Wir sind dankbar für die finanzielle Unterstützung von der National Natural Science Foundation (21675112), Key-Projekt von Wissenschaft und Technik Plan von Peking Education Commission (KZ201710028027) und Yanjing Young Scholar Program der Capital Normal University.

<ol>
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Die Autoren erklären keine konkurrierenden finanziellen Interessen.

Ein herausragender Vorteil von Aptameren ist, dass sie erkannt werden, durch die in-Vitro -Methode SELEX, während Antikörper über in Vivo Immunoreactions generiert werden. Daher können Aptamere mit gewünschten Spezifität durchdachte experimentellen Bedingungen ausgewählt werden, während Antikörper auf physiologischen Bedingungen beschränkt sind.
Um die Trennung der gebundenen Sequenzen von freien Sequenzen zu erleichtern, mehrere modifizierten SELEX vor kurzem beric...

Zusammen mit der rasanten wirtschaftlichen Entwicklung ist die Beschleunigung der Industrialisierung und Städtebau, Umweltbelastungen strenger als je zuvor. Typischen Umweltschadstoffen gehören Schwermetall-Ionen, Toxine, Antibiotika, Pestizide, endokrine Disruptoren und persistente organische Schadstoffe (POPs). Neben der Metall-Ionen und Giftstoffe, andere Schadstoffe sind kleine Moleküle, dass ganz oft bestehen aus einer Vielzahl von Artgenossen. Die giftigsten POPs zählen beispielsweise polychlorierte Biphenyle (PCB), polychlorierten Dibenzofuran (PCDFs), polyzyklische aromatische Kohlenwasserstoffe (PAK), polybromierten APEO Ether (PBDE), polychlorierten Dibenzo-p-Dioxin (PCDDs) und phthalic saure Ester (PAEs)1,2, die alle viele Artgenossen aus. Kleines Molekül Erkennung wurde vor allem durch Chromatographie/Mass Spectrometry-basierten Techniken wegen ihrer Vielfalt von Anwendungen3,4,5,6durchgeführt. Für vor-Ort-Erkennungen wurden Antikörper-basierten Methoden kürzlich entwickelten7,8,9. Da diese Methoden sehr spezifisch für eine bestimmte gleichartig sind, müssen mehrere Tests durchgeführt werden. Gravierender ist, dass die neuartige Kongenere wachsen so schnell, dass ihre Antikörper in der Zeit erzeugt werden können. Daher kann die Entwicklung von zielgruppenspezifischen Biosensoren, die insgesamt Level alle Artgenossen in einem Test zu überwachen eine unschätzbare Metrik zur Bewertung von Umweltbelastungen Status bereitstellen.
Vor kurzem wurden Nukleinsäure-Aptamere weithin als Erkennungselemente in verschiedenen Biosensoren Plattformen durch ihre Fähigkeit, eine Vielzahl von Zielen, von Ionen und kleinen Molekülen an Proteine und Zellen10,11 erkennen angewendet ,12. Aptamere werden durch eine in-vitro- Methode namens systematische Evolution von Liganden durch exponentielle Anreicherung (SELEX)13,14identifiziert. SELEX beginnt mit der zufällige synthetische Einzelstrang Oligonukleotid-Bibliothek, die ca. 1014-1015 Sequenzen enthält. Die Größe der zufälligen Bibliothek sorgt für die Vielfalt der RNA oder DNA-Kandidat Strukturen. Der typische SELEX-Prozess besteht aus mehrere Runden der Bereicherung bis die Bibliothek in Sequenzen mit hoher Affinität und Spezifität zum Ziel angereichert ist. Der endgültige angereicherte Pool dann sequenziert und die Dissoziation konstanten (K-d) und Selektivität gegen mögliche Störsubstanzen durch verschiedene Techniken wie z. B. bestimmt werden Filtern verbindlich, Affinitätschromatographie, Oberfläche Plasmon-Resonanz (SPR), etc. 15
Aufgrund der extrem schlechten Wasserlöslichkeit und Mangel an funktionellen Gruppen für Oberfläche Immobilisierung ist die Aptamer-Auswahl des POPs theoretisch schwierig. Die Entdeckung der Aptamere haben bedeutende Fortschritte für SELEX beschleunigt. Die Auswahl der gruppenspezifischen Aptamere für POPs wurde jedoch noch nicht gemeldet. Bisher wurden nur PCB-Bindung DNA Aptameren mit hoher Spezifität für eine bestimmte Artgenossen identifizierte16. PAEs werden hauptsächlich in Polyvinylchlorid Materialien, Wechsel Polyvinylchlorid aus einem harten Kunststoff zu einem elastischen Kunststoff, fungiert somit als Weichmacher eingesetzt. Einige PAEs als endokrine Disruptoren eingestuft wurden, können schwere Schäden verursachen, Leber- und Nierenfunktion, reduzieren die Beweglichkeit der männlichen Spermien und abnormen Spermien Morphologie und Hodenkrebs17führen kann. Verbindung- weder die gruppenspezifischen PAE-Bindung Aptamere sind berichtet worden.
Das Ziel dieser Arbeit ist es, eine repräsentative Protokoll bieten für die Auswahl von gruppenspezifischen DNA Aptameren, stark hydrophobe kleine Moleküle wie PAEs, eine repräsentative Gruppe von POPs. Wir zeigen auch die Anwendung von der ausgewählten Aptamer für Umweltverschmutzung Erkennung. Dieses Protokoll bietet Beratung und Einblicke für die Aptamer-Entdeckung des anderen hydrophoben kleine Moleküle.

