Assessing the aneurysm occlusion efficacy of a shear-thinning biomaterial in a 3D-printed model

Optimal thrombin injection method for the treatment of femoral artery pseudoaneurysm

BACKGROUND

Iatrogenic femoral artery pseudoaneurysm (IFP) incidence is increasing with increase in diagnostic and therapeutic angiography, and so, the less invasive percutaneous thrombin injection (PTI) is the most widely used treatment. Moreover, studies that minimize PTI complications and highlight therapeutic effects are lacking.

OBJECTIVES

This study performed in vitro thrombosis modeling of pseudoaneurysms and analyzed thrombosis within and thromboembolism outside the sac during thrombin injection.

METHODS

We evaluated PTI in terms of thrombin injection location (at the junction of the IFP sac and neck, the center, and the dome, located farthest from the neck of the sac), thrombin injection time (5 and 8 seconds), and blood flow rate (ranging from 210 mL/min to 300 mL/min). Porcine blood was used as the working fluid in this study.

RESULTS

Thrombin injection at the junction of the IFP sac and the pseudoaneurysm neck led to less thrombosis within the sac but substantial thrombi consistently outside the sac, whereas thrombin injected at the sac center mostly led to complete thrombosis within the sac, preventing further blood flow into the sac and reducing likelihood of thrombi outside the sac. A longer thrombin injection time enhanced the therapeutic effect and decreased the possibility of thromboembolism. Thromboembolism occurred more frequently at flow rates of >240 mL/min.

CONCLUSION

The thrombin injection site in a pseudoaneurysm significantly influences thrombogenesis within and thromboembolism outside the sac. Thus, slow and deliberate injection of thrombin into the center of the sac could potentially reduce complications and enhance treatment efficacy.

A Cohesive Shear-Thinning Biomaterial for Catheter-Based Minimally Invasive Therapeutics

Shear-thinning hydrogels are suitable biomaterials for catheter-based minimally invasive therapies; however, the tradeoff between injectability and mechanical integrity has limited their applications, particularly at high external shear stress such as that during endovascular procedures. Extensive molecular crosslinking often results in stiff, hard-to-inject hydrogels that may block catheters, whereas weak crosslinking renders hydrogels mechanically weak and susceptible to shear-induced fragmentation. Thus, controlling molecular interactions is necessary to improve the cohesion of catheter-deployable hydrogels. To address this material design challenge, we have developed an easily injectable, nonhemolytic, and noncytotoxic shear-thinning hydrogel with significantly enhanced cohesion via controlling noncovalent interactions. We show that enhancing the electrostatic interactions between weakly bound biopolymers (gelatin) and nanoparticles (silicate nanoplatelets) using a highly charged polycation at an optimum concentration increases cohesion without compromising injectability, whereas introducing excessive charge to the system leads to phase separation and loss of function. The cohesive biomaterial is successfully injected with a neuroendovascular catheter and retained without fragmentation in patient-derived three-dimensionally printed cerebral aneurysm models under a physiologically relevant pulsatile fluid flow, which would otherwise be impossible using the noncohesive hydrogel counterpart. This work sheds light on how charge-driven molecular and colloidal interactions in shear-thinning physical hydrogels improve cohesion, enabling complex minimally invasive procedures under flow, which may open new opportunities for developing the next generation of injectable biomaterials.