Chitosan is a biopolymer with both antibacterial and wound-healing properties. By linking fluorophores to chitosan oligomeres smart plasters can be produced, able to detect pathogenic bacteria via proteolytic activity. Therefore, production of designed chitosan for medical purpose is of special interest.
Engineering E. coli for specific synthesis of designer chitosan
Our primary wet-lab goal is to engineer a synthetic biological circuit for the specific synthesis of chitosans in E. coli. The chemical properties as well as the bioactivity of chitosans mainly depend on three variables: the length of the oligomers, their level of deacetylation and their patterns of deacetylation.
Our enzymatic approach includes three enzymes. A chitin synthase (Rhizobium leguminosarum bv. viciae) catalyzes the oligomerization of N-acetylglucosamine-UDP monomers to chitin oligomers (tetramers and pentamers). Furthermore, two chitin deacetylases that differ in their regioselectivity (Sinorhizobium meliloti (nodB) and Puccina graminis f. sp. tritici) are regulated orthogonally, making it possible to choose between two different types of deacetylation patterns.
Application of chitosan oligomers: chitosan hydrogel for bacterial enzyme detection
Downstream of the synthetic biological circuit for the synthesis of chitosan pentamers, we want to give an example for an explicit application of chitosan oligomers. This shall be accomplished by building a plaster for wounds carrying the chitosan hydrogel with chitosan oligomers linked to a fluorophore via a peptide chain. When the plaster is applied to a wound it can detect bacterial protease activities and thus diagnose wound infection. Proteases will cleave the peptide linker and release the fluorophore, that is then detectable via UV-light.
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