Aptamer Capture-SELEX Service
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Aptamer Capture-SELEX Service

Date：2026-01-07

Aptamer Capture-SELEX Service refers to a specialized, outsourced process where a company or academic core facility performs the entire Capture-SELEX procedure to develop DNA or RNA aptamers for a client’s specific target molecule.

This is a crucial service for researchers and companies who need high-affinity, specific aptamers but lack the specialized equipment, expertise, or time to run the SELEX process in-house.

Let’s break down what this service entails.

1. What is Capture-SELEX?

First, understand the standard SELEX (Systematic Evolution of Ligands by EXponential enrichment). It’s an iterative process to select aptamers from a vast random oligonucleotide library (10^14 – 10^15 different sequences).

Capture-SELEX is a specific variant designed primarily for small molecules or targets that are difficult to immobilize directly on a solid support without affecting their structure/function.

  • The Key Difference: Instead of immobilizing the target itself, a short, complementary “capture strand” is immobilized on beads or a surface. The initial ssDNA library is designed with a region complementary to this capture strand. The target is free in solution.

  • How it Works:

    1. The library is bound to the surface via the capture strand.

    2. The target molecule is introduced in solution.

    3. Only library sequences that fold into a structure capable of binding the target will undergo a conformational change. This binding event often weakens or releases their bond to the immobilized capture strand.

    4. These now-released, target-bound sequences are collected, amplified by PCR (for DNA) or RT-PCR (for RNA), and used as the library for the next selection round.

    5. Over 8-15 rounds, sequences that bind the target with high affinity and specificity are dramatically enriched.

2. What Does a Full “Capture-SELEX Service” Typically Include?

A professional service provider will manage the entire pipeline:

Phase Key Activities
1. Project Consultation & Design – Discuss target properties (size, charge, stability).
– Design the capture oligo and compatible library architecture.
– Define selection conditions (buffer, counter-selection targets, stringency).
2. Library Synthesis & Preparation – Chemical synthesis of the initial single-stranded DNA (ssDNA) library (~10^15 molecules).
– If RNA aptamers are desired, synthesis of the dsDNA template library for in vitro transcription.
3. The Capture-SELEX Cycles – Performing the iterative selection process (typically 8-15 rounds).
– Monitoring enrichment via quantitative PCR or other methods.
– Increasing stringency (e.g., reducing target concentration, adding washes, using counter-selection) to drive selection of high-affinity binders.
4. Next-Generation Sequencing (NGS) & Bioinformatic Analysis – Deep sequencing of enriched pools from the final rounds.
– Clustering analysis to identify sequence families.
– Ranking candidates based on frequency, fold-enrichment, and predicted secondary structure.
5. Aptamer Characterization & Validation – Chemical synthesis of the top 5-20 candidate aptamers.
– Affinity measurement (e.g., via Surface Plasmon Resonance (SPR), Bio-Layer Interferometry (BLI), or MST) to determine dissociation constant (Kd).
– Specificity testing against closely related molecules.
– Preliminary functional assays (e.g., inhibition, sandwich assay format).
6. Final Deliverables – A comprehensive report with all data.
– Sequences, structures, and binding characteristics of the lead aptamers.
– Physical aliquots of synthesized aptamers.

3. Key Advantages of Using a Service

  • Expertise & Experience: Avoid the steep learning curve and common pitfalls of SELEX.

  • Speed: Dedicated teams can complete the process in 3-6 months, much faster than an inexperienced lab.

  • Access to Specialized Equipment: NGS, SPR/BLI, HPLC purification, etc.

  • Higher Success Rate: Experienced providers know how to optimize conditions for difficult targets (e.g., toxins, small organics, peptides).

  • Objective Analysis: Bioinformatic pipelines are established to identify the best candidates, not just the most abundant ones.

4. Considerations When Choosing a Service Provider

  1. Target Compatibility: Confirm their experience with molecules similar to yours (size, class).

  2. Platform Expertise: Do they specialize in DNA, RNA, or modified nucleotides (e.g., 2′-F, 2′-O-Me for nuclease resistance)?

  3. Validation Depth: What level of binding characterization (Kd, specificity) is included? Is further truncation/minimization offered?

  4. IP and Confidentiality: Clearly defined ownership of the resulting aptamer sequences is critical. Ensure the contract states that you own the IP for the developed aptamers.

  5. Cost & Timeline: Costs can range from $30,000 to over $100,000 depending on target complexity, number of candidates validated, and depth of analysis.

5. Potential Service Providers (Examples)

  • Companies Specializing in Aptamer Development:

    • Aptamer Group (UK)

    • Aptus Biotech (Spain)

    • NeoVentures Biotechnology (Canada)

    • AminoTech (Korea)

    • Base Pair Biotechnologies (USA)

  • Academic Core Facilities or Tech Transfer Offices: Some universities with strong aptamer research groups offer fee-for-service SELEX.

  • Large CROs (Contract Research Organizations): Some may have a dedicated molecular recognition or diagnostics division.

Summary

Aptamer Capture-SELEX Service is a turnkey solution for generating custom aptamers, particularly suited for challenging small molecule targets. It transfers the technical complexity to experts, accelerating the path from a target idea to validated, high-quality aptamer reagents for use in diagnostics, therapeutics, sensors, or research tools.

When engaging a provider, focus on their relevant experience, the robustness of their validation package, and a clear IP agreement to ensure you receive functional aptamers and full rights to their use.