Construction and characterization of novel amperometric plant tissue-based biosensors

Thesis (Ph. D.)--University of Hawaii at Manoa, 1992.Includes bibliographical references (leaves 134-141)Microfiche.xiv, 141 leaves, bound ill. (some col.) 29 cmA biosensor is an analytical device in which a biological material, capable of specific chemical recognition, is in intimate contact with a physicochemical transducer to give an electrical signal. In this research, plant tissue materials (as the molecular recognition element) are coupled to electrochemical transducers to construct selective analytical biosensors for the detection of important analytes. The use of eggplant fruit as a source of polyphenol oxidase to construct an amperometric biosensor for catechol detection is demonstrated. Amperometric measurements are based on the detection of catechol quinone produced at the electrode surface. The characterization of the novel sensor with respect to biocatalytic loading, linear dynamic range, sensitivity, selectivity and lifetime is reported. A use of a novel thin layer electrode design, with a plant tissue reactor and a sensing tin oxide collector electrode, is reported for amperometric detection in flow injection analysis and compared with previous carbon paste electrode designs. Eggplant fruit containing the enzyme, polyphenol oxidase is used as the selective biocatalyst. The new system, evaluated for the case of catechol measurements, is shown to offer superior sensitivity, dynamic range and detection limits. In vitro cultured tobacco callus tissue, which contains high activity of peroxidase, is used to construct an amperometric biosensor for the detection of hydrogen peroxide. The tissue is incorporated into a carbon paste matrix along with ferrocene, an electron mediator. The detection of hydrogen peroxide was accomplished through its enzymatic reduction mediated by ferrocene. Comparison studies conducted with normally grown types of tobacco tissues indicate that the callus tissue has the highest biocatalytic activity and the least variance between tissue preparations with respect to sensor response toward hydrogen peroxide. Additionally, the sensor exhibits a remarkably long lifetime of about five months. Other important characteristics of the sensor include fast response times, wide dynamic range, and very low detection limits. The possibility of using genetically transformed (transgenic) plants; specifically, transgenic potato (Solanum tuberosum) and transgenic tobacco (Nicotiana tabacum), in the construction of an amperometric biosensor for the detection of phenyl-B-glucuronide was attempted as an application of recombinant DNA technology in biosensor construction