<table><tbody><tr><td>UV-2550</td><td>Shimadzu,Japan</td><td></td><td>protocol, section 3.8.2</td></tr><tr><td>DNA Engnine Thermal cycler,PTC0200</td><td>BIO-RAD</td><td></td><td>section 3.5.1.2 and 3.5.2</td></tr><tr><td>C1000 Touch</td><td>BIO-RAD</td><td></td><td>section 5.3.6 and 6.3</td></tr><tr><td>VMP3 multichannel potentiostat</td><td>Bio-Logic Science, Claix, France</td><td></td><td>section 7.4,7.8 and 7.11</td></tr><tr><td>Epoxy-activated Sepharose 6B</td><td>GE Healthcare (Piscataway, NJ, USA)</td><td>10220020</td><td>argarose beads, section 2.3 and 3.3</td></tr><tr><td>Dynabeads M-270 carboxylic acid magnetic beads</td><td>Invitrogen, USA</td><td>420420</td><td>magnetic beads,section 5.2. and 5.3</td></tr><tr><td>Premix Taq Hot Start Version</td><td>Takara,Dalian,China</td><td>R028A</td><td>polymerase, section 3.5.1.1</td></tr><tr><td>PARAFILM Sealing Membrane</td><td>Bemis, USA</td><td>PM-996</td><td>section 3.6.5</td></tr><tr><td>Lambda Exonuclease</td><td>Invitrogen, USA</td><td>EN0561</td><td>section3.7.1.2.The 10 &amp;times; reaction buffer is provided along with &amp;lambda; exonuclease by the provider.</td></tr><tr><td>Dr. GenTLE&lt;br/&gt; Precipitation Carrier</td><td>Takara,Dalian,China</td><td>9094</td><td>section 3.6.2 and 3.8.1</td></tr><tr><td>UNIQ-10 PAGE DNA recovery kit</td><td>Sangon Biotech (Shanghai)</td><td>B511135</td><td>section 4.2</td></tr><tr><td>SYBR Gold nucleic acid gel stain</td><td>Invitrogen, USA</td><td>1811838</td><td>nucelic acid stain dye, section 3.5.1.5</td></tr><tr><td>SYBR Premix Ex Taq II</td><td>Takara,Dalian,China</td><td>RR820A</td><td>polymerase mix contaning polymerase and dNTPs, section 5.3.5</td></tr><tr><td>2-(N-Morpholino)ethanesulfonic acid (MES)</td><td>Sigma-Aldrich</td><td>CAS: 1132-61-2</td><td>section 5.2.1</td></tr><tr><td>1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)</td><td>Invitrogen, USA</td><td>CAS: 25952-53-8</td><td>section 5.2.2</td></tr><tr><td>N-hydroxysuccinimide (NHS)</td><td>Sigma-Aldrich</td><td>6066-82-6</td><td>section 5.2.3</td></tr><tr><td>mercaptohexanol (MCH)</td><td>Sigma-Aldrich</td><td>CAS: 1633-78-9</td><td>section 7.7</td></tr><tr><td>Gold electrode</td><td>Shanghai Chenhua</td><td>CHI101</td><td>section 7.4. - 7.11</td></tr><tr><td>tris(2-carboxyethyl) phosphine hydrochloride (TCEP)</td><td>Sigma-Aldrich</td><td>CAS: 51805-45-9</td><td>section 7.5</td></tr><tr><td>O-(2-Mercaptoethyl)-O&#039;-methyl-hexa-(ethylene glycol)</td><td>Sigma-Aldrich</td><td>CAS: 651042-82-9</td><td>section 7.7</td></tr><tr><td>diethylhexyl phthalate (DEHP)</td><td>National Institute of Metrology, China</td><td>CAS: 117-81-7</td><td>section 7.11</td></tr><tr><td>Tween 20</td><td>Sigma-Aldrich</td><td>CAS: 9005-64-5</td><td>polyoxyethy-lene(20) sorbaitan monolaurate</td></tr><tr><td>Triton X-100</td><td>Sigma-Aldrich</td><td>CAS: 9002-93-1</td><td>non-ionic surface active agent</td></tr><tr><td>PBS</td><td>Sigma-Aldrich</td><td>P5368</td><td>10 mM phosphate buffer containing 1 M NaCl, pH 7.4</td></tr></tbody></table>

