title: Self-defensive antibacterial layer-by-layer hydrogel coatings with pH-triggered hydrophobicity.
abstract: 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.
authors: Department of Chemistry, Chemical Biology and Biomedical Engineering, Hoboken, NJ 07030, USA.
authors: Yiming
authors: Y
authors: Lu
authors: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
authors: Yong
authors: Y
authors: Wu
authors: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
authors: Jing
authors: J
authors: Liang
authors: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
authors: Matthew R
authors: MR
authors: Libera
authors: Department of Chemistry, Chemical Biology and Biomedical Engineering, Hoboken, NJ 07030, USA. Electronic address: ssukhish@stevens.edu.
authors: Svetlana A
authors: SA
authors: Sukhishvili
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D055119:Elastic Modulus; D005333:Fetus / Q000166:cytology; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008826:Microbial Sensitivity Tests; D053758:Nanoparticles / Q000737:chemistry; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013212:Staphylococcus epidermidis / Q000187:drug effects; D013535:Suspensions
chemical_list: D000900:Anti-Bacterial Agents; D020099:Coated Materials, Biocompatible; D011108:Polymers; D012996:Solutions; D013535:Suspensions; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D012825:Silicon
keywords: Antibacterial; Bacterial adhesion; Hydrogel; Surface modification