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…
What is a Stem Cell Aptamer Screening Service? It is a contract research service where a specialized lab uses Systematic Evolution of Ligands by EXponential Enrichment (SELEX) to discover and develop DNA or RNA aptamers that bind with high affinity and specificity to a target of your choice related to stem cells. Aptamers are often called "chemical antibodies." They are short, single-stranded oligonucleotides that fold into unique 3D shapes, allowing them to bind to targets like proteins, small molecules, or even whole cells. Core Targets for Stem Cell Applications The service can be tailored to screen for aptamers against: Specific Cell Surface Markers: (e.g., CD34, CD133, SSEA-4, TRA-1-60) for identification and isolation. Whole Live Stem Cells: To get aptamers that recognize the unique molecular signature of a specific stem cell type (e.g., mesenchymal stem cells, cancer stem cells, pluripotent stem cells). Differentiation State-Specific Targets: To distinguish between pluripotent, progenitor, and fully differentiated cells. Specific Stem Cell-Derived Products: (e.g., exosomes, vesicles). Typical Workflow of the Service A professional service provider will guide you through these stages: Phase Description Your Input 1. Project Design Defining the target (specific protein, cell line, primary cells), counter-selection cells (to ensure specificity), and desired aptamer properties (e.g., Kd, nuclease resistance). Provide target cells, control cells, and…
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 the Service? It's the process of using SELEX (Systematic Evolution of Ligands by EXponential Enrichment) to identify single-stranded DNA or RNA aptamers that can bind to a target cytokine. The service takes you from target selection to delivering validated aptamer candidates. Standard Workflow (What the Provider Does) Project Scoping & Target Preparation: Target: You specify the cytokine (e.g., TNF-α, IL-6, IFN-γ). The provider may require you to supply the purified, recombinant protein or offer to procure/produce it. Counter-SELEX: A critical step to ensure specificity. The provider will use related proteins (e.g., other cytokines, serum proteins) to eliminate aptamers that bind non-specifically. Library Design & SELEX Cycle: Starts with a vast random oligonucleotide library (10^14 - 10^15 unique sequences). Iterative rounds (8-15+) of: Binding: Incubating the library with the target cytokine. Partitioning: Separating bound from unbound sequences (e.g., via immobilization on beads, filters, or capillary electrophoresis). Amplification: PCR (for DNA) or RT-PCR (for RNA) to enrich the binding sequences. Stringency Increase: Gradually increasing washing rigor and introducing counter-selection to drive selection of high-affinity, specific binders. Next-Generation Sequencing (NGS) & Bioinformatics: After the final rounds, the enriched pool is sequenced using NGS. Bioinformatics tools analyze the data to identify enriched sequence families, consensus motifs, and predict secondary structures.…
What is an Aptamer? An aptamer is a short, single-stranded oligonucleotide (DNA or RNA) that folds into a unique 3D structure, allowing it to bind to a specific target molecule (like a protein) with similar specificity to an antibody. They are often called "chemical antibodies." Why Use a Screening Service Instead of In-House Development? Expertise & Equipment: The screening process (SELEX) requires specialized skills, robotics, and next-generation sequencing (NGS) infrastructure. Time & Cost Efficiency: Outsourcing can be faster and more cost-effective than setting up a new, complex pipeline. Higher Success Rate: Experienced providers have optimized protocols for difficult targets (e.g., membrane proteins, toxic proteins). The Core Process: SELEX The standard method is SELEX (Systematic Evolution of Ligands by EXponential Enrichment). A professional service will offer advanced variants of this process. A Typical Service Workflow: Project Consultation & Design: Target Characterization: Discussion about your protein (purified? membrane-bound? post-translational modifications?). Selection Strategy: Choosing the best SELEX method (e.g., Capillary Electrophoresis-SELEX (CE-SELEX) for very high affinity, Cell-SELEX for cell-surface targets, Toggle-SELEX for cross-species specificity). Counter-Selection: Designing the process to avoid binding to non-target proteins (e.g., carrier proteins, related isoforms). Library Synthesis & Preparation: Creation of a vast random oligonucleotide library (typically 10¹³ - 10¹⁵ unique sequences). The Selection Rounds (Cycles of SELEX): Binding: Incubating the library with the…