phthalic acid ester-binding dna aptamer selection, characterization, and application to an electrochemical aptasensor

Phthalsäure Acid Ester (PAEs) einer der wichtigsten Gruppen von persistenten organischen Schadstoffen. Die gruppenspezifische Erkennung von PAEs ist sehr erwünscht, aufgrund der schnellen Anbau von Artgenossen. DNA-Aptameren zunehmend als Erkennungselemente auf Biosensor Plattformen angewendet wurden, aber Auswahl Aptamere auf stark hydrophobe niedermolekularer Ziele, wie z. B. PAEs, wird selten berichtet. Diese Arbeit beschreibt eine Perle basierende Methode entwickelt, um gruppenspezifische DNA Aptameren, PAEs auswählen. Die Aminogruppe funktionalisiert Dibutyl Phthalat (DBP-NH2) wie das Anker-Ziel wurde synthetisiert und an den Epoxy-aktivierte Agarose-Perlen immobilisiert ermöglicht die Anzeige der phthalic Estergruppe an der Oberfläche der Immobilisierung Matrix und Daher ist die Auswahl der gruppenspezifischen Bindemittel. Wir entschlossen die Dissoziation Konstanten der Aptamer Kandidaten durch quantitative Polymerisation Kettenreaktion gepaart mit magnetische Trennung. Die relativen Affinitäten und Selektivität der Aptamere für andere PAEs wurden durch die wettbewerbsfähige Assays bestimmt, wo die Aptamer-Kandidaten der DBP-NH2 Pre begrenzt waren magnetische Beads angebracht und veröffentlicht, um den Überstand nach Inkubation mit die getesteten PAEs oder andere potenziellen störenden Substanzen. Die wettbewerbsfähigere Assay wurde angewendet, weil sie einen einfache Affinität Vergleich zwischen PAEs bereitgestellt, die keine funktionellen Gruppen für Oberfläche Immobilisierung hatte. Schließlich demonstriert die Herstellung eines elektrochemischen Aptasensor und benutzte es für Gromer und selektive Detektion von bis(2-ethylhexyl) Phthalat. Dieses Protokoll bietet Einblicke für die Aptamer-Entdeckung des anderen hydrophoben kleine Moleküle.

