Customized Aptamer Selection refers to a tailored process of identifying and developing aptamers—short, single-stranded DNA or RNA molecules—that specifically bind to a target molecule (proteins, small molecules, cells, or pathogens) according to a client’s specific requirements. Unlike standard aptamer screening, it focuses on individualized targets, binding conditions, and functional needs. Key Features: Target Specificity: Aptamers are selected for high affinity and specificity to a particular target. Flexible Design: Can be designed for proteins, peptides, small molecules, ions, or whole cells. Binding Conditions Customization: pH, temperature, ionic strength, or buffer system can be tailored. Functional Application: Aptamers can be developed for diagnostics, therapeutics, biosensors, or research. High-Throughput & Efficiency: Advanced techniques allow rapid screening for optimal aptamers. Typical Workflow: Target Analysis: Understanding target structure and function. Library Preparation: Generate a diverse pool of oligonucleotides. SELEX (Systematic Evolution of Ligands by EXponential enrichment): Iterative selection process to enrich high-affinity aptamers. Binding Affinity Testing: Determine Kd (dissociation constant) and specificity. Sequence Optimization & Modification: Chemical modifications for stability or functionalization. Delivery of Customized Aptamer: Ready for research, diagnostics, or therapeutic use. Common Applications: Diagnostics: Biosensors for disease markers. Therapeutics: Targeted drug delivery. Research Tools: Protein purification or molecular imaging. Environmental Monitoring: Detection of…
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 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 Whole Cell-SELEX? SELEX (Systematic Evolution of Ligands by EXponential enrichment) is a technique used to develop aptamers—single-stranded DNA or RNA oligonucleotides that bind to a specific target molecule with high affinity and specificity, akin to antibodies. Whole Cell-SELEX is a variant where the target is not a purified protein, but an entire living cell. This is crucial for discovering aptamers against: Native cell-surface proteins in their natural conformation and modification state. Complex membrane protein complexes. Disease-specific cell markers (e.g., on cancer cells, pathogens) without prior knowledge of the specific molecular target. Specific cell types in a heterogeneous mixture (e.g., cancer stem cells within a tumor). A service provider performs this technically demanding and iterative process on behalf of researchers or companies. The Core Process of a Whole Cell-SELEX Service A typical service workflow involves close collaboration with the client: 1. Project Design & Consultation Defining Targets: Client specifies the positive selection cell (e.g., human glioblastoma cells) and the critical negative/counter selection cell (e.g., normal astrocytes or a related cell line). This is key to generating selective aptamers. Library Design: The service provider uses a vast (10^14 - 10^15 sequences) random oligonucleotide library. 2. The SELEX Cycle (Iterative Rounds) This is the core experimental phase performed by the service provider: Incubation: The library is incubated…
Membrane Protein Aptamer Screening Service is a highly specialized contract research service designed to discover aptamers that bind to integral membrane proteins, such as GPCRs, ion channels, transporters, and receptor tyrosine kinases. This is one of the most challenging and technically demanding areas of aptamer development due to the inherent complexity of maintaining the native structure and function of membrane proteins outside their lipid environment. Unique Challenges & Solutions: Target Integrity: The target protein must be kept in its native, correctly folded conformation. Services use advanced systems like: Nanodiscs: Membrane proteins embedded in a lipid bilayer stabilized by a belt protein (e.g., MSP). Proteoliposomes: Reconstituted into lipid vesicles. Detergent Micelles: Using compatible mild detergents. Whole Cell-SELEX (or Cell-SELEX): Using live cells expressing the target protein, ensuring native presentation and post-translational modifications. Hydrophobicity: The screening process must manage hydrophobic surfaces to prevent non-specific selection of sequences that simply bind lipids or detergents through careful counter-selection strategies. Specialized Screening Workflow: 1. Project Design & Target Presentation: Define Target & Goal: Specify the membrane protein (e.g., human EGFR, specific GPCR) and desired aptamer function (antagonist, agonist, simple binder for detection). Choose Presentation Platform: This is the most critical decision. The provider will advise on the optimal system: Purified Protein in Mimetics: Best for defined specificity…
Enzyme Aptamer Screening Service is a specialized contract research service where providers employ SELEX (Systematic Evolution of Ligands by EXponential Enrichment) to discover aptamers that bind with high specificity and affinity to a target enzyme. These aptamers can be designed not only to bind but also to modulate the enzyme's activity (inhibit or activate), making them powerful tools for therapeutics, diagnostics, and biochemical research. Key Differentiators from Antibody Screening: Functional Screening: A major goal is often to identify inhibitory or activating aptamers. Therefore, the screening process may incorporate activity-based selection or functional assays early on. Target Site Complexity: The target can be the entire enzyme, its active site, an allosteric site, or a specific conformational state (e.g., open vs. closed). Conformational Sensitivity: Enzymes are dynamic. Aptamers can be selected to recognize a specific functional conformation, which is a unique advantage. Typical Screening Workflow: 1. Project Design & Target Preparation: Define Objective: Is the goal pure detection, potent inhibition, allosteric modulation, or capturing a specific enzyme form? Enzyme Quality: Requires a highly pure, functional, and correctly folded enzyme. Activity assays confirm functionality. Selection Strategy: Choice of Toggle SELEX (for broad species cross-reactivity), Capture SELEX, or innovative methods like ExSELEX (for complex biological fluids). 2. The SELEX Process with a Functional Focus: Binding & Stringency: Standard incubation, washing, and elution cycles are performed. Functional Partitioning (Optional…
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…