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…
What is an Aptamer? An aptamer is a short, single-stranded DNA or RNA oligonucleotide that folds into a specific 3D structure, allowing it to bind to a target molecule (like a cytokine) with high affinity and specificity, akin to a monoclonal antibody. Why Target Cytokines with Aptamers? Cytokines are key signaling proteins in immune and inflammatory responses. Dysregulation is implicated in diseases like: Autoimmune disorders: Rheumatoid arthritis, psoriasis, inflammatory bowel disease. Cancer: Tumor microenvironment signaling. Cytokine Storms: Severe COVID-19, sepsis. Neurological diseases. Aptamers offer advantages over traditional antibody-based therapies: High Specificity: Can distinguish between closely related cytokine isoforms or conformational states. Controlled Synthesis: Chemically produced, no batch-to-batch variation. Modifiability: Easily conjugated with drugs, fluorophores, or nanoparticles. Low Immunogenicity: Less likely to cause an immune response. Stability: Generally more stable than proteins. The Aptamer Screening Service Workflow (SELEX) A professional service will manage the entire SELEX (Systematic Evolution of Ligands by EXponential Enrichment) process. Here’s a typical pipeline: Phase 1: Project Design & Target Preparation Consultation: Define the goal—neutralization, detection, or delivery. Target Selection: Which cytokine? (e.g., TNF-α, IL-6, IL-1β, IFN-γ). Requires a high-purity, bioactive protein. Services often help with recombinant expression/purification if needed. Library Design: A vast random-sequence oligonucleotide library (10^14-10^15 unique sequences) is the starting point. Libraries can be DNA, RNA, or contain modified…
What is an Aptamer? An aptamer is a short, single-stranded DNA or RNA oligonucleotide that binds to a specific target molecule (like a protein) with high affinity and specificity. They are often called "chemical antibodies" but offer advantages like smaller size, chemical stability, and in-vitro generation. The Core Service: SELEX (Systematic Evolution of Ligands by EXponential Enrichment) The standard method for aptamer screening is SELEX. A specialized service will manage this entire iterative, high-complexity process for you. General SELEX Workflow: Target Preparation & Immobilization: Your service provider will prepare your purified protein. It is often immobilized on a solid support (beads, column, plate) to separate bound from unbound sequences. Incubation with Library: A vast, random synthetic oligonucleotide library (10^13 - 10^15 unique sequences) is incubated with the target. Partitioning: Weak or non-binding sequences are washed away. Tightly bound aptamers are retained. Elution & Amplification: The bound sequences are eluted and amplified by PCR (for DNA) or RT-PCR (for RNA). Stringency & Counter-SELEX: Subsequent rounds introduce increased washing stringency and incubation with non-target molecules (e.g., similar proteins, immobilization matrix) to filter out non-specific binders. This is crucial for specificity. Cloning & Sequencing: After 8-15 rounds, the enriched pool is cloned and sequenced to identify individual candidate aptamers. Characterization &…
1. Core Concept: What is Capture-SELEX? Capture-SELEX (Systematic Evolution of Ligands by EXponential Enrichment) is an advanced selection technique used to discover single-stranded DNA or RNA aptamers that bind to a specific target molecule. The key innovation is that the target molecule is immobilized (or "captured") on a solid support via a short, known oligonucleotide sequence that is part of the initial random library. This makes it exceptionally powerful for selecting aptamers against small molecules or targets without natural immobilization sites. 2. The Key Differentiator: How It Differs from Classical SELEX Classical SELEX: The target itself is immobilized directly on a surface (e.g., a bead or plate). This can sometimes lead to aptamers that bind to the surface or the immobilized region of the target, which may not function well in solution. Capture-SELEX: The library itself is immobilized via a complementary "capture sequence." Only sequences that bind to the free, unmodified target in solution undergo a conformational change that releases them from the capture strand for collection. 3. Step-by-Step Process of a Capture-SELEX Service A service provider will typically manage this entire pipeline: Step 1: Project Design & Library Synthesis You define the target (e.g., a small molecule, protein, cell). The service designs a custom single-stranded DNA (ssDNA) library: [5' Fixed Primer Sequence - RANDOM Region…
