Abstract
Bio-functionalization of polymeric substrate is versatile technique to exploit biological activities in numerous engineering applications. In particular, functionalization with biological receptors has been used to develop highly sensitive biosensors. In this study, we have functionalized polydiacetylene(PDA) vesicles with antibodies as biological receptors through chemical conjugation for the use of biosensor. In fact, the PDA vesicles have unique chromatic property that is blue-to-red color transition upon external stimuli such as temperature, pH and mechanical stress. Once a specific target molecule binds to the antibody on the surface of the PDA vesicles, the color of PDA vesicles irreversibly turns to red. These antibody conjugated PDA vesicles were encapsulated within hydrogel matrix to enhance biological activity. It was demonstrated that reaction sensitivity of the hydrogel encapsulated biosensor was increased by molecular confinement effect. Furthermore, hydrogel in a bead form was created using a droplet generating microfluidic device that has flow focusing microchannels. Reaction sensitivity was futher enhanced when biosensors were encapsulated in a bead form. In this case, phosphinothricin acetyltransferase (PAT), which is herbicide resistant protein that is related to marker of genetically modified (GM) crops was used as a model target. Using hydrogel bead biosensor presented in this study, PAT protein can be detected with naked eyes in a concentration as low as 20nM. This concept to detect low concentration of biomolecules can be potentially applied to other biosensors or analytical devices.
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