Local Water Content in Polymer Gels Measured with Super‐Resolved Fluorescence Lifetime Imaging

Angewandte Chemie International Edition, vol. 63, pp. e202318421

Abstract

Abstract Water molecules play an important role in the structure, function, and dynamics of (bio‐) materials. A direct access to the number of water molecules in nanoscopic volumes can thus give new molecular insights into materials and allow for fine‐tuning their properties in sophisticated applications. The determination of the local water content has become possible by the finding that H2O quenches the fluorescence of red‐emitting dyes. Since deuterated water, D2O, does not induce significant fluorescence quenching, fluorescence lifetime measurements performed in different H2O/D2O‐ratios yield the local water concentration. We combined this effect with the recently developed fluorescence lifetime single molecule localization microscopy imaging (FL‐SMLM) in order to nanoscopically determine the local water content in microgels, i.e. soft hydrogel particles consisting of a cross‐linked polymer swollen in water. The change in water content of thermo‐responsive microgels when changing from their swollen state at room temperature to a collapsed state at elevated temperature could be analyzed. A clear decrease in water content was found that was, to our surprise, rather uniform throughout the entire microgel volume. Only a slightly higher water content around the dye was found in the periphery with respect to the center of the swollen microgels.

Authors 8

1. Sankar Jana Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

2. Oleksii Nevskyi

   University of Göttingen

   Affiliation as printed

   Third Institute of Physics – Biophysics Georg August University 37077 Göttingen Germany

3. Hannah Höche Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

4. Leon Trottenberg Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

5. Eric Siemes Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany

6. Jörg Enderlein

   University of Göttingen · Multiscale Bioimaging

   Affiliation as printed

   Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC) Georg August University 37077 Göttingen Germany

   Third Institute of Physics – Biophysics Georg August University 37077 Göttingen Germany

7. Alexandre Fürstenberg

   University of Geneva

   Affiliation as printed

   Department of Physical Chemistry and Department of Inorganic and Analytical Chemistry University of Geneva 1211 Geneva Switzerland

   Department of Physical Chemistry and Department of Inorganic and Analytical Chemistry University of Geneva 1211 Geneva Switzerland

8. Dominik Wöll corresponding Aachen Institute of Physical Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany