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Kou HS, Lo ST, Wang CC. One Single Tube Reaction of Aptasensor-Based Magnetic Sensing System for Selective Fluorescent Detection of VEGF in Plasma. BIOSENSORS 2023; 13:574. [PMID: 37366939 DOI: 10.3390/bios13060574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 05/16/2023] [Accepted: 05/22/2023] [Indexed: 06/28/2023]
Abstract
In this study, a simple, easy and convenient fluorescent sensing system for the detection of the vascular endothelial growth factor (VEGF) based on VEGF aptamers, aptamer-complementary fluorescence-labeled probe and streptavidin magnetic beads was developed in one single tube. The VEGF is the most important biomarker in cancer, and it is investigated that the serum VEGF level varied according to the different types and courses of cancers. Hence, efficient quantification of VEGF is able to improve the accuracy of cancer diagnoses and the precision of disease surveillance. In this research, the VEGF aptamer was designed to be able to bind with the VEGF by forming G-quadruplex secondary structures; then, the magnetic beads would capture the non-binding aptamers due to non-steric interference; and finally, the fluorescence-labeled probes were hybridized with the aptamers captured by the magnetic beads. Therefore, the fluorescent intensity in the supernatant would specifically reflect the present VEGF. After an overall optimization, the optimal conditions for the detection of VEGF were as followed, KCl, 50 μM; pH 7.0; aptamer, 0.1 μM; and magnetic beads, 10 μL (4 μg/μL). The VEGF could be well quantified within a range of 0.2-2.0 ng/mL in plasma, and the calibration curve possessed a good linearity (y = 1.0391x + 0.5471, r = 0.998). The detection limit (LOD) was calculated to be 0.0445 ng/mL according to the formula (LOD = 3.3 × σ/S). The specificity of this method was also investigated under the appearance of many other serum proteins, and the data showed good specificity in this aptasensor-based magnetic sensing system. This strategy provided a simple, sensitive and selective biosensing platform for the detection of serum VEGF. Finally, it was expected that this detection technique can be used to promote more clinical applications.
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Affiliation(s)
- Hwang-Shang Kou
- School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Shao-Tsung Lo
- School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Chun-Chi Wang
- School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan
- Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung 807, Taiwan
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2
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Chen J, Liu X, Xu M, Li Z, Xu D. Accomplishment of one-step specific PCR and evaluated SELEX process by a dual-microfluidic amplified system. BIOMICROFLUIDICS 2021; 15:024107. [PMID: 33841601 PMCID: PMC8024032 DOI: 10.1063/5.0045965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 03/22/2021] [Indexed: 06/12/2023]
Abstract
One of the main obstacles for systematic evolution of ligands by exponential enrichment (SELEX) failure is the generation of a non-specific product, as selection-inherent amplification procedures tend to form by-products, which prevents the enrichment of target-binding aptamers. Herein, we reported a dual-microfluidic amplified system (dual-MAS) based on the real-time polymerase chain reaction (PCR) detection chip and the large volume PCR chip for one-step specific PCR and for evaluating the SELEX process. First, it is a simple method to accomplish analytical PCR and amplification PCR in one step, and the optimal number of cycles for generating the specific PCR product is the cycles when the slope of the linear amplification period of the real-time PCR curve begins to decrease. Second, the time used by the dual-MAS for generating a specific PCR product is reduced to 30 min, and the multi-functional dual-MAS can simultaneously evaluate the SELEX process by providing important information on the amounts of enriched sequences and the library diversity in every round of SELEX. In addition, pollution contamination and fragment loss can be significantly avoided in the closed chip. Last, the specific PCR product, the amounts of enriched sequences, and the library diversity can be obtained for every single SELEX in just 30 min. Compared with current methods, this system can reduce the time for generating a specific PCR product and SELEX, and it is easier to choose the optimal number of cycles for a specific PCR product. In a word, it is a sensitive, simple, and rapid strategy to improve the specificity of the PCR product and make the process of SELEX in a controlled way.
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Affiliation(s)
- Jing Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xiaohui Liu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Meng Xu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Zhoumin Li
- Jinling College, Nanjing University, Nanjing 210089, China
| | - Danke Xu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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3
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Mohammadinezhad R, Jalali SAH, Farahmand H. Evaluation of different direct and indirect SELEX monitoring methods and implementation of melt-curve analysis for rapid discrimination of variant aptamer sequences. ANALYTICAL METHODS : ADVANCING METHODS AND APPLICATIONS 2020; 12:3823-3835. [PMID: 32676627 DOI: 10.1039/d0ay00491j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Systematic Evolution of Ligands by Exponential enrichment (SELEX) is an iterative method for in vitro selection of aptamers from a random synthetic oligonucleotide library. Successful retrieving of aptamers by SELEX relies on optimization of various steps including target immobilization, aptamer partitioning, amplification, and ssDNA generation, which all require spending considerable effort and cost. Furthermore, due to the random nature of the initial library, SELEX may redirect toward the selection of low-affinity aptamers that are over-represented in the ssDNA population due to PCR bias. Thus, precise monitoring of the SELEX process is crucial to ensure the selection of target-specific aptamers. In the present study, we investigated the reliability and simplicity of different direct and indirect monitoring methods including UV-Vis spectroscopy, real-time PCR quantification and melt-curve analysis, electrophoretic mobility shift assay (EMSA) and enzyme-linked oligonucleotide assay (ELONA) for selection of DNA aptamers for a protein target. All the examined methods were capable of illustrating the gradual evolution of specific aptamers by the progression of SELEX and showed almost similar results regarding the identification of the enriched round of selection. Moreover, we describe the use of melt-curve analysis in the colony real-time PCR method as a simple, robust, and repeatable tool for pre-sequencing separation of distinct aptamer clones.
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Affiliation(s)
- Rezvan Mohammadinezhad
- Research Institute for Biotechnology and Bioengineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran.
