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 Whole-cell SELEX? Whole-cell SELEX (Systematic Evolution of Ligands by EXponential enrichment) is a technique used to discover aptamers (single-stranded DNA or RNA molecules) that bind specifically to a target living cell. Unlike traditional SELEX that uses a purified protein target, whole-cell SELEX presents the target in its native, complex cellular environment. This allows for the selection of aptamers against: Native cell-surface proteins in their proper folding and post-translational modifications. Complex targets like transmembrane receptors in their natural lipid environment. Unknown surface biomarkers without prior knowledge of the cell's molecular makeup. Specific cell states (e.g., activated, cancerous, infected) based on differences in surface expression. The Core Process: How Whole-cell SELEX Works A professional service will manage this complex, iterative pipeline: Library & Design: Starting with a vast, random synthetic oligonucleotide library (10^14 - 10^15 unique sequences). Positive Selection: Incubating the library with the target cells (e.g., cancer cells, stem cells, bacteria). Aptamers that bind to any surface structure are retained. Counter-Selection (Critical Step): The bound pool is then exposed to non-target or control cells (e.g., healthy cells, a different cell line). Sequences that bind to these are discarded. This step is crucial for generating specificity. Elution & Amplification: Aptamers specifically bound to the target cells are recovered, amplified by PCR…
