Cellulose-derived biocatalysts and neutralizing gels for pesticides: how to eliminate and avoid intoxication?

Abstract

The threat of intoxication by organophosphates – pesticides and chemical warfare – is a real concern worldwide. Fast, efficient and non-aggressive approaches for prevention and treatment are required. The use of functionalized biopolymers towards chemical neutralization of organophosphate is strategic since it is environmentally friendly. Herein, three carboxymethyl cellulose-derived biocatalysts were achieved via covalent functionalization with hydroxamates and imidazoles, targeted on the carboxylic acids of the cellulosic biopolymer. The aimed strategy was successful, confirmed by characterizations with Fourier-transform infrared spectroscopy, potentiometric titration, thermogravimetric analysis, zeta potential titrations, size-exclusion chromatography with multi-angle static light scattering, colorimetric test with iron (III) and rheological assays. The materials in colloidal form were highly reactive in the catalytic neutralization -evaluated by kinetic studies - with rate enhancements up to 10⁷-fold for the real-life Paraoxon, compared to the reaction in the absence of biocatalysts. Chemical selectivity towards the phosphorus center was accomplished – the desirable pathway that leads to less toxic products – and maintained the reactivity for at least 5 reaction cycles. Furthermore, the biocatalysts were processed as neutralizing gels aiming for skin intoxication prevention against organophosphates. Indeed, in vitro permeation assays evidenced that the gels eliminated 100% of the toxic agent after 24 hours. The gels were able to destroy the organophosphates, whilst the phenolic degradation product was detected in assay. Thus, these results emphasize the potential of biocompatible polymeric materials as interesting platforms to anchor reactive groups to design catalytic materials aiming chemical decontamination and security.