Tissue-SELEX Aptamer Screening Service

Tissue-SELEX Aptamer Screening Service

This refers to a specialized contract research service that uses Systematic Evolution of Ligands by EXponential Enrichment (SELEX) to discover aptamers that specifically bind to molecular targets within a complex tissue environment, rather than purified proteins or isolated cells.

Core Concept & Key Differentiator

While Cell-SELEX uses whole live cells as targets, Tissue-SELEX advances the complexity by using:

• Tissue sections (fresh, frozen, or FFPE – Formalin-Fixed Paraffin-Embedded)

• Tissue homogenates

• Tissue-specific extracellular matrix (ECM) components

The goal is to find aptamers that recognize targets in their native, histological context, preserving post-translational modifications and local microenvironments. This is crucial for developing reagents for histopathology and tissue-specific targeting.

Typical Workflow

1. Target Preparation: Provider prepares or client supplies well-characterized tissue sections (often on glass slides). Counter-selection tissues (e.g., healthy vs. diseased, organ A vs. organ B) are critical.

2. SELEX on Tissue: The oligonucleotide library is incubated directly on the tissue section. After washing, bound sequences are eluted, often by laser capture microdissection of bound areas or direct extraction.

3. Amplification & Iteration: Recovered sequences are amplified (PCR) and used for subsequent selection rounds, with increasing stringency.

4. Sequencing & Analysis: High-throughput sequencing (NGS) identifies enriched sequence families.

5. Validation: Top candidates are synthesized and validated via:

   • Tissue Staining: Fluorescently-labeled aptamers used like antibodies in immunohistochemistry (IHC).

   • Specificity: Testing on tissue microarrays (TMAs) containing multiple organ/disease types.

   • Affinity Measurement: Using target-expressing cells or recombinant protein if the target is identified.

Major Applications

• Histopathology Diagnostics: Develop aptamer-based probes for detecting cancer, fibrosis, or other diseases in tissue biopsies. (Alternative to antibodies for IHC)

• Biomarker Discovery: Identify novel tissue-specific or disease-specific molecular signatures.

• In Vivo Imaging & Targeting: Select aptamers that bind tissue targets in their native state, for use in targeted drug delivery or imaging agents.

• Tissue Engineering: Select aptamers that bind specific ECM components to direct cell growth or material integration.

Advantages of Tissue-SELEX

• Context Matters: Finds aptamers to targets in their natural conformation and tissue architecture.

• Discovery Power: Can uncover unexpected targets relevant to tissue morphology or disease.

• Direct Application: Selected aptamers are pre-validated for use on tissue samples, bridging discovery and diagnostic utility.

What to Look for in a Service Provider

• Experience with Tissue Handling: Expertise in pathology, microtomy, and histology.

• Advanced Elution Methods: Capabilities like laser capture microdissection for precise recovery.

• Validation Platform: Access to tissue microarrays (TMAs) and automated staining platforms for high-throughput validation.

• Pathology Consultancy: Ability to provide expert interpretation of staining patterns.