Wir entwickelt und synthetisiert die Aminogruppe funktionalisiert Dibutyl Phthalat (DBP-NH2) als Anker Ziel (Abb. 1F). Wir spielten dann die DNA-Aptamer-Auswahl der PAEs mit DBP-NH2 als Anker Ziel und im Anschluss an das klassische Ziel Immobilisierung basierende Methode (Abbildung 2). In jeder Runde war eine pilot PCR durchgeführt mit der denaturierten Seite optimieren die Zykluszahl PCR (<strong class="xf...

Watch this Scientific Journal Video about Phthalic Acid Ester-Binding DNA Aptamer Selection, Characterization, and Application to an Electrochemical Aptasensor at JoVE.com

Phthalic Acid Ester-Binding DNA Aptamer Selection, Characterization, and Application to an Electrochemical Aptasensor

Ein Protokoll für die in-vitro- Selektion und Charakterisierung von gruppenspezifischen Phthalsäure Acid Ester-Bindung DNA Aptameren wird vorgestellt. Die Anwendung von der ausgewählten Aptamer in einem elektrochemischen Aptasensor ist ebenfalls enthalten.

Phthalsäure Acid Ester-Bindung DNA-Aptamer Auswahl, Charakterisierung und Anwendung eines elektrochemischen Aptasensor

Phthalic acid esters (PAEs) areone of the major groups of persistent organic pollutants. The group-specific detection of PAEs is highly desired due to the ...

phthalic-acid-ester-binding-dna-aptamer-selection-characterization

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

9.7K Aufrufe.  Capital Normal University. Ein Protokoll für die in-vitro- Selektion und Charakterisierung von gruppenspezifischen Phthalsäure Acid Ester-Bindung DNA Aptameren wird vorgestellt. Die Anwendung von der ausgewählten Aptamer in einem elektrochemischen Aptasensor ist ebenfalls enthalten.

Serie: Phthalic Acid Ester-Binding DNA Aptamer Selection, Characterization, and Application to an Electrochemical Aptasensor

Fabrication of Electrochemical-DNA Biosensors for the Reagentless Detection of Nucleic Acids, Proteins and Small Molecules

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. Many patients would be better served by rapid, bedside tests. To this end our laboratory and others have developed a versatile, reagentless 
biosensor platform that supports the quantitative, reagentless, electrochemical detection of nucleic acids (DNA, RNA), proteins (including antibodies) and small 
molecules analytes directly in unprocessed clinical and environmental samples. In this video, we demonstrate the preparation and use of several biosensors in this 
"E-DNA" class. In particular, we fabricate and demonstrate sensors for the detection of a target DNA sequence in a polymerase chain reaction mixture, an HIV-specific antibody and the drug cocaine. The preparation procedure requires only three hours of hands-on effort followed by an overnight incubation, and their use requires only minutes.

"E-DNA" sensors, reagentless, electrochemical biosensors that perform well even when challenged directly in blood and other complex matrices, have been adapted to the detection of a wide range of nucleic acid, protein and small molecule analytes. Here we present a general procedure for the fabrication and use of such sensors.

Herstellung von elektrochemischen DNA Biosensoren für die Reagenzienfreier Nachweis von Nukleinsäuren, Proteinen und kleinen Molekülen

As medicine is currently practiced, doctors send specimens to a central laboratory for testing and thus must wait hours or days to 
receive the results. ...

