【作者】 曾宪冬；

【导师】 魏万之；

【作者基本信息】 湖南大学 ， 分析化学， 2010， 博士

【摘要】 生物传感器是以生物识别性单元作为主要功能性元件,能够感受到特定的目标物质,并通过特定的换能器将这种感知转换成可识别信号的装置或器件。作为现代分析化学研究的热门课题,生物传感器是一门由化学、生物、医学、物理、电子技术等多种学科互相渗透成长起来的新学科,具有选择性高、分析速度快、操作简单、价格低廉以及可进行在线甚至活体分析等特点,在环境监测、临床诊断、食品工业等领域都得到了高度的关注和广泛的应用。本论文针对生物传感器研究的关键问题,即如何将生物成份稳定、高活性地固定到换能器表面,使用不同的材料、不同的修饰方法制备了一系列新型电化学生物传感器和一些无酶的电化学传感器,并将其应用于生化分析中。采用各种电化学技术,如循环伏安法(CV)、电化学交流阻抗法(EIS)、时间-电流曲线(i-t)等,以及紫外可见分光光度法(UV-vis)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线能量散射谱(EDS)等技术详细研究了电化学传感器的结构、性质及其检测性能。本论文主要研究工作如下：(1)首先制备了一种新型的聚丙烯酰胺/壳聚糖半互穿聚合物网络水凝胶并将其用于对氧化还原性蛋白质血红蛋白的固定。该复合物水凝胶为蛋白质的固定提供了一个良好的微环境。通过SEM、UV-vis以电化学循环伏技术对固定在水凝胶中的血红蛋白进行了表征。紫外可见光谱研究结果表明固定于该复合物水凝胶中的血红蛋白能很好地保持其二级结构。循环伏安实验表明固定化的血红蛋白能与电极之间发生直接电子传递,在pH 7.0的磷酸盐缓冲溶液中,异相电子传递速率常数为5.51±0.30s-1。同时,固定于水凝胶膜中血红蛋白保持了很好的生物活性,对H2O2有良好的电催化性能。催化电流与H2O2的浓度在5×10-6 M-4.2x10-4 M内呈良好的线性。相比于单独的聚丙烯酰胺水凝胶,该复合物水凝胶固定的Hb膜具有更好的稳定性。(2)通过π-π作用,利用DNA对单壁碳纳米管(SWCNTs)进行功能化,并通过DNA功能化的SWCNTs将辣根过氧化物酶(HRP)固定于玻碳(GC)电极表面。循环伏安实验表明固定于DNA-SWCNTs上HRP能成功地实现其直接电化学。DNA作为SWCNTs与HRP直接的夹层,能有效地保持HRP的活性。与HRP-SWCNTs/GC及HRP-DNA/GC电极相比,HRP-DNA-SWCNTs/GC电极具有更好的电化学特性。所制备的HRP-DNA-SWCNTs/GC电极可以用来作为一个第三代H202生物传感器。通过实验详细探讨了pH以及检测电位对该生物传感器性能的影响。在最优检测条件下,响应电流与H202的浓度在6.0×10-7-1.8x10-3M的范围呈线性相关,最低检测限达到了3.0×10-7M。该生物传感器具有良好的重现性和稳定性,并能用于实际样品的检测。(3)通过静电相互作用,利用层层自组装的方法,我们将负电荷的DNA-SWCNTs与正电荷的Hb组装在电极表面,构筑了(Hb/DNA-CNTs)n多层膜。循环伏安实验表明固定于多层自组装膜中的Hb保持了良好的生物活性,能与电极之间发生直接电子转移。其式电位与电解液的pH值呈线性关系,表明了Hb与电极之间的直接电子传递是一电子一质子的电化学反应。同时,固定于多层膜内的Hb能很好地保持其生物活性,对H2O2具有良好的催化性能。能用于构建无试剂的H202生物传感器。这种基于酶和纳米复合物材料之间的层层自组装技术为构建无媒介体的生物传感器提供了一种有效的方法,同时也为可控地构造功能性的纳米结构生物界面提供了一个很好的实验模型。(4)首先将纳米金粒子通过电沉积的方法修饰于平面金电极表面,制备了纳米金电极,再将纳米金电极置于苯醌(BQ)、壳聚糖(CS)、离子液体(IL)、葡萄糖氧化酶(GOD)的混合溶液中,通过电沉积构建了一个灵敏的葡萄糖生物传感器。BQ的电化学还原消耗了质子,增大了电极附近溶液的pH值,从而使得壳聚糖变得不溶,沉积于电极表面,同时,GOD与IL也可以共沉积于电极表面。所构建的生物传感器能快速地对葡萄糖响应(<5 s),在最优实验条件下,该生物传感器具有很高的响应灵敏度(14.33μAmM-1 cm-2),是普通的平面金电极上所构建的生物传感器的2.8倍。其检测限达到了1.5×10-6M,比普通的平面金电极上所构建的生物传感器低20倍。同时,该生物传感器具有很宽的线性范围,良好的重现性,稳定性以及较好选择性,并能用于实际血清样品中葡萄糖浓度的测定。(5)通过简单的直流电沉积方法,可以将DNA-Cu2+复合物固定于GC电极表面。沉积于电极表面的DNA-Cu2+复合物对H202具有良好的电催化性能。基于此我们构建了一个灵敏的无酶H202传感器。为了获得最大的灵敏度,通过实验详细研究了沉积液中Cu2+浓度和沉积时间等电沉积条件以及pH值和检测电位等检测条件对H202在DNA-Cu2+/GC电极上的响应电流的影响。在最优条件下,该传感器对H202响应的线性范围为8.0×10-7 M-4.5×10-3 M,灵敏度为40.25μAmM-1,检测限为2.5×10-7 M,响应时间在4 s以内。相比于酶传感器,所构建的无酶H2O2传感器表现出更好的稳定性和重现性。(6)将CNTs、Nafion、铜纳米粒子(Cunano)结合,制备了新型纳米复合材料材料Cunano/CNTs-Nf,并用于对亚硝酸盐的检测。Nafion能使CNTs得到很好地分散,同时能于Cu2+结合,然后通过电化学还原Cu2+,使得Cunano沉积于CNTs上。采用SEM, TEM, EDS对制备的Cunano/CNTS-Nf纳米复合物进行了表征,结果表明Cunano均匀地分布于CNTs表面,直径在30 nm左右。电化学实验表明,该纳米复合物对亚硝酸根具有良好的催化活性,能在一个较低的电位下(-0.05 V)实现对亚硝酸根的检测。在最优实验条件下,该纳米复合物修饰的电极对亚硝酸盐检测的线性范围为1.0×10-6 M-6.0x10-4 M,检测限为8.0x10-8 M。由于较低的检测电位,CUnano/CNTs-Nf修饰的电极具有良好的稳定性和抗干扰能力。更多还原

【Abstract】 A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component, which transforms the signal resulting from the interaction of the analyte with the biological element into easily measured and quantified signal. As a hot topic in analytical chemistry, biosensor is an interdisciplinary approach including chemistry, biology, medical science, physics and electronics. Due to their high sensitivity, rapidity, simplicity, low-cost and potential ability for real-time and on-site analysis, biosensors have attracted wide attentions and applied widely in various areas including environmental monitoring, clinical diagnosis, food industry and so on. Focusing on the key issue of biosensors fabrication, how to immobilize biological component onto transducer surface with high stability and high activity, this dissertation