. אנחנו אסירי תודה על תמיכה כספית של הטבע הקרן הלאומית למדע (21675112), מפתח הפרויקט בתכנית למדע וטכנולוגיה של בייג'ינג ועדת החינוך (KZ201710028027), Yanjing הצעיר המלומד תוכנית של הון רגיל אוניברסיטת...

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המחברים מצהירים שום עניין פיננסי מתחרות.

אחד מהיתרונות aptamers יוצא מן הכלל הוא כי הם מזוהים באמצעות השיטה במבחנה SELEX, בעוד נוגדנים נוצרים באמצעות ויוו immunoreactions. לכן, ניתן לבחור aptamers עם ירידה לפרטים היעד הרצוי בתנאים ניסיוני מעוצב היטב, ואילו נוגדנים מוגבלים בתנאים פיזיולוגיים.
כדי להקל על ההפרדה של רצפי מאו?...

יחד עם התפתחות כלכלית מהירה, האצה של ה תיעוש, הבנייה העירונית, זיהום סביבתי הוא חמור יותר מאי פעם. טיפוסי מזהמים סביבתיים כוללים יונים של מתכות כבדות, רעלים, אנטיביוטיקה, חומרי הדברה, משבשים האנדוקרינית ו מזהמים אורגניים מתמיד (אבא). מלבד יונים מתכתיים, רעלים, מזהמים אחרים הם מולקולות קטנות לעיתים קרובות מכילים מגוון רחב של congeners. לדוגמה, הטיילת הרעילים ביותר לכלול polychlorinated biphenyls (PCBs), פחמימנים ארומטיים polycyclic (PAHs), polybrominated biphenyl קטונים (PBDEs), dibenzo-p-דיוקסין polychlorinated (PCDDs), polychlorinated dibenzofuran (PCDFs), ו phthalic חומצה אסטרים (פאיס)1,2, אשר כולם מורכב congeners רבים. גילוי מולקולה קטנה בוצעה בעיקר על-ידי טכניקות מבוססות ספקטרומטר מסה/כרומטוגרפיה בשל מגוון של יישומים3,4,5,6. עבור גילויים באתר, נוגדן מבוססי שיטות לאחרונה היה מפותח7,8,9. עם זאת, מאז שיטות אלה הם מאוד ספציפי congener מסוימים, יש לבצע בדיקות מרובות. מה זה חמור יותר הוא כי הרומן congeners לגדול כל כך מהר, כי לא ניתן ליצור נוגדנים שלהם בזמן. לכן, ההתפתחות של קבוצה ספציפית ביולוגיים כדי לנטר את רמות סך כל congeners במבחן אחד עשוי לספק מדד לא בפז להערכת מצב זיהום סביבתי.
לאחרונה, חומצת גרעין aptamers נרחב הוחלו כרכיבים זיהוי של פלטפורמות שונות biosensing עקב שלהם יכולת זיהוי מגוון רחב של מטרות, יונים ומולקולות קטנות חלבונים ותאים10,11 ,12. Aptamers מזוהים באמצעות שיטה במבחנה בשם האבולוציה שיטתית של ליגנדים מאת העשרה מעריכית (SELEX)13,14. SELEX מתחיל עם הספרייה oligonucleotide אקראיים סינתטי לחוט אחד, אשר מכיל כ רצפים15 14-10 10. הגודל של הספרייה אקראי מבטיחה את המגוון של המבנים המועמד RNA או DNA. תהליך SELEX טיפוסי מורכב מספר סיבובים של העשרה עד הספרייה מועשר ברצפים עם זיקה גבוהה וספציפיות אל המטרה. מועשר בבריכה הסופי אז הוא רציף, ולסנן קבועי דיסוציאציה (דK) ואת סלקטיביות נגד פוטנציאל חומרים מפריעות נקבעים על-ידי טכניקות שונות כגון איגוד, כרומטוגרפיית זיקה משטח פלזמון תהודה (SPR), וכו '. 15
בשל מסיסות המים ירודה ביותר וחוסר קבוצות פונקציונליות עבור משטח הנייח, הבחירה aptamer של סבא קשה באופן תיאורטי. התקדמויות משמעותיות עבור SELEX יש speeded את הגילוי של aptamers. עם זאת, הבחירה של קבוצה ספציפית aptamers עבור סבא יש וטרם דווחו. עד כה, רק מחייב PCB DNA aptamers עם ירידה לפרטים גבוה עבור congener מסוימים כבר מזוהה16. פאיס משמשים בעיקר בחומרים פוליוויניל כלוריד, שינוי במבנהו מפלסטיק קשיח לפלסטיק גמיש, ובכך כסוכנות מרכך ומגמיש. כמה פאיס זוהו משבשים האנדוקרינית, יכול לגרום נזק חמור בכבד, תפקוד כליות, להפחית את תנועתיות הזרע הגברי, עלול לגרום סרטן האשכים17ומורפולוגיה זרע לא תקין. המתחם - וגם המיועדות לקבוצות PAE מחייב aptamers דווחו.
מטרת עבודה זו היא לספק פרוטוקול ייצוגית לבחירת המיועדות לקבוצות aptamers דנ א כדי מאוד הידרופובי מולקולות קטנות כגון פאיס, קבוצה ייצוגית של אבא. אנחנו גם להוכיח את היישום של aptamer שנבחר לגילוי זיהום סביבתי. פרוטוקול זה מספק הדרכה ותובנות על גילוי aptamer של מולקולות קטנות הידרופוביות אחרות.

