The specific screening process and sample requirements will vary according to the target characteristics and experimental requirements. The process of cell targeting aptamers screening is mainly based on SELEX technology and optimized using the aptamer cell selex method to meet the screening needs at the cellular level. A aptamer library containing a large number of random nucleic acid sequences (DNA or RNA, typically between 20 and 60 nucleotides in length) is constructed. Specific molecules on target cells or cell surfaces are used as targets (cell culture, purification, or labeling). The target cells are mixed with nucleic acid sequences from the aptamer library, and after incubation, the nucleic acid sequences bind to molecules on the surface of the target cells. The nucleic acid sequence that binds to the target is separated through filtration, centrifugation, magnetic bead separation, and other methods. The combined nucleic acid sequence is eluted and collected for the next round of screening. The secondary library is generated by amplifying the eluted nucleic acid sequence using PCR technology. The steps of binding, separation, elution, and amplification are repeated to gradually enrich high affinity aptamers. Through sequencing and sequence analysis, candidate aptamers were identified from the final enriched library. Simply put, SELEX technology…
As a functional nucleic acid, aptamer has many advantages. Based on its high specificity, it can accurately find the target molecule, thus avoiding the interference caused by nonspecific binding. Through in vitro selection technology (SELEX) screening, aptamers can be synthesized rapidly and in large quantities without complex biological preparation process. Aptamers have good chemical stability, can keep their structure and function unaffected under a variety of environmental conditions, and have higher thermal stability and lower immunogenicity. The molecular weight of aptamers is relatively small, making it easier for them to penetrate cell and tissue barriers and reach the site of action quickly. The core of aptamer screening is SELEX technology, which can accurately screen nucleic acid molecules that can achieve highly specific binding with specific targets from a large number of nucleic acid libraries with diverse sequences after multiple rounds of selection and amplification cycles. DNA or RNA aptamers obtained by in vitro screening technology have a unique three-dimensional structure, which can accurately identify and tightly bind to the corresponding target molecules. Compared with traditional antibodies, aptamers exhibit a variety of advantages, such as thermal stability, chemical synthesis and modification ability, and low immunogenicity. These characteristics together determine the great…
Cell Nucleic Acid Aptamer Screening Service KMD Bioscience has many years of research experience in the field of drug antibodies, and has accumulated profound experience in antibody development, aptamer screening, aptamer assay, affinity maturation, etc. KMD Bioscience can provide aptamer screening services for a variety of sample types, such as proteins, peptides, amino acids, small molecular substances, cells and bacteria, metal ions, etc. KMD Bioscience can provide customized in vitro aptamer screening services to ensure efficient, accurate and rapid screening of aptamer sequences required by customers. In addition, KMD Bioscience can provide customers with upstream and downstream services covering aptamer screening, from gene analysis and synthesis, aptamer in vitro screening, aptamer synthesis, aptamer assay, to affinity determination. KMD Bioscience can provide strong support for subsequent functional verification of aptamers (including but not limited to affinity verification, competitive ELISA verification, in vitro targeted cell functional verification (such as in vitro recognition and inhibition function verification of nucleic acid aptamers, in vitro flow cytometry blocking function verification, etc.), and in vivo functional verification (such as in vivo targeted inhibition function verification of aptamers, signal pathway blocking function verification, etc.), laying a solid foundation for subsequent work of customers, such as downstream research and development of targeted specific molecular drugs. The nucleic acid aptamer screening…
