John B. Matson, Samuel I. Stupp
Bio-materials made from small peptide chains are ideal for creating scaffolds for tissue regeneration. Small peptides can assemble into spheres, cylinders, tubes, and many other useful scaffolding structures.
Classes of Filamentous Supra-molecular Scaffolds
Peptide amphiphiles are short chain peptides with a hydrophobic tail attached to a lipid chain capable of self assembly into various types of supra-molecular structures. Matson and Stupp developed peptide amphiphiles that consisted of ” a β-sheet forming region of 4–8 amino acids directly adjacent to a palmitic acid tail,” which induced the peptide into a cylindrical nano fiber formation. The β-sheet influenced the mechanical properties of the peptides and twisting of the β-sheet could create a less stiff or stiffer material. Hydrogels were created using these peptide amphiphiles through the addition of electrolytes or by changing the pH.
The peptide scaffolds can be used as a template for inducing chemical reactions. Matson and Stupp utilized the “hydrophobic core of PA nanofibers as a foundation to promote the “topochemical polymerization of a set of diacetylene-containing PAs.” The polymerization process increased the mechanical strength of the material and allowed for “micro patterning of the PA gel surface.”
The PA nanofibers provided a foundation for biomineralization, specifically of HAP, “an inorganic component of bone derived from calcium and phosphate.” The one dimensional and three dimensional nanofiber gels were both able to facilitate bone growth effectively.
The use of epitopes in scaffolding has become a topic of interest due to their ability to mimic the structural and adhesive processes seen in the extra cellular matrix. Matson and Stupp explored the combination of epitopes as a bio active sequence on PAs. PAs can join to form nanofibers with multiple epitopes that are available for “interaction with cell surface receptors.”
Synthetic scaffolds made from PAs can be used to control stem cell differentiation, a key problem seen in regenerative medicine practices. Utilizing different surface types, such as smooth or with holes, Matson and Stupp were able to increase the expression of specific cellular markers to achieve proper cellular differentiation. Protein and Small Molecule Delivery