Hydrodynamic Spinning of Protein Fractal Aggregates into Core–Shell Fibers

Using fractal protein aggregates as building blocks, porous fibers were produced. The suspension of aggregates was coinjected with a solution of calcium chloride. Sol–gel transition of the suspension was induced by diffusion of calcium ions in the jet. The production of these fibers required a precise control of both hydrodynamic and physicochemical conditions as hydrodynamic instabilities competed with the gelation kinetics. By increasing the calcium concentration, several regimes were observed: swollen, dispersed, and shrunk fibers. In the first regime, homogeneous fibers were obtained. In the last one, osmotic phenomena led to a spontaneous core–shell structure with a dense shell.