基于纳米金的分子印迹传感器检测果蔬中的氧化乐果和乐果

以甲基丙烯酸为功能单体,氧化乐果为印迹分子,构建了一种可用于检测果蔬中氧化乐果和乐果的分子印迹传感器。在金电极上电沉积金纳米粒子,然后将修饰电极浸入10 mL含有氧化乐果和甲基丙烯酸的聚合物溶液中进行9次循环电聚合(-0.3~0.3 V),无水甲醇/乙酸洗涤除去模板分子。循环伏安法和电化学阻抗谱表征传感器,差分脉冲伏安法用于电化学测量过程。当孵育时间为5 min,磷酸盐缓冲液为pH 7.0时,氧化乐果和乐果的线性范围分别为0.1~26 nmol/L和5~20 nmol/L,线性回归方程分别为Ip=0.6619c(mol/L)+3.1703(R²=0.9954)和I_p=0.5267c(mol/L)+6.4028(R²=0.9902),检测限分别为0.1 pmol/L和1 pmol/L。该分子印迹传感器对敌百虫、倍硫磷、马拉硫磷、高灭磷、氯丹、溴氰菊酯和呋喃丹基本没有电流响应,对分析氧化乐果和乐果具有潜在的应用价值。     

Direct detection and discrimination of double-stranded oligonucleotide corresponding to hepatitis C virus genotype 3a using an electrochemical DNA biosensor based on peptide nucleic acid and double-stranded DNA hybridization

Development of an electrochemical DNA biosensor for the direct detection and discrimination of double-stranded oligonucleotide (dsDNA) corresponding to hepatitis C virus genotype 3a, without its denaturation, using a gold electrode is described. The electrochemical DNA sensor relies on the modification of the gold electrode with 6-mercapto-1-hexanol and a self-assembled monolayer of 14-mer peptide nucleic acid probe, related to the hepatitis C virus genotype 3a core/E1 region. The increase of differential pulse voltammetric responses of methylene blue, upon hybridization of the self-assembled probe with the target ds-DNA to form a triplex is the principle behind the detection and discrimination. Some hybridization experiments with non-complementary oligonucleotides were carried out to assess whether the developed DNA sensor responds selectively to the ds-DNA target. Diagnostic performance of the biosensor is described and the detection limit was found to be 1.8 × 10⁻¹² M in phosphate buffer solution, pH 7.0. The relative standard deviation of measurements of 100 pM of target ds-DNA performed with three independent probe-modified electrodes was 3.1%, indicating a remarkable reproducibility of the detection method.     

Aptamer-based electrochemical sensors that are not based on the target binding-induced conformational change of aptamers

This study describes a new kind of aptamer-based electrochemical sensor that is not based on the target binding-induced conformational change of the aptamers by using a 15-mer thrombin-binding aptamer (5'-GGTTGGTGTGGTTGG-3') as the model oligonucleotide. The sensors are developed by first self-assembling the aptamer (i.e. a thrombin-binding aptamer) onto an Au electrode and then hybridizing the assembled aptamer with a ferrocene (Fc)-labeled short aptamer-complementary DNA oligonucleotide to form an electroactive double-stranded DNA (ds-DNA) oligonucleotide onto the Au electrode. The binding of the target (i.e. thrombin) towards the aptamer essentially destroys the Watson-Crick helix structure of the ds-DNA oligonucleotide assembled onto the electrode and leads to the dissociation of the Fc-labeled short complementary DNA oligonucleotide from the electrode surface to the solution, resulting in a decrease in the current signal obtained at the electrode, which can be used for the determination of the target. With the thrombin-binding aptamer as the model oligonucleotide, the current decrease obtained with the aptamer-based electrochemical sensors is linear with the concentration of thrombin within the concentration range from 0 to 10 nM (DeltaI/nA = 6.7C(thrombin)/nM + 2.8, gamma = 0.975). Unlike most kinds of existing aptamer-based electrochemical sensor, the electrochemical aptasensors demonstrated here are not based on the conformational change of the aptamers induced by the specific target binding. Moreover, the aptasensors are essentially label-free and are very responsive toward the targets. This study may pave a facile and general way to the development of aptamer-based electrochemical sensors.     

