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 Bacterial Aptamer Screening Service? It is a specialized contract research service where a provider uses Systematic Evolution of Ligands by Exponential Enrichment (SELEX) to discover and develop single-stranded DNA or RNA aptamers that bind with high affinity and specificity to a bacterial target. The target can be: Whole bacterial cells (e.g., E. coli O157:H7, Salmonella typhimurium). Specific bacterial components (e.g., surface proteins like pili, flagella, capsular polysaccharides, secreted toxins). Key virulence factors (e.g., endotoxins like LPS). The resulting aptamers are powerful recognition elements for diagnostics, therapeutics, and research. Core Steps in the Service Pipeline A typical full-service offering includes: 1. Project Design & Target Preparation: Consultation: Defining the goal (e.g., detection of a specific strain, therapeutic neutralization). Target Choice: Deciding between whole cells (for broad detection) or purified components (for precise targeting). Counter-SELEX: Using related non-target cells (e.g., non-pathogenic strain) to eliminate cross-reactive aptamers and ensure specificity. 2. Library Synthesis & SELEX Process: Library Design: Using a random-sequence oligonucleotide library (typically ~10^14 different molecules). Selection Rounds (8-15 cycles): Iteratively incubating the library with the target, washing away unbound sequences, eluting the bound ones, and amplifying them via PCR (for DNA) or RT-PCR (for RNA). Monitoring: Using quantitative PCR or flow cytometry to track enrichment progress. 3. Next-Generation Sequencing (NGS) & Bioinformatics:…
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…
What is the Core Service? The service provider uses an iterative, in vitro selection process called SELEX (Systematic Evolution of Ligands by EXponential Enrichment) to screen vast random oligonucleotide libraries (10^14 - 10^15 unique sequences) against your target protein. The output is a set of characterized aptamer sequences that bind to the viral capsid. Standardized Screening Workflow A professional service will manage this entire pipeline: 1. Project Design & Target Preparation: Target Discussion: Defining the specific capsid protein (e.g., HIV-1 CA, HBV core, SARS-CoV-2 N), its form (full-length, domain, assembled capsid/nucleocapsid), and purity. Target Immobilization: The protein is often immobilized on a solid support (beads, plate) to facilitate separation of bound/unbound sequences. Some services offer solution-phase or capillary electrophoresis (CE-SELEX) methods for higher stringency. 2. SELEX Selection Rounds (Cycles 5-15): Incubation: The oligonucleotide library is incubated with the target. Partitioning: Unbound sequences are washed away; bound sequences are retained. Elution: Bound aptamers are eluted (e.g., by heating, denaturing agents). Amplification: Eluted aptamers are amplified by PCR (for DNA) or RT-PCR (for RNA). Purification: The amplified pool is purified for the next selection round. Counter-Selection: To ensure specificity, the pool is often passed through a negative control (e.g., irrelevant protein, cell lysate) to remove non-specific binders. 3. Sequencing & Identification: High-Throughput…
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…
1. What Are Aptamers? Aptamers are short, single-stranded DNA or RNA oligonucleotides (typically 20-80 bases) that fold into specific 3D structures, allowing them to bind to target molecules (like hormones) with high affinity and specificity, similar to antibodies. They are often called "chemical antibodies." 2. Why Target Hormones with Aptamers? Hormones are critical signaling molecules (e.g., insulin, cortisol, thyroid hormones, estradiol, adrenaline). Aptamers against them offer unique advantages: High Specificity: Can distinguish between structurally similar hormones (e.g., T3 vs. T4). Synthetic & Reproducible: Produced chemically with minimal batch-to-batch variation. Stability: More thermally stable than antibodies. Modifiability: Can be easily labeled with fluorescent dyes, quenchers, or nanoparticles for detection. Low Immunogenicity: Ideal for in vivo diagnostic or therapeutic applications. 3. Core Components of the Screening Service A full-service provider would typically offer the following pipeline: a. Design & Library Construction: Use of a vast random oligonucleotide library (10^14 - 10^15 unique sequences). Customization of library design based on hormone properties (small molecule vs. peptide/protein). b. SELEX Process (The Core Screening): This is an iterative, in vitro selection process. Incubation: The library is exposed to the target hormone (immobilized or in solution). Partitioning: Unbound sequences are washed away; bound sequences (aptamer candidates) are retained. Elution & Amplification: Bound sequences are eluted and amplified by PCR…
