1. What is SELEX? SELEX stands for Systematic Evolution of Ligands by EXponential enrichment. It is a laboratory technique used to identify aptamers—short single-stranded DNA or RNA sequences that can bind specifically to a target molecule (proteins, small molecules, cells, or even viruses). Aptamers act similarly to antibodies but are synthetic, highly stable, and can be chemically modified. 2. Principle of SELEX The SELEX process is based on iterative rounds of selection and amplification: Library Preparation Start with a large randomized pool of oligonucleotides (typically 10^13–10^15 unique sequences). Each sequence is a potential aptamer candidate. Binding (Target Incubation) Incubate the library with the target molecule. Only sequences that can bind the target will stay attached; non-binders are washed away. Partitioning (Separation of Binders and Non-binders) Physically separate bound sequences from unbound sequences. Techniques depend on the target (magnetic beads, affinity columns, etc.). Elution Bound sequences are eluted (released) from the target. Amplification The eluted sequences are amplified using PCR (for DNA aptamers) or RT-PCR (for RNA aptamers). This generates an enriched pool for the next round. Iterative Rounds Steps 2–5 are repeated for 8–15 rounds to gradually enrich sequences with high affinity and specificity for the target. Sequence Identification After…
In recent years, various screening methods have been developed to generate aptamers more reliably and efficiently. These include Systematic Evolution of Ligands by Exponential Enrichment (SELEX) and its various derivative techniques, such as magnetic bead SELEX, capture SELEX, graphene oxide SELEX, cell-SELEX, capillary electrophoresis SELEX, and atomic force microscopy SELEX. This review summarizes these methods and analyzes the key characteristics, advantages, and limitations of each SELEX approach (see Table 1). The wide application of aptamers has driven the continuous development of SELEX technology. Over recent decades, numerous new methods for screening aptamers have emerged, significantly reducing the screening time from weeks to just hours. Table 1. Advantages and disadvantages of SELEX method currently used. Method Key Aspects Advantages Disadvantages Target small molecule compounds Agarose affinity chromatography SELEX The aptamers that can bind to the target can be isolated by fixing the small molecular target with agarose affinity chromatography column The most traditional aptamer screening method with the longest application time Low separation efficiency, requires relatively large amounts of elution materials MB-SELEX SsDNA or target was fixed with magnetic beads, and the bound sequence was separated from the unbound sequence by magnetic field. Avoid changes in the inherent structure of the target…
Aptamer Screening Service Deliverables (KMDBioscience) Upon successful completion of the screening project, we will provide you with the following deliverables: Aptamer(s) with High Affinity: At least one confirmed aptamer sequence demonstrating high binding affinity to your specified target. Plasmid DNA: The identified aptamer sequence(s) will be provided in a stable plasmid vector, ready for your downstream applications, amplification, and sequence verification. Comprehensive Screening Report: A detailed final report containing: Target Information: Description and specifications of the screening target. Selection Protocol: The complete, step-by-step methodology used for the aptamer selection (SELEX). Key Raw Data: Representative data from critical selection rounds. Aptamer Sequencing: The full DNA sequence(s) of the delivered aptamer(s). Affinity Assay Data: Detailed results and analysis from the binding affinity measurements (e.g., Kd determination via Capillary Electrophoresis).
Aptamer Characterization Services: Ensuring the Precision and Reliability of Your Aptamer Development At KMD Bioscience, we understand that discovering an aptamer is just the first step. The true journey to a successful diagnostic, therapeutic, or sensor application hinges on rigorous and comprehensive Aptamer Characterization. Our specialized characterization services are designed to transform your promising aptamer sequences into well-understood, reliable, and high-performance molecular tools. We provide the critical data and validation needed to advance your projects with confidence. Why is Aptamer Characterization Essential? Unlike traditional antibodies, aptamers offer unparalleled advantages in stability, manufacturability, and design flexibility. However, to fully leverage these benefits, thorough characterization is non-negotiable. It confirms that the selected aptamer not only binds but does so with the specificity, affinity, and functionality required for your specific application. Our services mitigate risk, save valuable time and resources, and provide the foundational data for regulatory submissions. Our Comprehensive Suite of Characterization Services We employ a multi-faceted approach, utilizing state-of-the-art biophysical and analytical techniques to profile every critical aspect of your aptamer. 1. Affinity & Binding Kinetics Analysis Precise measurement of the binding strength is fundamental. We determine the dissociation constant (K<sub>D</sub>) and analyze real-time interaction kinetics. Primary Platform: Biolayer Interferometry (BLI). This label-free…
Aptamer Optimization Services at KMD Bioscience At KMD Bioscience, we understand that discovering an aptamer is just the first step. The journey from a promising initial sequence to a robust, high-performance molecule ready for real-world applications requires rigorous refinement and enhancement. This is where our specialized Aptamer Optimization Services come into play. We provide a comprehensive suite of strategies to elevate your aptamer candidates, ensuring they meet the highest standards of affinity, specificity, stability, and functionality for your specific needs. Why Optimize Your Aptamers? Initial selections (SELEX) often yield aptamers with potential but suboptimal characteristics. Optimization is crucial to: Enhance Binding Affinity & Specificity: Achieve stronger and more selective target binding, reducing off-target interactions. Improve Stability: Increase resistance to nuclease degradation and thermal denaturation for reliable performance in complex environments (e.g., serum, cellular lysates). Modify Functional Properties: Tailor aptamers for downstream applications such as diagnostics, therapeutics, or imaging. Reduce Length & Cost: Shorten sequences without compromising activity, leading to more economical synthesis. Our Core Optimization Strategies Truncation & Minimization: We systematically analyze the secondary and tertiary structure of your parent aptamer to identify the minimal essential binding region. Removing non-essential nucleotides creates shorter, more cost-effective, and often higher-activity variants. Mutational Analysis & Affinity Maturation: Using site-directed…
Excellent topic. Aptamer Screening refers to the process of identifying specific, high-affinity nucleic acid ligands (DNA or RNA aptamers) that bind to a target molecule of interest. It's often called SELEX (Systematic Evolution of Ligands by EXponential enrichment). Here’s a comprehensive breakdown of the screening process, its applications, and key considerations. 1. The Core Principle: SELEX SELEX is an iterative, in vitro combinatorial chemistry technique. The fundamental idea is to start with a vast, random library of nucleic acid sequences (up to 10^15 different molecules), expose them to the target, separate the binders from non-binders, amplify the binders, and repeat the cycle until a population of strong, specific binders is enriched. 2. General SELEX Workflow (Step-by-Step) A typical screening cycle involves: Step 1: Library Preparation A synthetic oligonucleotide library is created with a central random region (20-60 nucleotides) flanked by constant primer regions for PCR amplification. Library Diversity: Key to success. A 40-nucleotide random region represents ~10^24 possible sequences. Step 2: Incubation & Binding The library is incubated with the target molecule (protein, small molecule, cell, etc.). Conditions (buffer, temperature, ionic strength) are controlled to influence selection pressure. Step 3: Partitioning (The Most Critical Step) This step physically separates target-bound sequences from unbound ones. The…
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