Development of a molecularly imprinted polymer specific for ochratoxin A : theoretical and sensor applications
In this work the development of two molecularly imprinted polymers, specific for ochratoxin A, is presented. Ochratoxin A is produced by several Aspergillus and Penicillium species and is common in cereals and other starch rich foods and has also been found in coffee, dried fruits, wine, beer and meats. It demonstrates potent teratogenic, immunosuppressive, mutagenic and carcinogenic properties. The toxin is also linked to Balkan Endemic Nephropathy, a chronic kidney disease found in South-Eastern Europe. Due to this the European Union has set limits on foodstuffs ranging between 2-10 ng g-1. Therefore the requirement of a simple and inexpensive biosensor to monitor this legislation is a necessity. Currently detection is performed by chromatographic methods such as HPLC, and by ELISA formats. In this work two polymeric materials, rationally designed by computational modelling and synthesised using molecular imprinting, are studied. The modelling is complimented with a Nuclear Magnetic Resonance (NMR) study. The first polymer (Polymer A) consisted of 1 mol of acrylamide and 1 mol of methacrylic acid to 1 mol of template. This material demonstrated an unusual binding mechanism, working solely in aqueous solvents. A theoretical mechanism for this binding is presented and discussed. The second polymer, again rationally designed, but under different conditions, consisted of 1 mol of N,N- diethylamino ethyl methacrylate (DEAEM) to 1 mol of template. This polymer demonstrated high affinity for the template in acetonitrile. Polymer A is used in combination with an ion-exchange SPE protocol (developed for this purpose) for the extraction of OTA from maize. Both polymer compositions are used in development of a MIP membrane optical sensor, with partial success seen in the detection of OTA in grape juice and white wine.