Antimicrobial Activities of Thermoplastic Polyurethane/Clay Nanocomposites against Pathogenic Bacteria

As a thermoplastic polymer with an impressive combination of mechanical properties and biological compatibility, thermoplastic polyurethane (TPU) is one of the important polymers used in various applications such as biomaterials, conducting materials, and tissue engineering. Nanocomposites made of TPUs with nanoclays were prepared by melt-compounding, and the effects of clay on antibacterial activities and physical properties of nanocomposites were investigated. X-ray powder diffraction, water contact angle, and TEM results were analyzed to investigate the effects of dispersion and modification of clays in TPU/clay nanocomposites. Using the pour plating method, scanning electron microscopy technique, and disk diffusion test, TPU/clay nanocomposites were observed to show contact killing activity against bacteria. The antibacterial activities of TPU/clay nanocomposites were found to be affected by the dispersion state and amount of organic modifier of clays. TPU nanocomposites containing 5 wt % organically modified clay showed 98.5% killing efficiency against Gram-negative Escherichia coli and 99.9% against Gram-positive Staphylococcus aureus, while neat TPU showed almost none. The positively charged quaternary ammonium salt groups of clay in TPU/clay nanocomposites interacted with the negatively charged cytoplasmic membrane of bacteria, and the dead bacteria were eliminated by weakened adhesion on hydrophobic backbone surfaces.