Revealing the True Morphological Structure of Macroporous Soft Hydrogels for Tissue Engineering

Abstract

(1) Background: Macroporous hydrogel scaffolds based on poly [N-(2-hydroxypropyl) methacrylamide] are one of the widely studied biocompatible materials for tissue reparation and regeneration. This study investigated the morphological changes during hydrogel characterization which can significantly influence their future application. (2) Methods: Three types of macroporous soft hydrogels differing in pore size were prepared. The macroporosity was achieved by the addition of sacrificial template particles of sodium chloride of various sizes (0–30, 30–50, and 50–90 µm) to the polymerizing mixture. The 3D structure of the hydrogels was then investigated by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). The SEM was performed with specimens rapidly frozen to various temperatures, while non-frozen gels were visualized with LSCM. (3 and 4) Results and Conclusion: In comparison to LSCM, the SEM images revealed a significant alteration in the mean pore size and appearance of newly formed multiple connections between the pores, depending on the freezing conditions. Additionally, after freezing for SEM, the gel matrix between the pores and the fine pores collapsed. LSCM visualization aided the understanding of the dynamics of pore generation using sodium chloride, providing the direct observation of hydrogel scaffolds with the growing cells. Moreover, the reconstructed confocal z-stacks were a promising tool to quantify the swollen hydrogel volume reconstruction which is not possible with SEM.

Image analysis method for heterogeneity and porosity characterization of biomimetic hydrogels

“…Readers are encouraged to refer to the studies specialized on the imaging of different hydrogel network by Kalasova et. al 1 and Pradny et. al 2 .…”

Compressive Mechanical Behavior of Partially Oxidized Polyvinyl Alcohol Hydrogels for Cartilage Tissue Repair

“…Moreover, an additional characterization of the microstructure and porosity of PVA hydrogels could be carried out to determine the void ratio by means of different methods. For example, cryogenic Scanning Electron Microscopy (cryo-SEM) is often adopted to determine the pore size through image analysis [ 54 , 55 ]; however, cryo-SEM does not allow to accurately determine the total volume of porosity in a bulk sample. Also, the relaxation times measured via nuclear magnetic resonance (NMR) in hydrogels have been used to obtain the pore radius distribution profiles [ 56 ].…”

The potential of eggshell hydroxyapatite, collagen, and EGCG (HAp-Col-EGCG) scaffold as a pulp regeneration material

“…The morphology of the HAp-Col-EGCG scaffold was analyzed using SEM-EDX (Hitachi S4700, Tokyo, Japan). Before the SEM imaging, HAp-Col-EGCG hydrogels were freeze-dried at − 80 °C for 24 h. The freeze-dried samples were coated with an Au layer, and we measured the largest and smallest pore diameters ( Mulyawan et al, 2022 , Podhorská et al, 2020 ).…”