Title: Molecularly imprinted polymers as selective sorbents for recognition in complex aqueous samples.
Author: Sofia NESTORA
National thesis number: 2017COMP2346
- In this thesis, we have demonstrated the feasibility of preparing highly selective molecularly imprinted polymers (MIPs) for recognition in complex aqueous matrices with applications in cosmetics and food technology. MIPs are synthetic tailor-made receptors, with binding affinities and specificities comparable to those of natural antibodies. Their molecular recognition properties, combined with their high stability, mechanical robustness, low cost and easy synthesis make them extremely attractive as selective capture materials with applications in analytical and preparative separations, sensing and drug delivery, among others. However, their selective recognition in aqueous samples still remains problematic and is one of the reasons for their so far lilited commercial expansion. In the first part, we developed a water compatible MIP for its application as an active ingredient in a deodorant. Body odors are mainly due to volatile fatty acids generated from their glutamine conjugate precursors by hydrolytic enzymes from bacteria present on the skin. Most currently marketed anti-perspirants and deodorants contain, respectively aluminum salts and unspecific antibacterials. However, the extremely wide use of these products requires alternative solutions with regard to various problems (environmental, respect of skin ecosystem, toxicity, etc.). For this reason, a MIP was developed to capture the glutamine conjugate precursors so that they are no longer available to the bacteria, thus preventing their transformation to malodorous compounds. In order to generate binding selectivity in aqueous environments, an amidinium-based monomer which can form a strong stoichiometric electrostatic interaction with the carboxyl groups on the template, was synthesized. The MIP, blended in a dermo-cosmetic formulation, could capture selectively the glutamine precursors, amidst a multitude of other molecules present in human sweat. Furthermore, the MIP did not affect the skin bacteria, paving the way to an innovative and ‘safer ‘ future-generation deodorant. In the second part, we developed a fast and efficient procedure based on molecularly imprinted solid phase extraction (MISPE) for the selective clean-up of betanin and its stereoisomer isobetanin from red beetroot extracts. Betanin is a natural pigment with significant antioxidant and biological activities currently used as food colorant. Dipicolinic acid was used as template for the MIP synthesis, because of its structural similarity to the chromophore group of betanin The MISPE procedures were optimized allowing the almost complete removal of carbohydrates and the majority of proteins, resulting in high extraction recovery of betanin / isobetanin in a single step. Moreover, the whole extraction procedure was performed in environmentally friendly solvents with either ethanol or water. To conclude, we believe that this study paves the way towards the development of a new generation of water compatible MIPs with improved recognition properties in highly complex aqueous environments, and should be applicable to other biotechnological and biomedical areas as well.