What is Capture-SELEX? Unlike traditional SELEX where the target is immobilized, Capture-SELEX immobilizes the initial DNA library itself via a short complementary "capture" sequence. The key target molecule is free in solution. Binding occurs when an aptamer candidate in the library binds to the target, causing a structural change that releases it from the immobilization surface. This approach offers distinct advantages: Ideal for small molecules and proteins: Especially targets that are difficult to immobilize without affecting their structure. Minimizes non-specific binding: Selection pressure is purely for target-induced structure formation/release. Enriches for structure-switching aptamers: Resulting aptamers often undergo conformational change upon binding, making them excellent for biosensor development. Typical Capture-SELEX Screening Service Workflow A professional service provider will manage this complex, iterative process from start to finish. Here’s what you can expect: Phase 1: Project Design & Library Preparation Consultation & Target Specification: Defining target properties, desired affinity (Kd), specificity (against which counter-targets), and buffer conditions. Customized Library Design: Designing a single-stranded DNA library (10^14 - 10^15 unique sequences) with: A central random region (e.g., 30-50 nucleotides). Fixed primer regions for PCR amplification. A capture sequence region complementary to an immobilized oligonucleotide. Immobilization Matrix Preparation: Coupling the complementary "capture" oligonucleotides to a solid support (e.g., magnetic beads, chromatography resin). Phase 2: The Iterative Selection (SELEX) Cycles…
What is an Antibody Aptamer Screening Service? It is a specialized contract research service where a biotechnology company uses SELEX (Systematic Evolution of Ligands by EXponential Enrichment) or advanced variations of it to discover and develop aptamers that bind with high affinity and specificity to a target antibody. Antibody: A large, Y-shaped protein produced by the immune system to identify and neutralize pathogens. Aptamer: A short, single-stranded DNA or RNA oligonucleotide (or a modified derivative) that folds into a specific 3D structure, enabling it to bind to a target molecule with antibody-like specificity. Often called "chemical antibodies." The goal of the service is to provide clients with synthetic, recombinant-like binding molecules as alternatives or complements to traditional monoclonal antibodies. Why Screen for Aptamers Against Antibodies? Aptamers offer distinct advantages, making them attractive for various applications: Anti-Drug Antibody (ADA) Detection: Develop aptamer-based assays to detect and quantify ADAs in clinical trials for biotherapeutics. Diagnostic Tools: Create aptamer sensors (aptasensors) to detect specific antibody biomarkers for diseases (e.g., autoantibodies in autoimmune disorders). Therapeutic Neutralization: Discover aptamers that can bind and neutralize pathological antibodies (e.g., in autoimmune diseases like lupus or myasthenia gravis). Purification & Pull-Down: Use aptamers as ligands in chromatography or in assays to capture and isolate specific antibodies from complex…
What is a Metal Ion-Targeted Aptamer Screening Service? It is a contract research service where a specialized laboratory uses an in vitro selection process (most commonly SELEX - Systematic Evolution of Ligands by EXponential Enrichment) to identify single-stranded DNA or RNA oligonucleotides (aptamers) that bind with high affinity and specificity to a specific metal ion (e.g., Pb²⁺, Hg²⁺, UO₂²⁺, As³⁺, Cd²⁺). Unlike aptamers for proteins, metal ion aptamers often rely on the ion's unique coordination chemistry to induce a specific fold or structural switch in the oligonucleotide. Core Service Workflow (The Screening Process) A typical service provider would follow these steps: Design & Library Synthesis: Creation of a vast random-sequence oligonucleotide library (10¹⁴ - 10¹⁵ different sequences). Target Preparation: The target (e.g., Pb²⁺) is often presented in a specific buffer system that controls charge, pH, and the presence of competing ions to drive selection for the desired specificity. Selection Rounds (SELEX Cycle): Binding: Incubate the library with the target metal ion. Partition: Separate metal-bound sequences from unbound ones. This is the most critical and challenging step for small ions. Techniques include: Immobilization: Cheating the ion to a solid support (beads). Capture-SELEX: Using a complementary strand or an auxiliary molecule. Size-based separation: If binding induces a conformational change (e.g., dimerization). Amplification: PCR (for…
What is an Aptamer? First, a quick definition: Aptamers are short, single-stranded DNA or RNA oligonucleotides that bind to a specific target molecule (like proteins, toxins, cells) with high affinity and specificity. They are often called "chemical antibodies" but offer advantages like easier synthesis, higher stability, and lower cost. What is Toxin-Targeted Aptamer Screening? This service involves the in vitro selection and development of custom aptamers designed to bind specifically to a toxic substance. The core technology is called SELEX (Systematic Evolution of Ligands by EXponential enrichment). The process screens vast random libraries (10^14 - 10^15 different sequences) against the toxin to isolate the few sequences that bind tightly and specifically. Key Steps in the Service Pipeline Project Consultation & Target Definition: Clarify the toxin (e.g., mycotoxins like Aflatoxin B1, marine toxins like Saxitoxin, bacterial toxins like Botulinum, environmental toxins like heavy metals). Define the desired application (Detection/Biosensing, Neutralization, Capture/Purification). Specify the sample matrix (food extract, blood serum, environmental water). Library Design & SELEX Strategy: Design of a naive single-stranded DNA or RNA library. Choosing the appropriate SELEX variant: Negative Selection/Counter-SELEX: To exclude sequences that bind to similar non-toxin molecules or the assay matrix (crucial for specificity). Capture-SELEX: For small toxins that can't be immobilized. Cell-SELEX: If the…
What is an Aptamer Screening Service? It is a contract-based service where a specialized laboratory uses Systematic Evolution of Ligands by EXponential enrichment (SELEX) to discover single-stranded DNA or RNA molecules (aptamers) that bind with high affinity and specificity to your target molecule (e.g., a protein, an antibody's constant region, or a cell-surface receptor). Core Service Components A full-service provider typically offers an end-to-end pipeline: 1. Project Design & Target Preparation Consultation: Defining the goal (e.g., detection, inhibition, delivery). Target Characterization: Ensuring the target (purified protein, antibody, receptor-expressing cells) is properly formatted and validated. Negative Selection/Counter-SELEX: Designing the screening to avoid binders to similar, non-target structures (e.g., the Fc region of a different antibody isotype, a common cell surface protein). 2. Library & Selection (The Core SELEX Process) Library Design: Using a diverse random oligonucleotide library (typically 10^14 - 10^15 unique sequences). Selection Method: The choice of method is critical and depends on the target: Protein SELEX: For purified, soluble targets immobilized on beads or in solution. Cell-SELEX: For membrane receptors in their native conformation on live cells. Excellent for discovering aptamers to unknown receptor complexes. Capture-SELEX/Toggle-SELEX: For difficult-to-immobilize targets or to increase stringency. In Vivo SELEX: For discovering aptamers that home to specific tissues in vivo. Iterative Rounds: Typically 8-15 rounds of…
