| Nanofibers play important mechanical roles in the body. Collagen, the most abundant protein in humans, forms fibers which comprise part of the extracellular matrix and tissues such as bone, cartilage and blood vessels, to name a few. Fibrinogen, a plasma protein, is converted into fibrin fibers which form the mechanical and structural support for blood clots. Biomimetic nanofibers can be synthesized outside of the body through the process of electrospinning. The mechanical properties of electrospun collagen and fibrinogen fibers are important because of their potential for tissue engineering, due to their biocompatibility. We studied the mechanical properties of individual electrospun collagen and fibrinogen fibers using a combined atomic force microscopy and optical microscopy technique. Using the same technique we also studied the mechanical properties on individual fibrin fibers. The mechanical properties of blood clots have been shown to be related to diseases and disorders yet the mechanisms responsible for their mechanical properties are relatively unknown.;Electrospun type I collagen and electrospun fibrinogen fibers both showed viscoelastic properties. The extensibility of electrospun fibrinogen is 130% and its average modulus is 10 MPa. Electrospun collagen, on the other hand is less extensible, 33% extensibility, and siffer with a bending modulus of 7.5 GPa. Both fibers show strain softening, however, collagen shows extreme strain softening and therefore only a bending modulus is given.;Native crosslinked fibrin fibers have similar properties to electrospun fibrinogen fibers. Crosslinked fibers have an extensibility of 130% and a modulus of 14 MPa. Uncrosslinked fibers are more extensible at 226% strain and softer with a modulus of 4 MPa. Crosslinked fiber rupture more often than crosslinked joints while uncrosslinked fibers rupture less often than uncrosslinked joints. Fibrin fibers with only alpha crosslinks are as extensible as uncrosslinked fibrin fibers but have a modulus in between crosslinked and uncrosslinked fibrin, of 10 MPa. Alpha crosslinked fibrin fibers have a larger elastic limit, 95% strain, than both uncrosslinked and crosslinked. Lastly, preliminary studies of individual fibrin fibers from patients with type 2 diabetes show no difference in modulus when compared with control patient fibrin samples. |