Forschung

Biotechnik

Mapping the Binding Site of an Aptamer on ATP Using MicroScale Thermophoresis

Characterization of molecular interactions in terms of basic binding parameters such as binding affinity, stoichiometry, and thermodynamics is an essential step in basic and applied science. MicroScale Thermophoresis (MST) is a sensitive biophysical method to obtain this important information. Relying on a physical effect called thermophoresis, which describes the movement of molecules through temperature gradients, this technology allows for the fast and precise determination of binding parameters in solution and allows the free choice of buffer conditions (from buffer to lysates/sera). MST uses the fact that an unbound molecule displays a different thermophoretic movement than a molecule that is in complex with a binding partner. The thermophoretic movement is altered in the moment of molecular interaction due to changes in size, charge, and hydration shell. By comparing the movement profiles of different molecular ratios of the two binding partners, quantitative information such as binding affinity (pM to mM) can be determined. Even challenging interactions between molecules of small sizes, such as aptamers and small compounds, can be studied by MST. Using the well-studied model interaction between the DH25.42 DNA aptamer and ATP, this manuscript provides a protocol to characterize aptamer-small molecule interactions. This study demonstrates that MST is highly sensitive and permits the mapping of the binding site of the 7.9 kDa DNA aptamer to the adenine of ATP.

MicroScale Thermophoresis (MST) is a sensitive technology to characterize aptamer-target interactions. This manuscript describes an MST protocol to characterize aptamer-small molecule interactions.

Kartierung der Bindungsstelle eines Aptamer auf ATP Mit Micro Thermophorese

Characterization of molecular interactions in terms of basic binding parameters such as binding affinity, stoichiometry, and thermodynamics is an ...

Biochemie

Bacterial Detection &amp; Identification Using Electrochemical Sensors

Electrochemical sensors are widely used for rapid and accurate measurement of blood glucose and can be adapted for detection of a wide variety of analytes. Electrochemical sensors operate by transducing a biological recognition event into a useful electrical signal. Signal transduction occurs by coupling the activity of a redox enzyme to an amperometric electrode. Sensor specificity is either an inherent characteristic of the enzyme, glucose oxidase in the case of a glucose sensor, or a product of linkage between the enzyme and an antibody or probe.
Here, we describe an electrochemical sensor assay method to directly detect and identify bacteria. In every case, the probes described here are DNA oligonucleotides. This method is based on sandwich hybridization of capture and detector probes with target ribosomal RNA (rRNA). The capture probe is anchored to the sensor surface, while the detector probe is linked to horseradish peroxidase (HRP). When a substrate such as 3,3',5,5'-tetramethylbenzidine (TMB) is added to an electrode with capture-target-detector complexes bound to its surface, the substrate is oxidized by HRP and reduced by the working electrode. This redox cycle results in shuttling of electrons by the substrate from the electrode to HRP, producing current flow in the electrode.

Bacterial Detection & Identification Using Electrochemical Sensors

We describe an electrochemical sensor assay method for rapid bacterial detection and identification. The assay involves a sensor array functionalized with DNA oligonucleotide capture probes for ribosomal RNA (rRNA) species-specific sequences. Sandwich hybridization of target rRNA with the capture probe and a horseradish peroxidase-linked DNA oligonucleotide detector probe produces a measurable amperometric current.

Bakterielle Erkennung und Identifizierung mit elektrochemischen Sensoren

Electrochemical  sensors are widely used for rapid and accurate measurement of blood glucose and  can be adapted for detection of a wide variety of ...

Electronic Tongue Generating Continuous Recognition Patterns for Protein Analysis

In current protocol, a combinatorial approach has been developed to simplify the design and production of sensing materials for the construction of electronic tongues (eT) for protein analysis. By mixing a small number of simple and easily accessible molecules with different physicochemical properties, used as building blocks (BBs), in varying and controlled proportions and allowing the mixtures to self-assemble on the gold surface of a prism, an array of combinatorial surfaces featuring appropriate properties for protein sensing was created. In this way, a great number of cross-reactive receptors can be rapidly and efficiently obtained. By combining such an array of combinatorial cross-reactive receptors (CoCRRs) with an optical detection system such as surface plasmon resonance imaging (SPRi), the obtained eT can monitor the binding events in real-time and generate continuous recognition patterns including 2D continuous evolution profile (CEP) and 3D continuous evolution landscape (CEL) for samples in liquid. Such an eT system is efficient for discrimination of common purified proteins.

