The SELEX method, the selection process used by Novaptech for the identification of aptamers
Aptamer selection is a biotechnological process we use to identify oligonucleotides (DNA or RNA) that bind specifically to a given target.
This SELEX method, which stands for Systematic Evolution of Ligands by EXponential enrichment, involves several cycles of aptamer binding to the target, followed by the separation of the complexes formed, amplification of the bound aptamers and their reintroduction into the next selection cycle.
This process progressively enriches the aptamer population into molecules that have a high affinity for the intended target. Ultimately, this makes it possible to isolate aptamers withoptimal binding properties for diagnostic, therapeutic, analytical or research applications.
The SELEX method, the selection process used by Novaptech for the identification of aptamers
About nucleic acid aptamers & in vitro selection
Aptamers : a definition
Aptamers are single-stranded nucleic acids (DNA or RNA) that fold into complex structures. They are able to bind with high affinity and specificity to a pre-determined target. They can be defined as “artificial antibodies”. Aptamers are selected from a randomly synthesized oligonucleotide library containing about 1015 different sequences through an iterative in vitro selection process alternating binding and amplification steps.
The in vitro selection process
Selection of aptamers is achieved by mixing the target with the library. Partitioning between target-bound and free sequences is performed by various methods : filtration, chromatography, centrifugation. Target-bound oligonucleotides are PCR-amplified and the resulting pool is mixed with the target under increased selection pressure. The procedure is repeated several times. Among millions of sequences, the strongest binders will «survive » the directed evolution. Aptamers are identified following sequencing.
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What is SELEX ?
SELEX is a cutting-edge technique used to identify, from a vast library of oligonucleotide
sequences, those with the ability to bind specifically and strongly to a given target, be it a small
molecule, a protein or even intact cells.
This process, mastered by Novaptech experts, exploits molecular diversity to isolate aptamers
displaying high affinity and specificity for their target.
How does the SELEX method work ?
The SELEX approach to aptamer selection is a highly complex method that begins with the
synthesis of an oligonucleotide library exhibiting a huge diversity, essential for identifying
sequences with specific affinity for a given target.
Through a series of successive steps: binding, separation and amplification, this process refines
and enriches this library into highly specific aptamers.
This systematic approach ensures efficient and accurate selection, paving the way for
innovative applications in various fields of research and therapeutics.
1. Creating a library : The SELEX method begins with the generation of a library containing
a wide variety of oligonucleotide sequences. This diversity is essential for successful selection,
as it offers a broad spectrum of potential aptamer candidates.
2. Target binding : Sequences are brought into contact with the target of interest. Only those
that bind to the target are retained for subsequent steps, while non-binders are eliminated.
3. Separation and recovery : Aptamer-target complexes are separated from non-binding
sequences. This stage involves various separation methods such as filtration, the use of affinity
columns or centrifugation.
4. Amplification : The bound aptamers are then amplified, either by PCR for DNA or by
reverse transcription followed by PCR for RNA, to generate the enriched library for an
additional selection cycle.
5. Targeted enrichment : The binding, separation and amplification process is repeated
over several cycles to progressively enrich the library with sequences with the highest
affinity for the target.
SELEX applications and benefits
The SELEX selection principle has revolutionized the development of tools for a multitude of applications, ranging from medical diagnostics and environmental detection to therapeutic targeting. Aptamers selected via SELEX by Novaptech offer several advantages over traditional antibodies, including greater stability, less costly synthesis and absence of batch-to-batch variability.
Applications :
· Medical diagnostics : Used in the early detection of diseases through the identification of specific biomarkers. · Therapeutics : Enable the development of new drugs and/or the targeting of diseased cells without affecting healthy cells. · Environmental analysis : Detects specifically contaminants or toxins in water, air, and soil. 1. · And more : actually any application involving antibodies can be translated in and benefit from aptamers
Advantages over antibodies :
· Greater stability : Aptamers are more resistant to temperature and pH variations. · Cost-effective synthesis : Aptamers are less expensive to produce. · Reproducibility : Aptamers minimize batch-to-batch variations, ensuring consistent quality. · Flexibility of modification : Aptamers can be easily modified to improve binding or stability. · Non-immunogenicity : They are less likely to trigger undesirable immune responses.
Why is SELEX the best technology for strong affinity and high specificity ligands ?
The SELEX process stands out from other ligand selection methods, such as immunoselection
or chemical screens, mainly because of its high specificity, speed and low cost.
Unlike immunoselection, which relies on the time-consuming and costly production of
antibodies, the SELEX principle enables rapid and efficient selection of aptamers, depending
on the nature of the oligonucleotides, without the need for alive biological systems (cells or
animals).
As for chemical screening, although broad in its approach, it does not guarantee the high
specificity achieved by SELEX.
SELEX offers a more targeted and cost-effective method of identifying molecules with a strong
affinity for their target, making this technique particularly attractive for the development of
rapid test kits and devices.
The future of SELEX aptamer selection
Innovations in SELEX, driven by Novaptech, such as the integration of high-throughput
technologies, have transformed aptamer selection, making the process faster and more accurate.
Our high-throughput SELEX aptamer selection principle uses massive sequencing and
screening techniques to analyze millions of sequences simultaneously.
As for future prospects, the ongoing evolution of SELEX, combined with Novaptech’s
expertise, promises to open up new avenues in the research and development of innovative
treatments.
With the technological advances and research carried out by Novaptech, the SELEX process
continues to evolve, integrating high-throughput methods and computational analysis to
accelerate aptamer selection and identification. These innovations promise to further broaden
the application of aptamers in research.
The SELEX ability to isolate highly specific molecules makes it an essential pillar in the field
of biotechnology. With this application in aptamer selection, Novaptech is paving the way for
discoveries that will transform our approach to disease detection and treatment.
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