The area of biosensors have received great attention over the past three decades. The development of enzyme-based amperometric biosensors is the most rapidly growing in this area. This thesis focuses on new designs and fabrication of amperometric biosensors.; Screen-printed technology is a very important technique in the fabrication of amperometric biosensors for clinically and environmentally important species. A commercialized screen-printed microelectrode array was coupled to electrochemical codeposition of enzyme and metal for highly sensitive and selective determinations of glucose and lactate. The metallization scheme was then extended to the fabrication of screen-printed glucose strips by using palladium- and ruthenium-dispersed carbon, which were utilized in the preparation of inks. The printing process was thus simplified while sensitivity and selectivity were also greatly enhanced. These metallized electrodes offer efficient electrocatalytic action towards not only the detection of enzymatically-liberated peroxide but also that of dihydronicotinamide adenine dinucleotide. Phenol amperometric electrodes were also fabricated by directly mixing commercial carbon ink with tyrosinase.; Several new materials such as ultrathin porous carbon film and epoxy-based carbon paste were used in the development of novel biosensors in order to improve the stability of biosensors. Better selectivity was obtained through the use of rhodium-dispersed carbon paste for the detection of lactate. It was also illustrated that the TTF{dollar}sp+{dollar}/TTF mediating couple can be effectively retained in the membrane of a glucose biosensor if condensation carboxymethylated {dollar}beta{dollar}-cyclodextrin polymer was employed. A great sensitivity enhancement was demonstrated by a bioamplification scheme. Organic-phase biosensors based on the entrapment of enzymes within poly(ester-sulfonic acid) coating were developed for the determination of phenols and peroxides. The chelating agent EDTA was incorporated with enzyme and mediator in carbon paste matrix to eliminate the inhibitory effects.; In order to extend the application scope, amperometric remote biosensors and chemical sensors were developed for on-site, real-time monitoring of environmental samples. Carbon paste tyrosinase and horseradish-dimethylferrocene remote electrodes were constructed by connecting the probe with a long-shielded cable to the instrument for the measurements of phenols and peroxides, respectively. Remote monitoring was extended to effective electrocatalytic detection of environmentally important compounds like hydrazine and its derivatives by using a glassy carbon remote electrode modified with 3,4-dihydroxybenzaldehyde.
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