Berggren C, Johansson G
Chemical Center, University of Lund, Sweden.
Anal Chem. 1997 Sep 15;69(18):3651-7. doi: 10.1021/ac970203e.
Capacitive immunosensors were made by coupling monoclonal antibodies to thioctic acid, which had self-assembled on a gold electrode. Surface areas that were not covered were plugged with 1-dodecanethiol to make the layer dense and insulating. Cyclic voltammetry showed that the hexacyanoferrate redox reactions were blocked by this procedure. The capacitance of the electrode was evaluated from the current transients obtained when a potentiostatic step was applied. The immunosensor was placed in a flow system, and a capacitance decrease could be observed after injection of an unlabeled antigen. It was linear over almost three decades when plotted vs the logarithm of the antigen concentration. Human chorionic gonadotropin hormone could be determined in the range 1 pg/mL-1 ng/mL, with a detection limit of 0.5 pg/mL (15 10(-15) M). A similar response was obtained with immobilized F(ab)2 fragments. No cross-reactivity was observed with the thyrotropic hormone, which has one chain in common with gonadotropin. Monoclonal antibodies toward interleukin-2 immobilized on the immunosensor gave also a response over 1 pg/mL-1 ng/mL, with a detection limit of 1 pg/mL. An immunosensor with monoclonal antibodies toward human albumin gave a calibration curve with lower slope than the other proteins but still with a detection limit of 1 pg/mL.
电容式免疫传感器是通过将单克隆抗体与已自组装在金电极上的硫辛酸偶联制成的。未覆盖的表面积用1-十二烷硫醇堵塞，以使层致密且绝缘。循环伏安法表明，该过程阻断了六氰合铁酸盐的氧化还原反应。通过施加恒电位阶跃时获得的电流瞬变来评估电极的电容。将免疫传感器置于流动系统中，注入未标记抗原后可观察到电容降低。当与抗原浓度的对数作图时，它在近三个数量级内呈线性。人绒毛膜促性腺激素可在1 pg/mL - 1 ng/mL范围内测定，检测限为0.5 pg/mL（15×10⁻¹⁵ M）。固定化的F(ab)₂片段也获得了类似的响应。与促甲状腺激素未观察到交叉反应，促甲状腺激素与促性腺激素有一条共同链。固定在免疫传感器上的抗白细胞介素-2单克隆抗体在1 pg/mL - 1 ng/mL范围内也有响应，检测限为1 pg/mL。一种带有抗人白蛋白单克隆抗体的免疫传感器给出的校准曲线斜率比其他蛋白质低，但检测限仍为1 pg/mL。