多指示剂标记适体探针卡那霉素传感器的电化学行为与分析性能

以三分子亚甲基蓝(MB)标记适体探针为分子识别元件,构建了一种卡那霉素生物传感器。该传感器采用目标物诱导探针构型变化的信号转导机制。以Au-S化学法将适体探针自组装于金电极表面形成稳定的单分子层传感界面,利用交流伏安法和循环伏安法考察了传感过程的基础电化学行为和传感器分析性能。在优化条件下,相比于单分子MB标记,该传感器的界面电活性和电流输出效率获得了明显提升。在PBS中用于目标物卡那霉素检测,检出限为3.3 nmol/L,电流响应平衡时间为15 s,同时具有高选择性、强抗污检测能力和好的平行构建稳定性。该方法检测过程免样品前处理,无需添加辅助试剂。     

Highly Sensitive and Selective Amperometric Sensor for Iodate Based on 9,10-Phenanthrenequinone Derived Graphene

We reported on a new amperometric sensor for the sensitive and selective determination of iodate in table salt. The iodate sensor was constructed by the integration of a novel nanocomposite which was made from 9,10-phenanthrenequinone(PQ) and graphene(GP) with a glassy carbon electrode(GCE). The synthesized graphene and the nanocomposite were well characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), Fourier transform infrared(FTIR) spectroscopy and Raman spectroscopy. We fully studied the electrochemical behavior and kinetic characteristics of the PQ/GP nanocomposite at GCE. The PQ/GP electrode shows a good electrochemical catalytic activity towards the reduction of iodate, which makes itself a sensitive and selective electrochemical sensor for iodate. The iodate sensor displays a high sensitivity(1.04 mA·mmol·L^-1), a low detection limit(1.0×10^-8 mol/L), a rapid response(less than 2 s), and a broad linear range(from 5.0×10^-8 mol/L to 6.0×10^-3 mol/L ). In addition, the sensor is interference free. The practical application of the proposed sensor was tested by the detection of iodate in table salt.     

An Electrochemical DNA Biosensor for the Detection of the Apa I Polymorphism in the Vitamin D Receptor Gene Using Meldola's Blue as a Hybridization Indicator

Electrochemical detection of nucleic acid base mismatches related to Apa I single nucleotide polymorphism (SNP) in the vitamin D receptor gene was performed successfully using 7‐dimethyl‐amino‐1,2‐benzophenoxazinium salt (Meldola's blue, MDB) with 10.9 pmol/100 μL of detection limit. MDB reduction signals obtained from probe, mismatch(probe‐SNP containing target) and hybrid(probe‐target) modified pencil graphite electrode(PGE) increased respectively. The sensor was able to clearly distinguish perfect match from mismatch DNA in a 30 min. detection time. Several factors affecting on the hybridization and indicator response are studied to maximize sensitivity and selectivity. The advantages of the biosensor are discussed in comparison with previous electrochemical assays for DNA hybridization.     

Attachment of DNA to the carbon fiber microelectrode via gold nanoparticles for simultaneous determination of dopamine and serotonin.

A novel biochemical sensor was fabricated on a carbon fiber microelectrode, which consisted of an inner layer of electrodeposited gold nanoparticles, as a nano-array electrode, and an outer layer of electrodeposited calf thymus ds-DNA at +1.5 V vs. SCE. This modified electrode was characterized by X-ray photoelectron spectroscopy, scanning electron microscope, atomic force microscopy, cyclic voltammetry and differential pulse voltammetry (DPV). It was found that this electrochemical sensor exhibits a strong catalytic activity toward the oxidation of dopamine (DA), serotonin (5-HT) and ascorbic acid (AA), as a result of resolving the anodic voltammetric peaks of DA, 5-HT and AA into three well-defined peaks. Simutaneous DPV determination of DA and 5-HT can be achieved in the presence of 2000-fold AA. The modified electrode shows good sensitivity, selectivity and stability.     

Y-type, C-rich DNA probe for electrochemical detection of silver ion and cysteine

An electrochemical assay for the detection of silver ion was reported, which was based on the interaction of the Y-type, C-rich ds-DNA with Ag(+). Upon addition of Ag(+), Y-type, C-rich ds-DNA could form an intramolecular duplex, in which Ag(+) can selectively bind to cytosine-cytosine (C-C) mismatches forming C-Ag(+)-C complex. The binding result was evaluated by electrochemical impedance spectroscopy (EIS) and analyzed with the help of Randles' equivalent circuits. The differences of charge transfer resistance, ΔR(CT), after and before the addition of Ag(+), allows the detection and quantitative analysis of Ag(+) with a detection limit of 10 fM. Moreover, cysteine (Cys) was applied to remove Ag(+) from the C-Ag(+)-C complex, which allowed the Ag(+) sensor to be reproduced. In the same way, ΔR(CT) for the C-Ag(+)-C system in the absence and presence of Cys allows the detection of Cys at a concentration as low as 100 fM. Finally, the potential application of the Ag(+) sensor was also explored, such as in lake and drinking water.     

