Characterisation and performance of hydrogel tissue scaffolds

Abstract

Porosity over a broad range (typically 0.001–300 μm in diameter) of tissue scaffolds provides appropriate conditions for diffusion and adsorption of small molecules and macromolecules, migration of cells through the scaffold, and adequate cell proliferative capacity. Characterisation of pores over this large range poses a problem especially when analysing soft polymer hydrogels, as no one methodology can adequately cover the entire range. This work describes a combined technique used for evaluation of the porous structure of a collagen hydrogel (dermal substitute Integra®) on the basis of NMR-cryoporometry (sensitive to nanopores) and confocal laser scanning microscopy (CLSM) imaging (sensitive to macropores). Thermodesorption of water, diffusion of proteins through a collagen membrane, migration and growth of normal primary human skin fibroblasts, and the interaction kinetics of 3T3 mouse fibroblast cells (using a quartz crystal microbalance) with collagen were analysed with respect to the porous structure of the material. The contribution to the total porosity of pores with a diameter of less than 100 nm is low, at approximately 3–5%, a figure estimated using the methods described above. However, these pores are the main contributor to the specific surface area (S ≈ 120 m2 g−1) as larger diameter macropores, with diameters of 20–200 μm, have a much lower surface area at S ≈ 0.4 m2 g−1 relative to their large pore volume V = 14.4 cm3 g−1

Cryogels: Morphological, structural and adsorption characterisation

“…However, in some papers, the PSD and other textural characteristics were determined in detail using mercury porosimetry [78] and analysis of images [3,76,[105][106][107][108]. There are several papers describing the PSD of native polymer cryogels over the total range of pore sizes from narrow nanopores (d nn < 2 nm) to macropores at d macro > 100…”

“…m [3,[105][106][107][108]. In these papers, the structural characterisation was based on several techniques such as confocal laser scanning microscopy (CLSM), SEM, cryo-SEM, and other microscopic techniques with subsequent quantitative analysis of microscopic images of both native hydrated and freeze-dried cryogels.…”

“…In the case of preparation of AC filled cryogels [105][106][107][108], PVA as a matrix polymer and glutaraldehyde (GA) as a cross-linker were used at a varied ratio of their concentrations. The cryogel synthesis is relatively simple, which is an important advantage of this technique.…”

“…For deeper 21 insight into this problem, these characteristics were studied in detail for both native hydrated and freeze-dried samples of the same cryogels [105][106][107][108]. The cryogel samples for SEM analysis were prepared by freeze-drying during relatively long time [105,106]. After drying, specimens were mounted on metal stubs fitted with adhesive carbon pads, sputter coated with palladium and examined using SEM.…”

“…2a) was not done [76]. We calculated the PSD ( simplified approach in comparison with the techniques described in papers [105][106][107][108], vide infra).…”