组成图示
点击图片查看大图 · 依据论文自动绘制
传感器类型
其他（电容生物传感器）
检测对象
免疫球蛋白G（IgG）、心肌肌钙蛋白T（cardiac troponin T, TnT）；样品基质：PBS缓冲液、心脏病患者人血清
检测原理
该传感器为无标记电容免疫传感器。抗体通过戊二醛共价固定于铝电极表面，TnT通道还先形成2-氨基乙硫醇自组装单层以提高固定。当目标抗原（IgG或TnT）与固定抗体结合后，电极间生物分子层厚度、介电性质和界面电荷再分布发生变化。论文用等效电路描述：固定层引入电导Gb、电容Cb和边缘电容Cbio；抗原结合主要使Gb增大，从而在低频下提高平行等效电容Cp。测量时以1 kHz交流信号激励双电极，读取电容变化并计算相对电容变化(C-C0)/C0。抗原浓度越高，结合量越多，界面电导/极化变化越大，低频电容相对变化越大。
检测灵敏度
检测范围: 0.07 to 6.83 ng/mL（人血清）；0.01 ng/mL to 5 ng/mL（PBS）
效应效果
器件在PBS中可检测0.01–5 ng/mL TnT，在心脏病患者人血清中可检测0.07–6.83 ng/mL TnT，覆盖临床相关水平。选择性方面，anti-TnT电极暴露10 µg/mL非特异IgG后电容无明显变化；TnT溶液50 ℃加热30 min后响应降低，说明信号来自抗体-抗原结合。电容测量RSD在100–300 Hz约1.5%，较高频率低于0.3%；但相对电容变化样品间RSD约20%，作者认为重现性和校准尚未优化。与ELISA/ECLIA相比，该方案无需标记、步骤少，可用1 kHz便携电容表测量，具有低成本POC潜力，但商业化仍需微流控等优化。
传感器的构成
- 基底/绝缘介质：Si <100>晶圆经湿氧化形成350 nm SiO2层，作为电容介质与器件支撑
- 换能电极：热蒸发80 nm Al并光刻成两条平面Al条，宽1.5 mm、间距2 mm，用于电容测量
- 识别元件（IgG通道）：抗人IgG抗体（anti-IgG）与2.5%戊二醛混合后直接固定于Al表面，用于捕获IgG
- 识别元件（TnT通道）：2-氨基乙硫醇（cysteamine）自组装单层（SAM）修饰Al，经戊二醛活化后固定抗人TnT抗体（anti-TnT），用于捕获TnT
- 封闭剂：50 mM甘氨酸（glycine）封闭未反应醛基与非特异位点
中文摘要
本文研究一种简化的测量方案与器件结构，旨在开发低成本、无标记、即时检测（POC）电容生物传感器。其检测原理为：抗体与抗原结合后，两个平面铝电极之间的低频电容发生增加。器件以氧化硅片为基底，热蒸发铝形成两条平面电极，并在电极表面固定抗体层；固定方式包括直接戊二醛共价固定和经2-氨基乙硫醇自组装单层（SAM）活化后固定。作者以免疫球蛋白G（IgG）和心肌肌钙蛋白T（TnT）为分析物验证该方案。器件在心脏病患者人血清中可检测0.07–6.83 ng/mL的TnT，在磷酸盐缓冲液（PBS）中可检测0.01–5 ng/mL的TnT。论文还建立了等效电路模型，可复现实验电容—频率曲线。该方案采用1 kHz单频测量、铝电极和微型化双电极结构，有望降低仪器成本并实现便携化POC检测。
英文摘要
A simplified measurement scheme and device structure aiming at developing a low cost, label-free, point-of-care capacitive biosensor were investigated. The detection principle is the increase of low frequency capacitance between two planar Al electrodes observed after antibody-antigen interaction. The electrodes, deposited on oxidized Si wafers, were covered with an antibody layer, with and without using self-assembled thiol monolayer. Immunoglobulin G (IgG) and cardiac troponin T (TnT) were used as analytes to asses this proposal. The device was able to detect successfully TnT levels in the range 0.07 to 6.83ng/mL in human serum from patients with cardiac diseases and in the range 0.01ng/mL to 5ng/mL for TnT in phosphate buffer saline. An equivalent circuit model able to reproduce the general behavior of experimental capacitance versus frequency curves was presented. The investigated features that have potential to reduce costs and simplify measurements were: use of single, low frequency (1kHz) measurement signal, within the range of low cost portable capacitance meters; employment of a lower cost electrode material, aluminum, instead of gold electrodes; and use of simple and miniaturized planar two-electrodes arrangement, thus making a portable system for point-of-care applications.