Thermoresponsive properties of polyacrylamides in physiological solutions

Polymer solutions with a lower critical solution temperature (LCST) undergo reversible phase separation when heated above their cloud point temperature ( T CP or CPT). As such, they have been proposed for a wide range of biomedical applications, from injectable drug depots to switchable coatings for...

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Bibliographic Details
Published in:Polymer chemistry 2021-09, Vol.12 (35), p.577-584
Main Authors: Kolouchová, Kristýna, Lobaz, Volodymyr, Beneš, Hynek, de la Rosa, Victor R, Babuka, David, Švec, Pavel, ernoch, Peter, Hrubý, Martin, Hoogenboom, Richard, Št pánek, Petr, Groborz, Ond ej
Format: Article
Language:English
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Abbreviations
Acrylamide
Biomedical materials
Cell adhesion
Heat measurement
NMR
Nuclear magnetic resonance
Phase separation
Photon correlation spectroscopy
Physiology
Polyacrylamide
Polyisopropyl acrylamide
Polymer chemistry
Polymers
Proteins
Refractivity
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Summary:Polymer solutions with a lower critical solution temperature (LCST) undergo reversible phase separation when heated above their cloud point temperature ( T CP or CPT). As such, they have been proposed for a wide range of biomedical applications, from injectable drug depots to switchable coatings for cell adhesion. However, in systematic studies, the T CP of these thermoresponsive polymers has been mostly measured in non-physiological solutions, thereby hindering the development of their medicinal applications. Here, we analysed the thermoresponsive properties of four acrylamide-based polymers with LCST, namely poly[( N -2,2-difluoroethyl)acrylamide] ( pDFEA ), poly[( N -isopropyl)acrylamide] ( pNIPAM ), poly[( N , N -diethyl)acrylamide] ( pDEA ), and poly[( N -acryloyl)pyrrolidine] ( pAP ). As shown by turbidimetry, their T CP in phosphate saline buffer (PBS) and foetal bovine serum (FBS) were consistently lower than those reported in the literature, typically assessed in pure water, even when using the same setup. In addition, these physiological solutions affected the variation of T CP as a function of polymer concentration (1.25 to 10.0 mg mL −1 ) and molar mass (20 to 50 kg mol −1 ). As shown by isothermal calorimetry, interactions between proteins in FBS and polymer aggregates were predominantly exothermic, which indicates that protein-polymer complexes are formed through enthalpically driven processes. In conclusion, the T CP of thermoresponsive polymers strongly depends on solvent composition and therefore should be measured under physiological conditions for future medicinal applications. We show that the cloud point temperature ( T CP ) of thermoresponsive polyacrylamides is considerably lower in physiologically relevant solvents (phosphate-buffered saline, serum) than in pure water. This decrease of T CP may be critical for some biomedical applications.
ISSN:1759-9954
1759-9962
DOI:10.1039/d1py00843a