A portable point-of-care test device for gluten in food on the horizon There is no therapy for coeliac disease, the permanent intolerance to gluten by the immune system. The EU-funded project GEMS has developed a new chemical sensor to determine if a food is gluten free. Health © GEMS Coeliac disease affects between 1 % and 2 % of the European population, with estimated direct public health costs of around EUR 3 billion per year. For sufferers with coeliac disease, the symptoms can be severe. Autoimmune reactions cause destruction of the intestinal villi, finger-like protrusions in the small intestine. The result is reduced absorption of nutrients, possible malnutrition and permanent damage to the intestine. The issues and proposed solutions “There are no known medical treatments effective to cure coeliac disease, and the therapy is just a strict gluten-free diet for life,” points out Alessandra Maria Bossi, GEMS project coordinator and assistant professor at the Department of Biotechnology, University of Verona. “The core aim of the GEMS project was therefore to devise a portable chemical sensor for rapid point-of-care testing of the gluten content in food.” Criteria high on the list to fulfil were that it should offer high commercial value and be rapid and low cost as well as robust yet sensitive. Currently, test kits available for gluten testing are based primarily on an enzyme-linked immunosorbent assay (ELISA) that involve enzymes and antibodies. Gluten-free diet on the menu With funding from the Marie Skłodowska-Curie programme, the GEMS project developed an electrochemical method to recognise the gluten molecule. Harnessing the expertise in electrochemistry of Marie Curie fellow Zofia Iskierk with the experience of Bossi in recognition materials, the gluten-selective recognition unit was prepared using molecular imprinting polymer (MIP) technology. To implement the MIP, the researchers stamped molecular impressions of the target, a gluten epitope, a small distinctive portion of the gluten protein, to make the gluten-recognition polymer. Recognising gluten molecules, this selective material behaves in a way similar to antibodies. However, MIPs can be produced much more cheaply; their added advantages are robustness, extended shelf life and sterilisation compatibility. Broken down into stages, GEMS research has developed a protocol for unique gluten epitopes identification, and a method to identify the best monomer to use. For the electrodes, there is a synthesis protocol for MIP thin films and a characterisation profile of the physical appearance of the MIP electrodes. The functional characterisation of the selectivity and sensitivity of the MIP chemosensor was also assessed. Challenges and progress go hand-in-hand “The unexpected challenge in the GEMS project came along with the real sample testing,” Bossi emphasises. “Dealing with foodstuff in analytical terms can present many research hurdles. In particular, testing a wide range of gluten-containing foods involves analysis of the most diverse materials in terms of compositions and physical forms – from pizza to soup thickened with wheat flour.” The unexpected key question therefore was: How to treat the food samples prior to determine the gluten-content by means of the gluten-sensor? When testing the sensor's performance, researchers included entire gluten proteins as well as gluten extracts from semolina, rice and whey. For comparison, commercially available ELISA gluten kits were used. “The results obtained so far with the gluten sensor are encouraging,” concludes Bossi. “Along with the definition of pre-analytical procedures, further studies are needed on interference introduced to the sensing element by the molecular bonds in food and their influence on measurements.” The researchers estimate that a portable point-of-care pilot device is feasible in 2 years. Keywords GEMS, gluten, food, sensor, epitope, molecular imprinting polymer (MIP)
