Amperometric biosensor-based microsystems for detecting analytes of biomedical importance

Abstract: Monitoring in the biomedical field is rapidly emerging as the most important application area of miniaturized analytical devices. Diagnostics, disease monitoring, drug development, and medical research are important areas taking full advantage of the short response time, reduced sample consumption, low costs, and reduced power requirements of miniaturized analytical tools. Such tools can either integrate several standard analytical steps (micro-Total Analysis System, µTAS, or Lab-on-a-Chip) or consist only of detection units, which do not need sample preparation steps (e.g. microsystems based on biosensors). Electrochemical detectors are of special interest in developing miniaturized analytical devices, because they are simple, easy to miniaturize with already established technologies, do not require labeling procedures, and yield reliable results often without previous separation steps. Amperometric biosensor-based microsystems are analytical devices combining at micrometer scale the advantages of electrochemical detection with the selectivity of biological or biologically-derived sensing elements (e.g. the selectivity of an enzyme for its substrate). Several such microsystems are meeting the requirements of in vivo or ex vivo monitoring in the biomedical field. Needle type amperometric microsensors are currently used to monitor neurotransmitters in vivo in animal brain, microdialysis probes combined with flow-through biosensor-based microdetectors are used to monitor glucose and lactate from head trauma patients in neurointensive care, and ex vivo monitoring of glucose with portable amperometric biosensors is part of daily life for those suffering of diabetes. In addition, some of the new applications of amperometric microsensors (e.g. Scanning Electrochemical Microscopy, SECM) allow investigation of biochemical processes even at single cell level. This thesis is focusing on several aspects of amperometric biosensor-based microsystems: (i) biosensor improvement by use of both novel enzymes, and enzyme immobilization methods suitable for microelectrodes, (ii) new detection procedures/ schemes, based on surface patterned enzyme microstructures and Scanning Electrochemical Microscope, and (iii) device design, fabrication and evaluation.