Study of the cellulose-peptide conjugation for the development of antimicrobial cotton textiles

The aim of this thesis is the study of chemoselective ligations in the context of antimicrobial tissues. Cotton is the chosen textile because it is a natural fiber, widely produced, air permeable and easy to functionalize. The selected class of antimicrobial agents are antimicrobial peptides. In fact, they present a broad-spectrum mechanism of action. Thus, they are at a lower risk for the resistance development; they are produced by the immune system of different organisms, thus inherently biocompatible and biodegradable. Thiazolidine and oxime bonds are the selected ligation methods. They are formed by the reaction of an aldehyde and a β-amino thiol (Cysteine) and an alkoxyamine (Aminooxyacetic acid), respectively. The use of a covalent bond is due to the requirement to produce a functionalized textile that is durable, washable and reusable. The aldehyde is introduced at the C6 atom of the glucose unit of cotton cellulose by an enzymatic oxidation in a 2,2,6,6-Tetramethyl-1-piperidinyloxyical(TEMPO)/laccase/O2 system, whereas the Cysteine (Cys) and Aminooxyacetic acid (Aox) are introduced during the peptide synthesis at the N-terminal. Both the oxidizing and the conjugation reactions are interesting for the mild conditions at which they take place. All the peptides are synthetized through solid phase peptide synthesis (SPPS). Two model peptides are used for the study of the two ligation types. They both have a UV-vis active side chain, a detectable side chain and either a Cys or an Aox. The first is needed to follow the course of the reaction, the second allows to confirm the presence of the peptide on cotton by colorimetric tests and the last two are necessary for the effective ligation with the oxidized cotton. FT-IR analysis is performed to further confirm the presence of the peptides on cotton. The main goals of using these peptides are: the quantification of the peptide loading on different types of cotton, the rough estimation of the aldehyde content on cotton upon the re-use of the oxidizing solution and the evaluation the stability of the two bonds in different media. Finally, a short analogue of PMAP-36, an antimicrobial peptide, is linked to cotton using the above-mentioned strategy and the antimicrobic activity of the obtained material is tested.