<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

חומצה פתלית והפרופסור אסטרים (פאיס) של הקבוצות הגדולות של מזהמים אורגניים מתמיד. זיהוי המיועדות לקבוצות פאיס רצוי מאוד עקב גידול מהיר של congeners. DNA aptamers הוחלו יותר ויותר כרכיבים זיהוי בפלטפורמות ביוסנסור, אך בחירת aptamers לעבר מטרות מולקולה קטנה מאוד הידרופוביות, כגון פאיס, לעתים נדירות דווח. עבודה זו מתאר שיטה המבוססת על חרוז תוכנן כדי לבחור קבוצה ספציפית aptamers ה-DNA אל פאיס. קבוצת אמינו functionalized dibutyl פתלאט (DBP-NH2) המטרה עוגן היה מסונתז, ותשמרו על החרוזים מופעל אפוקסי agarose, מאפשר את התצוגה של קבוצת אסתר phthalic על פני השטח של המטריצה הנייח, ו לכן הבחירה של קלסרים קבוצה ספציפית. אנחנו נקבע את קבועי דיסוציאציה של המועמדים aptamer על ידי תגובת שרשרת הפילמור כמותיים בשילוב עם הפרדה מגנטית. הזיקות היחסי ואת מידת הבררנות של aptamers אל פאיס אחרים נקבעו על ידי מבחני תחרותי, שבו המועמדים aptamer היו ותחום מראש ל DBP-NH2 המצורפת beads מגנטי, שוחרר תגובת שיקוע על דגירה עם פאיס שנבדקו או חומרים מפריעות פוטנציאליים אחרים. וזמינותו תחרותי הוחל משום שסיפקה השוואה נתיישב זיקה בין פאיס שהיה אין קבוצות פונקציונליות עבור משטח הנייח. לבסוף, אנו הפגינו הזיוף של aptasensor אלקטרוכימי, השתמשו בו על זיהוי העדינה, סלקטיבי של פתלאט bis(2-ethylhexyl). פרוטוקול זה מספק תובנות על גילוי aptamer של מולקולות קטנות הידרופוביות אחרות.

אנו תוכנן, מסונתז פתלאט dibutyl את קבוצת אמינו functionalized (DBP-NH2) כיעד עוגן (איור 1F). אנחנו מכן ביצע את מבחר aptamer DNA פאיס באמצעות DBP-NH2 כיעד עוגן ובעקבות היעד הקלאסי מבוסס על הנייח השיטה (איור 2). בכל סבב, PCR פיילוט בוצעה באמצעות העמוד denatured כד...