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4
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Liu Q, Zhang W, Chen S, Zhuang Z, Zhang Y, Jiang L, LIN JS. SELEX tool: a novel and convenient gel-based diffusion method for monitoring of aptamer-target binding. J Biol Eng 2020; 14:1. [PMID: 31956340 PMCID: PMC6956507 DOI: 10.1186/s13036-019-0223-y] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 12/29/2019] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Aptamers, single-stranded DNAs or RNAs, can be selected from a library containing random sequences using a method called Systematic Evolution of Ligands by EXponential Enrichment (SELEX). In SELEX, monitoring the enriching statuses of aptamer candidates during the process is a key step until today. Conformational change of an aptamer caused by target-binding in gel can be used to indicate its statuses of binding. RESULTS In this study, an easy-to-implement gel-based diffusion method (GBDM) was developed to monitor the interaction between enriched aptamer candidates and their targets. In order to prove the concept, characterization of aptamers targeting their targets including protein (thrombin) and non-protein molecules (acetamiprid, ATP, atrazine, profenofos and roxithromycin), respectively, were performed using mini gels. Our method has advantages over the common methods including easy performed with labor- and time- saving in experimental operation. The concept has been proven by monitoring enrichment of dynamic aptamer candidate libraries targeting a small molecule 2,2-bis(4-chlorophenyl) acetic acid (DDA) during SELEX process. A mini gel cassette was designed and fabricated by our laboratory to make mini agarose gels for diffusion with different directions. CONCLUSIONS These results indicate that GBDM, in particular, chasing diffusion is suitable for monitoring the interaction between enriched aptamer candidates and their targets. These pioneering efforts are helpful for novel aptamer selection by breaking through the technical bottleneck of aptamer development and helpful for development of novel aptasensors.
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Affiliation(s)
- Qingxiu Liu
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Wei Zhang
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Siying Chen
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Zhenjing Zhuang
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Yi Zhang
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Lingli Jiang
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
| | - Jun Sheng LIN
- School of Medicine, Huaqiao University, 269 Chenghua Rd, Fengze, Quanzhou, 362021 Fujian China
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5
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Bhardwaj T, Rathore AS, Jha SK. The selection of highly specific and selective aptamers using modified SELEX and their use in process analytical techniques for Lucentis bioproduction. RSC Adv 2020; 10:28906-28917. [PMID: 35520059 PMCID: PMC9055848 DOI: 10.1039/d0ra03542d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/19/2020] [Indexed: 11/21/2022] Open
Abstract
Aptamers for Lucentis were selected using 10 rounds of a modified and highly stringent SELEX process. Affinity column chromatography was used for the binding, partitioning, and elution steps, and the regeneration of ssDNA was performed via asymmetric PCR in the SELEX process. The interaction of aptamers with Lucentis was studied by means of the HADDOCK web server docking program. In addition, the secondary structures of aptamers were interrogated using the mfold web server to check common regions responsible for better affinity towards Lucentis. The two best aptamers for Lucentis (aptamers 1 and 25) were found to have dissociation constant (Kd) values between 23 and 35 nM by means of thermofluorimetric and non-faradaic impedance spectroscopy (NFIS) analysis. The low dissociation constants in the nanomolar range showed the high specificities of the aptamers for Lucentis. Selectivity tests were also performed using both aptamers with different proteins in which negligible responses were obtained from interfering proteins with respect to Lucentis. Although neither of the two aptamers showed prominent responses to the interfering proteins, slightly better selectivity was shown by aptamer 1. The same aptamers were tested for their application in the detection of Lucentis in spiked and real media broth samples. For this detection test, interdigitated (IDT) gold electrodes on a glass substrate were fabricated using standard photolithography and thermal deposition techniques. NFIS measurements were used for the label-free detection of Lucentis in samples. The linear ranges of detection for aptamers 1 and 25 were found to be 22–100 nM and 40–100 nM, respectively. The LODs for aptamers 1 and 25 were calculated to be 22 nM and 40 nM, respectively, which were significantly better than the values from a HPLC-based detection method (about 240 nM). The real sample analysis results were cross-checked via a standard HPLC method, and better correlation was found between the HPLC and aptamer 1 results than the aptamer 25 results; hence, aptamer 1 can be further analyzed and tested for use in affinity column chromatography and detection-kit/chip-based PAT for Lucentis bioproduction. Highly specific and selective aptamers for Lucentis were selected using 10 rounds of a modified and highly stringent SELEX process.![]()
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Affiliation(s)
- Tanu Bhardwaj
- Centre for Biomedical Engineering
- Indian Institute of Technology
- New Delhi-110016
- India
| | - Anurag S. Rathore
- Department of Chemical Engineering
- Indian Institute of Technology
- New Delhi-110016
- India
| | - Sandeep Kumar Jha
- Centre for Biomedical Engineering
- Indian Institute of Technology
- New Delhi-110016
- India
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6
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Wang T, Chen C, Larcher LM, Barrero RA, Veedu RN. Three decades of nucleic acid aptamer technologies: Lessons learned, progress and opportunities on aptamer development. Biotechnol Adv 2018; 37:28-50. [PMID: 30408510 DOI: 10.1016/j.biotechadv.2018.11.001] [Citation(s) in RCA: 281] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/28/2018] [Accepted: 11/04/2018] [Indexed: 02/07/2023]
Abstract
Aptamers are short single-stranded nucleic acid sequences capable of binding to target molecules in a way similar to antibodies. Due to various advantages such as prolonged shelf life, low batch to batch variation, low/no immunogenicity, freedom to incorporate chemical modification for enhanced stability and targeting capacity, aptamers quickly found their potential in diverse applications ranging from therapy, drug delivery, diagnosis, and functional genomics to bio-sensing. Aptamers are generated by a process called SELEX. However, the current overall success rate of SELEX is far from being satisfactory, and still presents a major obstacle for aptamer-based research and application. The need for an efficient selection strategy consisting of defined procedures to deal with a wide variety of targets is significantly important. In this work, by analyzing key aspects of SELEX including initial library design, target preparation, PCR optimization, and single strand DNA separation, we provide a comprehensive analysis of individual steps to facilitate researchers intending to develop personalized protocols to address many of the obstacles in SELEX. In addition, this review provides suggestions and opinions for future aptamer development procedures to address the concerns on key SELEX steps, and post-SELEX modifications.
