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Ilyas A, Asghar W, Allen PB, Duhon H, Ellington AD, Iqbal SM. Electrical detection of cancer biomarker using aptamers with nanogap break-junctions. NANOTECHNOLOGY 2012; 23:275502. [PMID: 22706642 PMCID: PMC3404891 DOI: 10.1088/0957-4484/23/27/275502] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Epidermal growth factor receptor (EGFR) is a cell surface protein overexpressed in cancerous cells. It is known to be the most common oncogene. EGFR concentration also increases in the serum of cancer patients. The detection of small changes in the concentration of EGFR can be critical for early diagnosis, resulting in better treatment and improved survival rate of cancer patients. This article reports an RNA aptamer based approach to selectively capture EGFR protein and an electrical scheme for its detection. Pairs of gold electrodes with nanometer separation were made through confluence of focused ion beam scratching and electromigration. The aptamer was hybridized to a single stranded DNA molecule, which in turn was immobilized on the SiO(2) surface between the gold nanoelectrodes. The selectivity of the aptamer was demonstrated by using control chips with mutated non-selective aptamer and with no aptamer. Surface functionalization was characterized by optical detection and two orders of magnitude increase in direct current (DC) was measured when selective capture of EGFR occurred. This represents an electronic biosensor for the detection of proteins of interest for medical applications.
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Affiliation(s)
- Azhar Ilyas
- Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76011, USA
- Nanotechnology Research and Teaching Facility, University of Texas at Arlington, Arlington, Texas 76019, USA
- Nano-Bio Lab, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Waseem Asghar
- Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76011, USA
- Nanotechnology Research and Teaching Facility, University of Texas at Arlington, Arlington, Texas 76019, USA
- Nano-Bio Lab, University of Texas at Arlington, Arlington, Texas 76019, USA
| | - Peter B. Allen
- Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Holli Duhon
- Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Andrew D. Ellington
- Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Samir M. Iqbal
- Department of Electrical Engineering, University of Texas at Arlington, Arlington, Texas 76011, USA
- Nanotechnology Research and Teaching Facility, University of Texas at Arlington, Arlington, Texas 76019, USA
- Nano-Bio Lab, University of Texas at Arlington, Arlington, Texas 76019, USA
- Joint Graduate Committee of Bioengineering Program, University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Arlington, Texas 76010, USA
- Department of Bioengineering, University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, Arlington, Texas 76010, USA
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Abstract
Aptamers are small single-stranded nucleic acids that fold into a well-defined three-dimensional structure. They show a high affinity and specificity for their target molecules and inhibit their biological functions. Aptamers belong to the nucleic acids family and can be synthesized by chemical or enzymatic procedures, or a combination of the two. They can, therefore, be considered as both chemical and biological substances. This Review summarizes the most convenient approaches to their preparation and new developments in the field of aptamers. The application of aptamers in chemical biology is also discussed.
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Affiliation(s)
- Günter Mayer
- Life and Medical Sciences, Prog. Unit Chemical Biology and Medicinal Chemistry, University of Bonn c/o Kekulé-Institute for Organic Chemistry and Biochemistry, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany.
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Yoon H, Kim JH, Lee N, Kim BG, Jang J. A novel sensor platform based on aptamer-conjugated polypyrrole nanotubes for label-free electrochemical protein detection. Chembiochem 2008; 9:634-41. [PMID: 18247433 DOI: 10.1002/cbic.200700660] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We first present a simple yet versatile strategy for the functionalization of polymer nanotubes in a controlled fashion. Carboxylic-acid-functionalized polypyrrole (CPPy) nanotubes were fabricated by using cylindrical micelle templates in a water-in-oil emulsion system, and the functional carboxyl groups were effectively incorporated into the polymer backbone during the polymerization by using pyrrole-3-carboxylic acid (P3CA) as a co-monomer without a sophisticated functionalization process. It was noteworthy that the chemical functionality of CPPy nanotubes was readily controlled in both qualitative and quantitative aspects. On the basis of the controlled functionality of CPPy nanotubes, a field-effect transistor (FET) sensor platform was constructed to detect specific biological entities by using a buffer solution as a liquid-ion gate. The CPPy nanotubes were covalently immobilized onto the microelectrode substrate to make a good electrical contact with the metal electrodes, and thrombin aptamers were bonded to the nanotube surface via covalent linkages as the molecular recognition element. The selective recognition ability of thrombin aptamers combined with the charge transport property of CPPy nanotubes enabled the direct and label-free electrical detection of thrombin proteins. Upon exposure to thrombin, the CPPy nanotube FET sensors showed a decrease in current flow, which was probably attributed to the dipole-dipole or dipole-charge interaction between thrombin proteins and the aptamer-conjugated polymer chains. Importantly, the sensor response was tuned by adjusting the chemical functionality of CPPy nanotubes. The efficacy of CPPy nanotube FET sensors was also demonstrated in human blood serum; this suggests that they may be used for practical diagnosis applications after further optimization.
