Shear-thinning nanocomposite hydrogels for the treatment of hemorrhage

Abstract

Internal hemorrhaging is a leading cause of death after traumatic injury on the battlefield. Although several surgical approaches such as the use of fibrin glue and tissue adhesive have been commercialized to achieve hemostasis, these approaches are difficult to employ on the battlefield and cannot be used for incompressible wounds. Here, we present shear-thinning nanocomposite hydrogels composed of synthetic silicate nanoplatelets and gelatin as injectable hemostatic agents. These materials are demonstrated to decrease in vitro blood clotting times by 77%, and to form stable clot-gel systems. In vivo tests indicated that the nanocomposites are biocompatible and capable of promoting hemostasis in an otherwise lethal liver laceration. The combination of injectability, rapid mechanical recovery, physiological stability, and the ability to promote coagulation result in a hemostat for treating incompressible wounds in out-of-hospital, emergency conditions.

Keywords: hemorrhage; hydrogels; nanocomposites; shear thinning; synthetic silicate nanoplatelet.

Figure 1

Structure, injectability, and self-healing characteristics of nanocomposite hydrogels. (a) Schematic showing the preparation of the nanocomposite gels. The TEM image shows the size of the silicate nanoparticle (scale bar 50 nm). Images showing injection of nanocomposite hydrogel through a surgical needle (22 gauge) and recovery to form freestanding structures. (b) Zeta potential measurements demonstrate electrostatic interactions between negatively charged silicate and positively charged gelatin; 95% CI are shown for each point. (c) Small-angle X-ray scattering (SAXS) indicates that nanoplatelets are well dispersed and follow the model curve for scattering from dispersed thin disks. (d) Yield stress of gels as a function of nanoplatelet loading and solids fraction. (e) Recovery of the nanocomposites was observed by subjecting the hydrogel to alternating high and low strain conditions (100% strain and 1% strain) while monitoring the moduli of the composite. For all the nanocomposite hydrogels, more than 95% recovery was observed.

Figure 2

Effect of nanoplatelets on the clotting whole blood. (a) Clot formation as a function of time and nanocomposite composition. (b) Quantiative clot times for 6% and 9% nanocomposites. (One-way Anova followed by Tukey’s post-hoc analysis was performed; *p < 0.01; ***p < 0.001). (c) Clotting kinetics of blood when in contact with gelatin and nanocomposite monitored using shear rheology. (d) Comparison of clotting times for silicate-gelatin nanocomposite (NC) and commercial products.

Figure 3

In vivo evaluation of nanocomposite hydrogels as hemostats. (a) Subcutaneous injection and explantation of 9NC75 in rats. After 3 days, nanocomposite could be easily detected in the subcutaneous pockets, but the volume was already lower than at implantation. (b) H&E staining confirmed degradation of 9NC75 within 28 days, while the QuikClot particles were still present. Moreover, 9NC75 induced less chronic inflammation than QuikClot, indicated by severe mononuclear cell infiltration around QuikClot at day 28 (asterisks). Furthermore, the QuikClot samples were encapsulated by dense fibrous connective tissue (arrows). The potential of the nanocomposite to stop otherwise lethal bleeding was investigated using liver bleeding experiments in rats. (c) 9NC75 significantly improved the postinterventional survival (logrank (Mantel-Cox) test). (d) 9NC75 was effective in preventing blood loss as compared to untreated hemorrhage (***p < 0.001). (e) The small amount of 9NC75 (200 μL) was sufficient to stop bleeding and the superficial part of the 9NC75 was easily removed without causing rebleeding.