FVII Dependent Coagulation Activation in Citrated Plasma by Polymer Hydrogels

Poly(N-vinyl imidazole) Cross-Linked β-Cyclodextrin Hydrogel for Rapid Hemostasis in Severe Renal Arterial Hemorrhagic Model

A unique facile process has been adopted for fast assembly of a poly(N-vinyl imidazole) cross-linked β-cyclodextrin hydrogel through microwave-assisted free radical polymerization, using N,N'-methylenebis(acrylamide) cross-linker. The copolymer possesses positive surface charge, one of the characteristic properties of an ideal hemostatic hydrogel. The functionalized imidazole-based hydrogel demonstrates rapid, superior blood coagulation kinetics under in vitro and in vivo conditions. On application to a major renal arterial hemorrhagic model, this hydrogel shows better blood clotting kinetics, leading to complete hemostasis in as few as ∼144 ± 7 s. Additionally, 350 μL of whole blood was clotted instantly, in ∼35 s, and therefore, reinforcing its hemostatic potential. The hydrogel demonstrates excellent biocompatibility, when seeded with human dermal fibroblast cells, retaining the native property of its predecessor. In addition, the hydrogel presents excellent hemocompatibility when tested with whole blood with the highest hemolytic ratio of 1.07 ± 0.05%. Moreover, it also demonstrates potential as a carrier for sustained release of an anesthetic drug, lidocaine hydrochloride monohydrate (∼83% in 24 h). The rapid hemostatic behavior of the hydrogel is coupled with its cytocompatibility and hemocompatibilty properties along with controlled drug release characteristics. These behaviors evidently demonstrate it to be an excellent alternative for a superior hemostatic material for severe hemorrhagic conditions.

Intrarenal Toll-like receptor 4 and Toll-like receptor 2 expression correlates with injury in antineutrophil cytoplasmic antibody-associated vasculitis

In antineutrophil cytoplasmic antibody-associated vasculitis (AAV), Toll-like receptors (TLRs) may be engaged by infection-associated patterns and by endogenous danger signals, linking infection and innate inflammation with this autoimmune disease. This study examined intrarenal TLR2, TLR4, and TLR9 expression and renal injury in AAV, testing the hypothesis that increased TLR expression correlates with renal injury. Patients with AAV exhibited both glomerular and tubulointerstitial expression of TLR2, TLR4, and TLR9, with TLR4 being the most prominent in both compartments. Glomerular TLR4 expression correlated with glomerular segmental necrosis and cellular crescents, with TLR2 expression correlating with glomerular segmental necrosis. The extent and intensity of glomerular and tubulointerstitial TLR4 expression and the intensity of glomerular TLR2 expression inversely correlated with the presenting estimated glomerular filtration rate. Although myeloid cells within the kidney expressed TLR2, TLR4, and TLR9, TLR2 and TLR4 colocalized with endothelial cells and podocytes, whereas TLR9 was expressed predominantly by podocytes. The functional relevance of intrarenal TLR expression was further supported by the colocalization of TLRs with their endogenous ligands high-mobility group box 1 and fibrinogen. Therefore, in AAV, the extent of intrarenal TLR4 and TLR2 expression and their correlation with renal injury indicates that TLR4, and to a lesser degree TLR2, may be potential therapeutic targets in this disease.