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Affiliation(s)
- Hyeonseok Yoon
- Hyperstructured Organic Materials Research Center, School of Chemical and Biological Engineering, Seoul National University, Shinlimdong 56-1, Seoul 151-742, Korea
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Abstract
Herein, we report an approach for protein detection enhanced by ionic liquid (IL) selectors in capillary electrophoresis (CE), with avidin as a model protein. Hydrophilic ILs were added into the running buffer of CE and acted as selectors for sample injection, enriching the positive target and excluding the negative from the capillary. When using 3 % (v/v) IL selector, the detection sensitivity of avidin was improved by over one order of magnitude, while the interference from protein adsorption was effectively avoided, even in an uncoated capillary. The electrochemiluminescence method was initially used for IL-based CE with low noise that was independent of the IL concentration, making ILs almost transparent as additives in the electrophoresis buffer.
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Affiliation(s)
- Tao Li
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
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Li T, Li B, Dong S. Adaptive recognition of small molecules by nucleic acid aptamers through a label-free approach. Chemistry 2007; 13:6718-23. [PMID: 17506050 DOI: 10.1002/chem.200700068] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We report a novel label-free method for the investigation of the adaptive recognition of small molecules by nucleic acid aptamers using capillary electrophoresis analysis. Cocaine and argininamide were chosen as model molecules, and the two corresponding DNA aptamers were used. These single-strand DNAs folded into their specific secondary structures, which were mainly responsible for the binding of the target molecules with high affinity and specificity. For molecular recognition, the nucleic acid structures then underwent additional conformational changes, while keeping the target molecules stabilized by intermolecular hydrogen bonds. The intrinsic chemical and physical properties of the target molecules enabled them to act as indicators for adaptive binding. Thus any labeling or modification of the aptamers or target molecules were made obsolete. This label-free method for aptamer-based molecular recognition was also successfully applied to biological fluids and therefore indicates that this approach is a promising tool for bioanalysis.
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Affiliation(s)
- Tao Li
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Science, Changchun, Jilin 130022, China
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Prosperi D, Morasso C, Tortora P, Monti D, Bellini T. Avidin Decorated Core–Shell Nanoparticles for Biorecognition Studies by Elastic Light Scattering. Chembiochem 2007; 8:1021-8. [PMID: 17503421 DOI: 10.1002/cbic.200600542] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In this paper, a straightforward method based on elastic light scattering is shown to provide a sensitive and reliable tool for the quantitative determination of protein-ligand interactions that occur at the surface of suitably designed core-shell nanoparticles. The assay makes use of monodisperse nanocolloids that have minimal optical contrast with the aqueous environment. By properly coating the particles with avidin and oligo(ethylene glycol)-based amphiphiles, we developed a hybrid system that combines the availability of standard ligands with the necessary bioinvisibility towards the accidental adsorption of nonspecific macromolecules. This probe was employed to detect interactions between different kinds of biotinylated proteins, and it revealed high specificity and affinities in the low nanomolar range. In particular, we obtained an efficient avidin anchorage of biotinylated protein A on the surface of the nanoparticles, which we exploited as a functional probe for the rapid, quantitative, picomolar detection of human IgG antibodies. Overall, these light-scattering-based nanosensors appear as a simple and highly informative tool for proteomics studies.
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Affiliation(s)
- Davide Prosperi
- Istituto di Scienze e Tecnologie Molecolari, National Research Council (CNR), Via Golgi 19, 20133 Milano, Italy.
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