Measuring the Variability in Individual Fibrin Fiber Mechanics by AFM

Fibrin fibers are key elements in blood clots. Previous research has reported the mechanical properties of fibrin fibers formed from a single set of conditions. Here we expand on these findings and show variability in the mechanical properties of fibers when formed under various constituent concentrations.



Lateral force atomic force microscopy was used to measure fiber extensibility, the force required for fiber failure, and force-strain curves. Data was obtained for fibers formed with 0.1 mg/ml, 1 mg/ml, and 2 mg/ml of fibrinogen (Fgn). The data was split into two groups based on the mean and median values for the initial slope of the force-strain curve. Fibers formed with 0.1 mg/ml Fgn fell in the group with a lower initial slope and fibers formed with 2 mg/ml Fgn fell in the group with a higher initial slope, those formed with 1 mg/ml Fgn fell into both groups.



Softer fibers, those with a lower initial slope, ruptured at a lower force but they extended further than their counterparts with a larger slope. Fibrin fibers are reported to undergo an increase in the slope of their force-strain curve around 100 % strain. The data showed softer fibers extended further before their slope changed, to an average strain of 150 %. Fibers with an initially steep slope increased their slope at an average strain of 55 %. While these data are preliminary (n = 15 fibers), they provide insight into the variability of fibrin fiber mechanics and lead to questions about the mechanisms responsible for the variability.