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Roxanne Kieltyka

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Organization: Universiteit Leiden , Belgium
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Title: (PhD)
Evaluation of dextran(ethylene glycol) hydrogel films for giant unilamellar lipid vesicle production and their application for the encapsulation of polymersomes
Co-reporter:Nestor Lopez Mora;Yue Gao;M. Gertrude Gutierrez;Justin Peruzzi;Ivan Bakker;Ruud J. R. W. Peters;Bianka Siewert;Sylvestre Bonnet;Roxanne E. Kieltyka;Jan C. M. van Hest;Noah Malmstadt;Alexander Kros
Soft Matter (2005-Present) 2017 vol. 13(Issue 33) pp:5580-5588
Publication Date(Web):2017/08/23
DOI:10.1039/C7SM00551B
Giant Unilamellar Vesicles (GUVs) prepared from phospholipids are becoming popular membrane model systems for use in biophysical studies. The quality, size and yield of GUVs depend on the preparation method used to obtain them. In this study, hydrogels consisting of dextran polymers crosslinked by poly(ethylene glycol) (DexPEG) were used as hydrophilic frameworks for the preparation of vesicle suspensions under physiological ionic strength conditions. A comparative study was conducted using hydrogels with varied physicochemical properties to evaluate their performance for GUV production. The prepared GUVs were quantified by flow cytometry using the Coulter Principle to determine the yield and size distribution. We find that hydrogels of lower mechanical strength, increased swellability and decreased lipid interaction favour GUV production, while their resulting size is determined by the surface roughness of the hydrogel film. Moreover, we embedded polymersomes into the crosslinked hydrogel network, creating a DexPEG – polymersome hybrid film. The re-hydration of lipids on those hybrid substrates led to the production of GUVs and the efficient encapsulation of polymersomes in the lumen of GUVs.
Evaluation of dextran(ethylene glycol) hydrogel films for giant unilamellar lipid vesicle production and their application for the encapsulation of polymersomes
Co-reporter:Nestor Lopez Mora;Yue Gao;M. Gertrude Gutierrez;Justin Peruzzi;Ivan Bakker;Ruud J. R. W. Peters;Bianka Siewert;Sylvestre Bonnet;Roxanne E. Kieltyka;Jan C. M. van Hest;Noah Malmstadt;Alexander Kros
Soft Matter (2005-Present) 2017 vol. 13(Issue 33) pp:5580-5588
Publication Date(Web):2017/08/23
DOI:10.1039/C7SM00551B
Giant Unilamellar Vesicles (GUVs) prepared from phospholipids are becoming popular membrane model systems for use in biophysical studies. The quality, size and yield of GUVs depend on the preparation method used to obtain them. In this study, hydrogels consisting of dextran polymers crosslinked by poly(ethylene glycol) (DexPEG) were used as hydrophilic frameworks for the preparation of vesicle suspensions under physiological ionic strength conditions. A comparative study was conducted using hydrogels with varied physicochemical properties to evaluate their performance for GUV production. The prepared GUVs were quantified by flow cytometry using the Coulter Principle to determine the yield and size distribution. We find that hydrogels of lower mechanical strength, increased swellability and decreased lipid interaction favour GUV production, while their resulting size is determined by the surface roughness of the hydrogel film. Moreover, we embedded polymersomes into the crosslinked hydrogel network, creating a DexPEG – polymersome hybrid film. The re-hydration of lipids on those hybrid substrates led to the production of GUVs and the efficient encapsulation of polymersomes in the lumen of GUVs.
Aromatic Gain in a Supramolecular Polymer
Co-reporter:Victorio SaezTalens;Dr. Pablo Englebienne;Dr. Thuat T. Trinh;Willem E. M. Noteborn;Dr. Ilja K. Voets;Dr. Roxanne E. Kieltyka
Angewandte Chemie 2015 Volume 127( Issue 36) pp:10648-10652
Publication Date(Web):
DOI:10.1002/ange.201503905

Abstract

The synergy of aromatic gain and hydrogen bonding in a supramolecular polymer is explored. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self-assemble through a combination of hydrophobic, hydrogen-bonding, and aromatic effects into stiff, high-aspect-ratio fibers. UV and IR spectroscopy show electron delocalization and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units. The aromatic contribution to the interaction energy was further supported computationally by nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices, demonstrating greater aromatic character upon polymerization: at least 30 % in a pentamer. The aromatic gain–hydrogen bonding synergy results in a significant increase in thermodynamic stability and a striking difference in aggregate morphology of the bis(squaramide) bolamphiphile compared to isosteres that cannot engage in this effect.

Aromatic Gain in a Supramolecular Polymer
Co-reporter:Victorio SaezTalens;Dr. Pablo Englebienne;Dr. Thuat T. Trinh;Willem E. M. Noteborn;Dr. Ilja K. Voets;Dr. Roxanne E. Kieltyka
Angewandte Chemie International Edition 2015 Volume 54( Issue 36) pp:10502-10506
Publication Date(Web):
DOI:10.1002/anie.201503905

Abstract

The synergy of aromatic gain and hydrogen bonding in a supramolecular polymer is explored. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self-assemble through a combination of hydrophobic, hydrogen-bonding, and aromatic effects into stiff, high-aspect-ratio fibers. UV and IR spectroscopy show electron delocalization and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units. The aromatic contribution to the interaction energy was further supported computationally by nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices, demonstrating greater aromatic character upon polymerization: at least 30 % in a pentamer. The aromatic gain–hydrogen bonding synergy results in a significant increase in thermodynamic stability and a striking difference in aggregate morphology of the bis(squaramide) bolamphiphile compared to isosteres that cannot engage in this effect.

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