组成图示
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传感器类型
其他（电容式生物传感器）
检测对象
C-反应蛋白（C-reactive protein, CRP）；样品基质：PBS缓冲液（模拟样品，作者称可拓展至血清）
检测原理
该传感器采用无标记电容/介电检测原理。金叉指电极与NCD介电层构成电容器，金表面经MPA自组装层和EDC/NHS化学共价固定CRP抗体。当样品中的CRP抗原与表面抗体结合后，形成抗原-抗体复合物，使电极间介电层厚度、极化率和偶极矩发生变化。由于蛋白质复合物分子尺寸增大，其旋转弛豫时间变长，介电常数随频率的色散改变，进而引起电容和阻抗变化。测量在50–350 MHz范围内进行，并用Cole–Cole模型拟合弛豫时间τ和极化率常数m。CRP浓度升高时，τ由仅抗体的10^-16–10^-13 s增至10^-11 s，m由0.5093增至0.766，电容/介电响应随之增强，从而实现浓度依赖检测。
检测灵敏度
线性范围: 25–800 ng/ml（208 MHz下25–1000 ng/ml）；R^2 = 0.9255；CV: 1.72%
效应效果
在PBS缓冲液中，传感器对25–800 ng/ml CRP呈现浓度依赖响应，在208 MHz下线性范围可延至25–1000 ng/ml，R^2=0.9255，CV=1.72%。以800 ng/ml BSA作为阴性对照，未观察到明显非特异响应，表明抗体识别具有选择性。与文献方法相比，ELISA检出限约1 mg/l，SPR约2–5 mg/l，磁免疫分析约0.2 mg/l，适配体化学发光可达0.005 mg/l；本方法检测范围为0.025–0.8 mg/l，虽灵敏度不及部分标记方法，但无需荧光/化学发光标记，样品处理少，直接输出电信号，成本低。作者认为优化后可用于心血管风险早期诊断，但指出真实血清中离子导电损失和屏蔽可能限制电容信号。
传感器的构成
- 基底：硅(100)衬底，经金刚石粉抛光和超声处理，提供机械支撑与成核基础
- 介电层：纳米晶金刚石(NCD)薄膜，PECVD生长约1.5 μm，作为金电极间介电层并减少非特异吸附
- 粘附层：50 nm钨(W)层，DC溅射沉积，提高金与NCD表面粘附
- 换能电极：500 nm金(Au)叉指电极(GID)，24指、长750 μm、宽25 μm、间距25 μm，形成电容换能结构
- 微孔结构：SU-8微孔，深40 μm，图案化于GID上方，便于抗体固定与样品接触
- 自组装层：3-巯基丙酸(MPA)自组装单分子层(SAM)，在金表面形成羧基，用于共价固定抗体
- 识别元件：CRP单克隆抗体，100 μg/ml PBS孵育1 h，通过EDC/NHS活化羧基共价结合，捕获CRP抗原
- 封闭剂：100 mM乙醇胺/PBS，4 ℃孵育2 h，封闭未反应羧基，降低非特异结合
中文摘要
C-反应蛋白（CRP）是反映炎症和心血管疾病风险的潜在生物标志物。本研究开发了一种新型电容式生物传感器，用于检测CRP抗原。该传感器以纳米晶金刚石（NCD）薄膜为介电层，在其表面制备金叉指电极（GID）构成电容器。GID表面通过3-巯基丙酸自组装单分子层和EDC/NHS化学共价固定CRP抗体，并用傅里叶变换红外光谱和接触角测量确认固定。检测时，将不同浓度CRP抗原孵育于传感器表面，通过电容/介电常数测量获得响应。利用Cole–Cole模型估算弛豫时间和极化率常数：仅抗体时弛豫时间约为10^-16–10^-13 s，与CRP抗原孵育后增至10^-11 s，表明抗原被抗体捕获；极化率常数也随抗原浓度升高而增大。传感器响应同时依赖CRP浓度（25–800 ng/ml）和频率（50–350 MHz）。在优化条件下，该电容式生物传感器有望用于检测疑似患者中升高的蛋白风险标志物，辅助疾病早期诊断。
英文摘要
C-reactive protein (CRP) is a potential biomarker whose elevated levels in humans determine cardiovascular disease risk and inflammation. In this study, we have developed a novel capacitive biosensor for detection of CRP-antigen using capacitor with interdigitated gold (GID) electrodes on nanocrystalline diamond (NCD) surface. The NCD surface served as a dielectric layer between the gold electrodes. GID-surface was functionalized by antibodies and the immobilization was confirmed by Fourier transform spectroscopy (FT-IR) and contact angle measurements. The CRP-antigen detection was performed by capacitive/dielectric-constant measurements. The relaxation time and polarizability constants were estimated using Cole-Cole model. Our results showed that the relaxation time constant (tau) of only CRP-antibody was within 10(-16)-10(-13)s, which was increased to 10(-11)s after the incubation with CRP-antigen, suggesting that the CRP-antigen was captured by the antibodies on GID-surface. In addition, polarizability constant (m) of CRP was also increased upon incubation with increasing concentration of CRP-antigen. Our results showed that the response of GID-NCD-based capacitive biosensor for CRP-antigen was dependent on both concentration (25-800ng/ml) as well as frequency (50-350MHz). Furthermore, using optimized conditions, the GID-NCD based capacitive biosensor developed in this study can potentially be used for detection of elevated levels of protein risk markers in suspected subjects for early diagnosis of disease.