Self-assembled Peptide Hydrogels for Therapeutic H2S Delivery

Hydrogen sulfide (H2S) is a gasotransmitter that is produced endogenously and freely permeates cell membranes. It plays important roles in many physiological pathways, and by regulating these pathways, it provides many therapeutic effects. For example, H2S dilates vascular vessels, promotes angiogenesis, and protects cells from oxidative stress. Due to its therapeutic effects, H2S has been used as a potential treatment for diseases like diabetes, ischemia-reperfusion injuries, lung diseases, ulcers and edemas, among others. To apply H2S for therapeutic applications, two challenges need to be addressed. The first challenge is the H2S donor, which not only provides H2S but must be stable enough to avoid side effects caused by overdose; and the second challenge is the delivery strategies, which transport the H2S to the target sites. A series of S-aroylthiooximes (SATOs), an H2S releasing compound, were synthesized and conjugated to peptide sequences to form H2S-releasing aromatic peptide amphiphile (APA) hydrogels. APAs formed nanofibers, which were stabilized by beta-sheets and aromatic stacking. The self-assembled structures were affected by the substituents on the aromatic rings of SATOs, leading to the formation of twisted nanofibers. After the addition of cysteine, H2S was released from the APAs with half-lives ranging from 13 min to 31 min. The electron-donating groups slowed down the H2S release rate, while the electron-withdrawing groups accelerated the release rate. Therefore, the release rates of H2S were controlled by electronic effects. When self-assembled structures were formed, the H2S release rate was slowed down even more, due to the difficulties in cysteine diffusion into the core of the structures. Antimicrobial effects were also discovered using the H2S releasing APA hydrogels. The H2S-releasing dipeptides S-FE and S-YE formed self-assembled twisted nanoribbons and nanotubes, respectively. The non H2S-releasing control oxime dipeptides C-FE and C-YE were also synthesized. The C-FE formed nanoribbons while the C-YE only showed non-specific aggregates. S-FE and S-YE released H2S with peaking times of about 41 and 39 min. Both the self-assembled structures and the release rates were affected by their packing differences. In vitro and ex vivo experiments with Staphylococcus aureus (Xen29), a commonly found bacterium on burn wounds, showed significant antimicrobial effects. APAs S-FE and C-FE eliminated Xen29 and inhibited the biofilm formation, while S-FE always showed better effects than C-FE. These antimicrobial H2S-releasing APA hydrogels provide a new approach to treat burn wound infections, and provide healing benefits due to the therapeutic effects of H2S.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Macromolecular Science and Engineering

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2019

Author dc:creator

• Qian, Yun

Chair dc:contributor.committeechair

• Matson, John B.

Committee members dc:contributor.committeemember

• Whittington, Abby R.
• Barone, Justin R.
• Edgar, Kevin J.
• Davis, Richey M.

• Self-assembled peptide hydrogels
• hydrogen sulfide (H2S)
• controllable release
• anti-infection
• wound treatment

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:20695

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/101094