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Azad R, Lenßen P, Jia Y, Strauch M, Bener BA, Merhof D, Wöll D. Modeling the Temperature-Dependent Size Change of Polydisperse Nano-objects using a Deep Generative Model. NANO LETTERS 2024; 24:4447-4453. [PMID: 38588344 DOI: 10.1021/acs.nanolett.4c00267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
Modern microscopy techniques can be used to investigate soft nano-objects at the nanometer scale. However, time-consuming microscopy measurements combined with low numbers of observable polydisperse objects often limit the statistics. We propose a method for identifying the most representative objects from their respective point clouds. These point cloud data are obtained, for example, through the localization of single emitters in super-resolution fluorescence microscopy. External stimuli, such as temperature, can cause changes in the shape and properties of adaptive objects. Due to the demanding and time-consuming nature of super-resolution microscopy experiments, only a limited number of temperature steps can be performed. Therefore, we propose a deep generative model that learns the underlying point distribution of temperature-dependent microgels, enabling the reliable generation of unlimited samples with an arbitrary number of localizations. Our method greatly cuts down the data collection effort across diverse experimental conditions, proving invaluable for soft condensed matter studies.
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Affiliation(s)
- Reza Azad
- Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Pia Lenßen
- Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Yiwei Jia
- Institute of Imaging and Computer Vision, RWTH Aachen University, 52056 Aachen, Germany
| | - Martin Strauch
- Institute of Imaging and Computer Vision, RWTH Aachen University, 52056 Aachen, Germany
| | - Berk Alperen Bener
- Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany
| | - Dorit Merhof
- Institute of Image Analysis and Computer Vision, University of Regensburg, 93040 Regensburg, Germany
| | - Dominik Wöll
- Institute of Physical Chemistry, RWTH Aachen University, 52074 Aachen, Germany
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Simons J, Hazra N, Petrunin AV, Crassous JJ, Richtering W, Hohenschutz M. Nonionic Microgels Adapt to Ionic Guest Molecules: Superchaotropic Nanoions. ACS NANO 2024; 18:7546-7557. [PMID: 38417118 DOI: 10.1021/acsnano.3c12357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/01/2024]
Abstract
Microgels are commonly applied as solute carriers, where the size, density, and functionality of the microgels depend on solute binding. As representatives for ionic solutes with high affinity for the microgel, we study here the effect of superchaotropic Keggin polyoxometalates (POMs) PW12O403- (PW) and SiW12O404- (SiW) on the aqueous swelling and internal structure of nonionic poly(N-isopropylacrylamide) (pNiPAM) microgels by light scattering techniques and small-angle X-ray scattering. Due to their weak hydration, these POMs bind spontaneously to the microgels at millimolar concentrations. The microgels thus become charged and swell at low POM concentration, surprisingly without strongly increasing the volume phase transition temperature, and deswell at higher POM concentration. The swelling arises because of the osmotic pressure of dissociated counterions of the POMs, while the deswelling is due to POMs acting as physical cross-links in the microgels under screened electrostatics in NaCl or excess POM solution. This swelling/deswelling transition is sharper for PW than for SiW related to the lower charge density, weaker hydration, and stronger binding of PW. The POMs elicit qualitatively and quantitatively different swelling effects from ionic surfactants and classical salts. Moreover, the network softness and topology govern the swelling response upon POM binding. The softer the microgel, the stronger is the swelling response, while, inside the microgel, regions of high polymer density swell/contract more upon electric charging/cross-linking than regions with low polymer density. POM binding thus enables fine-tuning of microgel properties and highlights the role of network topology in microgel swelling. Because POMs decompose at an alkaline pH, these POM/microgel systems also exhibit pH-responsive swelling in addition to the typical temperature responsiveness of pNiPAM microgels.
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Affiliation(s)
- Jasmin Simons
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
| | - Nabanita Hazra
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
| | - Alexander V Petrunin
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
| | - Jérôme J Crassous
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
| | - Max Hohenschutz
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, DE-52074 Aachen, Germany
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Jana S, Nevskyi O, Höche H, Trottenberg L, Siemes E, Enderlein J, Fürstenberg A, Wöll D. Local Water Content in Polymer Gels Measured with Super-Resolved Fluorescence Lifetime Imaging. Angew Chem Int Ed Engl 2024; 63:e202318421. [PMID: 38165135 DOI: 10.1002/anie.202318421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 12/21/2023] [Accepted: 01/02/2024] [Indexed: 01/03/2024]
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 H2 O quenches the fluorescence of red-emitting dyes. Since deuterated water, D2 O, does not induce significant fluorescence quenching, fluorescence lifetime measurements performed in different H2 O/D2 O-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.
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Affiliation(s)
- Sankar Jana
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Oleksii Nevskyi
- Third Institute of Physics - Biophysics, Georg August University, 37077, Göttingen, Germany
| | - Hannah Höche
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Leon Trottenberg
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Eric Siemes
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Jörg Enderlein
- Third Institute of Physics - Biophysics, Georg August University, 37077, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Georg August University, 37077, Göttingen, Germany
| | - Alexandre Fürstenberg
- Department of Physical Chemistry and Department of Inorganic and Analytical Chemistry, University of Geneva, 1211, Geneva, Switzerland
| | - Dominik Wöll
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
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Sans J, Azevedo Gonçalves I, Quintana R. Establishing Quartz Crystal Microbalance with Dissipation (QCM-D) Coupled with Spectroscopic Ellipsometry (SE) as an Advantageous Technique for the Characterization of Ultra-Thin Film Hydrogels. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2312041. [PMID: 38438898 DOI: 10.1002/smll.202312041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/14/2024] [Indexed: 03/06/2024]
Abstract
Despite the considerable significance of utilizing ultra-thin film (utf) hydrogels as multipurpose platforms for biomedical applications, there is still an important lack of adequate characterization techniques suitable for such materials. In this Perspective, the use of quartz crystal microbalance with dissipation (QCM-D) coupled with spectral ellipsometry (SE) is presented as a potential tool for the complete characterization of utf-hydrogels due to its nanometric sensitivity and high versatility. Herein, the fundaments for utf-hydrogel characterization are settled down as far as the QCM-D/SE response is explored under a wide range of different in operando wet working conditions measurements such as temperature or liquid media, among others. Therefore, the design of measuring protocols capable to perform is proposed and compiled, for the first time, complete and precise characterization of the cross-link density, thickness variations (swelling ratio determination), stability analyses, and mechanical studies (including the simultaneous generation of stress-strain curves and the evaluation of the viscoelastic; leading to the final determination of the Poisson's ratio) under different in operando conditions. Finally, the future challenges and implications for the general characterization of soft-thin films are discussed.
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Affiliation(s)
- Jordi Sans
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, Esch/Alzette, L-4362, Luxembourg
- Departament d'Enginyeria Quínica EEBE Universitat Politècnica de Catalunya, C/ Eduard Maristany, 10-14, Barcelona, 08019, Spain
| | - Ingrid Azevedo Gonçalves
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, Esch/Alzette, L-4362, Luxembourg
- Department of Physics and Materials Science, University of Luxembourg, Esch-sur-Alzette, L-4365, Luxembourg
| | - Robert Quintana
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, Esch/Alzette, L-4362, Luxembourg
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