Simultaneous and Sensitive Detection of Cd(II) and Pb(II) Using a Novel Bismuth Film/Ordered Mesoporous Carbon‐molecular Wire Modified Graphite Carbon Paste Electrode

An electrochemical sensor for the simultaneous and sensitive detection of Cd(II) and Pb(II) is proposed on the basis of square‐wave anodic stripping voltammetry (SWASV) experiments using a novel bismuth film/ordered mesoporous carbon‐molecular wire modified graphite carbon paste electrode (Bi/OMC‐MW/GCPE). Ordered mesoporous carbon (OMC) and molecular wire (MW) (diphenylacetylene) were used as the modifier and binder, respectively. The Bi/OMC‐MW/GCPE was prepared with the addition of graphite powder, OMC and DPA at the ratio of 2 : 1 : 1. The electrochemical properties and morphology of the electrode were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), SWASV and scanning electron microscopy (SEM). The parameters affecting the stripping current response were investigated and optimized. The experimental results show that the prepared electrode exhibited excellent electrochemical performance, good electrical conductivity and a high stripping voltammetric response. Under optimized conditions, a linear range was achieved over a concentration range from 1.0 to 70.0 μg/L for both Cd(II) and Pb(II) metal ions, with detection limits of 0.07 μg/L for Cd(II) and 0.08 μg/L for Pb(II) (S/N=3) with the deposition time 150 s. Moreover, the sensor exhibited improved sensitivity and reproducibility compared to traditional CPEs. The fabricated electrode was then successfully used to satisfactorily detect Cd(II) and Pb(II) in real soil samples.     

纳米银/石墨烯修饰电极测定青蒿素

本文建立一种新型的青蒿素传感器。首先,在玻碳电极上滴涂氧化石墨,通过电化学方法将氧化石墨还原为石墨烯,然后,在石墨烯上沉积纳米银得到石墨烯/纳米银修饰电极,它作为检测青蒿素的电化学传感器。用此电极对青蒿素进行测定,并通过循环伏安法、差分脉冲伏安法、交流阻抗法等研究其电化学行为。该修饰电极在测定青蒿素溶液时,表现出较正的还原电位和较大的峰电流等优势;对其实验条件如电解质溶液的p H、应用电势等进行了探查,该电化学传感器在青蒿素溶液浓度范围为1.0×10-8~3.0×10-5mol/L时与其还原峰电流呈现良好的线性关系,最低检出限为1.2×10-9mol/L(S/N=3)。此外,对该传感器的稳定性和重现性等也进行了研究,获得令人满意的结果。     

基于石墨烯分子印迹电化学传感器测定芦丁

将石墨烯(GR)滴涂至裸Au电极表面,并以邻氨基酚为功能单体,芦丁为模板分子,制备了芦丁分子印迹膜电化学传感器,利用循环伏安法(CV)和差分脉冲伏安法(DPV)对制得的传感器进行了电化学性能研究,并且对制备条件和测定条件进行了优化。结果表明,与裸Au电极相比,该GR修饰的Au电极在[Fe(CN)_6]~(3-/4-)溶液中峰电流明显增大,显著提高了芦丁分子印迹传感器的灵敏度。在最优实验条件下,基于GR分子印迹电化学传感器在4.40×10~(-6)~2.80×10~(-4) mol/L范围内呈良好的线性关系,检测限为1.46×10~(-6) mol/L。用该传感器测定了黑茶中芦丁的含量,获得较好结果。     

盐酸普萘洛尔分子印迹电化学传感器的制备与研究

以盐酸普萘洛尔为目标模板分子,通过电聚合多巴胺,在多壁碳纳米管修饰的玻碳电极表面制备了对目标分子有特异响应的分子印迹电化学传感器.利用扫描电子显微镜、循环伏安法和差示脉冲伏安法对此传感器的表面形貌及性能进行了表征,并且优化了检测条件,研究了印迹传感器对模板分子及其结构类似物的选择性响应.结果表明:此传感器具有较好的选择性响应,而且碳纳米管的存在显著提高了传感器的灵敏度.盐酸普萘洛尔的浓度在0.20～100 μmol/L范围内与峰电流呈良好的线性关系;检出限为2.53×10-8 mol/L(S/N=3).此传感器还具有良好的稳定性和重现性.     

