Hierarchically aligned nano silver/chitosan–PVA hydrogel for point-of-use water disinfection: contact-active mechanism revealed

Abstract

The unsafe disposal of biomedical waste poses hazardous consequences to natural water resources, which may get contaminated through several means of leakage into waterways. Herein, the disinfection potential of nano-silver loaded chitosan–PVA hydrogel to completely eradicate biomedical contaminants coexisting with natural contaminants in environmental samples was successfully demonstrated for the first time. The polymeric network of the hydrogel served a dual role for in situ synthesis and immobilization of silver nanoparticles (AgNPs) simultaneously. Porous Ag-loaded hydrogels displayed a temperature-dependent swelling behavior and exhibited an improved mechanical strength (Young's modulus, 12.36 ± 0.29 MPa; elongation at break, 180%) by effectively distributing the external stress and restored its structural integrity. Complete disinfection (100% killing) could be achieved within 4 h against all the four tested contaminants, demonstrating a distinct strain-specific biocidal activity. Being a diffusion-controlled process, the oxidative dissolution of AgNPs deeply buried in the interiors of the hydrogel architectures was adversely affected on repeated use and restricted the maximum silver release to 38.8 ± 5.6 μg g⁻¹ hydrogel in an aqueous suspension over 7 days. Correlating the reusability and silver release kinetics, a predominant contact-active role of the hydrogel was envisaged via ‘capture and kill’ over leaching of silver ions for rapid water disinfection. The Ag-loaded hydrogels also severely inhibited the biofilm formation of Escherichia coli and Staphylococcus aureus till 48 h. Finally, the hydrogels could completely disinfect the natural water samples, i.e., river, ground, and tap water with inherited microbiota and biomedical contaminants in 2 h under the real conditions.