We propose to develop a novel fibrillar scaffold for artificial tissue growth that combines the key attributes of synthetic biomaterials and fibrillar biopolymers, Synthetic biomaterials allow for defined composition tailored for selective cell adhesion with no risk of viral or pathogen transmission. Fibrillar biopolymer gels, such as type I collagen and fibrin, allow cellularity to be obtained directly by cell entrapment during self-assembly and are conducive to structural and compositional remodeling. For the preparation of worm-like micelle (WLM) scaffolds we will use block copolymers that contain at least three distinct regions: a crosslinkable hydrophobic core, a hydrophilic corona, and a cell adhesion peptide. The hydrophobic core will be degradable under physiological conditions (e.g., polyaliphatic esters). Polyethylene oxide (PEO) will be used as the hydrophilic component and simple cell adhesion peptides will be conjugated to the PEO terminus. After formation of a cell suspension with the WLM in aqueous solution, the hydrophobic cores of the WLMs will be chemically fixed through simple catalytic cross linking, allowing direct cell entrapment into an entangled network of stable but ultimately degrading WLMs, analogous to the fibrillar bi0polymers. Rheometry, cryo-TEM, and SAXS will be used to verify the integrity of the WLM network and to characterize physical properties relevant to cell-network mechanical interactions that lead to network contraction and alignment when a mechanical constraint is applied. The molecular parameters of the amphiphilic block copolymers will be systematically tuned to control the WLM formation, crosslinking density, degradation rates and ultimate mechanical behavior. Efforts to approximate the relevant material properties of the biopolymer gels will be emphasized. With cells entrapped into a cross-linked WLM network, cell induced network compaction and alignment will be analyzed using quantitative polarized light microscopy, and the evolving WLM degradation and ECM deposition characterized using biochemical and histological analyses. Molecular weights and cross-link density will be adjusted accordingly, and various degradable cores will be pursued as necessary, if degradation and deposition occur on disparate time scales. Cell viability and polymer degradation will be monitored. Ultimate mechanical properties, ECM composition, and ECM structure of the artificial tissues following in vitro incubation will be compared to soft connective tissues. The resultant artificial tissues will be assayed in a rat subcutaneous implantation model to assess biocompatibility.
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| Jain, Sumeet; Bates, Frank S (2003) On the origins of morphological complexity in block copolymer surfactants. Science 300:460-4 |
