Preparation of chitosan-nylon-6 blended membranes containing silver ions as antibacterial materials

Chitosan-nylon-6 blended membranes were prepared by combining solvent evaporation and a phase inversion technique, and then used to chelate silver ions. Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) were used to study the antibacterial properties of the membranes. Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) indicated hydrogen-bond interactions between chitosan and nylon-6. From the scanning electron microscopy (SEM) pictures, it was observed that with the increase of nylon-6 content, the blended membrane gradually became a material with porous morphology. After chelating silver ions, the tensile strength of the membranes increased. The antibacterial activity with the variation of chitosan content, the pH value and the concentration of the silver nitrate solution used to prepare Ag(+)-loaded membranes were investigated systematically. The results indicated that the chitosan-nylon-6 blended membranes with Ag(+) were antibacterial to both Gram-positive bacteria and Gram-negative bacteria. The antibacterial activity improved with the increased chitosan content due to the larger amount of silver ions loaded. The antibacterial property of the chitosan-nylon-6 blended membranes could be primarily attributed to the content of chitosan and silver ions as well as the surface morphology of the membranes.