Amperometric biosensor for glyphosate based on the inhibition of tyrosinase conjugated to carbon nano-onions in a chitosan matrix on a screen-printed electrode.

Glyphosate [N-(phosphonomethyl)glycine] is the most frequently used herbicide to date. Due to its indiscriminate use, it has become a globally occurring pollutant of surface waters. A biosensor for glyphosate is described here that consists of a carbon nano-onion/tyrosinase conjugate immobilized in a chitosan matrix on a screen-printed electrode.

Kinetic, spectroscopic and computational docking study of the inhibitory effect of the pesticides 2,4,5-T, 2,4-D and glyphosate on the diphenolase activity of mushroom tyrosinase.

The inhibitory effect of 2,4,5-T, 2,4-D, glyphosate and paraquat on the diphenolase activity of mushroom tyrosinase for oxidation of L-DOPA has been investigated by kinetic measurements, fluorescence spectroscopy and computational docking analysis. 2,4,5-T and 2,4-D inhibit the diphenolase activity of the enzyme following a competitive mechanism, while glyphosate is a mixed inhibitor according to Lineweaver-Burk kinetic analysis. The inhibitory activity follows the order glyphosate >2,4,5-T > 2,4-D with IC values of 65, 90 and 106 μM, respectively.

Preparation and characterization of alkaline phosphatase, horseradish peroxidase, and glucose oxidase conjugates with carboxylated carbon nano-onions.

Carbon nanomaterials have emerged as suitable supports for enzyme immobilization and stabilization due to their inherently large surface area, high electrical conductivity, chemical stability, and mechanical strength. In this paper, carbon nano-onions (CNOs) were used as supports to immobilize alkaline phosphatase, horseradish peroxidase, and glucose oxidase. CNOs were first functionalized by oxidation to generate carboxylic groups on the surface followed by the covalent linking of using a soluble carbodiimide as coupling agent.