Thixotropic peptide-based physical hydrogels applied to three-dimensional cell culture

Pseudopeptides containing the D-Oxd or the D-pGlu [Oxd = (4R,5S)-4-methyl-5-carboxyl-oxazolidin-2-one, pGlu = pyroglutamic acid] moiety and selected amino acids were used as low molecular weight gelators (LMWGs) to prepare strong and thixotropic hydrogels at physiological pH. The addition of calcium chloride to the gelators solutions induces the formation of insoluble salts that get organized in fibers at a pH close to the physiological one. Physical characterization of hydrogels was carried out by morphologic evaluation and rheological measurements and demonstrate that the analyzed hydrogels are thixotropic, as they have the capability to recover their gel-like behavior. As these hydrogels are easily injectable and may be used for regenerative medicine, they were biologically assessed by cell seeding and viability tests. Human gingival fibroblasts were embedded in 2% hydrogels: all the hydrogels allow the growth of encapsulated cells with a very good viability. The gelators toxicity may be correlated with their tendency to self-assemble, and is totally absent when the hydrogel is formed.