Kinetic properties of aryldialkylphosphatase immobilised on chitosan myristic acid nanogel

Abstract

Organophosphorus (OP) compounds are extensively used in agricultural practice for pest management. However, their residues have a long half-life in the ecosystem as well as in the agro-products, posing a serious threat to human and animal health. Aryldialkylphosphatase (EC 3.1.8.1) is widely used in detoxification procedures. In the present study, aryldialkylphosphatase was immobilised on synthesised cross-linked nano-sized gel particles, also known as nanogels, in order to enhance the enzyme's physicochemical properties. Accordingly, a new nanogel consisting of chitosan and myristic acid (CMA nanogel) was synthesised and characterised by way of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The aryldialkylphosphatase-CMA nanogel conjugate was then assayed by FTIR, and its physicochemical characteristics were also investigated. The data obtained from SEM and TEM showed the nanogels to be homogenous spherical particles less than 50 nm in diameter. The proper formation of the nanogel and nanobioconjugate was also confirmed by FTIR spectra. In comparison with the free enzyme, the pH and thermal stability of the aryldialkylphosphatase were enhanced by the covalent immobilisation. Moreover, the immobilised enzyme could maintain approximately half of its activity over more than one month. The kinetic parameters of the aryldialkylphosphatase-CMA nanogel conjugate were also shown to undergo remarkable improvements, hence the synthesised CMA-nanogel could act as a promising support for aryldialkylphosphatase immobilisation. It is suggested that the aryldialkylphosphatase-CMA nanogel could be used for detoxifying paraoxon; a nerve agent. Further clinical experiments are underway.