Self-assembling peptide nanofibers promoting cell adhesion and differentiation

There is an increasing need for the development of functional artificial extracellular matrices (ECMs) for tissue engineering. Recently, we have successfully designed a self-assembling peptide, named E1Y9, to construct functional ECMs. We describe here an enhancement of abilities of E1Y9 materials to promote cell adhesion and differentiation, using functional peptide sequences derived from natural extracellular matrix proteins. We designed functionalized self-assembling peptides, RGDS-conjugated E1Y9 (E1Y9-RGDS) and IKVAV-conjugated E1Y9 (E1Y9-IKVAV). E1Y9-RGDS and E1Y9-IKVAV formed peptide nanofibers in a similar manner to E1Y9, with β-sheet secondary structures. Surfaces coated with peptide nanofibers displayed the higher bioactivities of E1Y9-RGDS for cell adhesion and E1Y9-IKVAV for cell differentiation than those of E1Y9, with the activities being dependent on the concentrations of the functional peptides. These functionalized peptides will be useful for the construction of functional ECMs in cell and tissue engineering.

Biocatalytically triggered co-assembly of two-component core/shell nanofibers

For the development of applications and novel uses for peptide nanostructures, robust routes for their surface functionalization, that ideally do not interfere with their self-assembly properties, are required. Many existing methods rely on covalent functionalization, where building blocks are appended with functional groups, either pre- or post-assembly. A facile supramolecular approach is demonstrated for the formation of functionalized nanofibers by combining the advantages of biocatalytic self-assembly and surfactant/gelator co-assembly. This is achieved by enzymatically triggered reconfiguration of free flowing micellar aggregates of pre-gelators and functional surfactants to form nanofibers that incorporate and display the surfactants' functionality at the surface. Furthermore, by varying enzyme concentration, the gel stiffness and supramolecular organization of building blocks can be varied.

More than just bare scaffolds: towards multi-component and decorated fibrous biomaterials

We are entering a new phase in biomaterials research in which rational design is being used to produce functionalised materials tailored to specific applications. As is evident from this Themed Issue, there are now a number of distinct types of designed, self-assembling, fibrous biomaterials. Many of these are ripe for development and application for example as scaffolds for 3D cell culture and tissue engineering, and in templating inorganic materials. Whilst a number of groups are making headway towards such applications, there is a general challenge to translate a wealth of excellent basic research into materials with a genuine future in real-life applications. Amongst other contemporary aspects of this evolving research area, a key issue is that of decorating or functionalising what are mostly bare scaffolds. There are a number of hurdles to overcome to achieve effective and controlled labelling of the scaffolds, for instance: maintaining biocompatibility, i.e., by minimising covalent chemistry, or using milder bioconjugation methods; attaining specified levels of decoration, and, in particular, high and stoichiometric labelling; introducing orthogonality, such that two or more functions can be appended to the same scaffold; and, in relevant cases, maintaining the possibility for recombinant peptide/protein production. In this critical review, we present an overview of the different approaches to tackling these challenges largely for self-assembled, peptide-based fibrous systems. We review the field as it stands by placing work within general routes to fibre functionalisation; give worked examples on our own specific system, the SAFs; and explore the potential for future developments in the area. Our feeling is that by tackling the challenges of designing multi-component and functional biomaterials, as a community we stand to learn a great deal about self-assembling biomolecular systems more broadly, as well as, hopefully, delivering new materials that will be truly useful in biotechnology and biomedical applications (107 references).