Abstract
•Biochromic cotton fabric was prepared for detection of bacterial metabolites.•Hydrazone was synthesized by an azo-coupling of tricyanofuran and diazonium salt.•Calcium alginate was applied as crosslinker to fasten hydrazone onto cotton fabric.•Red shift was monitored from 454 nm (red) to 605 nm (purple) for Gram–ve bacteria.•Complete blue shift to 454 nm (yellow) was detected for Gram + ve bacteria.
Increasing the incidence of infectious diseases and antibiotic-resistant bacteria results in threats to both economy and man health. Cotton textiles are characterized by cellulosic fibrous morphology with high surface area, flexibility, biocompatibility, comfortability, and environmentally-friendly. Tricyanofuran hydrazones (TCFH) have been proved to be efficient halochromic and biochromic indicators. TCFH was synthesized by azo-coupling tricyanofuran with the corresponding diazonium salt. Biochromic textile assay were developed by the incorporation of tricyanofuran hydrazone chromophore into cotton fibers for detection of bacterial pathogens for various potential applications such as foodstuff packaging, healthcare and medical textiles. In order to avoid steric hindrance of TCFH molecular switching, calcium alginate capsules with higher surface area enclosing active detection sites of TCFH were successfully prepared and cross-linked in situ to form a thin layer onto cotton surface by dip-coating. The growth of bacteria usually affects the pH value of the surrounding environment. The absorbance spectra showed a blue shift from red to yellow at 454 nm during the growth of L. acidophilus as Gram-positive bacteria. Likewise, the growth of E. coli (Gram-negative bacteria) showed a red shift from 454 nm (red) to 605 nm (purple). Those colorimetric changes could be attributed to pH-driven charge delocalization on the tricyanofuran hydrazone molecular structure, which were proved by CIE Lab parameters and absorption spectra. The morphology of dyed cotton assays were examined by a number of analytical methods. The cytotoxicity, colorfastness and comfortability of the textile assays were also investigated.