组成图示
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传感器类型
电化学生物传感器
检测对象
葡萄糖（glucose, D-glucose）；样品基质为磷酸盐缓冲液（PBS, pH 7.4），面向生理血糖范围检测
检测原理
葡萄糖与氧气透过环氧-聚氨酯（EPU）半透膜扩散至葡萄糖氧化酶（GOx）层。GOx催化D-葡萄糖氧化生成葡萄糖酸和过氧化氢（H2O2）。在0.7 V（vs SCE）恒电位下，H2O2在碳纳米管（CNT）纳米纱纤维刷状端表面被氧化，释放电子；电子经高导电DWNTs纤维网络传导至连接端，由恒电位仪记录为安培电流。CNT纤维的纳米多孔结构、刷状多纳米电极端和热退火提高的导电性促进酶活性中心与电极间的电子转移，使电流随葡萄糖浓度升高而增大，在2–30 mM范围内呈线性。EPU膜限制扩散并扩展线性范围。
检测灵敏度
LOD: 25 μM（Au镀层）；未镀金下限: 2 mM；线性范围: 2–30 mM；灵敏度: 7.2 nA mM−1（退火）、0.96 nA mM−1（未退火）、~6.8 nAmM−1（Au镀层）；热退火提升: 7.5倍；R^2 = 0.991（退火）、0.997（未退火）
效应效果
与Pt–Ir线圈相比，退火CNT纤维阳极峰电流23.3 μA mm−2（Pt–Ir 11.3），ΔEp 93 eV（Pt–Ir 177 eV），响应约10 s，快于20–200 s。退火灵敏度7.2 nA mM−1，未退火0.96 nA mM−1，热退火提高7.5倍；线性2–30 mM，R^2=0.991/0.997，优于或可比Pt线圈（1–6 nA mM−1、1–25 mM）。未退火传感器24 °C 5 mM葡萄糖PBS中10–70天稳定，90天下降；4 °C PBS 3个月亦下降。镀金端灵敏度约6.8 nA mM−1，检测下限由2 mM延至25 μM，范围25 μM–30 mM。作者认为可用于植入式、环境监测和低浓度药物检测。
传感器的构成
- 换能器电极：CNT纳米纱纤维（CNT nano-yarn fiber，DWNTs同心多层纳米多孔网络，直径约28 μm），作为微电极并传导电子
- 绝缘封装层：硅橡胶管（silastic tubing）与树脂胶（R.S resin adhesive），绝缘并固定纤维，露出1 mm刷状传感端和5 mm连接端
- 识别/催化元件：葡萄糖氧化酶（GOx），通过戊二醛（glutaraldehyde）在牛血清白蛋白（BSA）基质上交联固定于刷状端，催化葡萄糖氧化
- 信号产物：过氧化氢（H2O2），由GOx催化葡萄糖与O2生成，在0.7 V vs SCE被氧化产生电流
- 半透膜：环氧-聚氨酯（EPU）膜（PU、环氧树脂A/B、Brij 30/THF溶液浇铸，80 °C固化），控制葡萄糖和O2扩散并扩展线性范围
- 电极连接层：金（Au，约30 nm）镀层涂覆于CNT纤维连接端，降低接触电阻并扩展低浓度检测范围
中文摘要
本文设计了一种基于碳纳米管（CNT）纳米纱纤维的新型刷状电极，用于电化学生物传感器，并验证其作为酶法葡萄糖生物传感器的有效性。该CNT纳米纱纤维通过化学气相沉积（CVD）气流反应直接纺丝制备，以乙醇和丙酮混合物为碳源、铁纳米颗粒为催化剂。纤维直径约28 μm，由双壁碳纳米管（DWNTs）同心压实成多层纳米多孔网络结构。循环伏安测试表明，与Pt–Ir线圈电极相比，CNT纤维具有更优的电催化活性。将纤维电极端冷冻断裂形成刷状纳米结构，并在牛血清白蛋白（BSA）存在下用戊二醛交联固定葡萄糖氧化酶（GOx），外层包覆环氧-聚氨酯（EPU）半透膜。与标准参比电极对比测试显示，微型CNT纤维电极检测葡萄糖的灵敏度、线性范围和线性均优于Pt–Ir线圈电极。250 °C退火30 min可使葡萄糖灵敏度提高7.5倍；未退火CNT纤维传感器可稳定使用70天；在电极连接端镀金可将葡萄糖检测下限延伸至25 μM。结果表明，CNT纳米纱纤维在葡萄糖生物传感中表现出优于传统Pt–Ir电极的性能。
英文摘要
A novel brush-like electrode based on carbon nanotube (CNT) nano-yarn fiber has been designed for electrochemical biosensor applications and its efficacy as an enzymatic glucose biosensor demonstrated. The CNT nano-yarn fiber was spun directly from a chemical-vapor-deposition (CVD) gas flow reaction using a mixture of ethanol and acetone as the carbon source and an iron nano-catalyst. The fiber, 28 microm in diameter, was made of bundles of double walled CNTs (DWNTs) concentrically compacted into multiple layers forming a nano-porous network structure. Cyclic voltammetry study revealed a superior electrocatalytic activity for CNT fiber compared to the traditional Pt-Ir coil electrode. The electrode end tip of the CNT fiber was freeze-fractured to obtain a unique brush-like nano-structure resembling a scale-down electrical 'flex', where glucose oxidase (GOx) enzyme was immobilized using glutaraldehyde crosslinking in the presence of bovine serum albumin (BSA). An outer epoxy-polyurethane (EPU) layer was used as semi-permeable membrane. The sensor function was tested against a standard reference electrode. The sensitivities, linear detection range and linearity for detecting glucose for the miniature CNT fiber electrode were better than that reported for a Pt-Ir coil electrode. Thermal annealing of the CNT fiber at 250 degrees C for 30 min prior to fabrication of the sensor resulted in a 7.5 fold increase in glucose sensitivity. The as-spun CNT fiber based glucose biosensor was shown to be stable for up to 70 days. In addition, gold coating of the electrode connecting end of the CNT fiber resulted in extending the glucose detection limit to 25 microM. To conclude, superior efficiency of CNT fiber for glucose biosensing was demonstrated compared to a traditional Pt-Ir sensor.