Polymer ummantelte Peptidnanoröhren: Synthese, Strukturuntersuchungen & Eigenschaften.
Final Report Abstract
When conjugating small peptides to synthetic polymers, i.e. designing so-called peptidepolymer hybrid materials, one can make use of peptide modules to ,,guide“ the structure of soft polymeric and supramolecular materials. With respect to the latter, in our group, we have developed so-called “peptide polymer nanotubes” (PPNTs), which are shape-defined nanoscale rod-like objects having a core-shell morphology, where self-assembled cyclic peptides form a stiff inner core, surrounded by a soft polymeric shell. PPNTs can be prepared via in-situ surface-initiated atom transfer radical polymerization (ATRP) from the surface of the self-assembled cyclic peptide nanotubes decorated with ATRP-initiator sites on the outer surface (PNT-ini). In a previous study it was shown in first experiments that the diameter and length of PPNTs in the dry, solvent-free state is directly coupled, i.e. an increase in mass of tethered polymer chains results in an increase of the diameter of PPNTs, and simultaneously, a decrease of the length of PPNTs. At the end of this previous work, there was the hypothesis that the length reduction of PPNTs can be attributed to strong polymer-polymer interactions, i.e. ‘excluded volume interactions’, leading to strong lateral stress across the PPNT-backbone. In the present studies, we designed PMMA-grafted peptide nanotubes. These materials were characterized with respect to structure-evolution at varying molar mass, and grafting density of the peptide-attached polymer. Our further investigations showed that indeed, the length reduction is independent of the chemistry of the grafted polymers. In order to understand this in more detail, we described this length reduction for the first time, using a simple scaling analysis that was initially derived for so-called molecular bottle brushes. At high grafting densities, the length of peptide-polymer hybrid nanotubes follows a My8 dependency, whereas at low grafting density, and/or at low molar mass of grafted polymers, no break-up of the hybrid materials was observed. Thus, we learned that the structure of the hybrid nanorod is not only guided by the “structure-guiding” capability of the self-assembling cyclic peptide, but it is strongly influenced by the length and grafting density of the peptide-attached polymer molecules. Next, we showed that by (in situ) cross-linking the shell of peptide-polymer nanotubes, length and diameter can be independently addressed through adjusting appropriate polymerization parameters. However, we also discovered limitations with respect to control the the structure of shell cross-linked peptide polymer nanotubes. The latter is likely due to limitations of using ATRP in surface-initiated (in situ) cross-linking reactions. To overcome these limitations, one may think of using other polymerization techniques in the future, or to develop cross-linked peptide polymer nanotubes by forming a polymer network after polymerization. Finally, we developed for the first time a PEGylated CP-ini molecule, which is soluble in a number of different organic solvents and thus may become interesting to broaden possibilities with respect to self-assembly of functional cyclic peptides in future work. Initially, we intended to also study the self-assembly of such peptide-polymer molecules, as well as investigate the structure of peptide-polymer hybrids in contact with solvents. Due to unforeseen circumstances (moving of the whole group from Freiburg to Darmstadt in 2008), unfortunately these exciting questions have yet not been addressed.
Publications
- Polymer-wrapped peptide nanotubes: peptide-grafted polymer mass impacts length and diameter, Small 2008, 4, 1008-1016
J. Couet, and M. Biesalski
- Surface-initiated polymerization from self-assembled tubular macroinitiators. Freiburg, 2008
J. Couet
- Tailor-made peptide-polymer hybrid materials: from peptide-guided polymer nanostructures to bioactive surfaces that promote the adhesion of living cells. Universität Freiburg 2008
M. Biesalski
- Polymer-wrapped peptide nanotubes: peptide-grafted polymer mass impacts length and diameter, Phys. Stat. Solidi A 2010, 3, 468-473
R. Gokhale, J. Couet, and M. Biesalski
- Synthesis and Characterization of Polymer Coated, Self-Assembled Peptide Nanotubes - towards Tailor-Made Soft Nanorods Darmstadt, 2012
R. Gokhale:
