Systematic Evolution of Ligands by Exponential Enrichment (SELEX) is a powerful in vitro selection technique used to identify high-affinity nucleic acid ligands, known as aptamers, from large random sequence libraries. Since its inception in 1990 by Tuerk and Gold, SELEX has revolutionized the field of molecular recognition, offering a robust method for generating specific binding molecules for a wide array of targets.

Methodology

The SELEX process typically consists of several iterative rounds, each comprising the following steps:

1. Library Generation: A diverse library of oligonucleotides (10^12 - 10^15 unique sequences) is synthesized, each containing a central random region flanked by constant primer binding sites.
2. Target Binding: The library is incubated with the target molecule under specific conditions to allow binding interactions.
3. Partitioning: Bound sequences are separated from unbound ones using techniques such as affinity chromatography, filtration, or capillary electrophoresis.
4. Amplification: The bound sequences are eluted and amplified via PCR (for DNA) or RT-PCR followed by in vitro transcription (for RNA).
5. Conditioning: The amplified pool is prepared for the next round of selection.

This cycle is repeated 8-15 times, progressively enriching the pool with high-affinity binders.

Variations and Advancements

Several modifications to the classical SELEX protocol have been developed:

• Cell-SELEX: Targets whole cells, useful for identifying cell-specific aptamers.
• Capillary Electrophoresis SELEX (CE-SELEX): Utilizes CE for partitioning, reducing selection rounds.
• Microfluidic SELEX: Employs microfluidic devices for more efficient selection.
• Counter-SELEX: Incorporates negative selection steps to enhance specificity.

Applications

SELEX-derived aptamers find applications in various fields:

• Diagnostics: As recognition elements in biosensors and imaging probes.
• Therapeutics: As targeted drug delivery vehicles or direct therapeutic agents.
• Analytical Chemistry: For separation and purification of biomolecules.
• Molecular Biology: As tools for studying protein-nucleic acid interactions.

Advantages and Limitations

Advantages of SELEX include its ability to generate highly specific aptamers, its in vitro nature allowing for selection under various conditions, and the ease of aptamer synthesis and modification. However, limitations include the potential for selecting amplification artifacts and the challenge of identifying aptamers for some targets, particularly small molecules.

Conclusion

SELEX represents a significant advancement in molecular biology, offering a systematic approach to developing nucleic acid-based affinity reagents. As the technique continues to evolve, it promises to play an increasingly important role in both basic research and applied biotechnology.

SBS Genetech's SELEX Services

Service Overview

SBS Genetech offers comprehensive SELEX services to meet the diverse needs of our clients. Our SELEX service includes:

• Custom Aptamer Library Generation: We create a highly diverse library of oligonucleotides tailored to your specific requirements.
• Target Binding and Partitioning: Using state-of-the-art techniques, we ensure high-efficiency binding and separation processes.
• Iterative Selection and Amplification: We perform multiple rounds of selection and amplification to enrich high-affinity aptamers.
• Sequence Identification: Final aptamer sequences are identified using advanced Next-Generation Sequencing (NGS) technology.

Sample Requirements

For optimal results, clients are required to provide:

• Proteins: 200 μg of biotin-labeled target protein with >90% purity.
• Small Molecules: Sample mass, concentration, volume, and storage conditions, with purity >95% (recommended).
• Cells/Bacteria: Specific requirements and quantities to be determined upon consultation.

Deliverables

Upon completion, SBS Genetech delivers:

• Selected Aptamer Sequences: Five high-affinity aptamer sequences chosen by the client.
• Comprehensive Report: Includes NGS sequencing results and a detailed experimental report (experimental procedures, enrichment rate data, relevant photos).

Related Services

SBS Genetech also offers:

• Aptamer Affinity Characterization: To assess the affinity between the selected aptamers and their targets. Specific charges are available upon request.

Why Choose SBS Genetech?

With our expertise and advanced facilities, SBS Genetech ensures high-quality SELEX services, providing reliable and efficient solutions for your research and development needs. Our team is committed to delivering precise, high-affinity aptamers to support your diagnostic, therapeutic, and analytical applications. Get in touch with us today to explore how SELEX can elevate your laboratory work and accelerate scientific discovery.