Production of Chitosan/Zinc Oxide Complex by Ultrasonic Treatment with Antibacterial Activity

This study was conducted with the objective of investigating the physical and antimicrobial properties of structured zinc oxide compounds in chitosan submitted to different times of ultrasonic treatment. Zinc oxide particles were dispersed in water and coated with medium molar mass chitosan and two other sonicated samples, following a simple methodology. Before drying, the chitosan/zinc oxide water suspensions were characterized by rheological tests. Their rheological behavior depended on the period of time during which the chitosan sample was submitted to ultrasound. After drying, the microparticles were characterized by infrared spectroscopy, atomic absorption spectrophotometry and scanning electron microscopy (SEM). The microparticles were investigated as for their particle size distribution (PSD). SEM and PSD results revealed that the chitosan/zinc oxide microparticles had a multimodal dispersion. The antibacterial activity of the neat zinc oxide nanoparticles and of the microparticles was evaluated against Escherichia coli and Staphylococcus aureus. The results showed that the ZnO nanoparticles had a lower minimum bactericidal concentration (500 μm/mL against E. coli and 650 μm/mL against S. aureus) than the chitosan-coated/ZnO microparticles. The microparticles with the lowest average particle size and the highest homogeneity exhibited the highest antibacterial activity against both bacteria. This result was attributed to the additional antibacterial activity of soluble zinc ions and of the chitosan sample.