Size and Density of Fibers in Fibrin and Other Filamentous Networks from Turbidimetry: Beyond a Revisited Carr–Hermans Method, Accounting for Fractality and Porosity.

The Carr-Hermans method [Macromolecules 1978, 11, 46-50], often used for determining the fibers diameter d and density p in fibrin or other filamentous networks from turbidity data, is found to be remarkably inaccurate when the system's mass fractal dimension D-m is >1. An expanded approach based on the knowledge of the system D-m and pore size xi which can be accurately recovered from low-angle elastic light scattering data or estimated from confocal microscopy, is proposed. By fitting the turbidity data with a function obtained by numerically integrating the fibrin-optimized scattering form factor of a network of cylindrical elements, both d and p can be independently recovered. Numerical simulations were employed to validate the reliability and accuracy of the method, which is then applied to evolving fibrin gels data. More in general, this method is extendible to the analysis of other filamentous networks that can be represented as ensembles of cylindrical elements.