In the exchange program between the University of Camerino (Italy) and the Vietnam National University of Agriculture within the framework of the Erasmus KA171 Project (Project code: 2022-1-IT02-KA171-HED-000073309), a scientific seminar titled "Pathogen Detection Tools: Introduction to Aptamer and SELEX" was scheduled for the morning of May 12, 2025. The event was organized by the "Microorganisms and Food Safety" research group at the Faculty of Food Science and Technology, Vietnam National University of Agriculture (VNUA). The seminar featured PhD candidate Katherin Peñaranda from the University of Camerino, Italy. Attendees included members of the research group, faculty members, researchers, technicians from the Faculties of Food Science and Technology, and Biotechnology, as well as interested students.
The seminar aimed to provide an overview of advanced techniques in biosensing, focusing on aptamers – synthetic DNA or RNA molecules that bind specifically to target pathogens – and the SELEX process (Systematic Evolution of Ligands by EXponential enrichment), a method for selecting high-affinity aptamers. These technologies had significant applications in food safety and pathogen detection.
Aptamers were first discovered in 1990 by Larry Gold and Craig Tuerk through the development of the SELEX (Systematic Evolution of Ligands by EXponential Enrichment) process. These molecules are short, single-stranded DNA or RNA sequences that fold into specific three-dimensional structures, enabling them to bind selectively to target molecules, including proteins, small molecules (such as antibiotics and drugs), and specific cell types like bacteria and viruses. Due to their high specificity and affinity, aptamers have been referred to as "chemical antibodies." They are significantly smaller than natural antibodies, typically ranging from 12 to 30 kilodaltons (kDa) compared to the 150–170 kDa size of conventional antibodies. This smaller size allows for better tissue penetration and faster systemic clearance. Aptamers can be synthesized chemically, offering advantages such as lower production costs, rapid synthesis times, and high batch-to-batch reproducibility. Unlike natural antibodies, which are primarily generated against protein targets, aptamers can be engineered to bind a broader range of targets, including non-immunogenic and toxic molecules.
The SELEX technique was employed as a screening method to isolate aptamers from a library comprising approximately 10²³ sequences of 20-60 nucleotides with diverse structures generated randomly. This process aimed to identify aptamers with high sensitivity and selectivity toward specific target molecules. The selection involved incubating the aptamer library with the target, allowing binding interactions to occur. Aptamers that did not bind to the target were removed through washing steps. This cycle of binding, washing, and amplification was repeated for 8 to 15 cycles to enrich for aptamers with high affinity and specificity. In each cycle, non-binding sequences were eliminated, progressively refining the pool toward aptamers capable of specific target recognition. The target molecules, often proteins, were immobilized on magnetic bead-containing buffers to facilitate easy separation and recovery after each washing and separation step. This approach allowed for efficient partitioning of bound from unbound sequences, enhancing the specificity of the selected aptamers.
The seminar was a great success with a lively exchange between the participants and Katherin, helping to open up a new research direction to apply advanced molecular biology techniques to problems in the field of food technology, creating interdisciplinary connections to help solve problems related to the control of pathogens as well as chemical residues in the current management of food quality and safety.
Le Thien Kim - Research group: Microbiology and Food safety