Interactions between prokaryotic polysaccharides and colloidal magnetic nanoparticles for bacteria removal: A...

Highly stable, colloidal iron oxide nanoparticles with an oxyhydroxide-like surface were used as bacteria-capturing nano-baits. Peptidoglycan isolated from Listeria spp was used as bacteria polysaccharide model, and the nanoparticle binding was characterized showing a Langmuir isotherm constant, K_L, equal to 50 ± 3 mL mg^-1. The chemical affinity was further supported by dynamic light scattering, transmission electron microscopy, and infrared and UV-Vis data, pointing at the occurrence of extended, coordinative multiple point bindings. The interaction with Gram (+) (Listeria spp) and Gram (-) (Aeromonas veronii) bacteria was shown to be effective and devoid of any toxic effect. Moreover, a real sample, containing a population of several oligotrophic bacteria strains, was incubated with 1 g L^-1 of nanoparticle suspension, in the absence of agitation, showing a 100 % capture efficiency, according to plate count. A nanoparticle regeneration method was developed, despite the known irreversibility of such bacterial-nanosurface binding, restoring the bacteria capture capability. This nanomaterial represents a competitive option to eliminate microbiological contamination in water as an alternative strategy to antibiotics, aimed at reducing microbial resistance dissemination. Finally, beyond their excellent features in terms of colloidal stability, binding performances, and biocompatibility this nanoparticle synthesis is cost effective, scalable, and environmentally sustainable.