Research Progress in Area 2 方向 ( 二 ) 課題進展 143 Abstract Marine pathogens cause severe economic losses in the Pearl River Delta every year due to infection of aquacultural populations. Bacterially caused diseases, such as Vibriosis, are some of the worst offenders. To facilitate reliable and sensitive monitoring, an impedimetric biosensor specific to pathogenic marine bacteria will be developed and integrated with a microfluidic platform to ensure simple operation and a fast response time. The size of bacteria makes them ideal for impedimetric sensing, as the area covered on a microelectrode during a binding event creates a proportional response in the charge transfer resistance as measured by electrochemical impedance spectroscopy. Strategies for decreasing background noise and increasing response will be investigated, including the use of nanoporous gold as an electrode material and the surface density of recognition molecules. Several sensors will be made specific to species of the genera Vibrio and Streptococcus and tested on both simulated and real fish farm water samples. Research Activities and Progress • Cultured Vibrio parahaemolyticus for use as a reference analyte; • Investigated the effects of temperature, stir rate, addition of surfactants, and electrode orientation on dynamic hydrogen bubble templated (DHBT) nanoporous gold; • Tested the interfering effects of seawater samples on charge transfer resistance on bare electrode; • Performed initial testing of planar electrode impedimetric sensor with buffer samples spiked with V. parahaemolyticus. Key Findings • DHBT gold morphology is highly dependent on the uniformity of the underlying gold substrate; • A plating potential of -4 V with 0.01% Triton X-100 and 500 RPM stirring provides optimal nanoporous gold morphology; • Ferricyanide is a suitable redox probe for this system; • Binding of target bacteria decreases charge transfer resistance, likely due to the high ionic strength of marine bacteria’s cytoplasm; • Presence of target bacteria generates a drop in charge transfer resistance of up to 60%. Research Output Publication 0 Trained personnel 3 Development of an Impedimetric Biosensing System for the Detection of Marine Pathogens Prof. Minhua Shao The Hong Kong University of Science and Technology Fig. 1 A wafer of in-house fabricated sensors (a) and an SEM image of DBHT nanoporous gold (b).
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