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
L-乳酸（L-lactate）；样品基质：磷酸盐缓冲液、商业牛奶、人血清
检测原理
该传感器以pTTCA/MWNT复合膜为界面，LDH和NAD+共价/吸附固定于膜上。当L-乳酸进入检测液时，LDH催化乳酸与NAD+反应生成丙酮酸、NADH和H+；生成的NADH在0.3 V（vs Ag/AgCl）电极表面被氧化为NAD+，释放电子并产生安培电流。由于NADH氧化电流与乳酸浓度成正比，稳态电流随乳酸浓度增加而增大。pTTCA/MWNT复合膜通过高导电通道、大比表面积和共价固定策略提高酶负载量与电子转移速率，实现低电位检测，减少干扰物影响。
检测灵敏度
LOD: 1 μM；线性范围: 5–90 μM；灵敏度: 0.0106 μA/μM；R^2 = 0.9995；S/N = 3
效应效果
传感器对谷氨酸、抗坏血酸、葡萄糖、尿酸、多巴胺和对乙酰氨基酚（各0.5 mM）无安培响应，对5 μM乳酸有明显响应，选择性良好。5 μM乳酸连续5次测量RSD为4.3%；0.5 μM乳酸传感器间和运行间RSD分别为1.7%和1.1%。4 ℃保存30天后仍保持98%初始灵敏度，10 s内达到95%稳态电流。实际样品稀释1000倍后标准加入法测得人血清乳酸0.22±0.01 mM、牛奶0.18±0.006 mM，RSD 5.8%；与生化分析仪结果（血清0.24±0.01 mM、牛奶0.174±0.01 mM）一致。相比pTTCA/LDH/NAD+电极，灵敏度提高40倍以上。
传感器的构成
- 基底/换能器电极：金电极（Au electrode，直径3 mm，面积0.196 cm2），作为工作电极提供电子转导与安培检测界面
- 纳米材料修饰层：酸化羧基化多壁碳纳米管（MWNT，4–12 nm），与TTCA共电聚合形成复合膜，提高导电性、比表面积和电子转移
- 导电聚合物固定层：聚-5,20-50,200-噻吩-30-羧酸（pTTCA），由TTCA单体在0–1.6 V电聚合，提供羧基用于共价固定LDH和NAD+
- 交联活化试剂：EDC和NHS，活化pTTCA/MWNT膜中游离羧基，促进酶氨基与羧基形成酰胺键
- 识别元件：乳酸脱氢酶（LDH，兔肌肉，811 U/mg），催化L-乳酸氧化为丙酮酸并还原NAD+
- 辅因子/信号前体：氧化型烟酰胺腺嘌呤二核苷酸（NAD+），作为LDH辅因子，反应生成NADH并在电极氧化产生电流
- 检测介质/电化学池：磷酸盐缓冲液（PB，pH 6.8）、Ag/AgCl参比电极和铂丝对电极，维持酶活性并实现恒电位安培检测
中文摘要
本文报道了一种基于导电聚合物聚-5,20-50,200-噻吩-30-羧酸（pTTCA）与多壁碳纳米管（MWNT）复合膜修饰金电极的安培法乳酸生物传感器。乳酸脱氢酶（LDH）和氧化型烟酰胺腺嘌呤二核苷酸（NAD+）被共固定于pTTCA/MWNT复合膜上，其中酶通过氨基与膜中羧基形成共价键而稳定固定。作者采用石英晶体微天平（QCM）、扫描电子显微镜（SEM）和电化学方法对修饰电极进行表征，并优化了施加电位、pH和温度等实验参数。结果表明，pTTCA/MWNT复合膜可负载足量酶并促进电子转移，使灵敏度、稳定性和重现性显著提高。传感器在5–90 μM范围内线性良好（R^2=0.9995），灵敏度约为0.0106 μA/μM，基于信噪比3的检出限为1 μM。该传感器成功用于商业牛奶和人血清中L-乳酸浓度的检测。
英文摘要
An amperometric lactate biosensor was developed based on a conducting polymer, poly-5,2'-5',2''-terthiophene-3'-carboxylic acid (pTTCA), and multiwall carbon nanotube (MWNT) composite on a gold electrode. Lactate dehydrogenase (LDH) and the oxidized form of nicotinamide adenine dinucleotide (NAD(+)) were subsequently immobilized onto the pTTCA/MWNT composite film. The modified electrode was characterized by quartz crystal microbalance (QCM), scanning electron microscopy (SEM), and electrochemical experiments. The detection signal was amplified by the pTTCA/MWNT assembly onto which a sufficient amount of enzyme was immobilized and stabilized by the covalent bond formation between the amine groups of enzyme and the carboxylic acid groups of the pTTCA/MWNT film. Experimental parameters affecting the sensor responses, such as applied potential, pH, and temperature, were assessed and optimized. Analytical performances and dynamic ranges of the sensor were determined, and the results showed that the sensitivity, stability, and reproducibility of the sensor improved significantly using pTTCA/MWNT composite film. The calibration plot was linear (r(2)=0.9995) over the range of 5 to 90 microM. The sensitivity was approximately 0.0106 microA/microM, with a detection limit of 1 microM, based on a signal/noise ratio of 3. The applicability of the sensor for the analysis of l-lactate concentration in commercial milk and human serum samples was demonstrated successfully.