Neuronal contact guidance in magnetically aligned fibrin gels: Effect of variation in gel mechano-structural properties

Neurite outgrowth from chick dorsal root ganglia entrapped in isotropic and magnetically aligned fibrin gels was studied, and the dependence on the diameter of the fibrin fibrils was characterized. The fibrin fibril diameter was varied, as inferred from turbidity measurements, by using different Ca²⁺ concentrations in the fibrin-forming solution, but this variation was accomplished without affecting the degree of magnetic-induced alignment, as directly visualized in fluorescently spiked gels. Magnetically aligned fibrin gels possessing different fibril diameters but similar alignment resulted in drastic changes in the contact guidance response of neurites, with no response in gels formed in 1.2mM Ca²⁺ (having smaller fibril diameter, ca. 150nm), but a strong response in gels formed in 12 and 30mM Ca²⁺ (having larger fibril diameter, ca. 510nm) with an attendant two-fold increase in neurite length. These changes are attributed to variation of the mechano-structural properties of the network of aligned fibrils as the fibril diameter is varied.