A novel approach is described for construction of electronic tongue (eT), which greatly simplifies the design and production of sensing materials, and allows the eT to generate continuous evolution profiles and landscapes for samples in liquid. The obtained eT is efficient for common protein analysis such as discrimination.

Elektronische Zunge generieren Continuous Erkennungsmuster für die Protein-Analyse

In current protocol, a combinatorial approach has been developed to simplify the design and production of sensing materials for the construction of ...

Kinetic Screening of Nuclease Activity using Nucleic Acid Probes

Nucleases are a class of enzymes that break down nucleic acids by catalyzing the hydrolysis of the phosphodiester bonds that link the ribose sugars. Nucleases display a variety of vital physiological roles in prokaryotic and eukaryotic organisms, ranging from maintaining genome stability to providing protection against pathogens. Altered nuclease activity has been associated with several pathological conditions including bacterial infections and cancer. To this end, nuclease activity has shown great potential to be exploited as a specific biomarker. However, a robust and reproducible screening method based on this activity remains highly desirable.
Herein, we introduce a method that enables screening for nuclease activity using nucleic acid probes as substrates, with the scope of differentiating between pathological and healthy conditions. This method offers the possibility of designing new probe libraries, with increasing specificity, in an iterative manner. Thus, multiple rounds of screening are necessary to refine the probes&#39; design with enhanced features, taking advantage of the availability of chemically modified nucleic acids. The considerable potential of the proposed technology lies in its flexibility, high reproducibility, and versatility for the screening of nuclease activity associated with disease conditions. It is expected that this technology will allow the development of promising diagnostic tools with a great potential in the clinic.

Altered nuclease activity has been associated with different human conditions, underlying its potential as a biomarker. The modular and easy to implement screening methodology presented in this paper allows the selection of specific nucleic acid probes for harnessing nuclease activity as a biomarker of disease.

Kinetisches Screening der Nuklease-Aktivität mit Nukleinsäuresonden

Nucleases are a class of enzymes that break down nucleic acids by catalyzing the hydrolysis of the phosphodiester bonds that link the ribose sugars. ...

Primer-Free Aptamer Selection Using A Random DNA Library

Aptamers are highly structured oligonucleotides (DNA or RNA) that can bind to targets with affinities comparable to antibodies 1. They are identified through an in vitro selection process called Systematic Evolution of Ligands by EXponential enrichment (SELEX) to recognize a wide variety of targets, from small molecules to proteins and other macromolecules 2-4. Aptamers have properties that are well suited for in vivo diagnostic and/or therapeutic applications: Besides good specificity and affinity, they are easily synthesized, survive more rigorous processing conditions, they are poorly immunogenic, and their relatively small size can result in facile penetration of tissues.
Aptamers that are identified through the standard SELEX process usually comprise ~80 nucleotides (nt), since they are typically selected from nucleic acid libraries with ~40 nt long randomized regions plus fixed primer sites of ~20 nt on each side. The fixed primer sequences thus can comprise nearly ~50% of the library sequences, and therefore may positively or negatively compromise identification of aptamers in the selection process 3, although bioinformatics approaches suggest that the fixed sequences do not contribute significantly to aptamer structure after selection 5. To address these potential problems, primer sequences have been blocked by complementary oligonucleotides or switched to different sequences midway during the rounds of SELEX 6, or they have been trimmed to 6-9 nt 7, 8. Wen and Gray 9 designed a primer-free genomic SELEX method, in which the primer sequences were completely removed from the library before selection and were then regenerated to allow amplification of the selected genomic fragments. However, to employ the technique, a unique genomic library has to be constructed, which possesses limited diversity, and regeneration after rounds of selection relies on a linear reamplification step. Alternatively, efforts to circumvent problems caused by fixed primer sequences using high efficiency partitioning are met with problems regarding PCR amplification 10.
We have developed a primer-free (PF) selection method that significantly simplifies SELEX procedures and effectively eliminates primer-interference problems 11, 12. The protocols work in a straightforward manner. The central random region of the library is purified without extraneous flanking sequences and is bound to a suitable target (for example to a purified protein or complex mixtures such as cell lines). Then the bound sequences are obtained, reunited with flanking sequences, and re-amplified to generate selected sub-libraries. As an example, here we selected aptamers to S100B, a protein marker for melanoma. Binding assays showed Kd s in the 10-7 - 10-8 M range after a few rounds of selection, and we demonstrate that the aptamers function effectively in a sandwich binding format.

