Compositional alterations of fibrin-based materials for regulating in vitro neural outgrowth

The purpose of this investigation was to evaluate dorsal root ganglion (DRG) cell outgrowth in a biosynthetic material made from PEGylated fibrinogen and in thrombin-polymerized fibrin hydrogels. The hypothesis stipulated that changing the composition of the biosynthetic constituents of the hydrogel can be used to better regulate the rate of DRG cell invasion when compared to reconstituted fibrin hydrogels. The composition of the biosynthetic hydrogel was controlled by the relative amount of poly(ethylene glycol) (PEG) to fibrinogen or by the fibrinogen concentration in the material. Other PEGylated protein hydrogels including PEGylated collagen and PEGylated albumin were used as positive and negative controls, respectively, for DRG cell outgrowth studies. The PEGylated fibrinogen hydrogels readily supported extensive outgrowth of sprouting neurites and invading glial cells from encapsulated DRGs in the presence of nerve growth factor. The PEGylated fibrinogen hydrogels exhibited preferential neurite invasion whereby the nonneuronal cells were observed lagging behind the invading neurites. Hydrogels containing more PEG or fibrinogen reduced the lag between the cell types and also the overall rate of the cellular invasion. Time-lapse video microscopy and quantitative cellular invasion data were used to illustrate the effectiveness of controlling DRG cell outgrowth characteristics in PEGylated fibrinogen hydrogels when compared to their respective reconstituted protein hydrogel counterparts.