An emission color-changeable sensor for biothiol using a water-soluble conjugated polymer in a paper-based strip

We investigated a paper-based sensor strip containing a water-soluble conjugated polymer (WSCP) for the detection of biothiols, including cysteine (Cys) and homocysteine (Hcy). The newly synthesized WSCP had triphenylamine groups with aldehyde pendants for interaction with the aminothiol group-containing amino acids such as Cys and Hcy to form five- and six-membered cyclic rings, respectively.We found that the paper-based sensor strip exhibited a visually noticeable fluorescence color change (violet-to-red) upon exposure to biothiols, mainly because of electronic changes in the polymer backbone via a reaction between the aldehyde group of the polymer and the aminothiol moiety in biothiol amino acids.