Abstract
Enzymatic detection of organophosphate (OP) compounds can be tailored using highly sensitive and selective enzymes in the development of biosensors. Previously, mutant (YT) phosphotriesterase (PTE) was reported to efficiently hydrolyze Sp and Rp enantiomers of phosphotriester. This study reports the use of phosphotriesterase mutant YT (YT-PTE) immobilized onto reduced graphene oxide (rGO) and fabricated onto a screen-printed carbon electrode (SPCE) for electrochemical detection of OP compounds. Immobilization of YT-PTE onto rGO was secured using N-hydroxysuccinimide (NHS) and N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide (EDC) cross-linker, and the resulting immobilized enzyme was able to retain up to 90% of its activity. Electrochemical analysis of the SPCE/rGO/YT-PTE showed detection of paraoxon in a linear range of 1 mM–0.005 μM with its limit of detection as low as 0.11 μM. SPCE/rGO/YT-PTE exhibited high selectivity towards paraoxon and parathion and have good reproducibility. Furthermore, detection of paraoxon was also possible in a real water sample with only minor interferences.
Highlights
Enzymatic detection of organophosphate (OP) compounds can be tailored using highly sensitive and selective enzymes in the development of biosensors
Immobilization of YTPTE onto reduced graphene oxide (rGO) changed the morphology of screen-printed carbon electrode (SPCE)/rGO/YTPTE into a more compact and smoother appearance as shown in Figure 1(b). is morphology is attributed to the formation of an immobilized YT-PTE layer on top of rGO, which inadvertently indicated the success of immobilization of the enzyme onto rGO surfaces [46]
The incorporation of rGO as the support for immobilizing YT-PTE aided in the electron transfer flow within the biosensor. e constructed biosensor was shown to be able to detect the oxidation signal of pNP, which is a product of enzymatic hydrolysis of paraoxon. e electrochemical sensor utilizing rGO and YTPTE in this work recorded a linear range of 1 mM–0.05 μM with a detection limit measured at 0.11 μM
Summary
Enzymatic detection of organophosphate (OP) compounds can be tailored using highly sensitive and selective enzymes in the development of biosensors. Is study reports the use of phosphotriesterase mutant YT (YT-PTE) immobilized onto reduced graphene oxide (rGO) and fabricated onto a screen-printed carbon electrode (SPCE) for electrochemical detection of OP compounds. Phosphotriesterase (PTE), a type of OPH, has been shown to be able to hydrolyze OP compounds such as paraoxon and parathion exceptionally well [13, 14]. In addition to high affinity towards various OP compound enantiomers, they exhibit enhanced kinetic value resulting in a faster hydrolysis rate of OP compound than other mutant variants and wild-type PTE [15]. Is enzyme is a suitable candidate for the development of a biosensor utilizing an on-site detection method where the OPH will act as a bioreceptor that is fabricated onto a screen-printed electrode to allow for the electrochemical detection of specific OP compounds [16]. In addition to the detection ability against OP compounds, using PTE as a biosensor is a technique that can be done in a relatively short amount of time and both the electrode and enzyme are relatively inexpensive [17]
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