Label-Free Fluorescent Aptasensor Based on a Graphene Oxide Self-Assembled Probe for the Determination of Adenosine Triphosphate

A sensitive and selective fluorescent aptasensor for adenosine triphosphate (ATP) was fabricated, composed of unbound SYBR Green I, graphene oxide, and a label-free detection probe. When ATP and complementary DNA of a signal probe were introduced, π-stacking interactions repelled the probe from the graphene oxide and formed a DNA-SYBR Green I duplex structure, triggering an increase in the fluorescence. ATP was determined over a linear range of 10 to 700 nM with a detection limit of 1 nM. The method displayed good selectivity, and is currently the most sensitive ATP fluorescence method. Furthermore, prominent fluorescence signals were also obtained in cellular assays. Consequently, the biosensor may have significant applications in protein, pathogenic microorganisms, and small molecule detection.     

基于铂纳米颗粒@金属有机骨架纳米模拟酶的无标记电化学赭曲霉毒素适体传感器的构建

以具有类过氧化物酶性质的Pt NPs@Mn-MOF纳米复合材料作为电极基底, 采用丝网印刷电极构建了一种无标记型电化学适体传感器, 用于赭曲霉毒素(OTA)的检测. 利用Pt NPs@Mn-MOF的模拟酶特性, 将其作为电极基底用于捕获OTA适体链, 同时催化H₂O₂还原产生电流响应信号. OTA的引入会减少纳米酶的催化活性位点, 从而导致电流信号降低. 在0.01~300 ng/mL范围内, 随着OTA浓度的增加, 电流响应值逐渐降低; 采用计时电流法检测电流响应信号, 从而间接实现了对OTA的定量检测. 此外, 该生物传感器通过U盘式小型工作站进行检测, 不仅可与电脑连接进行检测, 还可与手机连接进而实现实时检测, 并且其检测灵敏度高、 重现性好, 检出限低至3.33 pg/mL(S/N=3). 该传感器可用于真实玉米样品中OTA的检测, 在真菌毒素现场检测中展现出潜在的应用价值.     

Electrochemical Aptasensor for the Determination of Ochratoxin A at the Au Electrode Modified with Ag Nanoparticles Decorated with Macrocyclic Ligand

An electrochemical aptasensor for ochratoxin A (OTA) detection has been developed on the base of a gold electrode covered with electropolymerized neutral red and silver nanoparticles obtained by chemical reduction with macrocyclic ligands bearing catechol fragments. Thiolated aptamers against OTA were covalently attached to silver nanoparticles via Ag? S bonding. The interaction with OTA induced the conformational switch of the aptamer, which caused increase of the charge transfer resistance measured by EIS in the presence of ferricyanide ions. The LOD achieved (0.05 nM) was comparable to other electrochemical aptasensors employing sophisticated assembling technique and enzyme amplification of the signal. The aptasensor was validated in spiked beer samples. The recovery of the OTA determination was found to be 66.3±14.1 % for light beer and 64.3±1.8 % for dark beer.     

A Novel Fluorescent Probe for ATP Detection Based on Synergetic Effect of Aggregation-induced Emission and Counterion Displacement

In this work,a fluorescent probe(TPEBe-I)was developed for adenosine triphosphate(ATP)detection based on the synergetic effect of aggregation-induced emission and counterion displacement.TPEBe-I gave weak emission in aqueous solution due to the heavy-atom effect of counter iodide ion.However,upon the addition of ATP,the new aggregate complex(TPEBe-ATP)was formed between the cationic unit of TPEBe-I and ATP through electrostatic interactions,which not only restricted the intramolecular motion of luminogen but also eliminated the quenching effect of iodide ion.As a result,the fluorescent light-up detection for ATP was successfully achieved.Moreover,TPEBe-I exhibited high selectivity towards ATP and showed a wide linear detection region towards the logarithm of ATP concentration(5—600μmol/L)with a detection limit of 1.0μmol/L,enabling TPEBe-I as a promising probe for ATP quantitative analysis.     

Simple and Fast Picomolar Detection of Ochratoxin A Using a Reusable Label Free Aptasensor Built with a Layer‐by‐layer Procedure

A label free impedimetric aptasensor for simple, fast and reusable picomolar detections of Ochratoxin A (OTA) in grape juices was designed. Two main factors were observed to affect the accurate detections of the toxin: i‐lateral interactions between self‐assembled aptamers ii‐ adsorption of large molecules present in complex matrixes like grape juices. Lateral interactions between aptamers were minimized by constructing the aptasensor in a Layer‐by‐Layer procedure. The interferences associated to the unspecific and irreversible adsorption of large molecules present in grape juice, were reduced by submitting samples to ultrafiltration prior to analysis. With this protocol, a 0.12 pM limit of detection and 0.24 pM limit of quantification in spiked grape juices were achieved after only 5–7 mins of interaction with the samples. The presented aptasensor can be recovered after a simple immersion in hot water (90 °C) for ten minutes.     