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Affiliation(s)
- Tao Wang
- Centre for Comparative Genomics, Murdoch University, Perth 6150, Australia; Perron Institute for Neurological and Translational Science, Perth 6009, Australia; School of Nursing, Zhengzhou University & Nursing Department, The First Affiliated Hospital of Zheng Zhou University, Zhengzhou 450001, China
| | - Changying Chen
- School of Nursing, Zhengzhou University & Nursing Department, The First Affiliated Hospital of Zheng Zhou University, Zhengzhou 450001, China
| | - Leon M Larcher
- Centre for Comparative Genomics, Murdoch University, Perth 6150, Australia
| | - Roberto A Barrero
- Centre for Comparative Genomics, Murdoch University, Perth 6150, Australia
| | - Rakesh N Veedu
- Centre for Comparative Genomics, Murdoch University, Perth 6150, Australia; Perron Institute for Neurological and Translational Science, Perth 6009, Australia.
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7
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Li Z, Munro K, Narouz MR, Lau A, Hao H, Crudden CM, Horton JH. Self-Assembled N-Heterocyclic Carbene-Based Carboxymethylated Dextran Monolayers on Gold as a Tunable Platform for Designing Affinity-Capture Biosensor Surfaces. ACS APPLIED MATERIALS & INTERFACES 2018; 10:17560-17570. [PMID: 29741868 DOI: 10.1021/acsami.8b02595] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Sensor surfaces play a predominant role in the development of optical biosensor technologies for the analysis of biomolecular interactions. Thiol-based self-assembled monolayers (SAMs) on gold have been widely used as linker layers for sensor surfaces. However, the degradation of the thiol-gold bond can limit the performance and durability of such surfaces, directly impacting their performance and cost-effectiveness. To this end, a new family of materials based on N-heterocyclic carbenes (NHCs) has emerged as an alternative for surface modification, capable of self-assembling onto a gold surface with higher affinity and superior stability as compared to the thiol-based systems. Here we demonstrate three applications of NHC SAMs supporting a dextran layer as a tunable platform for developing various affinity-capture biosensor surfaces. We describe the development and testing of NHC-based dextran biosensor surfaces modified with each of streptavidin, nitrilotriacetic acid, and recombinant Protein A. These affinity-capture sensor surfaces enable oriented binding of ligands for optimal performance in biomolecular assays. Together, the intrinsic high stability and flexible design of the NHC biosensing platforms show great promise and open up exciting possibilities for future biosensing applications.
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Affiliation(s)
| | | | | | | | - Hongxia Hao
- Collaborative Innovation Center of Judicial Civilization and Key Laboratory of Evidence Science , China University of Political Science and Law , Beijing 100088 , China
| | - Cathleen M Crudden
- Institute for Transformative Bio-Molecules (ITbM-WPI) , Nagoya University , Chikusa, Nagoya 464-8602 , Japan
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8
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Identification and characterization of nucleobase-modified aptamers by click-SELEX. Nat Protoc 2018; 13:1153-1180. [PMID: 29700486 DOI: 10.1038/nprot.2018.023] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Aptamers are single-stranded oligonucleotides that are in vitro-selected to recognize their target molecule with high affinity and specificity. As they consist of the four canonical nucleobases, their chemical diversity is limited, which in turn limits the addressable target spectrum. Introducing chemical modifications into nucleic acid libraries increases the interaction capabilities of the DNA and thereby the target spectrum. Here, we describe a protocol to select nucleobase-modified aptamers by using click chemistry (CuAAC) to introduce the preferred chemical modification. The use of click chemistry to modify the DNA library enables the introduction of a wide range of possible functionalities, which can be customized to the requirements of the target molecule and the desired application. This protocol yields modified DNA aptamers with extended interaction properties that are not accessible with the canonical set of nucleotides. After synthesis of the starting library containing a commercially available, alkyne-modified uridine (5-ethynyl-deoxyuridine (EdU)) instead of thymidine, the library is functionalized with the modification of choice by CuAAC. The thus-modified DNA is incubated with the target molecule and the best binding sequences are recovered. The chemical modification is removed during the amplification process. Therefore, this protocol is compatible with conventional amplification procedures and avoids enzymatic incompatibility problems associated with more extensive nucleobase modifications. After single-strand generation, the modification is reintroduced into the enriched library, which can then be subjected to the subsequent selection cycle. The duration of each selection cycle as outlined in the protocol is ∼1 d.
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9
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Amano R, Aoki K, Miyakawa S, Nakamura Y, Kozu T, Kawai G, Sakamoto T. NMR monitoring of the SELEX process to confirm enrichment of structured RNA. Sci Rep 2017; 7:283. [PMID: 28325909 PMCID: PMC5428055 DOI: 10.1038/s41598-017-00273-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 02/15/2017] [Indexed: 01/20/2023] Open
Abstract
RNA aptamers are RNA molecules that bind to a target molecule with high affinity and specificity using uniquely-folded tertiary structures. RNA aptamers are selected from an RNA pool typically comprising up to 1015 different sequences generated by iterative steps of selection and amplification known as Systematic Evolution of Ligands by EXponential enrichment (SELEX). Over several rounds of SELEX, the diversity of the RNA pool decreases and the aptamers are enriched. Hence, monitoring of the enrichment of these RNA pools is critical for the successful selection of aptamers, and several methods for monitoring them have been developed. In this study, we measured one-dimensional imino proton NMR spectra of RNA pools during SELEX. The spectrum of the initial RNA pool indicates that the RNAs adopt tertiary structures. The structural diversity of the RNA pools was shown to depend highly on the design of the primer-binding sequence. Furthermore, we demonstrate that enrichment of RNA aptamers can be monitored using NMR. The RNA pools can be recovered from the NMR tube after measurement of NMR spectra. We also can monitor target binding in the NMR tubes. Thus, we propose using NMR to monitor the enrichment of structured aptamers during the SELEX process.
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Affiliation(s)
- Ryo Amano
- Department of Life and Environmental Sciences, Faculty of Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016, Japan
| | - Kazuteru Aoki
- Ribomic Inc., 3-16-13 Shirokanedai, Minato-ku, Tokyo, 108-0071, Japan
| | - Shin Miyakawa
- Ribomic Inc., 3-16-13 Shirokanedai, Minato-ku, Tokyo, 108-0071, Japan
| | - Yoshikazu Nakamura
- Ribomic Inc., 3-16-13 Shirokanedai, Minato-ku, Tokyo, 108-0071, Japan
- Department of Basic Medical Sciences, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan
| | - Tomoko Kozu
- Research Institute for Clinical Oncology, Saitama Cancer Center, 818 Komuro, Ina, Kitaadachi-gun, Saitama, 362-0806, Japan
| | - Gota Kawai
- Department of Life and Environmental Sciences, Faculty of Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016, Japan
| | - Taiichi Sakamoto
- Department of Life and Environmental Sciences, Faculty of Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba, 275-0016, Japan.
