Nanostructuring biosynthetic hydrogels for tissue engineering: A cellular and structural analysis

The nanostructuring of hydrogel scaffolds used in tissue engineering provides the ability to control cellular fate and tissue morphogenesis through cell-matrix interactions. Here we describe a method to provide nanostructure to a biosynthetic hydrogel scaffold made from crosslinked poly(ethylene glycol)-fibrinogen conjugates (PEG-fibrinogen), by modifying them with the block-copolymer Pluronic (R) F127. The copolymeric additive self-assembled into micelles at certain concentrations and temperatures, thereby creating nanostructures within the crosslinked hydrogel. Small-angle X-ray scattering (SAXS) and transmission electron microscopy at cryogenic temperature were used to detect Pluronic (R) F127 micelles embedded within the crosslinked PEG-fibrinogen hydrogels. The density and order of the micelles within the hydrogel matrix increased as the relative Pluronic (R) F127 concentration was raised. The transient stability of the micelles within the hydrogel network was analyzed using time-dependent swelling and Pluronic (R) F127 release measurements. These characterizations revealed that most of the Pluronic (R) F127 molecules diffuse out of the hydrogels after 4 days in aqueous buffer and SAXS analysis confirmed a significant change in the structure and interactions of the micelles during this time. Cell culture experiments evaluating the three-dimensional fibroblast morphology within the matrix indicated a strong correlation between cell spreading and the hydrogel's characteristic mesh size. The present research thereby provides a more quantitative understanding of how structural features in an encapsulating hydrogel environment can affect cell morphogenesis towards tissue regeneration. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.