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

פרוטוקול כדי להפוך את הבחירה במבחנה אפיון של חומצה פתלית המיועדות לקבוצות אסתר-איגוד ה-DNA aptamers מוצג. היישום של aptamer שנבחר ב aptasensor אלקטרוכימי נכלל גם.

חומצה פתלית אסתר מחייב DNA Aptamer ובחירת, אפיון, ליישום Aptasensor אלקטרוכימי

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

Research

JoVE Journal

Chemistry

9.8K Views.  Capital Normal University. פרוטוקול כדי להפוך את הבחירה במבחנה אפיון של חומצה פתלית המיועדות לקבוצות אסתר-איגוד ה-DNA aptamers מוצג. היישום של aptamer שנבחר ב aptasensor אלקטרוכימי נכלל גם.

Video: 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.

המצאה של אלקטרוכימי-DNA Biosensors לגילוי Reagentless של חומצות, חלבונים ומולקולות קטנות גרעין

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. ...

Bioengineering

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.

מיפוי אתר הקישור של Aptamer על ATP שימוש microscale Thermophoresis

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

Biochemistry

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.

גילוי חיידקים וזיהוי באמצעות חיישנים אלקטרוכימיים

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

A Microfluidic-based Electrochemical Biochip for Label-free DNA Hybridization Analysis

Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration of pre-processing steps. Utilizing these devices towards the analysis of DNA hybridization events is important because it offers a technology for real time assessment of biomarkers at the point-of-care for various diseases. However, when the device footprint decreases the dominance of various physical phenomena increases. These phenomena influence the fabrication precision and operation reliability of the device. Therefore, there is a great need to accurately fabricate and operate these devices in a reproducible manner in order to improve the overall performance. Here, we describe the protocols and the methods used for the fabrication and the operation of a microfluidic-based electrochemical biochip for accurate analysis of DNA hybridization events. The biochip is composed of two parts: a microfluidic chip with three parallel micro-channels made of polydimethylsiloxane (PDMS), and a 3 x 3 arrayed electrochemical micro-chip. The DNA hybridization events are detected using electrochemical impedance spectroscopy (EIS) analysis. The EIS analysis enables monitoring variations of the properties of the electrochemical system that are dominant at these length scales. With the ability to monitor changes of both charge transfer and diffusional resistance with the biosensor, we demonstrate the selectivity to complementary ssDNA targets, a calculated detection limit of 3.8 nM, and a 13% cross-reactivity with other non-complementary ssDNA following 20 min&#160;of incubation. This methodology can improve the performance of miniaturized devices by elucidating on the behavior of diffusion at the micro-scale regime and by enabling the study of DNA hybridization events.

We present a microfluidic-based electrochemical biochip for DNA hybridization detection. Following ssDNA probe functionalization, the specificity, sensitivity, and detection limit are studied with complementary and non-complementary ssDNA targets. Results illustrate the influence of the DNA hybridization events on the electrochemical system, with a detection limit of 3.8 nM.

Biochip אלקטרוכימי מבוסס Microfluidic לניתוח הכלאה DNA ללא תווית

Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration ...

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.

לשון אלקטרונית יצירת דפוסי הכרה רציפה לניתוח חלבון

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

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.

פריימר ללא aptamer לבחירה באמצעות ספריית ה-DNA אקראיים

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

Biology

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.

קביעת הקשר התרמודינמי והקינטי של אפטמר DNA וטטרציקלין באמצעות קלורימטריה איזותרמית טיטרציה

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.

התפתחות ביוסנסור אלקטרוכימי דנ א כדי לזהות חיידק והקאה

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.

זיהוי העדינה של סמנים ביולוגיים באמצעות הטבעה מולקולרית מבוסס ביוסנסור קיבולי

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

Immunology and Infection

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.

זיהוי מטרות מבוסס Aptamer המתאפשר על ידי תגובת הגברה מעריכית איזותרמית G-Quadruplex תלת-שלבית

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