Peptide-based self-assembling systems and their characterization by transmission electron microscopy
Yuwono, Virany Mylon
Hartgerink, Jeffrey D.
Doctor of Philosophy
In this work, several peptide-based self-assembling systems were studied. The first system is the peptide amphiphile nanofibers that serve as catalyst and organic template for silica mineralization from tetraethylorthosilicate (TEOS) precursors to synthesize silica nanotubes with tunable dimensions. The catalytic activities of peptide-amphiphiles containing lysine, histidine, or glutamic acid were compared and only peptide amphiphiles containing lysine or histidine were found to be good catalytic templates. The second self-assembling system is the multidomain peptide nanofibers that promote hydroxyapatite mineralization on their surface. The peptide sequence includes glutamic acids for calcium binding and cysteines for oxidative cross-linking. Addition of inorganic precursors yields hydroxyapatite-coated peptide nanofibers as characterized by vitreous ice cryo-TEM and energy dispersive x-ray spectroscopy. The third system is the 14-helix beta-peptides. Carefully designed beta-peptides have been observed to form lyotropic liquid crystals (LCs), whose liquid crystallinity is dependent on concentration and temperature. Cryo-TEM analysis was performed on two sets of liquid crystalline and non-liquid crystalline beta-peptides, each having the same amino acid composition but different sequence to study their nanostructures. Based on the cryo-TEM data, LC-forming beta-peptides are capable to self-assemble into higher ordered nanofibrous structure that becomes the mesogenic species in the liquid crystal. On the contrary, non-LC beta-peptides form only globular aggregates. Finally, transmission electron microscopy is highlighted as a characterization method in several projects. TEM analysis elucidates the degradation behavior of peptide amphiphile hydrogel extracellular matrix mimic that contains an enzyme-cleavable site. The peptide amphiphile hydrogel was evaluated as a tissue engineering scaffold by cell culture studies of two dental stem cell lines. The cell hydroxyapatite mineralization activity was analyzed using cryo-TEM, which revealed that the two cell lines exhibit different propensity towards mineral deposition. TEM and cryo-TEM were also performed to characterize peptide coated single-walled carbon nanotubes in an effort to non-covalently solubilize them in aqueous environment.
Inorganic chemistry; Organic chemistry