Development of an integrated thermal biosensor for the simultaneous determination of multiple analytes

A flow injection thermal microbiosensor was designed for the simultaneous determination of multiple analytes. The biosensor consisted of five thin-film thermistors which were located along a single microchannel. The device was fabricated on a quartz chip by micromachining. The feasibility of employing this system for the detection of two independent enzyme reactions was demonstrated using two different pairs of enzymes, urease-penicillinase and urease-glucose oxidase. The enzymes were immobilized on agarose beads, which were then sequentially packed into distinct regions of the microchannel. Using this method, samples containing urea mixed with penicillin V or with glucose were simultaneously analysed. Linear ranges of up to 20 mmol l^-1 urea, 40 mmol l^-1 penicillin V and 8 mmol l^-1 glucose (saturated with O₂) were obtained using a flow rate of 30 μl min^-1 and a sample volume of 20 μl. The relative standard deviations for urea and penicillin V assays were 1.13 and 2.42% for the first 100 samples and 1.17 and 2.78% for 200 samples, respectively. The sensor is capable of analysing 25 samples per hour.