QUANTITATION OF CHOLINE IN THE EXTRACELLULAR FLUID OF BRAIN-TISSUE WITH AMPEROMETRIC MICROSENSORS
QUANTITATION OF CHOLINE IN THE EXTRACELLULAR FLUID OF BRAIN-TISSUE WITH AMPEROMETRIC MICROSENSORS
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DOI：
10.1021/ac00089a006
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发表时间：
1994-09-01
影响因子：
7.4
通讯作者：
MICHAEL, AC
中科院分区：
文献类型：
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作者：
GARGUILO, MG;MICHAEL, AC
通过将辣根过氧化物酶和胆碱氧化酶固定到具有可交联氧化还原聚合物的碳纤维微圆柱电极上，制备了用于检测脑组织细胞外液中胆碱的电流微传感器。微圆柱体的直径为7或10μm，长度为200-400μm。为了检测胆碱，微传感器在相对于 SCE 的 -0.1 V 施加电位下运行。在此电位下，电极无法检测到脑组织中存在的抗坏血酸和其他容易氧化的干扰分子。然而，抗坏血酸可以通过在含酶聚合物膜中充当还原剂来干扰对胆碱的反应。因此，需要使用 Nafion 覆盖层，以便在存在生理相关浓度的抗坏血酸（类似于 200 μM）的情况下可靠地检测胆碱。 Nafion 涂层微传感器的检测限类似于 5 μM 胆碱，在 37 摄氏度下进行体外校准时，线性响应超过 100 μM。将微传感器暴露在脑组织中数小时，会导致氧化还原聚合物表面覆盖度损失不到 10%，对胆碱的敏感性损失不到 25%。为了评估微传感器监测脑组织中胆碱水平的能力，将少量胆碱溶液注射到距微传感器约1毫米的脑组织中。通过在体内实验后校准传感器，将微传感器处产生的电流转换为胆碱浓度。所得的胆碱浓度与通过适当的扩散方程预测的浓度非常一致。
Amperometric microsensors for the detection of choline in the extracellular fluid of brain tissue have been prepared by immobilizing horseradish peroxidase and choline oxidase onto carbon fiber microcylinder electrodes with a cross-linkable redox polymer. The microcylinders have diameters of 7 or 10 mu m and lengths of 200-400 mu m. To detect choline, the microsensors are operated at an applied potential of -0.1 V vs SCE. At this potential, ascorbate and other easily oxidizable interferent molecules present in brain tissue are not detected by the electrode. Ascorbate, however, can interfere with the response to choline by acting as a reducing agent in the enzyme-containing polymer film. So, a Nafion overlayer is required in order to reliably detect choline in the presence of physiologically relevant concentrations of ascorbate (similar to 200 mu M). The Nafion-coated microsensors have a detection limit of similar to 5 mu M choline and give a linear response beyond 100 mu M when calibrated in vitro at 37 degrees C. Exposure of the microsensors to brain tissue for several hours causes less than a 10% loss in redox polymer surface coverage and less than a 25% loss in sensitivity to choline. To assess the ability of the microsensors to monitor choline levels in brain tissue, small volumes of a choline solution were injected into brain tissue at a site about I mm away from a microsensor. The current arising at the microsensor was converted to choline concentration by calibrating the sensor following the in vivo experiment. The resultant choline concentrations were in excellent agreement with those predicted by appropriate diffusion equations.