Seite - (000251) - in Biomedical Chemistry: Current Trends and Developments

Fmoc-peptides (Orbach, 2009) Fluorenylmethoxy-carbonyl (Fmoc)-protected amino acids and dipeptides can form hydrogels. The Fmoc moiety is widely used as a protecting group in peptide synthesis and it was even reported that a number of Fmoc-amino acids show anti-inflammatory properties β-sheet (Loo, 2013; Hauser & Zhang, 2010) β-sheet peptides are ionic self-complementary, as a result of positive and negative side chains on one side of the β –sheet and hydrophobic side chains on the other. This motif causes the peptides to fold into β-sheet secondary structures with distinct hydrophobic and hydrophilic surfaces. The hydrophobic side forms a double sheet inside of a nanofiber and the hydrophilic side becomes the exterior of the nanofibers, which interacts with water molecules to form an extremely high water content hydrogel. The 4 ionic self-complementary peptides RADA16-I, RAD16-II, EAK-I and EAK16-II form stable β –sheet structures in water and undergo spontaneous assembly to form nanofiber scaffolds α-helical coiled coil (Stephanopoulos, 2013) α-helices result from the hydrogen bonding of a peptide backbone amide hydrogen to a backbone carbonyl four residues away. This motif results in a right-handed helical twist configuration. The formation of α-helices is determined by the amino acid sequence and is dependent on hydrophilic and hydrophobic amino acid residues organizing into a hydrophobic and a hydrophilic face. The gelation can be controlled using heat to provide a versatile scaffold for cell culture, especially when gel dissolution at elevated temperatures is desired. The α-helical peptide gels proved highly cytocompatible, and PC12 cells cultured in them were able to proliferate and differentiate Peptide amphiphiles (Cui, 2010; Matson, 2011; Matson & Stupp, 2012) Peptide amphiphiles are short peptide sequences attached to a hydrophobic tail, usually an alkyl chain. Peptide amphiphiles combine the structural features of amphiphilic surfactants with the functions of bioactive peptides and are known to assemble into a variety of nanostructures 3.1.3.4 Therapeutic Peptides and Market The obstacles that remain for the development of peptides as therapeutics are significant. As in all drug development, in vivo efficacy might differ from promising in vitro models. The reason can be the result of interactions with many in vivo components in the circulation, gastrointestinal tract, dermis, relative clearance and affinity to target receptors (Lin & Lowman, 2003). The main limitations generally attributed to therapeutic peptides are (i) oral bioavailability (injection is normally required), (ii) short half-life