High resolution imaging of soft alginate hydrogels by atomic force microscopy

Anita Akbarzadeh Solbu; Andre Koernig; Joachim S Kjesbu; Daria Zaytseva-Zotova; Marit Sletmoen; Berit L Strand

doi:10.1016/j.carbpol.2021.118804

High resolution imaging of soft alginate hydrogels by atomic force microscopy

Carbohydr Polym. 2022 Jan 15:276:118804. doi: 10.1016/j.carbpol.2021.118804. Epub 2021 Oct 23.

Authors

Anita Akbarzadeh Solbu¹, Andre Koernig², Joachim S Kjesbu³, Daria Zaytseva-Zotova⁴, Marit Sletmoen⁵, Berit L Strand⁶

Affiliations

¹ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: Anita.akbarzadeh@ntnu.no.
² JPKBioAFM Business, Bruker Nano GmbH, Berlin, Germany. Electronic address: Andre.Koernig@bruker.com.
³ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: joachim.s.kjesbu@ntnu.no.
⁴ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: Daria.zaitseva-zotova@ntnu.no.
⁵ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: Marit.sletmoen@ntnu.no.
⁶ NOBIPOL, Department of Biotechnology and Food Science, Norwegian University of Science and Technology, N-7491 Trondheim, Norway. Electronic address: berit.l.strand@ntnu.no.

PMID: 34823810
DOI: 10.1016/j.carbpol.2021.118804

Abstract

This work explores the largely unknown surface microstructure and elastic modulus of soft calcium-alginate hydrogels (E = 100-4500 Pa) in their hydrated state by atomic force microscopy (AFM) in quantitative imaging mode. Alginate concentration influenced the surface topography with surface roughness measured to be 101 ± 6 nm and 57 ± 1 nm for 0.5 and 2.0% (w/v) alginate, respectively. The calculated range of pore sizes increased with decreasing alginate concentration, with radii smaller than 360 nm, 570 nm and 1230 nm for 2.0%, 1.0% and 0.5% alginate, respectively. Small changes in calcium concentration (from 20 to 25 mM, 1.5% alginate) did not induce changes in surface microstructure, although it increased the elastic modulus mean values and distribution. Introducing oxidized or peptide-grafted alginate in the gels resulted in rougher surfaces, larger pore sizes and lower elasticity than the respective hydrogels with no modified alginate.

Keywords: AFM; Alginate; High resolution imaging; Hydrogels; Surface microstructure.