De novo designed positively charged tape-forming peptides: self-assembly and gelation in physiological solutions and their evaluation as 3D matrices for cell growth

Learning to control self-assembling nanostructures is currently one of the biggest challenges and promises in nanoscale science and nanotechnology. Nanostructured 3D matrices in particular are considered essential components in tissue engineering and regenerative medicine, e.g. as multifunctional scaffolds for cell encapsulation, growth and differentiation. Self-assembling peptide gels are a promising novel class of matrices for tissue engineering. Recently a new versatile family of negatively or positively charged tape-forming peptides have been de novo designed. These peptides were all found to self-assemble into nanostructured networks and gel cell transport medium in a simple, consistent and reproducible manner. Here we focus on the positively charged peptides of this family. We systematically changed the peptide to be amphiphilic or completely polar, or to be based on different polar uncharged amino acids (glutamine, serine, asparagine or threonine). The peptides were sterilised by gamma-irradiation and were all found to be biocompatible using the contact cytotoxicity test. L929 murine fibroblast cells were encapsulated in 3D cell cultures inside 2% w/v gels and their proliferation was measured after 14 days using the ATP Lite assay. In this way a structure-function activity was established. Trifluoroacetic acid present in the peptide from the purification step was found to have a negative effect on cell proliferation. Peptide self-assembly in physiological conditions was studied extensively using spectroscopic and microscopic techniques, allowing rationalization of the observed biological structure-function activity. This detailed and systematic study enables us to develop refined criteria for the design of positively charged tape forming peptides and gels for biological and medical applications.