Current Status and Future Directions of Aptamer Development Current Status Aptamers (often called "chemical antibodies") are single-stranded DNA or RNA oligonucleotides that bind to specific targets with high affinity and specificity. They are selected via SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Key Achievements: Therapeutic Applications: The first FDA-approved aptamer drug, Pegaptanib (Macugen), treats age-related macular degeneration by targeting VEGF. Diagnostics: Aptamers are used in biosensors (aptasensors) for detecting proteins, small molecules, and pathogens (e.g., COVID-19 detection platforms). Target Range: Successfully generated against diverse targets: ions, small molecules, proteins, cells, and even whole organisms. Technical Advances: Development of Cell-SELEX, in vivo SELEX, and high-throughput SELEX has expanded capabilities. Advantages Over Antibodies: Chemical synthesis: No batch-to-batch variation. Modifiability: Can be chemically modified for stability (e.g., nuclease resistance) and functionality. Wider target range: Can bind toxins or non-immunogenic targets. Current Challenges: Stability issues (especially RNA aptamers degrade in biological fluids). Limited commercialization beyond a few successes. SELEX process can be time-consuming and biased. Delivery challenges for therapeutic applications. Future Directions 1. Enhanced Selection Technologies Machine learning-guided SELEX: Using AI to predict binding motifs and reduce selection cycles. Microfluidic SELEX: Miniaturized, automated platforms for faster, more efficient selection. In vivo SELEX: Direct selection in living organisms for better therapeutic relevance. 2. Chemical Modifications &…
Of course. Aptamers, often called "chemical antibodies," are single-stranded DNA or RNA oligonucleotides that bind to specific targets with high affinity and specificity. Their unique properties—including in vitro selection (SELEX), chemical stability, low immunogenicity, and ease of modification—make them versatile tools across numerous fields. Here are the major application fields of aptamers, categorized for clarity: 1. Therapeutics This is one of the most active areas, with one approved drug (Macugen® for macular degeneration) and many in clinical trials. Antagonistic Therapeutics: Blocking the function of disease-related proteins (e.g., receptors, cytokines). Targeted Drug Delivery: Aptamers are conjugated to drugs, toxins, or nanoparticles to selectively deliver them to diseased cells (e.g., cancer cells), minimizing systemic side effects. Agonistic Therapeutics: Activating specific receptors to trigger therapeutic pathways. Antiviral/Antibacterial Agents: Binding to viral surface proteins or bacterial toxins to neutralize them. 2. Diagnostics and Biosensing Aptamers are core components of novel, rapid, and sensitive diagnostic platforms. Point-of-Care (POC) Tests: Used in lateral flow assays (like advanced pregnancy tests) for detecting pathogens (e.g., SARS-CoV-2), toxins, or biomarkers. Electrochemical and Optical Biosensors: Aptamers immobilized on electrodes or chips change signals upon target binding, enabling detection of targets from small molecules to whole cells. Medical Imaging: Radiolabeled or fluorescently labeled aptamers (optamers) act as contrast agents…
Key Characteristics and Working Principles of Aptamers 1. What is an Aptamer? An aptamer is a short, single-stranded oligonucleotide (DNA or RNA) obtained through in vitro selection, capable of binding to a specific target with high affinity and high specificity. Its name derives from the Latin "aptus" (meaning "to fit") and the Greek "meros" (meaning "part"). It can be regarded as a chemical antibody, but its essence is nucleic acid rather than protein. 2. Key Characteristics Compared to traditional antibodies, aptamers possess a series of outstanding advantages: High Affinity and High Specificity Can bind tightly to targets with dissociation constants (Kd) in the nanomolar (nM) or even picomolar (pM) range, similar to antibodies. Capable of distinguishing between targets with subtle differences, e.g., distinguishing phosphorylated from non-phosphorylated states of the same protein, recognizing minor conformational changes in proteins, or differentiating structurally similar molecules (like caffeine and theophylline). Extremely Broad Target Range Targets are not limited to immunogenic substances. From ions, small molecules, drugs, and toxins to proteins, viruses, bacteria, cells, and even entire tissues, aptamers can potentially be selected for almost any target. Chemical Synthesis and Modification Can be produced on a large scale, at low cost, and with high purity in vitro via solid-phase synthesis, ensuring minimal batch-to-batch variation.…