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10
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Sharma TK, Bruno JG, Dhiman A. ABCs of DNA aptamer and related assay development. Biotechnol Adv 2017; 35:275-301. [PMID: 28108354 DOI: 10.1016/j.biotechadv.2017.01.003] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/19/2016] [Accepted: 01/17/2017] [Indexed: 12/14/2022]
Abstract
This review is intended to guide the novice in aptamer research and development to understand virtually all of the aptamer development options and currently available assay modalities. Aptamer development topics range from discussions of basic and advanced versions of Systematic Evolution of Ligands by EXponential Enrichment (SELEX) and SELEX variations involving incorporation of exotic unnatural nucleotides to expand library diversity for even greater aptamer affinity and specificity to improved next generation methods of DNA sequencing, screening and tracking aptamer development throughout the SELEX process and characterization of lead aptamer candidates. Aptamer assay development topics include descriptions of various colorimetric and fluorescent assays in microplates or on membranes including homogeneous beacon and multiplexed Fluorescence Resonance Energy Transfer (FRET) assays. Finally, a discussion of the potential for marketing successful aptamer-based assays or test kits is included.
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Affiliation(s)
- Tarun Kumar Sharma
- Center for Biodesign and Diagnostics, Translational Health Science and Technology Institute, Faridabad, Haryana 121001, India; AptaBharat Innovation Private Limited, Translational Health Science and Technology Institute Incubator, Haryana 121001, India.
| | - John G Bruno
- Operational Technologies Corporation, 4100 NW Loop 410, Suite, 230, San Antonio, TX 78229, USA..
| | - Abhijeet Dhiman
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029, India.; Faculty of Pharmacy, Uttarakhand Technical University, Dehradun 248007, Uttarakhand, India
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11
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Fluorescence based Aptasensors for the determination of hepatitis B virus e antigen. Sci Rep 2016; 6:31103. [PMID: 27499342 PMCID: PMC4976349 DOI: 10.1038/srep31103] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/13/2016] [Indexed: 12/18/2022] Open
Abstract
This research is aimed at selecting specific aptamer of hepatitis B e antigen by SELEX and its applications. Hepatitis B e antigen (HBeAg) seroconversion is used as an indicator of virological response when treating patients suffering from chronic hepatitis B. HBeAg also indicates a high viremia and high infectivity in untreated patients. With HBeAg modified magnetic beads as targets, three groups of aptamers are successfully selected. These are the first reported DNA aptamers that can specifically bind to HBeAg. Based on the property that the conformation changes upon binding to its target, aptamer has emerged as ideal candidate in a variety of sensing applications. In this study, we present a simple strategy for aptamer-based fluorescence biosensors for the quantitative detection of HBeAg, in which a fluorescence labeled HBeAg aptamer serves as the molecular recognition element and a short DNA molecule that is complementary to the aptamer serves as the competitor. The LOD for HBeAg is 609 ng/mL. Later, the fluorescence system is deployed in HBeAg positive and negative blood serum (p < 0.05). The total detection assay could be completed in 2 min. These newly isolated aptamers could assist the diagnosis of chronic hepatitis B.
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12
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Morschheuser L, Wessels H, Pille C, Fischer J, Hünniger T, Fischer M, Paschke-Kratzin A, Rohn S. HPTLC-aptastaining - Innovative protein detection system for high-performance thin-layer chromatography. Sci Rep 2016; 6:26665. [PMID: 27220270 PMCID: PMC4879557 DOI: 10.1038/srep26665] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/03/2016] [Indexed: 02/07/2023] Open
Abstract
Protein analysis using high-performance thin-layer chromatography (HPTLC) is not commonly used but can complement traditional electrophoretic and mass spectrometric approaches in a unique way. Due to various detection protocols and possibilities for hyphenation, HPTLC protein analysis is a promising alternative for e.g., investigating posttranslational modifications. This study exemplarily focused on the investigation of lysozyme, an enzyme which is occurring in eggs and technologically added to foods and beverages such as wine. The detection of lysozyme is mandatory, as it might trigger allergenic reactions in sensitive individuals. To underline the advantages of HPTLC in protein analysis, the development of innovative, highly specific staining protocols leads to improved sensitivity for protein detection on HPTLC plates in comparison to universal protein derivatization reagents. This study aimed at developing a detection methodology for HPTLC separated proteins using aptamers. Due to their affinity and specificity towards a wide range of targets, an aptamer based staining procedure on HPTLC (HPTLC-aptastaining) will enable manifold analytical possibilities. Besides the proof of its applicability for the very first time, (i) aptamer-based staining of proteins is applicable on different stationary phase materials and (ii) furthermore, it can be used as an approach for a semi-quantitative estimation of protein concentrations.
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Affiliation(s)
- Lena Morschheuser
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Hauke Wessels
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Christina Pille
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Judith Fischer
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Tim Hünniger
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Markus Fischer
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Angelika Paschke-Kratzin
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
| | - Sascha Rohn
- University of Hamburg, Hamburg School of Food Science, Institute of Food Chemistry, Grindelallee 117, D-20146 Hamburg
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Ouellet E, Foley JH, Conway EM, Haynes C. Hi-Fi SELEX: A High-Fidelity Digital-PCR Based Therapeutic Aptamer Discovery Platform. Biotechnol Bioeng 2016; 112:1506-22. [PMID: 25727321 DOI: 10.1002/bit.25581] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 02/14/2015] [Indexed: 12/30/2022]
Abstract
Current technologies for aptamer discovery typically leverage the systematic evolution of ligands by exponential enrichment (SELEX) concept by recursively panning semi-combinatorial ssDNA or RNA libraries against a molecular target. The expectation is that this iterative selection process will be sufficiently stringent to identify a candidate pool of specific high-affinity aptamers. However, failure of this process to yield promising aptamers is common, due in part to (i) limitations in library designs, (ii) retention of non-specific aptamers during screening rounds, (iii) excessive accumulation of amplification artifacts, and (iv) the use of screening criteria (binding affinity) that does not reflect therapeutic activity. We report a new selection platform, High-Fidelity (Hi-Fi) SELEX, that introduces fixed-region blocking elements to safeguard the functional diversity of the library. The chemistry of the target-display surface and the composition of the equilibration solvent are engineered to strongly inhibit non-specific retention of aptamers. Partition efficiencies approaching 10(6) are thereby realized. Retained members are amplified in Hi-Fi SELEX by digital PCR in a manner that ensures both elimination of amplification artifacts and stoichiometric conversion of amplicons into the single-stranded library required for the next selection round. Improvements to aptamer selections are first demonstrated using human α-thrombin as the target. Three clinical targets (human factors IXa, X, and D) are then subjected to Hi-Fi SELEX. For each, rapid enrichment of ssDNA aptamers offering an order-nM mean equilibrium dissociation constant (Kd) is achieved within three selection rounds, as quantified by a new label-free qPCR assay reported here. Therapeutic candidates against factor D are identified.