Electrochemiluminescence Aptasensor for the MUC1 Protein Based on Multi‐functionalized Graphene Oxide Nanocomposite

The electrochemiluminescence (ECL) aptasensor was prepared for the detection of Mucin 1 based on its specific recognition by aptamer immobilized on multi‐functionalized graphene oxide nanocomposite, which was prepared with N‐(4‐aminobutyl)‐N‐ethylisoluminol (ABEI) and aptamer chemically bound to the surface of magnetic GO (nanoFe₃O₄@GO). ABEI and aptamer acted as the electrochemiluminophore and the capture device for Mucin 1 respectively. NanoFe₃O₄@GO brought multi‐functionalized graphene oxide nanocomposite attracted on the surface of magnetic glass carbon electrode through magnetism, enabled all the ABEI immobilized electrochemically active due to its good conductivity and thus then facilitated the sensitive detection of Mucin 1. In addition, the ECL aptasensor can be prepared through a one‐step process. Under optimal conditions, the ECL intensity of the aptasensor decreased proportionally to the logarithmic concentrations of Mucin 1 in the range of 0.005–1000 ng mL^?1. This aptasensor displays good specificity, stability, reproducibility and application. This method has a large potential because such a multi‐functionalized graphene oxide nanocomposite also may be applied to other ECL‐based aptasensors.     

A Label-Free Amperometric Immunoassay for Thrombomodulin Using Graphene/Silver-Silver Oxide Nanoparticles as a Immobilization Matrix

A simple, sensitive, and label-free electrochemical immunosensor has been developed for the measurement of serum thrombomodulin (TM), an endothelial glycoprotein which is associated with the progression and metastasis of tumors. At first, the graphene nanosheets, which were dispersed in Nafion solution, were used to coat the bare gold electrode. Then, silver-silver oxide nanoparticles (Ag-Ag₂O NPs) were immobilized on the graphene-modified electrode by a one-step electrochemical deposition method. Lastly, a thrombomodulin antibody (anti-TM) was attached via amido-Ag affinity. This strategy combines graphene/Ag-Ag₂O NPs hybrid materials as an immobilization matrix and Ag-Ag₂O NPs also as an electrochemical signal indication reagent. The main advantage of this strategy has two important aspects. One is the high stability and unique electronic properties of the graphene nanostructure. The other is the use of Ag-Ag₂O NPs as the immobilization matrix and redox probes, thus avoiding the laborious labeling protein operation. Using this strategy, the concentration of TM in the range of 0.1 to 20 ng/mL was detected, with a detection limit of 31.5 pg/mL (at 3σ). The proposed methodology demonstrates that the nanocomposite film composed of graphene and Ag-Ag₂O NPs is a potential for biosensor applications.     

A Fluorescent Probe for Hg2+ Based on Gold(I) Complex with An Aggregation‐Induced Emission Feature

A gold(I) complex that exhibited aggregation‐induced emission in acetonitrile‐water mixtures was designed. It showed high selectivity and sensitivity for Hg²⁺ in acetonitrile‐H₂O (1:1, V:V) solution. Dynamic light scattering measurements were conducted to verify that the addition of Hg²⁺ changed the particle size and induced fluorescence quenching.     

Signal-off Photoelectrochemical Aptasensor for S. aureus Detection Based on Graphite-like Carbon Nitride Decorated with Nickel Oxide

A signal-off photoelectrochemical (PEC) aptasensor was proposed for pathogenic bacteria detection based on graphite-like carbon nitride decorated with NiO. The S. aureus be captured by the specific recognition of DNA aptamer, which was immobilized on the PEC electrode surface according to the specific effect of carboxylic group and NiO. The PEC signal would be obviously suppressed due to the transfer blocking of electron donor to PEC active material surface by steric hindrance and electrostatic repulsion. The PEC aptasensor showed excellent specificity and high sensitivity for S. aureus, and this provides simple strategy to construct point-of-care testing aptasensor for bacteria analysis.     

Highly Sensitive Impedimetric Biosensor Based on Thermolysin Immobilized on a GCE Modified with AuNP-decorated Graphene for the Detection of Ochratoxin A

The fabrication of a thermolysin-based biosensor capable of detecting ochratoxin A (OTA) from food samples is described. The electrochemical deposition of calcium cross-linked cellulose film (CCLC) and gold nanoparticles (AuNPs) on graphene (GR) for modification of a glassy carbon electrode (GCE) is the first step. Then the thermolysin (TLN) enzyme in a polyvinyl alcohol (PVA)/polyethylenimine (PEI) matrix is immobilized. The impedimetric biosensor response is linear from 0.2 nM to 100 nM with a detection limit of 0.2 nM. The obtained stable and reproducible biosensor is then applied for the detection of OTA in spiked extracts from coffee beans.     