基于多壁碳纳米管/纳米铜复合材料的电化学传感器测定槐米中芦丁

以Nafion-多壁碳纳米管(MWNTs)薄膜修饰玻碳电极,采用恒电位法在其表面电沉积纳米Cu,研制了一种新型的芦丁电化学传感器。采用循环伏安法和电化学阻抗谱研究传感器在铁氰化钾-亚铁氰化钾体系中的电化学行为,以考察传感器的电化学性能,采用扫描电镜对传感器表面的形态进行了研究,并利用差分脉冲伏安法测定芦丁的含量。实验结果表明,该传感器对芦丁有较好的催化作用。在优化实验条件下,对芦丁检测的线性范围为1.0×10-8~1.0×10-6 mol/L,检出限为8.4×10-9 mol/L(S/N=3),回收率为98.1%~101%,该传感器制作简单,线性范围宽,灵敏度高,为槐米等样品中芦丁含量的检测提供了一种新的、行之有效的方法。     

基于金属有机框架结构的分子印迹聚合物电化学传感器检测猪尿中苯乙醇胺A

以苯乙醇胺 A ( PEA )为模板分子、对氨基苯硫酚( PATP )为功能单体和有机配体、金纳米颗粒( AuNPs)为金属中心,通过原位电聚合在金电极表面成功制备了具有金属有机框架( MOFs)结构的分子印迹聚合物( MIP)复合膜,构建了具有分子识别特性的复合膜电化学传感器,实现了对PEA的灵敏检测。采用电化学技术和扫描电镜对修饰电极进行表征。优化了扫描速率、pH值、洗脱时间和富集时间等检测条件。在优化条件下,此电化学传感器对PEA在1.0×10-13~1.0×10-9 mol/L范围内有很好的线性关系,相关系数达到0.996,检出限为1.0×10-13 mol/L。在猪尿液中添加不同浓度的PEA,回收率在92.7%~108.4%,相对标准偏差小于8.0%。本方法对实际猪尿中PEA的检测具有很好的灵敏度、特异性和稳定性。     

二氧化锆/石墨烯复合材料对亚硝酸盐的电化学传感研究

制备了一种二氧化锆/还原氧化石墨烯(ZrO2NPs/rGO)复合材料修饰电极的亚硝酸盐电化学传感器,并成功用于亚硝酸盐的检测.采用循环伏安法和电流-时间曲线考察了修饰电极的电化学行为.实验结果表明,ZrO2NPs/rGO复合材料修饰电极对亚硝酸盐具有良好的电流响应.在最优实验条件下,电流-时间曲线中的电流响应信号与亚硝酸盐浓度在3.0×10Symbolm@@_7～1.0×10Symbolm@@_6 mol/L和1.0×10Symbolm@@_6～6.0×10Symbolm@@_6 mol/L的范围内呈良好的线性关系,检测限为1.0×10Symbolm@@_7 mol/L(S/N 3).该传感器灵敏性高、稳定性和重现性好.使用此传感器检测实际样品香肠中的亚硝酸盐的回收率为93.7％～110.4％,相对标准偏差为1.6％～2.1％.     

Detection of dopamine at graphene-ZIF-8 nanocomposite modified electrode

A hybrid graphene-ZIF-8 (G-ZIF-8) nanocomposite modified electrode was prepared in our work. SEM characterization shows that nanocrystals of zeolitic imidazolate frameworks (ZIF-8) were homogeneously well-intergrown on the surface of graphene and thus the graphene sheets were refrained from restacking, which implies the high accessible surface area. The BET results further testifies that G-ZIF-8 composites had a larger surface area than 3D graphene. G-ZIF-8 modified electrode exhibited excellent electroanalytical performance for dopamine. The linear concentration range was from 3.0 μmol/L to 1.0 μmol/L with the detection sensitivity of 0.34 μA/μmol/L and the detection limit of 1.0 μmol/L was obtained. The interference study, electrode stability and reproducibility were carried out. In addition, the prepared sensor was applied to the detection of DA in serum sample with recoveries from 96.8% to 100.7%. It is believable that the structure characteristic of G-ZIF-8 nanocomposite is favorable for using MOFs to fabricate highly sensitive electrochemical sensor.     

