Tunable and modular assembly of polypeptides and polypeptide-hybrid biomaterials

Abstract

Biomaterials are materials that are speci cally designed to be in contact with biological systems and have for a long time been used in medicine. Examples of biomaterials range from sophisticated prostheses used for replacing outworn body parts to ordinary contact lenses. Currently it is possible to create biomaterials that can e.g. speci cally interact with cells or respond to certain stimuli. Peptides, the shorter version of proteins, are excellent molecules for fabrication of such biomaterials. By following and developing design rules it is possible to obtain peptides that can self-assemble into well-de ned nanostructures and biomaterials. e aim of this thesis is to create "smart" and tunable biomaterials by molecular self-assembly using dimerizing α-helical polypeptides. Two di erent, but structurally related, polypeptide-systems have been used in this thesis. e EKIV-polypeptide system was developed in this thesis and consists of four 28-residue polypeptides that can be mixed-and-matched to self-assemble into four di erent coiled coil heterodimers. e dissociation constant of the di erent heterodimers range from µM to < nM. Due to the large di erence in a nities, the polypeptides are prone to thermodynamic social self-sorting. e JR-polypeptide system, on the other hand, consists of several 42-residue de novo designed helix-loop-helix polypeptides that can dimerize into four-helix bundles. In this work, primarily the glutamic acid-rich polypeptide JR2E has been explored as a component in supramolecular materials. Dimerization was induced by exposing the polypeptide to either Zn 2+ , acidic conditions or the complementary polypeptide JR2K.By conjugating JR2E to hyaluronic acid and the EKIV-polypeptides to star-shaped poly(ethylene glycol), respectively, highly tunable hydrogels that can be self-assembled in a modular fashion have been created. In addition, self-assembly of spherical superstructures has been investigated and were obtained by linking two thiol-modi ed JR2E polypeptides via a disul de bridge in the loop region.e thesis also demonstrates that the polypeptides and the polypeptide-hybrids can be used for encapsulation and release of molecules and nanoparticles. In addition, some of the hydrogels have been explored for 3D cell culture. By using supramolecular interactions combined with bio-orthogonal I covalent crosslinking reactions, hydrogels were obtained that enabled facile encapsulation of cells that retained high viability.e results of the work presented in this thesis show that dimerizing α-helical polypeptides can be used to create modular biomaterials with properties that can be tuned by speci c molecular interactions. e modularity and the tunable properties of these smart biomaterials are conceptually very interesting and make them useful in many emerging biomedical applications, such as 3D cell culture, cell therapy, and drug delivery. II Populärvetenskaplig sammanfattningBiomaterialär material somär designade för a vara i kontakt med biologiskt material och har använts länge inom m...