Development of a biosensor for ergot alkaloids

Date: 1 June 2016

Venue: Campus Middelheim, A.143 - Middelheimlaan 1 - 2020 Antwerpen

Time: 2:00 PM

Organization / co-organization: Faculty of Science

PhD candidate: Elsa Rouah-Martin

Principal investigator: Ronny Blust & Johan Robbens

Short description: PhD defence of Mrs. Elsa Rouah-Martin - Faculty of Science



Abstract

Ergot alkaloids are mycotoxins which can be found in food and feed as a result of a contamination of cereal crops and grasses by fungi from the genus Claviceps. Their presence in food and feed can lead to severe poisoning in humans and animals. Several species of cereal crops and grasses are regularly concerned by ergot contamination, including some of economical importance such as wheat or sorghum. The aim of the PhD project was to produce a specific and sensitive aptamer-based biosensor for ergot alkaloids. DNA aptamers were selected for ergot alkaloids using a selection procedure, known as SELEX (Systematic Evolution of Ligands by Exponential enrichment). DNA aptamers having dissociation constants ranging in the nanomolar range were obtained, meaning that these aptamers can have a potentially low detection limit situated in the nanomolar range. A sensing solution was prepared by linking the selected aptamers to gold nanoparticles and it was possible to specifically detect ergot alkaloids in buffers and real matrix, i.e. a flour sample extract. Compounds which did not possess an ergoline 4-member ring were not recognized by the selected aptamers, even the ones containing an indole structure which partially resembles the chemical structure of ergoline; illustrating the excellent capabilities of aptamers to specifically differentiate between similar compounds. A specific color change and physical change were observed in presence of small ergot alkaloids, as the red solution immediately turned into a colorless solution and dark purple precipitate. Based on these findings, a solid phase extraction system was also prepared by grafting DNA aptamers onto a silica gel. Hereby, it was possible to specifically extract ergot alkaloids from an ergot contaminated flour sample. These studies showed that aptamers are suited as recognition elements to be used in sensors, and their remarkable properties make them more competitive than other biological recognition elements in terms of specificity, sensitivity and stability. We believe that aptamers are therefore promising to a highly growing market for specific sensors dedicated to food safety, point-of-care tests, and environmental safety.