Determination of pore size distribution at the cell-hydrogel interface
1 Department of Cell Technology and Applied Stem Cell Biology, Biotechnology and Biomedicine Centre (BBZ), University of Leipzig. Deutscher Platz 5, 04103, Leipzig, Germany
2 Institute for Medical Informatics, Statistics, and Epidemiology (IMISE), University of Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany
3 Interdisciplinary Center for Bioinformatics (IZBI), University of Leipzig, Härtelstraße 16-18, 04107 Leipzig, Germany
4 Materials Science Institute of Seville (Spanish National Research Council (CSIC) - University of Seville), Centro de Investigaciones Científicas Isla de la Cartuja, Avda. Americo Vespucio no. 49, 41092 Sevilla, Spain
5 Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Spain
6 Institute of Anatomy, Medicine Faculty, University of Leipzig, Liebigstrasse 13, 04103 Leipzig, Germany
Journal of Nanobiotechnology 2011, 9:24 doi:10.1186/1477-3155-9-24Published: 27 May 2011
Analyses 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.
Here, 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.
The 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.