SELEX protocols comprise multiple rounds of selection, each of which require regeneration of bound ligands, which in turn require fixed primer sequences flanking the random library regions. These fixed primer sequences can interfere with the selection process (false positives and negatives). Here we present a primer-free protocol.

Primer-Free Aptamer Selection mit einem zufälligen DNA-Bibliothek

Aptamers are highly structured oligonucleotides (DNA or RNA) that can bind to targets with affinities comparable to antibodies 1. They are identified ...

Biologie

Determining the Thermodynamic and Kinetic Association of a DNA Aptamer and Tetracycline Using Isothermal Titration Calorimetry

The determination of binding affinity and behavior between an aptamer and its target is the most crucial step in selecting and using an aptamer for application. Due to the drastic differences between the aptamer and small molecules, scientists need to put much effort into characterizing their binding properties. Isothermal Titration Calorimetry (ITC) is a powerful approach for this purpose. ITC goes beyond determining disassociation constants (Kd) and can provide the enthalpy changes and binding stoichiometry of the interaction between two molecules in the solution phase. This approach conducts continuous titration using label-free molecules and records released heat over time upon the binding events produced by each titration, so the process can sensitively measure the binding between macromolecules and their small targets. Herein, the article introduces a step-by-step procedure of the ITC measurement of a selected aptamer with a small target, tetracycline. This example proves the versatility of the technique and its potential for other applications.

The present protocol describes the use of Isothermal Titration Calorimetry (ITC) to analyze the association and dissociation kinetics of the binding between a DNA aptamer and tetracycline, including sample preparation, running standards and samples, and interpreting the resulting data.

Bestimmung der thermodynamischen und kinetischen Assoziation eines DNA-Aptamers und Tetracyclins mittels isothermer Titrationskalorimetrie

The determination of binding affinity and behavior between an aptamer and its target is the most crucial step in selecting and using an aptamer for ...

Development of an Electrochemical DNA Biosensor to Detect a Foodborne Pathogen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, significantly affecting the rate of human mortality and morbidity. Conventional methods for the detection of V. parahaemolyticus such as culture-based methods, immunological assays, and molecular-based methods require complicated sample handling and are time-consuming, tedious, and costly. Recently, biosensors have proven to be a promising and comprehensive detection method with the advantages of fast detection, cost-effectiveness, and practicality. This research focuses on developing a rapid method of detecting V. parahaemolyticus with high selectivity and sensitivity using the principles of DNA hybridization. In the work, characterization of synthesized polylactic acid-stabilized gold nanoparticles (PLA-AuNPs) was achieved using X-ray Diffraction (XRD), Ultraviolet-visible Spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Field-emission Scanning Electron Microscopy (FESEM), and Cyclic Voltammetry (CV). We also carried out further testing of stability, sensitivity, and reproducibility of the PLA-AuNPs. We found that the PLA-AuNPs formed a sound structure of stabilized nanoparticles in aqueous solution. We also observed that the sensitivity improved as a result of the smaller charge transfer resistance (Rct) value and an increase of active surface area (0.41 cm2). The development of our DNA biosensor was based on modification of a screen-printed carbon electrode (SPCE) with PLA-AuNPs and using methylene blue (MB) as the redox indicator. We assessed the immobilization and hybridization events by differential pulse voltammetry (DPV). We found that complementary, non-complementary, and mismatched oligonucleotides were specifically distinguished by the fabricated biosensor. It also showed reliably sensitive detection in cross-reactivity studies against various food-borne pathogens and in the identification of V. parahaemolyticus in fresh cockles.

