The role of concentration on drop formation and breakup of collagen, fibrinogen, and thrombin solutions during inkjet bioprinting

Abstract

AbstractThe influence of protein concentration on drop formation and breakup of aqueous solutions of fibrous proteins collagen, fibrinogen, and globular protein thrombin in different concentration regimes is investigated during drop-on-demand (DOD) inkjet bioprinting. The capillary-driven thinning and breakup of dilute (c/c* < 1, where c is the concentration and c* is the overlap concentration) collagen, fibrinogen, and thrombin solutions is predominantly resisted by inertial force on the initial onset of necking. The minimum diameter (Dfmin(t)) of the necked fluid up to the critical pinch-off time (tc) scales with time as Dfmin(t) ∼ (tc − t)2/3, a characteristic of potential flows. Although the capillary-driven thinning and breakup of semidilute unentangled collagen (1 ≤ c/c* ≤ 4) and fibrinogen (1 ≤ c/c* ≤ 1.3) solutions is predominantly resisted by inertial force on the initial onset of necking, the breakup of droplets is delayed beyond tc, where the minimum diameter of the necked fluid decreases exponentially with time because of the resistance of elastic force. The resistance of viscous force to the necking of both the dilute and semidilute untangled protein solutions is negligible. Aggregates or subvisible particles (between 1 and 100 μm) constantly disrupt the formation of droplets for the semidilute unentangled protein solutions, even when their inverse Ohnesorge number (Z) is within the printability range of 4 ≤ Z ≤ 14. Although aggregates are present in the dilute protein solutions, they do not disrupt the formation of droplets.