Determination of pore size distribution at the cell-hydrogel interface

Abstract

BackgroundAnalyses of the pore size distribution in 3D matrices such as the cell-hydrogel interface are very useful when studying changes and modifications produced as a result of cellular growth and proliferation within the matrix, as pore size distribution plays an important role in the signaling and microenvironment stimuli imparted to the cells. However, the majority of the methods for the assessment of the porosity in biomaterials are not suitable to give quantitative information about the textural properties of these nano-interfaces.FindingsHere, we report a methodology for determining pore size distribution at the cell-hydrogel interface, and the depth of the matrix modified by cell growth by entrapped HepG2 cells in microcapsules made of 0.8% and 1.4% w/v alginate. The method is based on the estimation of the shortest distance between two points of the fibril-like network hydrogel structures using image analysis of TEM pictures. Values of pore size distribution determined using the presented method and those obtained by nitrogen physisorption measurements were compared, showing good agreement. A combination of these methodologies and a study of the cell-hydrogel interface at various cell culture times showed that after three days of culture, HepG2 cells growing in hydrogels composed of 0.8% w/v alginate had more coarse of pores at depths up to 40 nm inwards (a phenomenon most notable in the first 20 nm from the interface). This coarsening phenomenon was weakly observed in the case of cells cultured in hydrogels composed of 1.4% w/v alginate.ConclusionsThe method purposed in this paper allows us to obtain information about the radial deformation of the hydrogel matrix due to cell growth, and the consequent modification of the pore size distribution pattern surrounding the cells, which are extremely important for a wide spectrum of biotechnological, pharmaceutical and biomedical applications.

Three-Dimensional-Engineered Matrix to Study Cancer Stem Cells and Tumorsphere Formation: Effect of Matrix Modulus

“…For example, HepG2 hepatocellular carcinoma cells form larger spheres when encapsulated in alginate gels with larger pore sizes. 72 The mesh size of the PEGDA gels was calculated from the modulus and equilibrium swelling ratio of the gels using the Peppas and Barr-Howell equation, as described. 73 As the macromer concentration was increased from 7.5% to 10%, 15%, 20%, and 25%, the mesh size decreased significantly from 93 -4 nm to 67 -3, 53 -3, 34 -2, and 25 -2 nm, respectively.…”

Alginic acid cell entrapment: a novel method for measuring in vivo macrophage cholesterol homeostasis

“…Lowering the alginate concentration increases the pore size ( 37 ). Leal-Egaña and colleagues ( 38 ) have determined the pore size distribution of different concentrations of alginate gels using both N 2 adsorption and image analysis. At both 0.8% and 1.4% alginate (w/v), the pore-size distribution ranged from <10 nm up to 70 nm, with the average pore size being greater at 0.8% alginate.…”

Biointerface dynamics – Multi scale modeling considerations

“…In that case, the second terms of Eqs. (25) and (26) additionally contribute to elastic Hookean behavior. When meso S → 1, we obtain C 0 D 1 t (ε m (r, t, )) → ∂ε m (r, t, )/∂t and r, t, )) → ∂θ m (r, t, )/∂t.…”

“…The first terms of the right hand side of Eqs. (25) and (26) represent the reversible (elastic) part and the second terms include the anomalous nature of the matrix stress generation. If the parameter m = 0, we obtain C 0 D 0 t (ε m (r, t, )) =ε m (r, t, ) and C 0 D 0 t (θ m (r, t, )) =θ m (r, t, ).…”

“…Matrix structural changes caused by immobilized cell aggregate expansion include the following steps: (1) immobilized aggregates induce radial deformations of surrounding hydrogel matrix during the aggregates expansion [25], (2) radial deformations induce generation of the matrix resistance stress around the aggregates [9,25,26], (3) generated resistance matrix stress induces feedback generation of the internal stress within the cell aggregates [18,26] and (5) the internal stress provokes a biological response of cells [8,9]. Immobilized cell aggregate rearrangement and growth is driven by the internal cell stress generated within the aggregate.…”