concentrated on the use of various materials and modification methods to prepare novel biosensors and electrochemically nonenzymatic sensor. Then, the fabricated electrochemical sensors were applied to bio/chemical analysis. Their structure, characteristics and performances have been investigated by electrochemical methods such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and current-time technique (i-t), ultraviolet-visible spectrophotometry (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), etc. The main points of this dissertation are summarized as follows:(1) Semi-interpenetrating polymer network (semi-IPN) hydrogel based on polyacrylamide (PAM) and chitosan was prepared to immobilize redox protein hemoglobin (Hb). The Hb-PAM-chitosan hydrogel film obtained has been investigated by scanning electron microscopy (SEM), UV-vis spectroscopy and cyclic voltammetry. UV-vis spectroscopy showed that Hb kept its secondary structure similar to its native state in the Hb-PAM-chitosan hydrogel film. Cyclic voltammogram of Hb-PAM-chitosan film modified glass carbon (GC) electrode showed that direct electron transfer between Hb and GC electrode occurred. The electron-transfer rate constant was about 5.51±0.30 s-1 in pH 7.0 buffers. Additionally, Hb in the semi-IPN hydrogel film retained its bioactivity and showed excellent electrocatalytic activity toward H2O2. The electrocatalytic current values were linear with increasing concentration of H2O2 in a wide range of 5-420μM. Compared with PAM hydrogel, Hb entrapped in PAM-chitosan semi-IPN hydrogel could exhibit better stability.(2) SWCNTs were functionalized by DNA through theπ-πinteractions between the nanotube sidewalls and the nucleic acid bases. Then the resulted DNA-SWCNTS hybrids were used to immobilize horseradish peroxidase (HRP) on glassy carbon (GC) electrode. Cyclic voltammetry showed that the direct electrochemistry of HRP immobilized on DNA-SWCNTs hybrids was achieved. The DNA interlayer between the SWCNTs and HRP could be used to keep the activity of HRP. Compared with HRP-SWCNTs/GC and HRP-DNA/GC electrodes, the prepared HRP-DNA-SWCNTs/GC electrode exhibited more excellent electrochemical properties. Thus, the prepared HRP-DNA-SWCNTs/GC electrode was proposed as a third-generation H2O2 biosensor. The effect of pH and applied potential on the performance of the biosensor was discussed in detail. Under the optimal conditions, a wide linear range of the propose biosensor for the detection of H2O2 was observed from 6.0×10-7 to 1.8×10-3 M. The detection limit was found to be 3.0×10-7 M. Furthermore, the proposed biosensor displayed very good reproducibility, high stability, and can be used to detect H2O2 in real samples.(3) Layer-by-layer assembly of Hb with DNA functionalized singlewall carbon nanotubes (DNA-SWCNTs) was achieved on glassy carbon electrode surface based on the electrostatic attraction between positively charged Hb and negatively charged DNA-SWCNTs hybrids. Cyclic voltammogram of (Hb/DNA-SWCNTs)n films modified electrodes indicated that direct electrochemistry of Hb was achieved. The dependence of the formal potential on solution pH indicated that one-proton transfer was coupled to each electron transfer in the direct electron transfer reaction. Additionally, Hb in the multilayer films retained its bioactivity and showed excellent electrocatalytic activity toward H2O2, suggesting that such multilayer films could be used as reagentless biosensors. The layer-by-layer assembly of enzymes with nano-hybrids provided a general and useful way to construct sensitive biosensors without using mediators. On the other hand, this would be used as an easily prepared experimental model to fabricate functional nanostructured biointerfaces.