Surface Plasmon Resonance SELEX Aptamer Screening Service
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Surface Plasmon Resonance SELEX Aptamer Screening Service

Date：2026-01-16

Core Principle: Real-Time Interaction Analysis

An SPR biosensor (e.g., Biacore, Nicoya Lifesciences) detects changes in the refractive index on a thin gold sensor surface.

  1. Target Immobilization: The pathogen target (e.g., a purified viral protein) is covalently coupled to the sensor chip surface in a controlled manner.

  2. Library Injection: The random-sequence DNA/RNA library is flowed over the chip in a continuous buffer stream.

  3. Real-Time Monitoring: The SPR signal (measured in Resonance Units, RU) increases as library members bind to the immobilized target.

  4. Precise Fraction Collection: Instead of manual washing and elution, the instrument’s microfluidic system can collect the specifically bound sequences by switching to an elution buffer (e.g., high salt, low pH, or denaturing conditions) at a precisely defined moment, often based on the real-time binding curve.

  5. Amplification: The collected fraction is PCR-amplified to generate the pool for the next round.

Typical SPR-SELEX Service Workflow

1. Chip Preparation & Target Immobilization:

  • The service provider will select an appropriate sensor chip (e.g., CMS carboxymethyl dextran) and optimal chemistry (amine coupling, streptavidin-biotin) to immobilize the client’s purified target, ensuring a stable, active, and oriented surface.

2. Selection Rounds with Kinetic Control:

  • Library Contact: The naïve or enriched pool is injected over the target surface and a reference surface (for subtraction of non-specific binding to the chip matrix).

  • Stringency Adjustment: Selection pressure is applied by controlling key parameters in real-time:

    • Contact/Injection Time: Short injections favor selection of aptamers with fast association rates (kᵒⁿ).

    • Dissociation/Washing Time: Allowing a long wash phase before collection favors selection of aptamers with slow dissociation rates (kᵒff) – i.e., high stability complexes.

    • Library Concentration: Using a low concentration of the pool relative to the target favors high-affinity binders.

  • Precision Elution & Collection: Bound sequences are eluted under controlled conditions, and the eluate is collected automatically by the instrument’s fraction collector.

3. Monitoring Progression in Real-Time:

  • The binding response (RU) for each selection round is directly observable. Successful enrichment is seen as an increasing binding signal from one round to the next using the same injection parameters.

4. Sequencing & Bioinformatics:

  • After typically 5-10 rounds, the enriched pool is subjected to NGS and bioinformatic analysis to identify candidate aptamer families.

5. Integrated Validation & Characterization:

  • A major advantage of SPR-SELEX is that the same platform used for selection is the gold standard for characterization.

  • Synthesized candidate aptamers are individually injected over the target surface at various concentrations to generate real-time sensograms.

  • This data is used to calculate precise kinetic rate constants (kᵒⁿ, kᵒff) and the equilibrium dissociation constant (Kᴅ), providing a full binding profile.

Key Advantages of the SPR-SELEX Method

Advantage Explanation
Label-Free & Real-Time Monitoring Provides immediate, quantitative feedback on enrichment success and binding quality at every round. No labeling of target or library required.
Precise Kinetic Selection Uniquely allows for the direct selection of aptamers based on binding kinetics (fast on-rate, slow off-rate), which is critical for diagnostic and therapeutic efficacy.
Controlled Stringency Flow-based washing and precise injection times allow for extremely reproducible and finely tuned selection pressure.
Minizes Non-Specific Binders A dedicated reference flow cell allows for real-time subtraction of signals from sequences that bind to the chip matrix itself.
Seamless Transition to Characterization Eliminates the need for a separate validation platform. High-quality kinetic and affinity data are a natural output of the process.
Low Sample Consumption Efficient microfluidic system uses small volumes of both target (for immobilization) and library per round.

Important Considerations for SPR-SELEX

  • Target Requirement: Requires a purified, soluble target that can be stably immobilized on a sensor chip without losing its native conformation. Ideal for proteins, peptides, and some small molecules/virions.

  • Complex Targets: Less straightforward for whole cells or complex membrane preparations, though possible with specialized chips/capture methods.

  • Expertise-Driven: Operation and data interpretation require significant expertise, making it an ideal outsourced service.

Deliverables from an SPR-SELEX Service

A top-tier service provider will deliver:

  1. Sensorgrams showing the binding progression across selection rounds.

  2. NGS report with top candidate aptamer sequences and family analysis.

  3. Comprehensive kinetic binding profiles for each lead aptamer, including kᵒⁿ, kᵒff, and Kᴅ values.

  4. Specificity data against related counter-targets.

  5. Recommendations for aptamer optimization (e.g., truncation based on predicted structure).

In summary, an SPR-SELEX Aptamer Screening Service is a premium, data-rich platform that leverages real-time biosensing technology to not only discover aptamers but also to pre-select them for desirable kinetic properties. It is the method of choice when high-precision kinetic data and controlled, solution-phase-like selection conditions are critical for the final application, such as in therapeutic development or high-performance diagnostics.