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…
