The Immobilized Polydiacetylene Vesicles on Polydimethylsiloxane Micropillars as Label-Free Bacterial Sensor Platform

Abstract

Due to the aggregated characteristic of polydiacetylene (PDA), the conventional two-dimensional based PDA sensor has low sensitivity. Thus, to improve the sensitivity of PDA by increasing the number and surface area of immobilized PDA, the PDA vesicles were immobilized on the micropillars structure. For the fabrication of the micropillars structure, polydimethylsiloxane (PDMS) was used to overcome the limitations imposed by the silicon-based fabrication. The PDA vesicles were immobilized by using glutaraldehyde on the amine modified template. The surface modifications of templates and PDA ii immobilization were characterized by using scanning electron microscope, atomic force microscope, contact angle analyzer and UV-Vis Spectrophotometer. The PDA-based label-free bacterial sensor platform utilized the colorimetric response of amine functionalized PDA vesicles toward surfactin, a bacterial cyclic lipopeptide commonly released by Bacillus species as an antibiotic. The detection range of the PDA-based label-free bacterial sensor in 2D and PDMS micropillars templates were measured with surfactin which induced a blue-to-red color shift selectively. The fluorescence of 2D sensor template was hardly observable until 500μM while PDMS micropillars sensor template was observable in the range of 5μM to 1 mM. The PDA on PDMS micropillars (PDA/PDMSm) sensor platform could detect the initial presence of 4x101 cells/ml of Bacillus subtilis that actively produced surfactin. Furthermore, the bacteria that are known to produce no surfactin were not detected by PDA/PDMSm sensor platform. Taken together, our results suggest that PDA/PDMSm sensor platform can sensitively and selectively be used for the high throughput detection and screening of surfactin-producing bacteria.