Self-assembly of Tyrosine-containing Peptides into Injectable Hydrogels with Distinct Nanostructures is Key in Determining Inflammatory Response of Macrophages

Self-assembling peptides (SAPs) are fully defined nanobiomaterials offering unprecedented opportunities to control nanostructure and chemical attributes to investigate and manipulate cellular signals. To investigate the influence of chemical and morphological characteristics on inflammatory signalling in native immunity, we designed five Beta-sheet SAPs: EFEFKFEFK (EF8), YEFEFKFEFK (YEF8), EFEFKFEFKY (EF8Y), YEFEFKFEFKY (YEF8Y) and EYEFKFEFK (EYF8) (F: phenylalanine; E: glutamic acid; K: lysine, Y: tyrosine). The position of tyrosine in the peptide sequence dictated the distinct self-assembly into nanostructures, with sequences EF8Y, YEF8Y, EYF8 self-assembling into thin nanofibers d≈3.8 ± 0.2 nm, YEF8 self-assembling into rod-like flat ribbons d>20 nm and EF8 (control) consisting of both types of self-assembled nanostructures. These distinct nanostructures induced contrasting inflammatory response of monocytic model THP-1 cells-derived macrophages (MΦs). Presence of soluble EF8 nanofibers (at 2 mM) induced anti-inflammatory response and polarization towards an M2 state, whereas YEF8 displayed tendency for inducing pro-inflammatory response and polarization towards M1 state. The EF8Y, YEF8Y, EYF8 SAPs did not induce an inflammatory response in our models. These results were validated using peripheral blood mononuclear cells (PBMCs)-derived MΦs from human donors, confirming the critical role of the EF8 and YEF8 SAPs as possible orchestrators of the repair of tissues or inducers of pro-inflammatory state, respectively. The same MΦs polarization responses from THP-1 derived cells cultured on 20 mM hydrogels. These findings will facilitate the utilization of this family of SAPs as immunomodulatory nanobiomaterials potentially changing the course of inflammation during the progression of various diseases.