氧化石墨烯表面新型磁性四溴双酚A印迹复合材料的制备及吸附性能

以二氧化硅包覆的磁性氧化石墨烯为载体, 利用热聚合方法制备了对四溴双酚A(TBBPA)有特异吸附效果的新型磁性印迹复合材料. 采用透射电子显微镜(TEM)、 扫描电子显微镜(SEM)、 傅里叶变换红外光谱(FTIR)、 热重分析(TGA)和样品振动磁强计(VSM)对该印迹复合材料进行了表征. 结果表明, 在氧化石墨烯表面制备了一层厚度为55~65 nm、 热稳定良好的磁性印迹层. 结合磁固相萃取技术(M-SPE)和高效液相色谱(HPLC)检测技术研究了该磁性印迹复合材料对四溴双酚A的吸附行为, 结果表明该印迹复合材料对四溴双酚A具有良好的选择吸附能力, 最大吸附量为16.33 mg/g. 结合HPLC检测技术, 该印迹复合材料可用于分离富集饮用水中的四溴双酚A.     

Bioorthogonal Turn‐On Probe Based on Aggregation‐Induced Emission Characteristics for Cancer Cell Imaging and Ablation

Bioorthogonal turn‐on probes have been widely utilized in visualizing various biological processes. Most of the currently available bioorthogonal turn‐on probes are blue or green emissive fluorophores with azide or tetrazine as functional groups. Herein, we present an alternative strategy of designing bioorthogonal turn‐on probes based on red‐emissive fluorogens with aggregation‐induced emission characteristics (AIEgens). The probe is water soluble and non‐fluorescent due to the dissipation of energy through free molecular motion of the AIEgen, but the fluorescence is immediately turned on upon click reaction with azide‐functionalized glycans on cancer cell surface. The fluorescence turn‐on is ascribed to the restriction of molecular motion of AIEgen, which populates the radiative decay channel. Moreover, the AIEgen can generate reactive oxygen species (ROS) upon visible light (λ=400–700 nm) irradiation, demonstrating its dual role as an imaging and phototherapeutic agent.     

基于环状DNA-银纳米簇荧光探针对微囊藻毒素-LR的传感检测

以新型环状DNA为模板, 制备了环状DNA-银纳米簇(Circular DNA-AgNCs)荧光探针, 构建了一种无酶无标记检测微囊藻毒素-LR(MC-LR)的荧光传感分析方法. 设计的环状DNA由MC-LR适体链(Apt)和适体链的互补链(cDNA)杂交形成, 且cDNA可作为DNA模板用于合成AgNCs. 利用透射电子显微镜(TEM)、 紫外-可见光谱(UV-Vis)和荧光光谱(FL)表征了AgNCs的形貌和光学特性.结果表明, 当存在目标物MC-LR时, 由于MC-LR与环状DNA中Apt高特异性和高亲和力结合, 导致环状DNA解体, 释放出的cDNA-AgNCs在610 nm处呈现强荧光. 在优化实验条件下, 环状DNA-AgNCs荧光探针对MC-LR检测的线性范围为0.005~500 μg/L, 检出限为1.7 ng/L(S/N=3). 该荧光探针具有制备简单、 无需任何标记和灵敏度高等特点, 为环境水样中微囊藻毒素-LR的快速和准确测定提供了一种简单、 可靠和有效的方法.     

基于氧化石墨烯和DNA量子点组装体的DNA二元逻辑检测及循环可逆设计

制备了水溶性的氧化石墨烯(GO)和以DNA为模板的Cd Te量子点(P1),通过GO与P1的π-π堆积作用组装构建了纳米生物传感器,将其用于双目标DNA分子的逻辑检测,实现了较高的选择性;通过改进DNA序列,实现了该传感器对双目标分子的可逆循环检测及重复利用.利用原子力显微镜(AFM)、透射电子显微镜、电泳和荧光光谱等方法对传感器的构建和检测过程进行了表征.该P1-GO纳米生物传感器在核酸检测等领域具有较大的应用前景.     

