Pathogen SELEX Aptamer Screening Service
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Pathogen SELEX Aptamer Screening Service

Date：2026-01-16

What is SELEX and What are Aptamers?

  • Aptamers: Often called “chemical antibodies,” they are short, single-stranded DNA or RNA oligonucleotides that fold into specific 3D shapes to bind with high affinity and specificity to a target molecule (e.g., a viral protein, whole bacterium, or parasite surface marker).

  • SELEX (Systematic Evolution of Ligands by EXponential enrichment): This is the iterative combinatorial chemistry process used to discover aptamers from a vast random library (10^14-10^15 unique sequences). It involves repeated cycles of: 1) Binding the library to the target, 2) Separating bound from unbound sequences, 3) Amplifying the bound sequences, and 4) Starting a new, enriched cycle.

Core Components of a Pathogen SELEX Service

A professional service will typically manage the entire pipeline:

1. Project Design & Target Preparation:

  • Consultation: Defining the precise target (e.g., whole inactivated SARS-CoV-2, Salmonella outer membrane protein, Plasmodium lysate).

  • Counter-SELEX: A critical step for pathogen specificity. The process is run against related non-targets (e.g., host cells, non-pathogenic bacterial strains) to filter out cross-reactive aptamers, ensuring the final aptamers distinguish between pathogen and non-pathogen.

2. The SELEX Execution:

  • Performing multiple (usually 8-15) rounds of the selection process under optimized conditions (buffer, temperature, washing stringency).

3. Next-Generation Sequencing (NGS) & Bioinformatics:

  • After the final rounds, the enriched pool is sequenced using NGS.

  • Bioinformatic analysis identifies sequence families, consensus motifs, and predicted secondary structures of the most enriched candidates.

4. Candidate Screening & Characterization:

  • Synthesis: The top 10-20 candidate sequences are chemically synthesized.

  • Initial Binding Tests: Validation via techniques like ELISA-style plate binding (ELASA), flow cytometry (for whole cells), or biolayer interferometry (BLI).

  • Affinity & Specificity Measurement: Determining the dissociation constant (Kd, often in nM to pM range) and testing against counter-targets.

5. Final Deliverables:

  • A report detailing the process and results.

  • A list of 3-5 validated aptamer sequences with confirmed binding data.

  • Optional: Modified aptamers (e.g., with biotin, fluorescent dyes, or chemical stabilization like 2′-F or 2′-O-methyl RNA).

Key Applications of Pathogen-Specific Aptamers

  • Rapid Diagnostics: Used in biosensors (aptasensors), lateral flow assays, or electrochemical platforms for point-of-care detection.

  • Therapeutics: As neutralizing agents to block viral entry or bacterial toxin function.

  • Targeted Drug Delivery: Conjugating aptamers to nanoparticles or drugs for specific pathogen targeting.

  • Research Tools: For pathogen imaging, purification, or detection in lab settings.

What to Look for in a Service Provider

Feature Why It’s Important
Experience with Pathogens Expertise in handling BSL-2/BSL-3 agents, working with complex targets (whole cells, envelopes).
Rigorous Counter-SELEX Strategy Essential for achieving high specificity and avoiding off-target binding.
NGS & Advanced Bioinformatics Moves beyond cloning, providing deep insight into the enriched pool.
In-house Characterization Ability to provide binding affinity (Kd) and specificity data upfront.
Aptamer Modification Options Chemical modifications are crucial for stability in real-world applications.
Clear Milestones & Deliverables Transparent project timeline, cost, and defined outputs.

Typical Workflow for a Client

  1. Initial Contact: Discuss your pathogen target, desired application, and specifications.

  2. Proposal & Quote: The provider will outline the SELEX strategy, timeline (often 3-6 months), and cost.

  3. Target Submission: You provide the purified target (e.g., protein, inactivated virus) and critical counter-targets.

  4. Service Execution: The provider runs the SELEX, NGS, and initial characterization.

  5. Delivery of Results: You receive the report, sequences, and validation data. You then own the IP for these specific aptamers for your defined application.

Advantages Over Traditional Antibody Development

  • In vitro process: No animal immunization required; can target toxins or non-immunogenic molecules.

  • Easier modification: Can be chemically synthesized and labeled with high reproducibility.

  • Stability: Generally more heat-stable than antibodies.

  • Reversibility: Can often be denatured and re-folded.

In summary, a Pathogen SELEX Aptamer Screening Service is a turnkey solution to obtain custom, high-affinity molecular recognition elements against your pathogen of interest, accelerating the development of novel diagnostic and therapeutic tools.

To proceed, you would search for companies or academic cores with keywords like “custom aptamer selection,” “SELEX service,” or “diagnostic aptamer development” and inquire specifically about their pathogen experience.