Escherichia coli is an enterobacteria considered one of the most pathogenic bacteria capable of causing diseases transmitted by contaminated food and water. Among them, enterohemorrhagic E. coli (EHEC) is the group with the highest prevalence in the most aggressive cases of diarrhea and serotype O157:H7 is the most found isolated which produces cytotoxins. For this reason, the timely detection of this pathogen is a topic of great importance in public health. The detection of E. coli is conventionally done through the use of microbiological and molecular tools. However, the long periods of time to issue a result has led to the search for new strategies for the detection and rapid identification of pathogens.

Aptamers are single stranded DNA or RNA oligonucleotides whose length should be less than 100 nucleotides. They adopt a three dimensional structure capable of recognizing a wide range of target molecules with a high selectivity and affinity such as proteins, carbohydrates, small molecules and even cells whole. Aptamers are isolated by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). One of potential uses of aptamers is in biosensors (aptasensors) due to their high productivity, affinity, selectivity and stability. The search for specific and sensitive aptamers for E. coli O157:H7 detection is still under study. In this work, Cell-SELEX (SELEX process adapted to cells) was performed using a 60 mer length random library by means of positive selection rounds using E. coli O157:H7 as target cell. Enterobacteria from other groups and gram positive bacteria were used as negative control. Aptamers with higher affinity were cloned, sequencing and bioinformatic analysis was carried out. These allowed the selection of candidate aptamers for in vitro assays. Finally, a specific aptamer with high affinity and ideal selectivity was selected for the detection of E. coli with a potential use for the development of aptasensors that allow early detection of acute diarrheal diseases.


Dr Jose Luis Ropero Vega is Associate Professor in the master’s program in Biotechnology at the Universidad de Santander (Colombia). He received his PhD degree from Universidad Industrial de Santander, Colombia. He has been working on the design, synthesis and study of nanomaterials for various applications. He is currently focused on two lines of research: on the one hand, the development of nanotransporters of biomolecules based on biopolymers and magnetic nanoparticles. On the other hand, the development of biosensors for detection of microorganisms of interest in public or environmental health and biomarkers for the early detection of diseases.