A novel receptor-free polydiacetylene nanofiber biosensor for detecting E. coli via colorimetric changes

A nanofiber-based polydiacetylene (PDA) biosensor was prepared with polyurethane (PU) to detect Escherichia coli. The main advantage of this PU-PDA nanofiber biosensor was the simplicity of the preparation method via electrospinning where no complex receptors were required to detect E. coli via colorimetric properties. Diacetylene monomers self-assembled during the electrospinning process that significantly enhanced the interaction between the PDA macromolecules and E. coli, resulting in high sensitivity of bacterial detection. Experiments showed that the PU-PDA nanofiber system was highly sensitive and could quickly detect E. coli by a colorimetric transition that is visible to the naked eye. The colorimetric property of the PU-PDA nanofiber was highly sensitive to organic solvents, suggesting potential for application in fingerprinting devices capable of distinguishing organic solvents. Additional experiments indicated that the color-changing substances (CCS) in the complex E. coli culture were not cell-associated, rather E. coli secretion associated. Further experiments were conducted to understand the nature of the CCS in E. coli culture and the results showed that the CCS are free extracellular polymeric substances (EPS) in E. coli culture.