Antibacterial and photo-catalytic composite nanofibres for filtration

The addition of inorganic colloids to polymer solutions allows the production of multi-component nanofibres by electrospinning. This process has been recently named "colloid electrospinning". In this work, composite nanofibres were produced by electrospinning water solutions of keratin (protein extracted from wool) containing colloids of Ag or TiO2 (by Colorobbia, Italy). A renewable natural polymer (keratin) is used in a process involving water instead of organic solvents and liquid dispersions instead of nano-powder. Colloidal stability in polymer solutions was evaluated to preserve nanoparticle dimension before electrospinning. The resulting nanofibres were made water insoluble by a simple heat treatments at 180°C in air. Porous nanofibrous structure resulted stable to water. Finally, the functional properties of the nanofibres were evaluated. Antibacterial tests (AATCC 100) against Escherichia coli on nanofibres with Ag and TiO2 were carried out. Photo-catalytic tests were performed in water under a 9 W/m2 UV light using Rhodamine B as a model molecule. Degradation was measured by color changes using a spectrophotometer. Nanoparticle-loaded nanofibres showed bacterial reductions of 95% for Ag and 97% for TiO2. Photo-catalytic degradation of Rhodamine B was 53% for TiO2-loaded nanofibres after 2 h under UV light, while nanofibres without TiO2 reached 12% of conversion. The results demonstrated that nanoparticle functionalities were preserved in electrospun keratin nanofibres.