Abstract
Magnetic nanoparticles of Fe3O4 were synthesized and characterized using transmission electron microscopy and X-ray diffraction. The Fe3O4 nanoparticles were found to have an average diameter of 5.48 ±1.37 nm. An electrochemical biosensor based on immobilized alkaline phosphatase (ALP) and Fe3O4 nanoparticles was studied. The amperometric biosensor was based on the reaction of ALP with the substrate ascorbic acid 2-phosphate (AA2P). The incorporation of the Fe3O4 nanoparticles together with ALP into a sol gel/chitosan biosensor membrane has led to the enhancement of the biosensor response, with an improved linear response range to the substrate AA2P (5-120 μM) and increased sensitivity. Using the inhibition property of the ALP, the biosensor was applied to the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). The use of Fe3O4 nanoparticles gives a two-fold improvement in the sensitivity towards 2,4-D, with a linear response range of 0.5-30 μgL-1. Exposure of the biosensor to other toxicants such as heavy metals demonstrated only slight interference from metals such as Hg2+, Cu2+, Ag2+ and Pb2+. The biosensor was shown to be useful for the determination of the herbicide 2, 4-D because good recovery of 95-100 percent was obtained, even though the analysis was performed in water samples with a complex matrix. Furthermore, the results from the analysis of 2,4-D in water samples using the biosensor correlated well with a HPLC method.
Highlights
Magnetic nanoparticles such as Fe3O4 nanoparticles have been widely used in the collection and separation of bioactive molecules, targeted drug delivery and biomedical applications
In this work we report the use of the enzyme alkaline phosphatase (ALP) together with the Fe3O4 nanoparticles to construct an enzyme based biosensor for 2,4-D determination
When the enzyme ALP was mixed with the Fe3O4 nanoparticles, the cluster-like structure disappeared completely and the nanoparticles seemed to be separated (Figure 2b)
Summary
Magnetic nanoparticles such as Fe3O4 nanoparticles have been widely used in the collection and separation of bioactive molecules, targeted drug delivery and biomedical applications. The many techniques of immobilization of biomolecules on the surface of magnetic nanoparticles have enabled the production of bioconjugates with magnetic properties and these substances are useful for the delivery and recovery of biomolecules in biomedical applications. Because of their submicron dimensions and special chemical and physical properties, Fe3O4 nanoparticles have been applied to the construction of biosensors based on DNA, proteins and enzymes with reported improved detection limits, sensitivity, and reduced response times. In this work we report the use of the enzyme alkaline phosphatase (ALP) together with the Fe3O4 nanoparticles to construct an enzyme based biosensor for 2,4-D determination. To demonstrate the usefulness of the biosensor developed, water samples from rice fields were analysed for 2,4-D with the biosensor
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