Simultaneous nucleophilic-substituted and electrostatic interactions for thermal switching of spiropyran: a new approach for rapid and selective colorimetric detection of thiol-containing amino acids

Anal Chem. 2012 Jun 5;84(11):4732-8. doi: 10.1021/ac203494e. Epub 2012 May 21.

Abstract

Complementary electrostatic interaction between the zwitterionic merocyanine and dipolar molecules has emerged as a common strategy for reversibly structural conversion of spiropyrans. Herein, we report a concept-new approach for thermal switching of a spiropyran that is based on simultaneous nucleophilic-substitution reaction and electrostatic interaction. The nucleophilic-substitution at spiro-carbon atom of a spiropyran is promoted due to electron-deficient interaction induced by 6- and 8-nitro groups, which is responsible for the isomerization of the spiropyran by interacting with thiol-containing amino acids. Further, the electrostatic interaction between the zwitterionic merocyanine and the amino acids would accelerate the structural conversion. As proof-of-principle, we outline the route to glutathione (GSH)-induced ring-opening of 6,8-dinitro-1',3',3'-trimethylspiro [2H-1-benzopyran-2,2'-indoline] (1) and its application for rapid and sensitive colorimetric detection of GSH. In ethanol-water (1:99, v/v) solution at pH 8.0, the free 1 exhibited slight-yellow color, but the color changed clearly from slight-yellow to orange-yellow when GSH was introduced into the solution. Ring-opening rate of 1 upon accession of GSH in the dark is 0.45 s(-1), which is 4 orders of magnitude faster in comparison with the rate of the spontaneous thermal isomerization. The absorbance enhancement of 1 at 480 nm was in proportion to the GSH concentration of 2.5 × 10(-8)-5.0 × 10(-6) M with a detection limit of 1.0 × 10(-8) M. Furthermore, due to the specific chemical reaction between the probe and target, color change of 1 is highly selective for thiol-containing amino acids; interferences from other biologically active amino acids or anions are minimal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / analysis*
  • Benzopyrans / chemistry*
  • Color
  • Colorimetry
  • Ethanol / chemistry
  • Glutathione / analysis
  • Hydrogen-Ion Concentration
  • Indoles / chemistry*
  • Nitro Compounds / chemistry*
  • Static Electricity
  • Stereoisomerism
  • Sulfhydryl Compounds / analysis*
  • Temperature
  • Water / chemistry

Substances

  • Amino Acids
  • Benzopyrans
  • Indoles
  • Nitro Compounds
  • Sulfhydryl Compounds
  • merocyanine
  • spiropyran
  • Water
  • Ethanol
  • Glutathione