Biomaterials and Advanced Technologies for Hemostatic Management of Bleeding

Bleeding complications arising from trauma, surgery, and as congenital, disease-associated, or drug-induced blood disorders can cause significant morbidities and mortalities in civilian and military populations. Therefore, stoppage of bleeding (hemostasis) is of paramount clinical significance in prophylactic, surgical, and emergency scenarios. For externally accessible injuries, a variety of natural and synthetic biomaterials have undergone robust research, leading to hemostatic technologies including glues, bandages, tamponades, tourniquets, dressings, and procoagulant powders. In contrast, treatment of internal noncompressible hemorrhage still heavily depends on transfusion of whole blood or blood's hemostatic components (platelets, fibrinogen, and coagulation factors). Transfusion of platelets poses significant challenges of limited availability, high cost, contamination risks, short shelf-life, low portability, performance variability, and immunological side effects, while use of fibrinogen or coagulation factors provides only partial mechanisms for hemostasis. With such considerations, significant interdisciplinary research endeavors have been focused on developing materials and technologies that can be manufactured conveniently, sterilized to minimize contamination and enhance shelf-life, and administered intravenously to mimic, leverage, and amplify physiological hemostatic mechanisms. Here, a comprehensive review regarding the various topical, intracavitary, and intravenous hemostatic technologies in terms of materials, mechanisms, and state-of-art is provided, and challenges and opportunities to help advancement of the field are discussed.

Blood-aggregating hydrogel particles for use as a hemostatic agent

The body is unable to control massive blood loss without treatment. Available hemostatic agents are often expensive, ineffective or raise safety concerns. Synthetic hydrogel particles are an inexpensive and promising alternative. In this study we synthesized and characterized N-(3-aminopropyl)methacrylamide (APM) hydrogel particles and investigated their use as a hemostatic material. The APM hydrogel particles were synthesized via inverse suspension polymerization with a narrow size distribution and rapid swelling behavior. In vitro coagulation studies showed hydrogel particle blood aggregate formation as well as bulk blood coagulation inhibition. In vivo studies using multiple rat injury and ovine liver laceration models demonstrated the particles' ability to aid in rapid hemostasis. Subsequent hematoxylin and eosin and Carstairs' method staining of the ovine liver incision sites showed significant hemostatic plug formation. This study suggests that these cationic hydrogel particles form a physical barrier to blood loss by forming aggregates, while causing a general decrease in coagulation activity in the bulk. The formation of a rapid sealant through aggregation and the promotion of local hemostasis through electrostatic interactions are coupled with a decrease in overall coagulation activity. These interactions require the interplay of a variety of mechanisms stemming from a simple synthetic platform.

Hemostatic polymers: the concept, state of the art and perspectives

This article presents a critical overview of the most significant developments in the use of polymers as hemostatic agents.

Hemostatic strategies for traumatic and surgical bleeding

Wide interest in new hemostatic approaches has stemmed from unmet needs in the hospital and on the battlefield. Many current commercial hemostatic agents fail to fulfill the design requirements of safety, efficacy, cost, and storage. Academic focus has led to the improvement of existing strategies as well as new developments. This review will identify and discuss the three major classes of hemostatic approaches: biologically derived materials, synthetically derived materials, and intravenously administered hemostatic agents. The general class is first discussed, then specific approaches discussed in detail, including the hemostatic mechanisms and the advancement of the method. As hemostatic strategies evolve and synthetic-biologic interactions are more fully understood, current clinical methodologies will be replaced.

Synthesis of Guanidinium Functionalized Polycarbodiimides and Their Antibacterial Activities

A family of guanidinium-side-chain functionalized polycarbodiimides has been synthesized by allowing an azido guanidinium salt to react with alkyne polycarbodiimides via the copper catalyzed [3 + 2] cycloaddition (Click) reaction. Poly-2(a-d) are cationic/amphiphilic polymers in which the global hydrophilic/hydrophobic balance has been tailored by local alteration of the length of alkyl side chain in the repeat unit of polymers prior to polymerization. The shorter alkyl chains yield water-soluble polymers, Poly-2c, -2d, and -2e. Antibacterial activities of these cationic polycarbodiimides have been investigated for Gram-positive and Gram-negative bacteria that include Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Acinetobacter baumannii. It was observed that the influence of hydrophobic-hydrophilic balance per repeat unit of these polymers have profound effects for both antimicrobial and hemolytic activities. In addition, these polycarbodiimide-guanidinium-triazole conjugates offered moderate to significant antibacterial activity and rapid interaction with red blood cells causing blood precipitation without significant hemolysis in case of Poly-2(b-e). This latter property has the potential to be exploited in the polymer coatings or wound protection.