Nanosensor based approaches for quantitative detection of heparin

Heparin, being a widely employed anticoagulant in numerus clinical complications, requires strict quantification and qualitative screening to ensure the safety of patients from potential threat of thrombocytopenia. However, the intricacy of heparin's chemical structures and low abundance hinders the precise monitoring of its level and quality in clinical settings. Conventional laboratory assays have limitations in sensitivity and specificity, necessitating the development of innovative approaches. In this context, nanosensors emerged as a promising solution due to enhanced sensitivity, selectivity, and ability to detect heparin even at low concentrations. This review delves into a range of sensing approaches including colorimetric, fluorometric, surface-enhanced Raman spectroscopy, and electrochemical techniques using different types of nanomaterials, thus providing insights of its principles, capabilities, and limitations. Moreover, integration of smart-phone with nanosensors for point of care diagnostics has also been explored. Additionally, recent advances in nanopore technologies, artificial intelligence (AI) and machine learning (ML) have been discussed offering specificity against contaminants present in heparin to ensure its quality. By consolidating current knowledge and highlighting the potential of nanosensors, this review aims to contribute to the advancement of efficient, reliable, and economical heparin detection methods providing improved patient care.

Perioperative Anaphylaxis

Anesthesiologists routinely manage patients receiving drugs and agents, all of which have the potential for anaphylaxis, the life-threatening presentation of an allergic reaction. Clinicians must be ready to diagnose and manage the acute cardiopulmonary dysfunction that occurs.

Mechanism, Functions, and Diagnostic Relevance of FXII Activation by Foreign Surfaces

Factor XII (FXII) is a serine protease zymogen produced by hepatocytes and secreted into plasma. The highly glycosylated coagulation protein consists of six domains and a proline-rich region that regulate activation and function. Activation of FXII results from a conformational change induced by binding ("contact") with negatively charged surfaces. The activated serine protease FXIIa drives both the proinflammatory kallikrein-kinin pathway and the procoagulant intrinsic coagulation cascade, respectively. Deficiency in FXII is associated with a prolonged activated partial thromboplastin time (aPTT) but not with an increased bleeding tendency. However, genetic or pharmacological deficiency impairs both arterial and venous thrombosis in experimental models. This review summarizes current knowledge of FXII structure, mechanisms of FXII contact activation, and the importance of FXII for diagnostic coagulation testing and thrombosis.

The Toxicology of Native Fucosylated Glycosaminoglycans and the Safety of Their Depolymerized Products as Anticoagulants

Fucosylated glycosaminoglycan (FG) from sea cucumber is a potent anticoagulant by inhibiting intrinsic coagulation tenase (iXase). However, high-molecular-weight FGs can activate platelets and plasma contact system, and induce hypotension in rats, which limits its application. Herein, we found that FG from T. ananas (TaFG) and FG from H. fuscopunctata (HfFG) at 4.0 mg/kg (i.v.) could cause significant cardiovascular and respiratory dysfunction in rats, even lethality, while their depolymerized products had no obvious side effects. After injection, native FG increased rat plasma kallikrein activity and levels of the vasoactive peptide bradykinin (BK), consistent with their contact activation activity, which was assumed to be the cause of hypotension in rats. However, the hemodynamic effects of native FG cannot be prevented by the BK receptor antagonist. Further study showed that native FG induced in vivo procoagulation, thrombocytopenia, and pulmonary embolism. Additionally, its lethal effect could be prevented by anticoagulant combined with antiplatelet drugs. In summary, the acute toxicity of native FG is mainly ascribed to pulmonary microvessel embolism due to platelet aggregation and contact activation-mediated coagulation, while depolymerized FG is a safe anticoagulant candidate by selectively targeting iXase.

The effect of increasing the sulfation level of chondroitin sulfate on anticoagulant specific activity and activation of the kinin system

Oversulfated chondroitin sulfate (OSCS) was identified as a contaminant in certain heparin preparations as the cause of adverse reactions in patients. OSCS was found to possess both plasma anticoagulant activity and the ability to activate prekallikrein to kallikrein. Differentially sulfated chondroitin sulfates were prepared by synthetic modification of chondroitin sulfate and were compared to the activity of OSCS purified from contaminated heparin. Whilst chondroitin sulfate was found to have minimal anticoagulant activity, increasing sulfation levels produced an anticoagulant response which we directly show for the first time is mediated through heparin cofactor II. However, the tetra-sulfated preparations did not possess any higher anticoagulant activity than several tri-sulfated variants, and also had lower heparin cofactor II mediated activity. Activation of prekallikrein was concentration dependent for all samples, and broadly increased with the degree of sulfation, though the di-sulfated preparation was able to form more kallikrein than some of the tri-sulfated preparations. The ability of the samples to activate the kinin system, as measured by bradykinin, was observed to be through kallikrein generation. These results show that whilst an increase in sulfation of chondroitin sulfate did cause an increase in anticoagulant activity and activation of the kinin system, there may be subtler structural interactions other than sulfation at play given the different responses observed.

