Biological designer self-assembling peptide nanofiber scaffolds significantly enhance osteoblast proliferation, differentiation and 3-D migration

Modular self-assembling biomaterials for directing cellular responses

Self-assembling biomaterials are promising as cell-interactive matrices because they can be constructed in a modular fashion, which enables the independent and simultaneous tuning of several of their physicochemical and biological properties. Such modularity facilitates the optimization of multi-component matrices for use in complex biological environments such as 3-D cell culture or scaffolds for regenerative medicine. This Highlight will discuss recent strategies for producing modular self-assembling biomaterials, with a particular focus on how ligand presentation and matrix mechanics can be controlled in modular ways. In addition, it will discuss key hurdles that remain for employing these materials as cell-interactive scaffolds in biomedical applications, particularly those that relate to how they may interface with the immune system.

Designer self-assembling peptide scaffolds for 3-d tissue cell cultures and regenerative medicine

Biomaterial science has made enormous progress in the last few decades. Nonetheless, innovative biomaterials are still urgently needed to provide in vitro cell-culture models that more closely resemble three-dimensional (3-D) cell interactions and cyto-architectures in bodies and tissues. In this review, the recent advances toward this goal through molecular engineering of various designer self-assembling peptide scaffolds are discussed. These peptide scaffolds can be commercially and custom-tailor synthesized materials with high purity and may be not only useful for specific 3-D tissue cell cultures but also for tissue repair and regenerative therapies. Furthermore, these designer self-assembling peptide scaffolds have recently become powerful tools for regenerative medicine to repair nervous tissue, to stop bleeding in seconds, to repair infarctuated myocardia, as well as being useful medical devices for slow drug release.

Charge transport and intrinsic fluorescence in amyloid-like fibrils

The self-assembly of polypeptides into stable, conductive, and intrinsically fluorescent biomolecular nanowires is reported. We have studied the morphology and electrical conduction of fibrils made of an elastin-related polypeptide, poly(ValGlyGlyLeuGly). These amyloid-like nanofibrils, with a diameter ranging from 20 to 250 nm, result from self-assembly in aqueous solution at neutral pH. Their morphological properties and conductivity have been investigated by atomic force microscopy, scanning tunneling microscopy, and two-terminal transport experiments at the micro- and nanoscales. We demonstrate that the nanofibrils can sustain significant electrical conduction in the solid state at ambient conditions and have remarkable stability. We also show intrinsic blue-green fluorescence of the nanofibrils by confocal microscopy analyses. These results indicate that direct (label-free) excitation can be used to investigate the aggregation state or the polymorphism of amyloid-like fibrils (and possibly of other proteinaceous material) and open up interesting perspectives for the use of peptide-based nanowire structures, with tunable physical and chemical properties, for a wide range of nanobiotechnological and bioelectronic applications.

The third dimension bridges the gap between cell culture and live tissue

Moving from cell monolayers to three-dimensional (3D) cultures is motivated by the need to work with cellular models that mimic the functions of living tissues. Essential cellular functions that are present in tissues are missed by 'petri dish'-based cell cultures. This limits their potential to predict the cellular responses of real organisms. However, establishing 3D cultures as a mainstream approach requires the development of standard protocols, new cell lines and quantitative analysis methods, which include well-suited three-dimensional imaging techniques. We believe that 3D cultures will have a strong impact on drug screening and will also decrease the use of laboratory animals, for example, in the context of toxicity assays.

Controlling cell adhesion to surfaces via associating bioactive triblock proteins

A surface functionalization strategy that produces substrates with well-controlled ligand density is critical to investigating the role of cell-substrate interactions in regulating cell adhesion, viability, migration, proliferation and differentiation. Towards this end, we have designed and synthesized a triblock protein, CRC, comprising a polyelectrolyte domain flanked by two amphiphilic leucine zipper domains. The amphiphilic end domains of CRC adsorb onto surfaces and preferentially associate into trimeric aggregates, forming a hydrogel coating layer. Under serum-free conditions, the CRC coating was found to render both 2D substrates and 3D scaffolds non-adhesive to cells. A RGDS sequence was inserted in the middle domain of CRC (generating the protein CRC-RGDS) and found to introduce cell-binding activity. Incorporation of the RGDS sequence did not significantly impact the surface activity of CRC, allowing us to titrate the RGDS surface density simply by adjusting the relative ratios of the two proteins. Ligand density dependent cell-substrate interactions were demonstrated in human foreskin fibroblasts, human umbilical vein endothelial cells, and rat neural stem cells. The versatility to functionalize a range of different substrate surfaces, combined with the ease of controlling surface ligand density, makes these triblock proteins an attractive tool for developing cell-specific surface coatings with tailored biofunctional attributes.