Photodynamic Antimicrobial Cellulosic Material Through Covalent Linkage of Protoporphyrin IX Onto Lyocell Fibers

Here, we report the preparation of porphyrin-functionalized Lyocell fibers according to an azide-alkyne click concept. First, azido-modified Lyocell fibers and alkynylated protoporphyrin building blocks were prepared through alkoxysilane chemistry and Steglich esterification, respectively. Lyocell fibers were pre-activated by swelling in organic solvents in order to increase the accessibility of hydroxyl groups in the subsequent silanization process. The azide-equipped cellulosic matrix reacted with the propargyl groups of the protoporphyrin IX derivative in a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC), by which protoporphyrin IX was introduced onto the surface of the Lyocell fibers. The modified building blocks and the final functionalized cellulosic materials were comprehensively characterized by FTIR, NMR, UV/Vis spectroscopy and elemental analysis. Photo-bactericidal activity of modified fibers against 2 gram-positive bacteria strains, including Staphylococcus aureus and Bacillus subtilis, were investigated and compared to those of unmodified and azido-modified Lyocell fibers. The results confirmed the photo-antibacterial activity of the synthesized fibers against both bacteria strains.