Agarose e

Hydrogels with distinct gelation mechanisms (physical, ionic, chemical crosslinking) [20 (link)] were studied. As an example of a physically crosslinked matrix, the linear thermoreversible polysaccharide agarose (Agarose E, Condalab, Madrid, Spain) at 1 wt.%, was used [21 (link)]. As an example of an ionically crosslinked matrix, sodium alginate (Sigma-Aldrich, Prague, Czech Republic) at 2 wt.% crosslinked by calcium chloride (Lach-Ner, Neratovice, Czech Republic) at a two to one weight ratio was chosen [22 (link)]. For chemically crosslinked hydrogels, poly(vinyl alcohol) (Sigma-Aldrich, Prague, Czech Republic) mixed with chitosan (low molecular weight, Sigma-Aldrich, Prague, Czech Republic) and crosslinked by epichlorohydrin (Sigma-Aldrich, Prague, Czech Republic) was employed [23 (link)]. L-α-Phosphatidylcholine (lecithin) was incorporated into all hydrogel samples before gelation at three different weight percentage concentrations (Sigma-Aldrich, Czech Republic, Prague).
The materials and their concentrations and ratios were selected on the basis of data previously reported [20 (link),21 (link),22 (link),23 (link),24 (link)] and can be seen in the table below (Table 10).

Differently crosslinked hydrogel matrices and the effect of lecithin on their properties were studied. Three different crosslinking mechanisms were studied: physical, ionic, and chemical. Agarose E was purchased from Condalab (Madrid, Spain), calcium chloride from Lach-Ner (Neratovice, Czech Republic), and sodium alginate, poly(vinyl alcohol), chitosan, epichlorohydrin, and L-α-Phosphatidylcholine (lecithin) were all purchased from Sigma-Aldrich (Prague, Czech Republic). Dyes used for diffusion experiments differed in charge: positively charged rhodamine 6G (Sigma-Aldrich, Prague, Czech Republic), negatively charged amido black 10B (Merck, Darmstadt, Germany), and eosin B (Sigma-Aldrich, Prague, Czech Republic) were used.