Antibacterial studies of inorganic nanoparticles (nps) have become important due to the increased bacterial resistance against antibiotics. We used Zinc oxide nanoparticles (ZnO nps), which possess excellent photocatalytic properties with a wide band gap (Eg), are listed as “generally recognized as safe” by the Food and Drug Administration (FDA) and have shown antibacterial activity (AA) against many bacterial strains. The AA of ZnO nps is partly attributed to the production of Reactive Oxygen Species (ROS) by photocatalysis. When ZnO nps in aqueous media are illuminated with an energy <Eg, electron-hole pairs are generated on nps surface reacting with water and Oxygen molecules to generate hydroxyl-radical (OH• ), superoxide-radical (O<sub>2</sub> •- ) and hydrogen-peroxide (H<sub>2</sub>O<sub>2</sub>). These ROS induce cell membrane damage resulting in cell death. However, the application of inorganic nps in medical treatments is limited due to the possible long-term side effects of nps release. To prevent its release, ZnO nps were dispersed into Polycaprolactone (PCL) fibers obtained by electrospinning technique. To optimize the use of ZnO nps concentration, we developed coreshell coaxial electrospun fibers where the core corresponded to PCL and the shell to a mixture of ZnO nps/PCL. Thus, ZnO nps were only dispersed on the surface of the fibers increasing its superficial contact area. We evaluated the AA against E. coli of different electrospun ZnO nps/PCL fibers under two different conditions: UVA pre-illumination and darkness. Preliminary results suggest that the AA against E. coli is better when electrospun ZnO nps/PCL were preilluminated with UVA than under darkness conditions.
This work reports the synthesis of amorphous TiO<sub>2</sub> matrix by sol-gel method at atmospheric
conditions. DA was encapsulated in a TiO<sub>2</sub> matrix to reduce its chemical instability. To TiO<sub>2</sub>/DA sample
was added the 15C5 to diminish the oxidation process. The stabilization process was followed by
absorption spectra, colour change and infrared spectroscopy. Oxidation processes of the DA were
identified by the presence of DA-quinone and DA-chrome. The TiO<sub>2</sub>/DA complex retarded the oxidation
process for 30 days, while the TiO<sub>2</sub>/DA/15C5 complex this period was extended for 47 days.
Photoconductivity studies were performed on both kinds of samples to analyze their charge transports.
The experimental data were fitted with straight lines at darkness and under illumination at 320 nm, 400
nm, and 515 nm. This indicates an ohmic behavior. Transport parameters were calculated. The conductive
effect is stronger under darkness than under illumination at 320 nm because the oxidation process in the
darkness is less intense than under illumination.