(4) First, nano-gold electrode was constructed by electrochemically depositing gold nanoparticles onto a flat gold electrode surface. Then the nano-gold electrode was immersed in the bath containing p-benzoquinone (BQ), chitosan (CS), glucose oxidase (GOD) and ionic liquid (IL) for fabrication of a sensitive glucose biosensor through electrodeposition. The proton consumption during electroreduction of BQ increased the local solution pH near the electrode surface and led to the deposition of CS hydrogel on the electrode surface. Co-deposition of GOD and IL with the CS hydrogel was achieved. The proposed biosensor exhibited a fast amperometric response (<5 s) to glucose. Under the optimal conditions, the proposed biosensor exhibited a high current sensitivity (14.33μA mM-1 cm-2), which was 2.8 times of the biosensor prepared by electrodepositing CS-IL-GOD biocomposite on flat gold electrode. The detection limit for glucose was 1.5μM, which was 20-fold lower compared to the biosensor prepared on flat gold electrode. Moreover, the proposed biosensor exhibited a wide linear range, high reproducibility, long-time storage stability and satisfactory anti-interference ability. The proposed biosensor can applied to detect glucose concentration in serum samples.(5) DNA-Cu2+ complex were immobilized on the surface of GC electrode through electrodeposition under controlled dc potential. The electrodeposited DNA-Cu2+ complex exhibited excellent electrocatalytic behavior towards H2O2. Thus, a nonenzymatic H2O2 sensor was fabricated. The effects of Cu2+ concentration, electrodeposition time and determination conditions such as pH value, applied potential on the current response of the DNA-Cu2+/GC electrode toward H2O2 were optimized to obtain the maximal sensitivity. Under the optimal conditions, the linear range for the detection of the H2O2 is 8.0×10-7 M to 4.5×10-3 M with a high sensitivity of 40.25μA mM-1, a low detection limit of 2.5×10-7 M and a fast response time of within 4 s. Compared with the traditional enzymic sensor, the nonenzymatic H2O2 sensor exhibited better stability and reproducibility.(6) A novel hybrid, based on the combination of CNTs, Nafion and copper nanoparticles (Cunano) was synthesized and used to determination of nitrite. Nafion was used to disperse CNTs and displayed interaction with Cu2+. Then, Cunano were deposited onto CNTs by electrochemically reduction of Cu2+. SEM, TEM and EDS were used to characterize the resulted Cunano/CNTs-Nf hybrid. The results demonstrated that Cunano uniformly coated on CNTs with an average size of 30 nm. The electrochemical experiments indicated that the Cunano/CNTs-Nf hybrid modified electrode showed high electrocatalytic activity for the reduction of nitrite and could used to detect nitrite under a low applied potential of-0.05 V. Under the optimal conditions, The linear range of the determination of nitrite at the Cunano/CNTs-Nf hybrid modified electrode was from 1.0×106 M to 6.0×10-4 M, and the detection limit was found to be 8.0×10-8 M. The low detection potential gived the Cunano/CNTs-Nf hybrid modified electrode good stability and anti-interferent ability.更多还原