Salt-induced fibrillogenesis of fibrinogen (SAL-FIB): In vitro experiments and simulations

• Applicants: Professorin Dr. Dorothea Brüggemann; Dr. Susan Köppen
• Subject Area: Biomaterials ; Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 462381005

Fibrous fibrinogen scaffolds are particularly attractive for tissue engineering applications since they closely mimic the architecture and biochemical composition of native blood clots. Different techniques are known to induce fibrillogenesis of fibrinogen under in vitro conditions including electrospinning, surface- and buffer-driven fiber formation as well as salt-induced self-assembly. However, to date it is not yet understood whether specific surface interactions or buffer conditions contribute to the in vitro fibrillogenesis of fibrinogen. Moreover, current studies on the molecular level of fibrinogen lack a clear understanding of the underlying atomistic processes. Therefore, our project will focus on the following question: Which mechanism drives fibrillogenesis of fibrinogen under in vitro conditions? To answer this question our project will use a multi-scale combination of closely connected simulative and experimental methods. For the first time, we will establish a complete molecular model of fibrinogen, that also includes posttranslational modifications. Based on experimental dynamic light scattering studies, where we will analyze the aggregation of fibrinogen in different buffer systems, this fibrinogen model will be used in molecular dynamics (MD) studies to analyze local ion distributions around the molecule. Subsequently, we will use our MD results to study whether salt ions are incorporated into fibrinogen molecules or into fibrinogen fibers upon drying. The associated experimental studies will involve turbidimetric measurements and analysis of the morphology and elemental composition of self-assembled fibrinogen nanofibers. To understand whether fiber assembly is accompanied or driven by changes in the fibrinogen conformation, we will screen self-assembled fibers for possible amyloid transitions and perform spectroscopic analyses. The resulting circular dichroism (CD) spectra will be compared to reference single molecule CD spectra with induced structural changes obtained by steered MD simulations.A major challenge in this project will be to discuss and interpret the single molecule information from MD simulations with respect to experimental results obtained from an ensemble of fibrinogen structures/conformations. In this context, the hydrodynamic radius and CD spectra will be two observables that will directly link our simulative and experimental studies. Only with this combined approach we will be able to propose a detailed mechanism for the in vitro fibrillogenesis of fibrinogen with a clear dependence on environmental parameters. The proposed project will therefore provide fundamental insights into in vitro fibrillogenesis of fibrinogen, which are necessary to develop a new class of fibrinogen nanofibers with defined structure-function-relationships.

• DFG Programme: Research Grants