Selection of aptamers against live E.coli cells using Cell SELEX.

Aptamers are oligonucleotides that bind with great specificity and affinity to a target molecule. These oligonucleotides are produced through the course of Systemic Evolution of Ligands by Exponential Enrichment (SELEX). SELEX is a combinatorial chemistry technique used to generate a random DNA or RNA library, which is then incubated with a target molecule. The binding aptamers are divided from the nonbinding random pool DNA/aptamers, and then amplified via polymerase chain reaction (PCR). Double stranded DNA molecules have been used to select against purified target molecules; in this study we have developed a selection technique using live Escherichia coli cells as a target and using Bacillus subtilis and Enterobacter aerogenes as negative controls. Aptamer pools obtained from approximately 8 rounds of Cell SELEX demonstrated an affinity for E .coli cells when tested via fluorescence detection.