Studies fo the microstructure of self-assembling peptides : effects of chemical cross-linking and growth characterization

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2005.Includes bibliographical references (p. 32-33).Peptide is a b iomaterial with great promise in tissue engineering because it has known to be capable of self-assembly. Also, the peptide scaffolds can support neuronal cell attachment, differentiation, and neuron outgrowth. They might therefore p lay a role as substrate for functional synapse formation between neurons. One important feature of peptide gel is that its modulus can modulate cell motility in combination with the observation that streptavidin and biotin can be used to increase the peptide gel's modulus as measured by rheometery that raises the prospect of controlling cell function by control of matrix physical properties. Atomic force microscope (AFM) was used to reveal the mechanism of modulus change at the nano and microscales. AFM images show that as the amount of biotinylated peptide increases, self-assembly effect is impeded and there are more but smaller aggregates. Streptavidin tethers to regular peptide as well as biotinylated peptide. Also, streptavidin and biotin can cross-link peptide fibrils. These AFM results can explain the increased modulus found by rheometry. To better describe the growth from individual monomers to filaments, and to exert a measure of control over the nature of network or characteristics of individual filaments requires a better fundamental understanding of the process of filament formation. Therefore, we observed the growth of RAD16- II by self-assembly in order to gain better understanding of process by which filaments grow. Through a combination of AFM and dynamic light scattering we are able to characterize peptide growth quickly and easily. Dynamic light scattering (DLS) provides a single and convenient means to follow peptide filament growth with time.by Woncheol Jeong.S.M