Self-defensive antibacterial layer-by-layer hydrogel coatings with pH-triggered hydrophobicity.
We report on negatively charged layer-by-layer (LbL) hydrogel films, which turn hydrophobic and bactericidal in response to bacteria-induced acidification of the medium. Single-component hydrogel thin films, abbreviated as PaAALbLs, consisting of chemically crosslinked poly(2-alkylacrylic acids) (PaAAs) with varying hydrophobicity [polymethacrylic acid (PMAA), poly(2-ethylacrylic acid) (PEAA), poly(2-n-propylacrylic acid) (PPAA) or poly(2-n-butylacrylic acid) (PBAA)]. With increasing polyacid hydrophobicity, the hydrogel films showed a decrease in water uptake and an increase in elastic modulus. Both parameters were strongly dependent on pH. At pH 7.4, hydrogels of higher hydrophobicity were more resistant to colonization by Staphylococcus epidermidis, with the PBAA coating showing almost negligible colonization. As the medium became more acidic due to bacterial proliferation, the more hydrophobic PEAALbL, PPAALbL and PBAALbL hydrogels became dehydrated and killed bacteria upon contact with the surface. The killing efficiency was strongly enhanced by the polymer hydrophobicity. The films remained cytocompatible with human osteoblasts, as indicated by the MTS assay and live/dead staining. Our approach exploits bacteria-responsive properties of the coating itself without the involvement of potentially toxic cationic polymers or the release of antimicrobial agents. These coatings thus demonstrate a novel approach to the antibacterial protection of tissue-contacting biomedical-device surfaces.
['Lu|Yiming|Y|', 'Wu|Yong|Y|', 'Liang|Jing|J|', 'Libera|Matthew R|MR|', 'Sukhishvili|Svetlana A|SA|']
D000900:Anti-Bacterial Agents D020099:Coated Materials, Biocompatible D055119:Elastic Modulus D005333:Fetus D006801:Humans D020136:Hydrogel, Polyethylene Glycol Dimethacrylate D006863:Hydrogen-Ion Concentration D057927:Hydrophobic and Hydrophilic Interactions D008826:Microbial Sensitivity Tests D053758:Nanoparticles D010006:Osteoblasts D011108:Polymers D012825:Silicon D012996:Solutions D017550:Spectroscopy, Fourier Transform Infrared D013212:Staphylococcus epidermidis D013535:Suspensions
Antibacterial Hydrogel Bacterial adhesion Surface modification