Immobilized laccases on modified magnetic nanoparticles for degradation of common psychiatric drugs used during COVID-19 pandemic

Abstract

The COVID-19 pandemic has brought several consequences to mental health in population, including depression, stress, anxiety, and related problems. Thus, it has been reported an increment on prescription rates of medicines to treat these disorders. Pharmaceuticals are considered as emerging pollutants (EP) of aquatic systems due to its persistence in waters since they are resistant to conventional wastewater treatments. Ecological and toxicological risks to environment, living organisms and human health derived EP have been demonstrated. Thus, different technologies have been applied to overcome this issue. Biocatalysis appears as a novel and suitable approach for the remotion of psychiatric drugs waters due to its important advantages, including biocompatibility and high power of degradation. Here, we implemented a biocatalytic system consisting of the immobilization of a purified cocktail of laccases Pycnoporus sanguineus on magnetic modified carbon nanofibers (mCNF) by physical adsorption, which was made to deal with low stability and non-reusability of the free enzymes. The structural and morphological characterization of the matrix nanomaterial and the immobilized enzyme was determined by SEM, EDS and FTIR. The enzymatic behavior of both, free and immobilized system was evaluated by the determination of the loading enzyme. The pH and storage stability were analyzed by measuring the enzymatic activity over ABTS. Finally, the immobilized system was evaluated in the degradation of 25 µg/mL of venlafaxine in ultrapure water and a real sample of wastewaters by using 10 mg of the immobilized biocatalyst. Results of the characterization confirmed the magnetic modification of the carbon nanofibers by the formation of iron oxide nanoparticles over the surface of the carbon nanofibers. Moreover, the maximum loading of laccases on the mCNFs was about 73 %, and the immobilized laccases exhibited excellent pH and storage stability. The highest enzymatic activity of the immobilized laccases was found to be at pH 5, in which the enzyme retained 75 % of its initial activity after 4 weeks at 4 °C. The immobilized laccases system has shown potential results in the degradation of venlafaxine in an aqueous medium. Finally, the nanobiocatalyst was able to remove the 69 % of the venlafaxine (VFX) after 18 h.