Microbead-assisted PDA sensor for the detection of genetically modified organisms

A simple and sensitive approach for the detection of marker protein, phosphinothricin acetyltransferase, from genetically modified crops was developed based on the colorimetric transition of polydiacetylene (PDA) vesicles in combination with silica microbeads. PDAs have attracted a great deal of interests as a transducing material due to their special features that allow colorimetric response to sensory signals, as well as their inherent simplicity. However, most PDA-based biosensors require additional analytical equipment such as a fluorescence microscope or UV–Vis spectrometer. In this study, we report a new approach to increase the degree of color transition by coupling antibody-conjugated PDA vesicles with silica microbeads in an effort to monitor the results with the unaided eye or simple RGB analysis. By immobilizing PDA vesicles on silica microbeads, we were able to overcome the disadvantages of colloidal PDA-based sensors and increase the degree of colorimetric changes in response to target molecules to a concentration as low as 20 nM. The additional stresses were given to PDA vesicles by antigen–antibody bridging of PDA vesicles coupled with microbeads, resulting in enhanced blue–red color transition. All the results showed that PDA vesicles in conjunction with silica microbeads will be a promising transducing material for the detection of target proteins in diagnostic and biosensing applications.