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14
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Ruff LE, Sapre AA, Plaut JS, De Maere E, Mortier C, Nguyen V, Separa K, Vandenbogaerde S, Vandewalle L, Esener SC, Messmer BT. Selection of DNA nanoparticles with preferential binding to aggregated protein target. Nucleic Acids Res 2016; 44:e96. [PMID: 26969734 PMCID: PMC4889931 DOI: 10.1093/nar/gkw136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 02/24/2016] [Indexed: 01/09/2023] Open
Abstract
High affinity and specificity are considered essential for affinity reagents and molecularly-targeted therapeutics, such as monoclonal antibodies. However, life's own molecular and cellular machinery consists of lower affinity, highly multivalent interactions that are metastable, but easily reversible or displaceable. With this inspiration, we have developed a DNA-based reagent platform that uses massive avidity to achieve stable, but reversible specific recognition of polyvalent targets. We have previously selected these DNA reagents, termed DeNAno, against various cells and now we demonstrate that DeNAno specific for protein targets can also be selected. DeNAno were selected against streptavidin-, rituximab- and bevacizumab-coated beads. Binding was stable for weeks and unaffected by the presence of soluble target proteins, yet readily competed by natural or synthetic ligands of the target proteins. Thus DeNAno particles are a novel biomolecular recognition agent whose orthogonal use of avidity over affinity results in uniquely stable yet reversible binding interactions.
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Affiliation(s)
- Laura E Ruff
- UCSD Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
| | - Ajay A Sapre
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
| | - Justin S Plaut
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093, USA
| | | | | | - Valerie Nguyen
- UCSD Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
| | - Kevin Separa
- UCSD Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
| | | | | | - Sadik C Esener
- Department of Nanoengineering, University of California San Diego, La Jolla, CA 92093, USA
| | - Bradley T Messmer
- UCSD Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
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15
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Aptameric Recognition-Modulated Electroactivity of Poly(4-Styrenesolfonic Acid)-Doped Polyaniline Films for Single-Shot Detection of Tetrodotoxin. SENSORS 2015; 15:22547-60. [PMID: 26370994 PMCID: PMC4610592 DOI: 10.3390/s150922547] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 08/31/2015] [Indexed: 11/23/2022]
Abstract
The work being reported is the first electrochemical sensor for tetrodotoxin (TTX). It was developed on a glassy carbon electrodes (C) that was modified with poly(4-styrenesolfonic acid)-doped polyaniline film (PANI/PSSA). An amine-end functionalized TTX-binding aptamer, 5′-NH2-AAAAATTTCACACGGGTGCCTCGGCTGTCC-3′ (NH2-Apt), was grafted via covalent glutaraldehyde (glu) cross-linking. The resulting aptasensor (C//PANI+/PSSA-glu-NH2-Apt) was interrogated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in sodium acetate buffer (NaOAc, pH 4.8) before and after 30 min incubation in standard TTX solutions. Both CV and EIS results confirmed that the binding of the analyte to the immobilized aptamer modulated the electrochemical properties of the sensor: particularly the charge transfer resistance (Rct) of the PANI+/PSSA film, which served as a signal reporter. Based on the Rct calibration curve of the TTX aptasensor, the values of the dynamic linear range (DLR), sensitivity and limit of detection (LOD) of the sensor were determined to be 0.23–1.07 ng·mL−1 TTX, 134.88 ± 11.42 Ω·ng·mL−1 and 0.199 ng·mL−1, respectively. Further studies are being planned to improve the DLR as well as to evaluate selectivity and matrix effects in real samples.
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16
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Darmostuk M, Rimpelova S, Gbelcova H, Ruml T. Current approaches in SELEX: An update to aptamer selection technology. Biotechnol Adv 2015; 33:1141-61. [PMID: 25708387 DOI: 10.1016/j.biotechadv.2015.02.008] [Citation(s) in RCA: 406] [Impact Index Per Article: 45.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 01/26/2015] [Accepted: 02/13/2015] [Indexed: 12/21/2022]
Abstract
Systematic evolution of ligands by exponential enrichment (SELEX) is a well-established and efficient technology for the generation of oligonucleotides with a high target affinity. These SELEX-derived single stranded DNA and RNA molecules, called aptamers, were selected against various targets, such as proteins, cells, microorganisms, chemical compounds etc. They have a great potential in the use as novel antibodies, in cancer theragnostics and in biomedical research. Vast interest in aptamers stimulated continuous development of SELEX, which underwent numerous modifications since its first application in 1990. Novel modifications made the selection process more efficient, cost-effective and significantly less time-consuming. This article brings a comprehensive and up-to-date review of recent advances in SELEX methods and pinpoints advantages, main obstacles and limitations. The post-SELEX strategies and examples of application are also briefly outlined in this review.
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Affiliation(s)
- Mariia Darmostuk
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic.
| | - Silvie Rimpelova
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic.
| | - Helena Gbelcova
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic; Institute of Medical Biology, Genetics and Clinical Genetics, Faculty of Medicine, Comenius University in Bratislava, Sasinkova 4, Bratislava 811 08, Slovak Republic.
| | - Tomas Ruml
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 5, Prague 6 166 28, Czech Republic.