A protocol for the development of an electrochemical DNA biosensor comprising a polylactic acid-stabilized, gold nanoparticles-modified, screen-printed carbon electrode to detect Vibrio parahaemolyticus is presented.

Entwicklung der eine elektrochemische DNA-Biosensor, einem Foodborne Krankheitserreger zu erkennen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, ...

Ultrasensitive Detection of Biomarkers by Using a Molecular Imprinting Based Capacitive Biosensor

The ability to detect and quantitate biomolecules in complex solutions has always been highly sought-after within natural science; being used for the detection of biomarkers, contaminants, and other molecules of interest. A commonly used technique for this purpose is the Enzyme-linked Immunosorbent Assay (ELISA), where often one antibody is directed towards a specific target molecule, and a second labeled antibody is used for the detection of the primary antibody, allowing for the absolute quantification of the biomolecule under study. However, the usage of antibodies as recognition elements limits the robustness of the method; as does the need of using labeled molecules. To overcome these limitations, molecular imprinting has been implemented, creating artificial recognition sites complementary to the template molecule, and obsoleting the necessity of using antibodies for initial binding. Further, for even higher sensitivity, the secondary labeled antibody can be replaced by biosensors relying on the capacitance for the quantification of the target molecule. In this protocol, we describe a method to rapidly and label-free detect and quantitate low-abundant biomolecules (proteins and viruses) in complex samples, with a sensitivity that is significantly better than commonly used detection systems such as the ELISA. This is all mediated by molecular imprinting in combination with a capacitance biosensor.

Here, we present a protocol for the detection and quantification of low abundant molecules in complex solutions using molecular imprinting in combination with a capacitance biosensor.

Gromer Nachweis von Biomarkern mithilfe einer molekularen Prägung basierte kapazitive Biosensor

The ability to detect and quantitate biomolecules in complex solutions has always been highly sought-after within natural science; being used for the ...

Immunologie und Infektion

Aptamer-Based Target Detection Facilitated by a 3-Stage G-Quadruplex Isothermal Exponential Amplification Reaction

Aptamers are target-recognition molecules that bind with high affinity and specificity. These characteristics can be leveraged to control other molecules with signal-generation capability. For the system described herein, target recognition through an aptameric domain, Stem II of a modified hammerhead ribozyme, activates the self-cleaving ribozyme by stabilizing the initially unstructured construct. The cis-cleaving RNA acts at the junction of Stem III and Stem I, creating two cleavage products. The longer cleavage product primes an isothermal exponential amplification reaction (EXPAR) of the two similar catalytically active G-quadruplexes. Those resulting amplification products catalyze peroxidase reduction, which is coupled to the reduction of a colorimetric substrate with an output that the naked eye can detect. The 3-part system described in the present study improves detection modalities such as enzyme-linked immunosorbent assays (ELISAs) by producing a visually detectable signal for indicating the presence of as low as 0.5 &#181;M theophylline in as little as 15 min.

The present protocol demonstrates the use of a fast, 3-stage, aptamer-based exponential amplification assay to detect targets. Sample preparation, signal amplification, and color development are covered to implement this system to recognize the presence of theophylline over that of caffeine.

Aptamer-basierte Target-Detektion durch eine 3-stufige isotherme G-Quadruplex-Amplifikationsreaktion

Aptamers are target-recognition molecules that bind with high affinity and specificity. These characteristics can be leveraged to control other molecules ...