Research Of Peptides/Surfactants Co-Assembling System

Self-assembly is a promising approach to fabricate novel materials and devices on nanoscale.Comparing with proteins and polypeptides,the self-assembly of short peptides offer various benefits for new material development,such as facilitation of synthesis,easy modification of molecular structures and rational fabrication of functional materials through“bottom-up”strategy.Building hybrid systems which contain peptides and heterogeneous components are less studied although it is a facil route to regulate the conformation and self-assembly morphology of peptides.In this thesis,we chose three peptides with different constructions in order to study relationship between peptide/surfactant structures and their co-assembly property of the hybrid systems.Meanwhile,properties of obtained co-assemblies were evalueated.The microstructures and properties of I₃E/C₁₄DMAO mixture were characterized by transmission electron microscopy（TEM）,scanning electron microscopy（SEM）,atomic force microscopy（AFM）and HAAKE rotational rheometer.Fourier transform infrared（FT-IR）,X-ray diffraction（XRD）and circular dichroism（CD）were used to explore the formation mechanism of different microstructures.It was found that,with the increasing of C₁₄DMAO,the self-assembly structures of I₃E/C₁₄DMAO mixture changed from nanofibers to nanosheets,and finally to wormlike micelles and spherical micelles.And the rheological properties of the mixture changed with the increasing of C₁₄DMAO concentration.Adding anionic surfactant SDS to a bola amphiphilic peptide KI₄K could result in the reconstruction ofβ-sheet secondary structure besides the changes in self-assembly morphologies from nanotubes to helical ribbons,nanofibers or straight nanotapes according to the negatively stained transmission electron microscopy,atomic force microscopy,circular dichroism spectroscopy and Fourier transform infrared spectroscopy results.Through comparison to other surfactants,including CTAB,C₁₂EO₄ and AOT,we proposed that the transitions of KI₄K self-assemblies induced by anionic surfactants could be mainly attributed to the effect of hydrophobic interaction and electrostatic attraction between surfactants and peptide molecules.At last,a lipopeptide OA-SS/nonionic surfactant F127 dug loading system was fabricated.The effects of preparation methods,peptide concentration,pH and buffer on vesicle morphology were invesgated using TEM.After corresponding conditional optimizations,vesicals were obtained through peptide self-assembing instead of the tradional thin lipid film hydration method.We found that adding surfactant F127 has a strong impact on vesicle size,Zeta potential,poly-dispersity index and the sustained-release properties.Ultimately,hybrid vesicles with higher encapsulation efficiency and better sustained-release perfomance were gained.