AbstractA Swiss University developed a self-assembled biopolymer composed of recombinant protein units that have peptide display capabilities and can form a functional matrix. Protein components can be customized to display biologically active motifs. The design offers controlled pluri-functionalization ideally suited for the development of bioscaffolds in cell-based applications. Industrial partners for joint further development, product adaptation to specific needs and licensing purposes are sought.
DetailsCurrent bioscaffolds of peptidic composition used in cell applications are difficult to functionalize efficiently. They have a limited capability to support multi-functionalization and a poorly controllable nanotopography (spatial distribution of functional groups). Attempts to modulate the display density of ligands on peptidic fibers using “doping” (i.e. mixing functionalized and passive building blocks) have proven unsatisfactory regarding the ratio of active/inactive ligand incorporated into the fibrils as well as their distribution, that was uneven. In addition, functional groups displayed on peptidic fibers often suffer from reduced reactivity compared to their free state in solution, probably due to accessibility restrictions.
A bioengineered protein polymer has now been devised by the Swiss University that offers versatile functionalization strategies, promising to ameliorate the limitations in the production of optimized cell scaffolds.
A self-assembling protein biopolymer with peptide display capabilities has been developed that can be processed into a functional mesh or matrix. Single fibers have a thickness of approx. 13 nm and are micrometers long (typically 5-10 um) (Fig 1a). They can form fibrous networks (Fig 1b). The protein components are produced recombinantly in high yield and can be “bottom-up” customized by standard protein engineering for the uncomplicated display of biologically active motifs or units, e.g. cell attachment motifs, enzymes, protein factors, etc. The current version of the polymer displays a popular poly-histidine affinity motif that can bind complementary targets. The displayed peptides are proven to be fully accessible and functional (Fig 1c). Display sites are localized at regular intervals of approx. 8-5 nm along the fiber resulting in nano-patterning (Fig 1c). The polymerizing protein unit contains several independent display sites arranged in a modular disposition that permit the simultaneous display of heterogeneous biological motifs, and the control of their relative distribution. Thus, the conceptual design of the polymer supports effective pluri-functionalization.
The properties of this polymer are ideally suited for the development of bioscaffolds for demanding cell-based applications, where cells are highly responsive both to the local topography of the scaffold and to the density of ligands (e.g. attachment sites) present on its surface and where multi-functionalization of the scaffold is of advantage. In particular, applications are envisioned in the encapsulation of (neural) stem cells to support multipotency while maintaining cell viability (ex vivo, and in vivo transplantation scenarios).
Other applications in chemistry and biology are foreseeable where the fiber might serve to organize matter in the fine nanoscale acting as a nanoconstruction platform. Specifically, relative arrangements of particles – alone or in combination - (e.g. gold, silver, magnetic nanoparticles and quantum dots) are achievable where the ordered array might exhibit exclusive physical properties. Other uses include the immobilization of enzymes organized into sequential patterns, leading to a local compartimentation of multi-step catalysis processes.
Fig 1: Electron microscopy images of a) a single fiber; b) a detail of the fibrous mesh; c) NTA-functionalized gold nanoparticles (5 nm in diameter) selectively bound to the fiber through the polyhistidine affinity motif displayed.
• Customizable protein polymer
• Building-blocks can be conveniently modified by protein engineering approaches
• Efficient display sites
• Modular design supports pluri-functionalization
• Modular design supports nano-patterning