact with thiol groups via Michael addition. However, several reports in literature have depicted varying interaction strategies (i.e., some suggesting only Michael-type addition) and there isn’t a consensus on the adhesion strategy. Finally, even though reports have suggested that chemical crosslinking occurs within the chitosan-catechol polymers, the mechanical properties of such polymers and their eventual effect on interfacial binding remain to be systematically investigated. We plan to conduct a study to fill in these gaps in the understanding of the bulk as well as interfacial binding characteristics of chitosan-catechol polymers.

Understanding the bioadhesion of chitosan-catechol polymers

2019 Spring National Meeting

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