Enhancing clot properties through fibrin-specific self-cross-linked PEG side-chain microgels

Abstract

Excessive bleeding and resulting complications are a major cause of death in both trauma and surgical settings. Recently, there have been a number of investigations into the design of synthetic hemostatic agents with platelet-mimicking activity to effectively treat patients suffering from severe hemorrhage. We developed platelet-like particles from microgels composed of polymers carrying polyethylene glycol (PEG) side-chains and fibrin-targeting single domain variable fragment antibodies (PEG-PLPs). Comparable to natural platelets, PEG-PLPs were found to enhance the fibrin network formation in vitro through strong adhesion to the emerging fibrin clot and physical, non-covalent cross-linking of nascent fibrin fibers. Furthermore, the mechanical reinforcement of the fibrin mesh through the incorporation of particles into the network leads to a ∼three-fold decrease of the overall clot permeability as compared to control clots. However, transport of biomolecules through the fibrin clots, such as peptides and larger proteins is not hindered by the presence of PEG-PLPs and the altered microstructure. Compared to control clots with an elastic modulus of 460+/-260 Pa, PEG-PLP-reinforced fibrin clots exhibit higher degrees of stiffness as demonstrated by the significantly increased average Younǵs modulus of 1770 +/±720 Pa, as measured by AFM force spectroscopy. Furthermore, in vitro degradation studies with plasmin demonstrate that fibrin clots formed in presence of PEG-PLPs withstand hydrolysis for 24 h, indicating enhanced stabilization against exogenous fibrinolysis. The entire set of data suggests that the designed platelet-like particles have high potential for use as hemostatic agents in emergency medicine and surgical settings.

Platelets and Fibrinogen: Emerging Complexity in Trauma-Induced Coagulopathy

“…65 Platelet-like microparticles have been developed that can stiffen a clot, induce retraction, and decrease susceptibility to fibrinolysis. 66,67 Perhaps the best-developed, a platelet analogue named Synthoplate (Haima Therapeutics) has shown promise. SynthoPlates are liposomes decorated with ligands that bind VWF, collagen, and fibrin, which allow them to recapitulate the binding properties of activated platelets.…”

Clot Structure and Implications for Bleeding and Thrombosis

“…Network permeability can be quantified using pressure-driven systems that examine fluid flow through a porous medium, such as a fibrin clot. [22][23][24] Although an indirect measure of pore size, this form of analysis provides insights into the porosity of fibrin clots, which can be an indicator for the degree of clot density and fibrinolysis resistance. Finally, mechanically based techniques are commonly used to analyze clot structure.…”

Hemostatic agents for prehospital hemorrhage control: a narrative review

“…Welsch et al reported different platelet-like particles carrying polyethylene glycol side chains and fibrintargeting single-domain variable fragment antibodies [125]. In vitro studies showed that the platelet-like particles were comparable to natural platelets with regards to enhancing the fibrin network formation through strong adhesion to the emerging fibrin clot and physical, noncovalent crosslinking of nascent fibrin fibers.…”