The thesis focuses on the application of L-amino acids oxidase (L-AAO) in biosensors. L-AAO was immobilized in various electrode systems, including a platinum electrode system, the commercial ARAS system and a thick film electrode system, by poly(carbamoy1) sulfonate hydrogel (PCS gel) in different experiments....[ Read more ]

The thesis focuses on the application of L-amino acids oxidase (L-AAO) in biosensors. L-AAO was immobilized in various electrode systems, including a platinum electrode system, the commercial ARAS system and a thick film electrode system, by poly(carbamoy1) sulfonate hydrogel (PCS gel) in different experiments.

Chapter 1 introduces the importance of amino acids to humans and science. There are many conventional analysis methods. Limitations make the analysis of amino acids complicated. To develop a new analysis method, “biosensors” are introduced. How biosensors work in the analysis of amino acids, is briefly described.

Chapter 2 presents the principle of electrochemical detection of amino acids in a platinum electrode system coupled with L-amino acid oxidase (L-AAO). The enzyme involved is L-amino acid oxidase (L-AAO). L-AAO has a broad substrate range of amino acids. The system of analysis is based on the detection of hydrogen peroxide formed during the enzymatic oxidation of amino acids by L-AAO. The signal is observed due to oxidation of hydrogen peroxide on the surface of the platinum electrode at a special potential.

Chapter 3 demonstrates the principle of electrochemical detection of amino acids in the commercial ARAS system coupled with L-amino acid oxidase (L-AAO). During the deamination of amino acids by L-AAO, oxygen is consumed as an electron acceptor for generation of hydrogen peroxide. The ARAS system (Dr. Bruno Lange GmbH, Berlin, Germany), a commercial biosensors system using a Clark-oxygen electrode, is used to monitor the change in oxygen level in the buffer.

Chapter 4 describes the use of thick film electrodes in the analysis of amino acids. The detection is also based on the enzymatic generation of hydrogen peroxide. This thick film electrode system integrates the working electrode, counter electrode and reference electrode. Analysis can be done rapidly by inserting the thick film electrode into an adaptor followed by addition of substrate.

Chapter 5 reports the application of an L-AAO/Pt electrode system. The application shows the practicality of this biosensor. A commercial sweetener, EQUAL^® Spoon for Spoon^®, was analysed. A good correlation was found between the experimental result and the labelled ingredients. This good correlation demonstrates the practicality of the L-AAO/Pt electrode. Also, the broad substrate range of the L-AAO increases the flexibility of utilizing the biosensor in different fields of analysis.

Chapter 6 describes the use of the layer-by-layer (LbL) technique in development of L-AAO μ-reactors. The layer-by-layer (LbL) technique is a novel technique in encapsulation of enzymes on the nanometer scale. To reduce the cost of investigation, the same class of enzyme with L-AAO, glucose oxidase (GOD) is used as the template to be encapsulated. The encapsulated GOD is then immobilized on the thick film electrode by the layer-by-layer (LbL) technique. The activity of the encapsulated enzyme and the practicality of immobilization are shown by applying the thick film electrode for analysis.