分子印迹聚合物修饰电化学晶体管检测抗坏血酸分子

以抗坏血酸(AA)为模板分子、邻苯二胺(o-PD)为功能单体,在金电极表面电聚合制备分子印迹聚合物膜(MIP),并以该MIP修饰的电极为栅极制备了具有高选择性、高灵敏度的AA电化学晶体管(OECT)传感器件。应用循环伏安法(CV)、交流阻抗法(EIS)对分子印迹聚合物电极进行一系列的表征与检测。实验结果表明:以pH=5.2,浓度为0.2mol/L HAc-NaAc(体积比2.1∶7.9)的缓冲液为背景溶液,o-PD与AA的物质的量之比为1∶2,以0.5V/s的扫描速率在0~0.8V内扫描20圈,所得分子印迹膜电极性能最佳。应用以该分子印迹修饰电极作为栅极的电化学晶体管检测AA,得到AA浓度的检测限为0.3μmol/L,沟道电流与AA浓度在0.3~3μmol/L(低浓度)与3~100μmol/L(高浓度)这2个范围内成线性关系。     

末端可裁切碳纳米管薄膜电极的制备及其双酚A电化学检测应用

通过真空抽滤方法得到均匀致密的高导电多壁碳纳米管(MWCNTs)薄膜,利用聚二甲基硅氧烷(PDMS)对其进行封闭处理,制备出末端可裁切的PDMS基柔性碳纳米管薄膜电极,其裁切端面为电化学传感界面。在十六烷基三甲基溴化铵(CTAB)的增敏作用下,所制备的电化学传感器对双酚A(BPA)具有灵敏的电化学响应,其峰电流与BPA浓度在0.05~0.5μmol/L和0.5~12μmol/L范围内呈良好的线性关系,检测限为50nmol/L。通过电极末端的重复裁切可避免电极污染,并实现电极表面的快速更新和重复使用。对同一支电极进行13次连续裁切,用于10μmol/L BPA的检测,其相对标准偏差为3.4%。将该传感器应用于热敏纸样品中BPA的检测,加标回收率在95%~105%之间。     

基于L-半胱氨酸/CdTe量子点修饰电极的电化学传感器的制备及其对Pb~(2+)的检测

成功制备了由L-半胱氨酸和CdTe量子点作为修饰材料的电化学传感器并用于水体中Pb~(2+)的检测。巯基丙酸修饰的CdTe量子点通过水相合成,表面含有大量羧基,与L-半胱氨酸表面的氨基形成酰胺键,修饰于金电极表面。通过荧光分光光度计、透射电子显微镜、红外光谱、X射线衍射对L-Cys/CdTe QDs复合材料进行表征。采用循环伏安法(CV)研究了L-Cys/CdTe QDs修饰成分在金电极上的电化学性能及CdTe量子点的最佳自组装时间。采用差分脉冲溶出伏安法(DPSV)研究了铅离子在修饰电极上的电化学行为。在优化实验条件下,Pb~(2+)浓度在1.0×10~(-6)~1.0×10~(-2) mol/L范围内与其峰电流呈良好的线性关系,相关系数(r2)为0.993 8,检出限(3σ,n=5)为4.0×10~(-7) mol/L。该传感器具有良好的重现性和稳定性,有望用于实际水样中铅离子的检测。     

An electrochemical DNA sensor for determination of 6-thioguanine using adsorptive stripping voltammetry at HMDE: An anticancer drug DNA interaction study

In the present study, the electrochemical behavior of 6-Thioguanine (6-TG) and its interaction with double-strand DNA (ds-DNA) were investigated at the surface of hanging mercury drop electrode (HMDE) in neutral media. The interaction of 6-TG with ds-DNA in neutral buffer was clearly demonstrated by the elimination of 6-TG signal and the advent of a new reduction peak. To investigate the interaction, various parameters including accumulation time and potential as well as ds-DNA concentration were optimized using a combination of adsorptive stripping voltammetry (AdSV) and square wave voltammetry (SWV) techniques. As a consequence a low detection limit of 1.1 μM was obtained in a dynamic range of 16.0 to 360.0 μM. To better understand the interaction mechanism between 6-TG anti-cancer drug and ds-DNA, cyclic voltammetry and UV-Vis spectroscopy measurements were carried out and the intercalation of 6-TG into ds-DNA was proposed as the plausible mechanism. The application of this screening assay in real sample analysis was investigated by using the procedure for determination of 6-TG in 6-Thioguanine tablets and also in spiked 6-TG blood serum. Overall, the results were indicative of a DNA sensor which could be applied effectively in the analysis of 6-TG in vitro.