Development of smart cotton fabrics immobilized with anthocyanin and potassium alum for colorimetric detection of bacteria

Novel smart biochromic cotton fibers were prepared via immobilization of the naturally occurring anthocyanin into cotton textile for identification of bacteria for many possible applications including monitoring healthcare, medical textiles and food packaging. Anthocyanin extract was easily isolated from red-cabbage, and applied onto cotton textiles using potassium alum as mordant. The presence of mordant/anthocyanin dyestuff particles (22–96 nm) on cotton surface was explored by transmission electron microscope (TEM). Growth of bacteria has been known to affect the pH of the medium. During the growth of E. coli (Gram-negative bacterium), the absorption spectral analysis demonstrated a blue shifting from 607 nm (purple) to 472 nm (pink). Similarly, the absorption spectra demonstrated a blue (hypsochromic) shifting from 607 nm (purple) to 438 nm (green) during the growth of L. acidophilus (Gram-positive bacterium). This color change can be ascribed to the pH-directed delocalization of electrons. Changes in color were explored by absorbance spectra and CIE Lab parameters. The morphologies of the anthocyanin-immobilized cotton were inspected by various analytical methods. The cytotoxic behavior and comfort properties of the dyed cotton were examined.