Structure of fibrin networks

The structure of fibrin gels grown at room temperature from fibrinogen solutions at sevei'al fibrinogen concentrations was investigated by means of elastic light scattering. By combining Classical Light Scattering (CLS) and Low-Angle Elastic Light Scattering (LAELS) an overall wavevector range of more than two decades was spanned, from 7.8 × 10² to 3.3 × 0⁵ cm^-1. The scattered intensity distribution I(q) of all the gels was characterized by three different regimes. For q = q₁ ∼ 2.5 × 10³ cm^-1, I(q) exhibits a maximum which indicates the presence of a long-range order in the gel structure, with an average mesh size ζ₁ = 2ζ/q₁ ∼ 25μm. For q₁ <q₂(q₂ ∼ 1-3 × 10⁵ cm^-1), the scattered intensity distribution decays with a power law characterized by the mass fractal exponent D_m = 1.20 ±0.05, which is typical of branched linear polymers. At larger wavevectors, for q > q2, there is a crossover to a scattering from surface fractals, where I(q) decays with a power law characterized by an exponent of ~ -4. The length scale ζ₂ = 1/q₂ ∼ 80 nm is an estimate of the average diameters of the gel fibers. All our results, including the kinetics of gel formation, can be described in terms of a simple model.