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17
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Luo Z, Zhou H, Jiang H, Ou H, Li X, Zhang L. Development of a fraction collection approach in capillary electrophoresis SELEX for aptamer selection. Analyst 2015; 140:2664-70. [DOI: 10.1039/c5an00183h] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A productive SELEX approach has been developed for generating high affinity aptamer.
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Affiliation(s)
- Zhaofeng Luo
- Hefei National Laboratory for Physical Science at the Microscale
- Core Facility Center for Life Sciences
- School of Life Sciences
- University of Science and Technology of China
- Hefei 230026
| | - Hongmin Zhou
- Hefei National Laboratory for Physical Science at the Microscale
- Core Facility Center for Life Sciences
- School of Life Sciences
- University of Science and Technology of China
- Hefei 230026
| | - Hao Jiang
- Hefei National Laboratory for Physical Science at the Microscale
- Core Facility Center for Life Sciences
- School of Life Sciences
- University of Science and Technology of China
- Hefei 230026
| | - Huichao Ou
- Hefei National Laboratory for Physical Science at the Microscale
- Core Facility Center for Life Sciences
- School of Life Sciences
- University of Science and Technology of China
- Hefei 230026
| | - Xin Li
- Institute of Technical Biology and Agriculture Engineering
- Key Laboratory of Ion Beam Bioengineering
- Hefei Institutes of Physical Science
- Chinese Academy of Sciences
- Hefei
| | - Liyun Zhang
- Institute of Technical Biology and Agriculture Engineering
- Key Laboratory of Ion Beam Bioengineering
- Hefei Institutes of Physical Science
- Chinese Academy of Sciences
- Hefei
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18
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Hünniger T, Wessels H, Fischer C, Paschke-Kratzin A, Fischer M. Just in time-selection: A rapid semiautomated SELEX of DNA aptamers using magnetic separation and BEAMing. Anal Chem 2014; 86:10940-7. [PMID: 25286022 DOI: 10.1021/ac503261b] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A semiautomated two-step method for in vitro selection of DNA aptamers using magnetic separation and solid-phase emulsion polymerase chain reaction has been developed. The application of a magnetic separator allows the simultaneous processing of up to 12 SELEXs (systematic evolution of ligands by exponential enrichment) with different targets or buffer conditions. Using a magnetic separator and covalent target immobilization on magnetic beads, the selection process was simplified and the substeps of aptamer/target incubation, washing, and elution of the aptamers were merged into one automated procedure called "FISHing". Without further processing the resulting FISHing eluates are suitable for BEAMing (beads, emulsion, amplification, and magnetics), which includes the amplification by emPCR (emulsion polymerase chain reaction) and strand separation by the implementation of covalently immobilized reverse primers on magnetic beads. The novel selection process has been proved and validated by selecting and characterization of aptamers to the wine fining agent lysozyme.
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Affiliation(s)
- Tim Hünniger
- Hamburg School of Food Science, Institute of Food Chemistry, University of Hamburg , Grindelallee 117, 20146 Hamburg, Germany
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19
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Vanbrabant J, Leirs K, Vanschoenbeek K, Lammertyn J, Michiels L. reMelting curve analysis as a tool for enrichment monitoring in the SELEX process. Analyst 2014; 139:589-95. [PMID: 24325000 DOI: 10.1039/c3an01884a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Current aptamer selection procedures enable limited control and transparency on how the DNA selection pool is evolving. Affinity tests and binding analyses are not always informative. Here we show that real-time PCR provides a valuable tool for the follow-up of aptamer selection. Limited time, work and amount of amplified ssDNA make this an interesting instrument to set-up a SELEX design and monitor the enrichment of oligonucleotides. reMelting Curve Analysis (rMCA) after reannealing under stringent conditions provides information about enrichment, compared to a random library. Monitoring the SELEX process and optimising conditions by means of the proposed methods can increase the selection efficiency in a controlled way. rMCA is applied in enrichment simulations and three different selection procedures. Our results imply that rMCA can be used for different SELEX designs and different targets. SELEX pool diversity analysis by rMCA has been proven to be a useful, reproducible tool to detect and evaluate enrichment of specific binding aptamers while the selection procedure is being performed.
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20
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Ouellet E, Lagally ET, Cheung KC, Haynes CA. A simple method for eliminating fixed-region interference of aptamer binding during SELEX. Biotechnol Bioeng 2014; 111:2265-79. [PMID: 24895227 DOI: 10.1002/bit.25294] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 05/07/2014] [Accepted: 05/12/2014] [Indexed: 01/20/2023]
Abstract
Standard libraries for systematic evolution of ligands by exponential enrichment (SELEX) typically utilize flanking regions that facilitate amplification of aptamers recovered from each selection round. Here, we show that these flanking sequences can bias the selection process, due in part to their ability to interfere with the fold or function of aptamers localized within the random region of the library sequence. We then address this problem by investigating the use of complementary oligonucleotides as a means to block aptamer interference by each flanking region. Isothermal titration calorimetry (ITC) studies are combined with fold predictions to both define the various interference mechanisms and assess the ability of added complementary oligonucleotides to ameliorate them. The proposed blocking strategy is thereby refined and then applied to standard library forms of benchmark aptamers against human α-thrombin, streptavidin, and vascular endothelial growth factor (VEGF). In each case, ITC data show that the new method effectively removes fixed-region mediated interference effects so that the natural binding affinity of the benchmark aptamer is completely restored. We further show that the binding affinities of properly functioning aptamers within a selection library are not affected by the blocking protocol, and that the method can be applied to various common library formats comprised of different flanking region sequences. Finally, we present a rapid and inexpensive qPCR-based method for determining the mean binding affinity of retained aptamer pools and use it to show that introduction of the pre-blocking method into the standard SELEX protocol results in retention of high-affinity aptamers that would otherwise be lost during the first round of selection. Significant enrichment of the available pool of high-affinity aptamers is thereby achieved in the first few rounds of selection. By eliminating single-strand (aptamer-like) structures within or involving the fixed regions, the technique is therefore shown to isolate aptamer sequence and function within the desired random region of the library members, and thereby provide a new selection method that is complementary to other available SELEX protocols.
