Wet extrusion of fibronectin-fibrinogen cables for application in tissue engineering

A method for the wet extrusion of human plasma-derived fibronectin-fibrinog en cables is described. Solutions of fibronectin and fibrinogen with and wi thout sodium alginate and carboxymethylcellulose (CMC) are tested. The theo logical properties of the protein solutions changed from Newtonian to shear thinning non-Newtonian in the presence of small quantities of these additi ves, the apparent viscosity increased, and the extrusion properties of the protein solutions improved. Cables were prepared using a capillary with a d iameter of 1 mm and overall length of 18 mm. Cable diameter was reduced to about 0.5 mm by drawing using a series of rollers. Cables prepared with sod ium alginate were found to have suitable properties, and those made with CM C were sticky and difficult to handle. Solutions containing no sodium algin ate required a minimum total protein concentration of about 70 mg/mL for ex trusion. Extruded cables were p repa red with solutions containing 140 mg/m L total protein with 12.9 mg/mL alginate thigh protein), and 46 mg/mL total protein with 47.6 mg/mL of sodium alginate thigh alginate). The mechanical strength of the extruded cables was within the range suitable for applicat ion in tissue engineering. Extrusion of the protein solutions into cables w as achieved in a coagulation bath. Cables with a mechanical strength of app roximately 30 N/mm(2), suitable for wound repair and nerve regeneration app lications, were prepared with a coagulation bath containing 0.25 M HCl, 2% CaCl2 at a pH of <0.9. These cables also had a large average elongation at break of 52%, and showed an increase in cable length after breakage (perman ent set) of 20%, demonstrating the potential for drawing the cables down to a fine diameter. <(c)> 2001 John Wiley & Sons, inc.