Development of needle-type biosensor system for monitoring of fish health

近年来，大规模爆发的致病性细菌感染导致大量鱼类死亡，给养鱼场造成了巨大的经济损失。因此，养鱼场有必要定期检查鱼的健康状况，并尽快发现异常情况。几项研究表明，血糖水平与鱼类的应激水平密切相关，并代表呼吸或营养紊乱的状态。最近的研究还表明，血液中胆固醇水平的降低是对细菌感染抵抗力降低的一个有用指标。因此，测定血糖和胆固醇对于确定鱼的健康状况是很重要的。为快速、简便地测定鱼类血液中的葡萄糖水平，研制了一种针式生物传感器系统。该传感器由针型中空容器（18号针）、固定化酶膜和钌配合物光纤探头组成。以葡萄糖氧化酶、叠氮化物悬垂型水溶性光聚合物和超薄透析膜为原料制备酶膜。将光纤探针插入放置在针状中空容器中的卷曲酶膜中。校正曲线对鱼血浆中葡萄糖水平呈线性关系。一次检测在3分钟内完成。在不更换酶膜的情况下，60次重现性良好。传感器被插入鱼的尾静脉来测量血糖水平。传感器在插入后立即做出反应，血糖水平可以监测。在48 ~ 157 mg d1-1范围内，传感器测定值与常规方法测定值具有良好的相关性（相关系数为0.9474）。

Mass outbreaks of pathogenic bacterial infections have killed large quantities of fish in recent years, causing great financial damage to fish farms. Periodic checks of fish health and detection of abnormalities as quickly as possible are thus necessary at fish farms. Several studies have shown blood glucose levels closely correlate to the level of stress in fish and represent the state of respiratory or nutritional disturbance. Recent studies have also clarified that decreased levels of blood cholesterol represent a useful indicator of reduced resistance to bacterial infection. In this manner, determination of blood glucose and cholesterol is important for ascertaining the health of fish. A needle-type biosensor system was developed for rapid and simple determination of glucose levels in fish blood. The sensor comprises a needle-type hollow container (18-gauge needle), immobilized enzyme membrane and optic fiber probe with ruthenium complex. The enzyme membrane was prepared from glucose oxidase, azide-unit pendant water-soluble photopolymer and an ultra-thin dialysis membrane. The optic fiber probe was inserted into the rolled enzyme membrane placed in the needle-type hollow container. The calibration curve was linear for glucose levels in fish plasma. One assay was completed within 3 min. A good reproducibility was observed for 60 times without exchange of the enzyme membrane. The sensor was inserted into the caudal vein of fish to measure blood glucose levels. The sensor responded immediately after insertion and glucose levels could be monitored. Good correlations were observed between values determined using the sensor and conventional methods in the range of 48-157 mg d1-1 (correlation coefficient, 0.9474).