A chiral species is a molecule that cannot be superimposed with its mirror image. Chiral molecules are consequently present as two stereoisomers, called enantiomers, and, importantly, they are the main building blocks of living organism. On a daily basis, chiral molecules are conventionally used and produced by pharmaceutical, food, agrochemical, perfume, and cosmetics industries. As a result, chiral waste becomes an extremely important issue at present. Chiral compounds can be ecologically hazardous, due to their high biological activity, creating a global pollution problem. Yet, the stereoisomerism of contaminants is presently not considered in detail. For example, ~25% of all pesticides produced are chiral compounds and in many cases they are used as racemic mixtures.
Usually, the interactions of enantiomers with the biological ecosystem, such as their uptake, metabolism, and excretion are stereoselective and the physiological activity of the enantiomers differs significantly. Accordingly, the environmental consequence of each enantiomer can be very distinctive, and the standard analysis of these compounds – without taking into account their chiral nature – overlooks and underestimates the biological impact of the pollutants. Due to the wide distribution of chiral waste, there is a critical need of systems able of stereospecific recognition. Standard analytical techniques used for sensitive and efficient chiral discrimination and separation are based on chiral chromatography, such as GC or HPLC, capillary electrophoresis, or special NMR and spectrophotometric methods. Although these are well established methodologies, they are not suitable for instant field monitoring procedures.
In this context, the development of low cost portable chemical sensors devices which are reliable, sensitive and rapid, capable of fast, simple and real-time in situ and on site analysis for sensing and discrimination of chiral molecules presents an attractive breakthrough target compared to existing standard instrumental methods.
However, the stereoselective detection of the chiral substances with chemical sensors is an arduous task, because, in contrast to chromatography or electrophoresis, sensors rely on a single binding event and the highly efficient discrimination of the receptor is an important prerequisite. Several examples of chemical probes able of differential binding in solution have been reported so far, but their corresponding application for the development of sensor technology is still missing, with only sparse numbers of devices able of chiral discrimination. Although this approach seems to be promising for the potential development of these sensing systems, a solid and rational technological pathway for the practical implementation of chiral sensors remains a futuristic and visionary scenario. The main objective of the proposed research project is the development of chemical sensors able to recognize chiral substances based on rationally designed sensing materials, with the aim of filling the existing gap between the production of enantioselective receptors and the realization of macroscopic devices. This strategy enables a novel sensor technology for the development of sensing systems able of chiral discrimination. The success of the INITIO project will also open the way to a further potential application of the developed devices for chiral pollutants removal, allowing prompt remedial procedures in an unprecedented environmental “theranostic” approach.