Rare-earth ions as antibacterial agents for woven wool fabric

Woven fabrics were bestowed with antibacterial property by the simple adsorption of rare-earth metal ions, and the underlying mechanism was investigated using electron spin resonance (ESR) spectroscopy. The adsorption of Ce³⁺ ions on wool, silk, and cotton fabrics resulted in significant inhibition of Staphylococcus aureus (a gram-positive bacterium), with maximum antibacterial activities (viable bacterial count compared to the reference) of 4.7, 5.8, and 5.2, respectively. Even after 50 wash cycles, the values remained at 3.9, 2.9, and 4.8, respectively. The adsorption of La³⁺ and Gd³⁺ ions on wool fabrics also resulted in antibacterial activities of 5.8 and 5.9, respectively. In addition, wool adsorbed with Ce³⁺ exhibits a satisfactory antibacterial activity of 6.2 against Escherichia coli (a gram-negative bacterium). Such bacterial inhibition is attributed to Fenton reactions between the adsorbed rare-earth ions and hydrogen peroxide (H₂O₂) produced during bacterial metabolism, as determined from the ESR spectra collected using the spin trap method in the presence of H₂O₂. The safety of cerium nitrate was also investigated, and no significant issues arose, indicating that it was a safe antibacterial agent. This facile method of imparting antibacterial properties to natural fabrics may be useful for preventing infections in humans.

The online version contains supplementary material available at 10.1007/s11696-021-01999-9.