Heparin Mimetics: Their Therapeutic Potential

Heparin mimetics are synthetic and semi-synthetic compounds that are highly sulfated, structurally distinct analogues of glycosaminoglycans. These mimetics are often rationally designed to increase potency and binding selectivity towards specific proteins involved in disease manifestations. Some of the major therapeutic arenas towards which heparin mimetics are targeted include: coagulation and thrombosis, cancers, and inflammatory diseases. Although Fondaparinux, a rationally designed heparin mimetic, is now approved for prophylaxis and treatment of venous thromboembolism, the search for novel anticoagulant heparin mimetics with increased affinity and fewer side effects remains a subject of research. However, increasingly, research is focusing on the non-anticoagulant activities of these molecules. Heparin mimetics have potential as anti-cancer agents due to their ability to: (1) inhibit heparanase, an endoglycosidase which facilitates the spread of tumor cells; and (2) inhibit angiogenesis by binding to growth factors. The heparin mimetic, PI-88 is in clinical trials for post-surgical hepatocellular carcinoma and advanced melanoma. The anti-inflammatory properties of heparin mimetics have primarily been attributed to their ability to interact with: complement system proteins, selectins and chemokines; each of which function differently to facilitate inflammation. The efficacy of low/non-anticoagulant heparin mimetics in animal models of different inflammatory diseases has been demonstrated. These findings, plus clinical data that indicates heparin has anti-inflammatory activity, will raise the momentum for developing heparin mimetics as a new class of therapeutic agent for inflammatory diseases.

Glycosaminoglycan-based resorbable polymer composites in tissue refurbishment

Regeneration of tissue structure with the aid of bioactive polymer matrices/composites and scaffolds for respective applications is one of the emerging areas of biomedical engineering. Recent advances in conjugated glycosaminoglycan (GAG) hybrids using natural and synthetic polymers have opened new avenues for producing a wide variety of resorbable polymer matrices. These hybrid scaffolds are low-immunogenic, highly biocompatible and biodegradable with incredible mechanical and tensile properties. GAG-based resorbable polymeric matrices are being exploited in migration of stem cells, cartilage and bone replacement/regeneration and production of scaffolds for various tissue engineering applications. In the current review, we will discuss the role of GAG-based resorbable polymer matrices in the field of regenerative medicine.

The contact activation and kallikrein/kinin systems: pathophysiologic and physiologic activities

The contact activation system (CAS) and kallikrein/kinin system (KKS) are older recognized biochemical pathways that include several proteins that skirt the fringes of the blood coagulation, fibrinolytic, complement and renin-angiotensin fields. These proteins initially were proposed as part of the hemostatic pathways because their deficiencies are associated with prolonged clinical assays. However, the absence of bleeding states with deficiencies of factor XII (FXII), prekallikrein (PK) and high-molecular-weight kininogen indicates that the CAS and KKS do not contribute to hemostasis. Since the discovery of the Hageman factor 60 years ago much has been learned about the biochemistry, cell biology and animal physiology of these proteins. The CAS is a pathophysiologic surface defense mechanism against foreign proteins, organisms and artificial materials. The KKS is an inflammatory response mechanism. Targeting their activation through FXIIa or plasma kallikrein inhibition when blood interacts with the artificial surfaces of modern interventional medicine or in acute attacks of hereditary angioedema restores vascular homeostasis. FXII/FXIIa and products that arise with PK deficiency also offer novel ways to reduce arterial and venous thrombosis without an effect on hemostasis. In summary, there is revived interest in the CAS and KKS due to better understanding of their activities. The new appreciation of these systems will lead to several new therapies for a variety of medical disorders.

Characterization of currently marketed heparin products: adverse event relevant bioassays

The polyanion oversulfated chondroitin sulfate (OSCS) was identified as a contaminant in heparin products and was associated with severe hypotensive responses and other symptoms in patients receiving the drug. The OSCS associated adverse reactions were attributed to activation of the contact system via the plasma mediator, activated factor XII (FXIIa), which triggers kallikrein (KK) activity. Unlike heparin alone, OSCS, is able to activate FXII in plasma and stably bind to FXIIa enhancing plasma KK activity and the induction of vasoactive mediators such as bradykinin (BK), C3a and C5a. Similarly OSCS can interfere with heparin neutralization by the polycationic drug protamine. Here, we assess heparin (heparin sodium, dalteparin, tinzaparin or enoxaparin)-protamine complex formation and plasma based bioassays of KK, BK and C5a in a 96-well plate format. We establish the normal range of variation in the optimized bioassays across multiple lots from 9 manufacturers. In addition, because other oversulfated (OS) glycosaminoglycans (GAGs) besides OSCS could also serve as possible economically motivated adulterants (EMAs) to heparin, we characterize OS-dermatan sulfate (OSDS), OS-heparan sulfate (OSHS) and their native forms in the same assays. For the protamine test, OS-GAGs could be distinguished from heparin. For the KK assay, OSCS and OSDS were most potent followed by OSHS, and all had similar efficacies. Finally, OSDS had a greater efficacy in the C5a and BK assays followed by OSCS then OSHS. These data established the normal range of response of heparin products in these assays and the alteration in the responses in the presence of possible EMAs.