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Affiliation(s)
- Eric Ouellet
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z4; Department of Chemical and Biological Engineering, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3; Biomedical Engineering Program, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3
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21
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Improvement of a streptavidin-binding aptamer by LNA- and α-l-LNA-substitutions. Bioorg Med Chem Lett 2014; 24:2273-7. [PMID: 24745966 DOI: 10.1016/j.bmcl.2014.03.082] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 03/24/2014] [Accepted: 03/25/2014] [Indexed: 12/20/2022]
Abstract
Forty modified versions of a streptavidin-binding aptamer each containing single or multiple LNA or α-l-LNA-substitutions were synthesized and their dissociation constants determined by surface plasmon resonance experiments. Both full-length and truncated versions of the aptamer were studied and compared with the unmodified DNA aptamers. A ∼two-fold improvement in binding affinity was achieved by incorporation of LNA nucleotides in the 3'-part of the stems of the streptavidin-binding aptamer whereas LNA- and α-l-LNA-substitutions in the terminal stem increased the serum stability.
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22
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Aita T, Nishigaki K, Husimi Y. Estimation of statistical binding properties of ligand population during in vitro selection based on population dynamics theory. Math Biosci 2014; 247:59-68. [DOI: 10.1016/j.mbs.2013.10.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 09/09/2013] [Accepted: 10/31/2013] [Indexed: 11/17/2022]
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23
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Streptavidin–biotin technology: improvements and innovations in chemical and biological applications. Appl Microbiol Biotechnol 2013; 97:9343-53. [DOI: 10.1007/s00253-013-5232-z] [Citation(s) in RCA: 238] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 08/29/2013] [Accepted: 09/02/2013] [Indexed: 12/25/2022]
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24
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Kuo TC, Lee PC, Tsai CW, Chen WY. Salt bridge exchange binding mechanism between streptavidin and its DNA aptamer--thermodynamics and spectroscopic evidences. J Mol Recognit 2013; 26:149-59. [PMID: 23345105 DOI: 10.1002/jmr.2260] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 11/05/2012] [Accepted: 12/04/2012] [Indexed: 12/19/2022]
Abstract
Protein-nucleic acids binding driven by electrostatic interactions typically are characterized by the release of counter ions, and the salt-inhibited binding association constant (K(a)) and the magnitude of exothermic binding enthalpy (ΔH). Here, we report a non-classical thermodynamics of streptavidin (SA)-aptamer binding in NaCl (140-350 mM) solutions near room temperatures (23-27 °C). By using isothermal titration calorimetry (ITC) and circular dichroism (CD)/fluorescence spectroscopy, we found that the binding was enthalpy driven with a large entropy cost (ΔH -20.58 kcal mol(-1), TΔS -10.99 kcal mol(-1), and K(a) 1.08 × 10(7) M(-1) at 140 mM NaCl 25 °C). With the raise of salt concentrations, the ΔH became more exothermic, yet the K(a) was almost unchanged (ΔH -26.29 kcal mol(-1) and K(a) 1.50 × 10(7) M(-1) at 350 mM NaCl 25 °C). The data suggest that no counter Na(+) was released in the binding. Spectroscopy data suggest that the binding, with a stoichiometry of 2, was accompanied with substantial conformational changes on SA, and the changes were insensitive to the variation of salt concentrations. To account for the non-classical results, we propose a salt bridge exchange model. The intramolecular binding-site salt bridge(s) of the free SA and the charged phosphate group of aptamers re-organize to form the binding complex by forming a new intermolecular salt bridge(s). The salt bridge exchange binding process requires minimum amount of counter ions releasing but dehydration of the contacting surface of SA and the aptamer. The energy required for dehydration is reduced in the case of binding solution with higher salt concentration and account for the higher binding exothermic mainly.
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Affiliation(s)
- Tai-Chih Kuo
- Department of Biochemistry, Taipei Medical University, Taipei, 11031, Taiwan
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25
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Funder ED, Jensen AB, Tørring T, Kodal ALB, Azcargorta AR, Gothelf KV. Synthesis of Dopamine and Serotonin Derivatives for Immobilization on a Solid Support. J Org Chem 2012; 77:3134-42. [DOI: 10.1021/jo2025477] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Erik Daa Funder
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Anne Bjørnskov Jensen
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Thomas Tørring
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Anne Louise Bank Kodal
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Ane Rebolledo Azcargorta
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
| | - Kurt Vesterager Gothelf
- Danish National Research
Foundation: Center for DNA
Nanotechnology (CDNA) at Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, DK-8000 Aarhus
C, Denmark
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26
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Aptamers and their biological applications. SENSORS 2012; 12:612-31. [PMID: 22368488 PMCID: PMC3279232 DOI: 10.3390/s120100612] [Citation(s) in RCA: 452] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 12/31/2011] [Accepted: 01/04/2012] [Indexed: 01/09/2023]
Abstract
Recently, aptamers have attracted the attention of many scientists, because they not only have all of the advantages of antibodies, but also have unique merits, such as thermal stability, low cost, and unlimited applications. In this review, we present the reasons why aptamers are known as alternatives to antibodies. Furthermore, several types of in vitro selection processes, including nitrocellulose membrane filtration, affinity chromatography, magnetic bead, and capillary electrophoresis-based selection methods, are explained in detail. We also introduce various applications of aptamers for the diagnosis of diseases and detection of small molecules. Numerous analytical techniques, such as electrochemical, colorimetric, optical, and mass-sensitive methods, can be utilized to detect targets, due to convenient modifications and the stability of aptamers. Finally, several medical and analytical applications of aptamers are presented. In summary, aptamers are promising materials for diverse areas, not just as alternatives to antibodies, but as the core components of medical and analytical equipment.
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27
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Schütze T, Wilhelm B, Greiner N, Braun H, Peter F, Mörl M, Erdmann VA, Lehrach H, Konthur Z, Menger M, Arndt PF, Glökler J. Probing the SELEX process with next-generation sequencing. PLoS One 2011; 6:e29604. [PMID: 22242135 PMCID: PMC3248438 DOI: 10.1371/journal.pone.0029604] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 12/01/2011] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND SELEX is an iterative process in which highly diverse synthetic nucleic acid libraries are selected over many rounds to finally identify aptamers with desired properties. However, little is understood as how binders are enriched during the selection course. Next-generation sequencing offers the opportunity to open the black box and observe a large part of the population dynamics during the selection process. METHODOLOGY We have performed a semi-automated SELEX procedure on the model target streptavidin starting with a synthetic DNA oligonucleotide library and compared results obtained by the conventional analysis via cloning and Sanger sequencing with next-generation sequencing. In order to follow the population dynamics during the selection, pools from all selection rounds were barcoded and sequenced in parallel. CONCLUSIONS High affinity aptamers can be readily identified simply by copy number enrichment in the first selection rounds. Based on our results, we suggest a new selection scheme that avoids a high number of iterative selection rounds while reducing time, PCR bias, and artifacts.
