Polymer-oligopeptide composite coating for selective detection of explosives in water

The selective detection of a specific target molecule in a complex environment containing potential contaminants presents a significant challenge in chemical sensor development. Utilizing phage display techniques against trinitrotoluene (TNT) and dinitrotoluene (DNT) targets, peptide receptors have previously been identified with selective binding capabilities for these molecules. For practical applications, these receptors must be immobilized onto the surface of sensor platforms at high density while maintaining their ability to bind target molecules. In this paper, a polymeric matrix composed of poly(ethylene-co-glycidyl methacrylate) (PEGM) has been prepared. A high density of receptors was covalently linked through reaction of amino groups present in the receptor with epoxy groups present in the co-polymer. Using X-ray photoelectron spectroscopy (XPS) and gas-chromatography/mass spectroscopy (GC/MS), this attachment strategy is demonstrated to lead to stably bound receptors, which maintain their selective binding ability for TNT. The TNT receptor/PEGM conjugates retained 10-fold higher TNT binding ability in liquid compared to the lone PEGM surface and 3-fold higher TNT binding compared to non-specific receptor conjugates. In contrast, non-target DNT exposure yielded undetectable levels of binding. These results indicate that this polymeric construct is an effective means of facilitating selective target interaction both in an aqueous environment. Finally, real-time detection experiments were performed using a quartz crystal microbalance (QCM) as the sensing platform. Selective detection of TNT vs DNT was demonstrated using QCM crystals coated with PEGM/TNT receptor, highlighting that this receptor coating can be incorporated as a sensing element in a standard detection device for practical applications.