Antoine Eyram Kwame, Aparna Sai Malisetty, Michael Maas, Susan Köppen, Lucio Colombi Ciacchi, Dorothea Brüggemann
Fibrinogen can self-assemble into nanofibers in the presence of salts without thrombin. Although kosmotropic anion-cation pairs are known to govern this process, the role of individual anions remains unclear. Here, we demonstrate that fibrinogen self-assembly follows a strongly anion-specific concentration-dependent pathway. Moderate phosphate concentrations produced interconnected nanofibrous networks that formed stepwise, whereas higher phosphate and all chloride conditions yielded macroporous aggregates. Elemental analysis revealed retention of sodium and phosphate within the fibers, indicating specific ion-protein interactions. Light-scattering analyses showed sigmoidal kinetics and concentration-dependent growth with phosphate, consistent with nucleation and fibril elongation, whereas chloride produced non-sigmoidal behavior indicative of disordered aggregation. Together, these results demonstrate that multivalent phosphate promotes controlled fibrillogenesis of fibrinogen, while monovalent chloride favors amorphous precipitation. This anion-directed assembly pathway provides an enzyme-free route to fabricate fibrinogen nanofibers with tunable architecture for various biomaterial applications.