一个基于NBD-NH2荧光团的增强型pH荧光探针及其细胞造影研究

本文以NBD-NH₂荧光团偶联N-(4-吡啶甲基)乙二胺质子受体构建了基于光致电子转移(PET)机制的pH探针NBD-Py。探针在pH5.0~8.5范围内显示pH降低导致的荧光增强响应,pK_a为6.48。响应不受胞内常见金属离子干扰且有良好的可逆性。研究表明质子受体中引入4-甲基吡啶修饰乙二胺是探针实现对弱酸/近中性pH响应的关键。HeLa细胞中的造影证实了探针的pHi造影能力和溶酶体靶向性能,为溶酶体pH相关的生理过程研究提供了新的可靠手段。     

基于氧化石墨烯荧光适体传感器的胰岛素检测

采用荧光基团(FAM)标记的核酸适体作为识别元件,氧化石墨烯为淬灭剂,建立了一种高选择性、高灵敏度的核酸适体传感器.核酸适体与氧化石墨烯结合后,荧光淬灭,此时溶液无荧光;加入胰岛素后,溶液中荧光得到恢复.利用荧光分析法检测加入胰岛素前后,溶液中荧光强度的变化,获取了荧光适体传感器的线性度和灵敏度,实现对胰岛素浓度的测定.结果表明,在5×10-8 ～ 1×10-5 mol/L范围内,胰岛素的浓度与溶液中荧光强度有良好的线性关系,检出限为10 nmol/L.采用此方法检测胰岛素,操作简便,检测速度快,准确性高,选择性好,检出限低.     

A Review of Glucose Biosensors Based on Graphene/Metal Oxide Nanomaterials

In recent years, considerable attention has been paid to developing economical yet rapid glucose sensors using graphene and its composites. Recently, the excellent properties of graphene and metal oxide nanoparticles have been combined to provide a new approach for highly sensitive glucose sensors. This review focuses on the development of graphene functionalized with different nanostructured metal oxides (such as copper oxide, zinc oxide, nickel oxide, titanium dioxide, iron oxide, cobalt oxide, and manganese dioxide) for use as glucose biosensors. Additionally, a brief introduction of the electrochemical principles of glucose biosensors (including amperometric, potentiometric, and conductometric) is presented. Finally, the current status and future prospects are outlined for graphene/metal oxide nanomaterials in glucose sensing.     

Design and Synthesis of New Acridone-Based Nitric Oxide Fluorescent Probe

Nitric oxide (NO) is an important signaling molecule involved in a wide range of physiological and pathological processes. Fluorescent imaging is a useful tool for monitoring NO concentration, which could be essential in various biological and biochemical studies. Here, we report the design of a novel small-molecule fluorescent probe based on 9(10H)acridone moiety for nitric oxide sensing. 7,8-Diamino-4-carboxy-10-methyl-9(10H)acridone reacts with NO in aqueous media in the presence of O₂, yielding a corresponding triazole derivative with fivefold increased fluorescence intensity. The probe was shown to be capable of nitric oxide sensing in living Jurkat cells.     

Sensitive Electrochemical Aptasensor for Thrombin Detection with Platinum Nanoparticles,Blocking Reagent‐Horseradish Peroxidase and Graphene Oxide as Enhancers

A highly sensitive thrombin electrochemical aptasensor with Pt nanoparticles, blocking reagent‐horseradish peroxidase (HRP) and inert graphene oxide (GO) as enhancers was successfully fabricated. Firstly, Pt nanoparticles with high surface to volume ratio could increase the amount of the immobilized redox probe hexacyanoferrate nanoparticles (NiHCFNPs) and effectively enhance the electron transfer. Secondly, HRP and Pt nanoparticles with high catalytic activity extremely amplify the electrochemical signal of NiHCFNPs toward H₂O₂. Lastly, inert graphene oxide (GO) labeled TBA could be used for enlarging the steric hindrance of thrombin. As a result, the aptasensor showed a high sensitivity with a detection limit of 500 fM.     

基于分子印迹聚合物掺杂氧化石墨烯膜的利巴韦林电位传感器

以利巴韦林为模板分子,甲基丙烯酸为功能单体,采用沉淀聚合法制备利巴韦林分子印迹聚合物(MIP).以利巴韦林分子印迹聚合物掺杂氧化石墨烯(GO)为离子载体,聚氯乙烯为基质,癸二酸二辛酯为增塑剂制备电极敏感膜.结果表明,敏感膜组成为100.8 mg MIP、14.7 mg GO、450.8 mg聚氯乙烯和901.6 mg癸二酸二辛酯,内充液组成为0.1 mol/L NaCl+0.05 mol/L NaAc-0.05 mol/L HAc缓冲溶液+ 1.0×10.-5 mol/L利巴韦林,电极的响应性能最好.此电极的能斯特响应斜率为45.565 mV/decade,线性范围为1.0×10.-6~1.0×10.-4 mol/L, 检出限为1.0×10.-7 mol/L(S/N=3),工作pH范围为3~5,响应时间小于3 min.此电极对利巴韦林具有高选择性,可用于检测饲料和注射液中利巴韦林含量,加标回收率为90%~110%,RSD为3.0%~7.9%.