Molecular engineering of selective recognition elements as coatings for sensor platforms

This dissertation focuses on the aspects of selectivity in chemical sensing systems. While a number of sensing platforms exist that are capable of highly sensitive detection, the common factor of poor selectivity continues to limit their widespread use. In this work, we explore the use of sequence specific biopolymers identified through combinatorial screening approaches for the creation of molecular recognition elements for chemical sensor coatings. Particularly, a library of bacteriophage was screened to identify which of the unique peptide sequences present on their protein coat could provide the highest affinity binding to a target chemical. We specifically targeted small molecules including trinitrotoluene (TNT) and dinitrotoluene (DNT). From phage display experiments, we identify consensus peptide motifs, and we analyzed their binding efficacy based on affinity and specificity. Additionally, we demonstrate that the standalone receptor for TNT could be incorporated into a polymeric coating while retaining its functionality. In doing so, a peptide based sensor coating was developed and implemented onto a common Quartz Crystal Microbalance sensing platform. Liquid phase experiments demonstrated the sensing ability of this system selectivity respond to TNT while remaining relatively inert to the analogue DNT molecule. Furthermore, a polymeric based sensing system was developed with the TNT receptive motif to create a widely deployable sensing system. Integration was simply a matter of coupling a chromic responsive polymer at the final step of receptor synthesis. In doing so, a modular sensing system was created which demonstrated target binding to small molecules, such as TNT, or large cells, such as fibroblasts, depending on the surface receptor motif Finally, we show that the fabrication approach could be optimized to enhance the sensitivity of the system to small molecule targets.;Our results demonstrate that short amino acid sequences can be identified through phage screening for small molecule binding and further developed into a sensor coating. The receptors may be implemented onto a common QCM based sensor or onto a newly develop chromic responsive system, thus demonstrating the broad sensor integration capabilities of these receptive motifs. We anticipate this approach may lead to furthering the development of molecular recognition elements by utilizing the biological toolkit of evolutionary screening for selective receptors. In the future, we hope such approaches will be used to gain a mechanistic understanding of molecular recognition which would have a profound impact on the chemical sensing community.