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Affiliation(s)
- Tatjana Schütze
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
- Institute for Chemistry/Biochemistry, Free University Berlin, Berlin, Germany
| | - Barbara Wilhelm
- Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Nicole Greiner
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
- Alacris Theranostics GmbH, Berlin, Germany
| | - Hannsjörg Braun
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
- Alacris Theranostics GmbH, Berlin, Germany
| | - Franziska Peter
- Institute of Biochemistry, Universität Leipzig, Leipzig, Germany
| | - Mario Mörl
- Institute of Biochemistry, Universität Leipzig, Leipzig, Germany
| | - Volker A. Erdmann
- Institute for Chemistry/Biochemistry, Free University Berlin, Berlin, Germany
| | - Hans Lehrach
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Zoltán Konthur
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Marcus Menger
- RiNA RNA-Netzwerk Technologien GmbH, Berlin, Germany
| | - Peter F. Arndt
- Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Jörn Glökler
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany
- Alacris Theranostics GmbH, Berlin, Germany
- * E-mail:
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28
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Liu JJ, Wang CL, Xi Q, Xu J, Deng B, Ding HM, Chu B, Su DH. Dissection of the functional structure of aptamer17, which specifically recognizes differentiated PC12 cells. Nucleic Acid Ther 2011; 21:225-9. [PMID: 21749299 DOI: 10.1089/nat.2011.0279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A specific single-stranded DNA (ssDNA) aptamer (aptamer17) that specifically recognizes differentiated PC12 cells had been previously obtained after 6 rounds of whole cell-based subtractive systematic evolution of ligands by exponential enrichment selection from a random ssDNA library. To further investigate the relationship between the structure and function of this aptamer, 3 truncated ssDNA aptamers were designed according to the predicted secondary structure of aptamer17. Our results show that the stem-loop is the core structure of the aptamers required for specific binding to differentiated PC12 cells, specifically loops I and II. Aptamer17 and the truncated aptamers with this basic structure could bind specifically to differentiated PC12 cells and identify these cells from a mixture of differentiated and undifferentiated PC12 cells. Therefore, truncated forms of aptamer17 may be useful in the clinic to identify undifferentiated and differentiated PC12 cells from a mixture of cells.
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Affiliation(s)
- Jiao-Jiao Liu
- Department of Stomatology, General Hospital of PLA, Beijing, China
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29
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Oh SS, Ahmad KM, Cho M, Kim S, Xiao Y, Soh HT. Improving aptamer selection efficiency through volume dilution, magnetic concentration, and continuous washing in microfluidic channels. Anal Chem 2011; 83:6883-9. [PMID: 21774453 PMCID: PMC3165111 DOI: 10.1021/ac201269f] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The generation of nucleic acid aptamers with high affinity typically entails a time-consuming, iterative process of binding, separation, and amplification. It would therefore be beneficial to develop an efficient selection strategy that can generate these high-quality aptamers rapidly, economically, and reproducibly. Toward this goal, we have developed a method that efficiently generates DNA aptamers with slow off-rates. This methodology, called VDC-MSELEX, pairs the volume dilution challenge process with microfluidic separation for magnetic bead-assisted aptamer selection. This method offers improved aptamer selection efficiencies through the application of highly stringent selection conditions: it retrieves a small number (<10(6)) of magnetic beads suspended in a large volume (>50 mL) and concentrates them into a microfluidic chamber (8 μL) with minimal loss for continuous washing. We performed three rounds of the VDC-MSELEX using streptavidin (SA) as the target and obtained new DNA aptamer sequences with low nanomolar affinity that specifically bind to the SA proteins.
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Affiliation(s)
- Seung Soo Oh
- Materials Department, University of California, Santa Barbara, CA 93106
| | - Kareem M. Ahmad
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106
| | - Minseon Cho
- Materials Department, University of California, Santa Barbara, CA 93106
- Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106
| | - Seon Kim
- Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106
| | - Yi Xiao
- Materials Department, University of California, Santa Barbara, CA 93106
- Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106
| | - H. Tom Soh
- Materials Department, University of California, Santa Barbara, CA 93106
- Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA 93106
- Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106
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Liu JJ, Wang CL, Xi Q, Xu J, Deng B, Ding HM, Chu B, Su DH. Dissection of the Functional Structure of Aptamer17, Which Specifically Recognizes Differentiated PC12 Cells. Oligonucleotides 2011. [DOI: 10.1089/oli.2011.0279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Bing T, Yang X, Mei H, Cao Z, Shangguan D. Conservative secondary structure motif of streptavidin-binding aptamers generated by different laboratories. Bioorg Med Chem 2010; 18:1798-805. [PMID: 20153201 DOI: 10.1016/j.bmc.2010.01.054] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 10/19/2022]
Abstract
Aptamers that are selected in vitro from random pools of DNA or RNA molecules by SELEX (Systematic evolution of ligands by exponential enrichment) technique have been extensively explored for analytical and biomedical applications. Although many aptamers with high affinity and specificity against specific ligands have been reported, there is still a lack of well characterized DNA aptamers. Here we report the selection of a group of aptamer candidates (85 mer) against streptavidin. Through comparing the predicted secondary structures of all the candidates, a conservative bulge-hairpin structure section (about 29 mer) was found, and then it was determined to be the binding motif to streptavidin. This binding motif was further discovered to also exist in streptavidin-binding aptamers (SBAs) selected by three other laboratories using different methods. The primary sequences of this secondary structure motif are very different, only several nucleotides in the loop and bulge area are critical for binding and other nucleotides are variable. The streptavidin binding of all the SBAs could be competed by biotin implying that they bind to the same site on streptavidin. These results suggest that the evolution of SBA is predominated by specific groups on streptavidin. The highly variable sequence composition of streptavidin-binding aptamer would make the design of aptameric sensor or device based on streptavidin more flexible and easy.
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Affiliation(s)
- Tao Bing
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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