Selective detection of Gram-negative bacteria and antibacterial properties of colorimetric polydiacetylene nanofibers

Colorimetric biosensors made by polydiacetylene nanofibers have been of great interest in developing novel strategies of rapid and in situ detection to bacterial infection that is a major concern for human fatalities around the world. Previous studies have focused on bacterial detection and the sensitivity of the detection that the PDA biosensors can offer. However, the selectivity of the detection to different bacterial strains has not been well understood. With the recent emergence of multiple drug-resistance bacterial strains, selective detection of bacteria demands more attention and cutting-edge tools. In this study, a polydiacetylene (PDA) nanofiber biosensor prepared via electrospinning was found effectively to offer selective detection of Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa via a rapid blue-to-red colorimetric change. The quantification of the colorimetric changes suggested that the biosensor selectivity was effective in identifying with Gram-negative bacteria over Gram-positive bacteria (Staphylococcus aureus). The selectivity was likely due to structural differences between Gram-positive bacteria and Gram-negative bacteria such as cell outer layer thickness, as well as different extracellular polymeric substances (EPS) released by different bacteria. In addition, the nanofiber biosensor demonstrated superior antibacterial properties that were evaluated using bacteria staining and electron microscopic techniques. A comprehensive analysis of the interaction between the PDA nanofibers and different bacteria was presented to provide insightful understanding of selective detection and antibacterial properties of the PDA nanofibers. The results suggested that PDA nanofibers have great potential in medical textiles, personal protective equipment, and other biomedical applications.