Dual self-assembly of supramolecular peptide nanotubes to provide stabilisation in water.
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ABSTRACT:
PROVIDER: S-EPMC6797743 | BioStudies |
REPOSITORIES: biostudies
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Project description:Peptide amphiphiles (PAs) previously designed in our laboratory are known to self-assemble into nanofibers that exhibit bioactivity both in vitro and in vivo. Self-assembly can be triggered by charge neutralization or salt-mediated screening of charged residues in their peptide sequences, and the resulting nanofibers can form macroscopic gels at concentrations as low as 0.5% by weight. Controlling the kinetics of gelation while retaining the bioactivity of nanofibers could be critical in tailoring these materials for specific clinical applications. We report here on a series of PAs with different rates of gelation resulting from changes in their peptide sequence without changing the bioactive segment. The pre-existence of hydrogen-bonded aggregates in the solution state of more hydrophobic PAs appears to accelerate gelation kinetics. Mutation of the peptide sequence to include more hydrophilic and bulky amino acids suppresses formation of these nuclei and effectively slows down gelation through self-assembly of the nanofiber network. The ability to modify gelation kinetics in self-assembling systems without disrupting bioactivity could be important for injectable therapies in regenerative medicine.
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Project description:The variety and complexity of DNA-based structures make them attractive candidates for nanotechnology, yet insufficient stability and mechanical rigidity, compared to polyamide-based molecules, limit their application. Here, we combine the advantages of polyamide materials and the structural patterns inspired by nucleic-acids to generate a mechanically rigid fluorenylmethyloxycarbonyl (Fmoc)-guanine peptide nucleic acid (PNA) conjugate with diverse morphology and photoluminescent properties. The assembly possesses a unique atomic structure, with each guanine head of one molecule hydrogen bonded to the Fmoc carbonyl tail of another molecule, generating a non-planar cyclic quartet arrangement. This structure exhibits an average stiffness of 69.6 ± 6.8 N m<sup>-1</sup> and Young's modulus of 17.8 ± 2.5 GPa, higher than any previously reported nucleic acid derived structure. This data suggests that the unique cation-free "basket" formed by the Fmoc-G-PNA conjugate can serve as an attractive component for the design of new materials based on PNA self-assembly for nanotechnology applications.
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Project description:Biocompatible hydrogels have a wide variety of potential applications in biotechnology and medicine, such as the controlled delivery and release of cells, cosmetics and drugs, and as supports for cell growth and tissue engineering. Rational peptide design and engineering are emerging as promising new routes to such functional biomaterials. Here, we present the first examples of rationally designed and fully characterized self-assembling hydrogels based on standard linear peptides with purely alpha-helical structures, which we call hydrogelating self-assembling fibres (hSAFs). These form spanning networks of alpha-helical fibrils that interact to give self-supporting physical hydrogels of >99% water content. The peptide sequences can be engineered to alter the underlying mechanism of gelation and, consequently, the hydrogel properties. Interestingly, for example, those with hydrogen-bonded networks of fibrils melt on heating, whereas those formed through hydrophobic fibril-fibril interactions strengthen when warmed. The hSAFs are dual-peptide systems that gel only on mixing, which gives tight control over assembly. These properties raise possibilities for using the hSAFs as substrates in cell culture. We have tested this in comparison with the widely used Matrigel substrate, and demonstrate that, like Matrigel, hSAFs support both growth and differentiation of rat adrenal pheochromocytoma cells for sustained periods in culture.
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Project description:We here report a new approach to develop self-healing shape memory supramolecular liquid-crystalline (LC) networks through self-assembly of molecular building blocks <i>via</i> combination of hydrogen bonding and coordination bonding. We have designed and synthesized supramolecular LC polymers and networks based on the complexation of a forklike mesogenic ligand with Ag<sup>+</sup> ions and carboxylic acids. Unidirectionally aligned fibers and free-standing films forming layered LC nanostructures have been obtained for the supramolecular LC networks. We have found that hybrid supramolecular LC networks formed through metal-ligand interactions and hydrogen bonding exhibit both self-healing properties and shape memory functions, while hydrogen-bonded LC networks only show self-healing properties. The combination of hydrogen bonds and metal-ligand interactions allows the tuning of intermolecular interactions and self-assembled structures, leading to the formation of the dynamic supramolecular LC materials. The new material design presented here has potential for the development of smart LC materials and functional LC membranes with tunable responsiveness.
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Project description:The enzymatic cleavage of a peptide amphiphile (PA) is investigated. The self-assembly of the cleaved products is distinct from that of the PA substrate. The PA C16-KKFFVLK is cleaved by ?-chymotrypsin at two sites leading to products C16-KKF with FVLK and C16-KKFF with VLK. The PA C16-KKFFVLK forms nanotubes and helical ribbons at room temperature. Both PAs C16-KKF and C16-KKFF corresponding to cleavage products instead self-assemble into 5-6 nm diameter spherical micelles, while peptides FVLK and VLK do not adopt well-defined aggregate structures. The secondary structures of the PAs and peptides are examined by FTIR and circular dichroism spectroscopy and X-ray diffraction. Only C16-KKFFVLK shows substantial ?-sheet secondary structure, consistent with its self-assembly into extended aggregates, based on PA layers containing hydrogen-bonded peptide headgroups. This PA also exhibits a thermoreversible transition to twisted tapes on heating.
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