An aptamer is a short, single-stranded DNA or RNA sequence that is synthesized artificially. It can fold into a specific three-dimensional structure (such as a hairpin, bulge, G-quadruplex, etc.), enabling it to bind to a target molecule with high specificity and high affinity. You can think of it as a "chemical antibody," but its essence is not protein—it is nucleic acid. Key Characteristics and Advantages (Compared to Traditional Antibodies) Characteristic Aptamer Traditional Antibody Nature Single-stranded DNA or RNA (nucleic acid) Protein Production Chemical synthesis in vitro, controllable process, minimal batch-to-batch variation Biological production in vivo (using animal cells), potential batch-to-batch variation Stability Very high. Heat-resistant, can be stored long-term at room temperature, can undergo repeated denaturation and renaturation without losing activity Relatively low. Usually requires low-temperature storage, prone to denaturation and loss of activity Immunogenicity Generally low or none, unlikely to cause an immune response May cause an immune response (especially heterologous antibodies) Modification & Labeling Very easy. Can precisely incorporate fluorescent groups, chemical modifications, linkers, etc., during synthesis More difficult, modifications may affect binding capability Target Range Very broad. From ions and small molecules to proteins, whole cells, viruses, and even bacteria Primarily targets immunogenic biomacromolecules Molecular Size Small (typically 5-15 kDa), strong tissue penetration Large (~150…
Technical Document: Aptamer Screening – Principles, Applications, and Advances Document Version: 1.0 Date: October 26, 2023 Subject: Overview of the methodologies and diverse applications of aptamer screening technologies. 1.0 Executive Summary Aptamer screening, primarily through the Systematic Evolution of Ligands by EXponential enrichment (SELEX) process, is a high-throughput in vitro technology for identifying single-stranded DNA or RNA oligonucleotides (aptamers) with high affinity and specificity for a target molecule. This document outlines the core principles of aptamer screening and its transformative applications across diagnostics, therapeutics, biotechnology, and environmental monitoring. Aptamers, often termed "chemical antibodies," offer advantages such as in vitro synthesis, low immunogenicity, and ease of modification, making them powerful tools in molecular recognition. 2.0 Introduction to Aptamer Screening Aptamers are short, synthetic oligonucleotides that fold into defined three-dimensional structures, enabling them to bind to targets ranging from small ions and organic molecules to proteins, cells, and even whole organisms. The process of discovering these binding sequences is called aptamer screening. The gold standard method is SELEX, a repetitive cycle of: Incubation: A vast, random oligonucleotide library (10^14–10^15 sequences) is exposed to the target. Partitioning: Target-bound sequences are separated from unbound ones. Amplification: The bound sequences are amplified via PCR (for DNA) or RT-PCR (for RNA). Conditioning: The enriched pool is prepared for the next selection…
Aptamer Screening Methods Introduction Aptamers are single-stranded DNA or RNA oligonucleotides that bind to specific target molecules with high affinity and specificity. The Systematic Evolution of Ligands by EXponential enrichment (SELEX) process is the primary method for aptamer development. The choice of screening strategy depends critically on the nature of the target—its size, structure, chemical properties, and available functional groups for immobilization. This document outlines established and emerging SELEX methodologies tailored for different target classes: small molecules, proteins, and whole cells. 1. Screening Methods for Small Molecule Compounds Small molecule targets (MW < 1000 Da, e.g., toxins, antibiotics, hormones) present unique challenges due to their simple structure, limited binding sites, low affinity for nucleic acids, and difficulty in separation from unbound sequences. Screening strategies often require immobilization of the target or the library, with optimized separation techniques. 1.1. Agarose Affinity Chromatography SELEX Principle: The small molecule target is covalently coupled to cross-linked agarose beads packed into a chromatography column. A nucleic acid library is passed through; bound sequences are retained and later eluted for amplification. Process: Typically requires 3–18 selection rounds. Applications: Early and successful selection of aptamers for dyes, ATP, S-adenosylhomocysteine, L-arginine, coenzyme A, kanamycin, and benzylpenicillin. Advantages: Mature, reliable technology. Limitations: Requires large…
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…
