טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDantus Mauricio
SubjectEnantio-Selective Sensing of Gas-Phase Analytes using
Microcantilevers Coated with Chiral Polymers
DepartmentDepartment of Chemistry
Supervisor Professor Yoav Eichen
Full Thesis textFull thesis text - English Version


Abstract

Asymmetric interactions have a significant impact in nature. This is due to the phenomenon known as the homo-chirality of life. The phenomenon is expressed in nature in the fact that most amino acids are in the L configuration while most sugars are D-sugars. Homo-chirality is interesting primarily because of the absence of the enantiomeric form of life, which would have exactly the same vitality and overall properties. Additionally, being homo-chiral, biology reacts to enantiomers in very different ways. We encounter asymmetric enantio-selective interactions in various fields in our daily life. Our reaction to flavors, fragrances and the pharmaceuticals many times depend on the enantiomeric form we are exposed to.

Considering the magnitude of the consequences of neglecting to do so, it is many times important to be able to assess the enantiomeric purity of chiral moieties that interact with our body. A tragic example for that is the infamous case of the Thalidomide. A medicine that aimed to alleviate, among other things, morning sickness of pregnant women. The desired effect was achieved by one enantiomer of Thalidomide. Tragically, the other enantiomer was found to cause terrible malformations in developing embryos. There are various methods for asymmetric discrimination, all based on the interaction of the guest analyte with an asymmetric element, be it physical such as polarized light or chemical such as a single enantiomer of a chiral chemical entity.

In the present research thesis, we have used silicone microcantilever arrays selectively coated with a chiral polymer layer as our sensing system, focusing on enantiomeric discrimination. The microcantilevers are very sensitive to changes in the mechanical properties of the coating polymer layer. Exposing the system to an analyte leads to the plasticization of the polymer layer, inflicting surface stress on the microcantilever. The stress formed by the polymer layer is expressed as the bending of the cantilever. This bend can be detected optically using a displacement sensor. The main goal of this research was to develop and fine-tune a system for gas-phase enantioselective recognition. The hypothesis of this research was that due to the different interactions between a pair of enantiomers and a chiral polymer, the system would respond differently when exposed to one enantiomer or the other. We studied the mechanical properties of the polymer, and the effect of exposing the polymer to different analytes. The system was fine-tuned to receive a clear repeatable signal. We learned about the possibilities and potential of the newly developed device. In addition, we discovered good evidence for the detecting and discriminating abilities of the sensor, using various analytes and in very small concentration.