Characterization of a peptide biomaterial used for cell-seeded scaffolds with an analysis of relevant stem cell policy

Abstract

(cont.) We describe the ethical debate and political climate that led to the decision. An examination of the publication data shows that researchers in the United States have in fact remained leaders in the field until this point, in part because U.S. federal funding has also been available to early mover international groups who appear to have abided by the restrictions.

Restoring damaged or diseased tissue in the body may involve the use of biomaterial scaffolds that provide a responsive environment for cell proliferation. Such scaffolds may be used for in situ cell regeneration, where an implanted scaffold incites cell growth in the body, as well as for growing artificial tissue in vitro by seeding cells in a scaffold that will be implanted at a later stage of development or used for physiological tissue models. The research outlined in this thesis describes two methods of characterizing the stiffness of a biomaterial scaffold. It is well known that cell growth in vitro is affected by the moduli of the surrounding scaffold. Stiffness is also cited as a major factor affecting angiogenesis, the formation of new blood vessels. We describe a new rheometric method to examine the bulk mechanical properties of a self-assembling peptide biomaterial that spontaneously forms a filament network in a physiological salt solution and supports cell attachment and differentiation. This method has two major advantages: first, it reduces the time per sample and second, it can be used to analyze materials where cross-linkers must be added and washed out. We also have also used fluorescence microscopy and wrote a program to find the persistence length of actin filaments in the eventuality that peptide filaments can be reliable isolated. This self-assembling peptide biomaterial has shown great promise as a scaffold for differentiated cells and has also been shown to support adult liver stem cells. Therefore it is likely that it can support human embryonic stem cells. The second half of this thesis describes the ramifications of the policy decision on August 9, 2001 to limit federal funding to existing cell lines.