Quantitative analysis of antithrombin III binding site in low molecular weight heparins by exhausetive heparinases digestion and capillary electrophoresis

State-of-the-art chromatographic and mass spectrometric techniques in heparin structural analysis

Heparin is the most extensively used anticoagulant in clinical practice. It is a highly sulfated, linear polysaccharide composed of repeating disaccharide units. As a member of the glycosaminoglycan (GAG) family, heparin's complex structure features significant molecular weight variability, diverse sugar residues, and variable sulfation patterns. Low molecular weight heparins (LMWHs), produced through chemical or enzymatic depolymerization, are distinguished by their reduced molecular weight and offer therapeutic advantages, including lower bleeding risks, reduced immunogenicity, and higher bioavailability following subcutaneous administration. The structural intricacy of heparin-based drugs presents major challenges for quality control, clinical safety, process optimization, and therapeutic expansion. Advanced analytical methods, particularly LC and MS, remain at the forefront of efforts to elucidate the detailed structures of these drugs. This review highlights recent progress in chromatographic and MS-based analysis techniques for heparin and its derivatives, including the application of computational algorithms for structural elucidation. The focus is on the analytical methodologies, their innovations, and limitations, while also exploring how machine learning and bioinformatics tools are shaping the future of heparin quality control and therapeutic application. This comprehensive review provides a reference point for researchers engaged in the structural analysis of heparin-based drugs and offers insights into the future development of novel analytical strategies for improving the safety and efficacy of these critical anticoagulants.

Comprehensive chromatographic profiling and structural analysis of key anticoagulant components in enoxaparin

Heparin is the most widely used anticoagulant in clinical practice, with enoxaparin being one of the most important low molecular weight heparins (LMWHs). In this study, an antithrombin III (ATIII) affinity column was used. Enoxaparin and its oligosaccharides of varying sizes, prepared using preparative size exclusion chromatography (SEC), were fractionated through the ATIII affinity column. The different affinity fractions from each oligosaccharide size were profiled using strong anion exchange (SAX) chromatography. Each peak was automatically transferred to an SEC column for desalting prior to mass spectrometry (MS) analysis, which enabled structural identification using a multiple heart-cut (MHC) 2D LC-MS system (SAX-SEC-MS). The high-affinity fraction from enoxaparin was further analyzed using the MHC 2D LC system (SEC-SAX). SAX profiles of the high-affinity oligosaccharides, prepared by both size and affinity fractionation, were consistent with those obtained by direct SEC-SAX analysis. The possible sequences of several high-affinity hexasaccharides and the domain compositions of high-affinity octa- and decasaccharides in enoxaparin were further elucidated by disaccharide analysis after manual collection of the oligosaccharides. This work advances the understanding of enoxaparin's structural features and offers a potential approach to improve the quality of enoxaparin, as well as to identify key structural motifs in heparin/LMWHs that contribute to protein binding.

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

Protein interactors of 3-O sulfated heparan sulfates in human MCI and age-matched control cerebrospinal fluid

Heparan sulfates (HS) proteoglycans are commonly found on the cell surface and mediate many processes. Binding of HS ligands is determined by the sulfation code on the HS chain that can be N-/2-O/6-O- or 3-O-sulfated, generating heterogenous sulfation patterns. 3-O sulfated HS (3S-HS) play a role in several (patho)physiological processes such as blood coagulation, viral pathogenesis and binding and internalization of tau in Alzheimer's disease. However, few 3S-HS-specific interactors are known. Thus, our insight into the role of 3S-HS in health and disease is limited, especially in the central nervous system. Using human CSF, we determined the interactome of synthetic HS with defined sulfation patterns. Our affinity-enrichment mass spectrometry studies expand the repertoire of proteins that may interact with (3S-)HS. Validating our approach, ATIII, a known 3S-HS interactor, was found to require GlcA-GlcNS6S3S for binding, similar to what has been reported. Our dataset holds novel, potential HS and 3S-HS protein ligands, that can be explored in future studies focusing on molecular mechanisms that depend on 3S-HS in (patho)physiological conditions.

[Advances in heparin structural analysis by chromatography technologies]

Heparin （Hp） is the most widely used anticoagulant drug in the clinics， with an annual global output of over 10 billion dollars. Hp， a member of the glycosaminoglycans （GAGs）， is prepared from porcine intestinal mucosa via extraction， separation， and purification. Hp is a linear polysaccharide with repeating disaccharide units. Low-molecular-weight heparins （LMWHs） are depolymerized from Hp via chemical or enzymatic degradation. Compared with Hp， LMWHs exhibit less bleeding side effect， milder immunogenicity， and higher bioavailability when injected subcutaneously. In general， Hps， including LMWHs， are high complex drugs with large molecular weights （MWs）， inhomogeneous MW distributions， and structural heterogeneity， including different degrees and locations of sulfonation， and unique residues generated from different production processes. Thus， developing efficient analytical methods to elucidate the structures of Hps and characterize or quantitate their properties is extremely challenging. Unfortunately， this problem limits their quality control， production optimization， clinical safety monitoring， and new applications. Research has constantly sought to elucidate the complicated structures of Hp drugs. Among the structural analysis and quality control methods of Hp currently available， chromatographic methods are the most widely studied and used. However， no literature thoroughly summarizes the specific applications of chromatographic methods in the structural analysis， manufacturing process， and quality control of Hp drugs. This paper systematically organizes and describes recent research progresses of the chromatographic methods used to analyze Hp drugs， including the identification and composition of monosaccharides， disaccharides， oligosaccharides， and polysaccharides. The applications， innovations， and limitations of these chromatographic methods are also summarized in this review. The insights obtained in this study will help production and quality control personnel， as well as drug researchers， obtain a deeper understanding of the complex structures of Hp drugs. This paper also provides a comprehensive reference for the structural analysis and quality control of Hps， proposes ideas for the development of new quality control methods， and lays a strong foundation for the in-depth structural elucidation of Hp drugs.

Sequencing analysis of heparin reducing terminals with orthogonal chromatographic approaches

Heparin is a linear sulfated polysaccharide with a complex structure. It is important to figure out the sequences at the terminals of the sugar chains, as it will help us understand the heparin structure deeper and control its quality properly. The tetrasaccharide linkage region (LR) could be a tag to help us find out heparin terminals after digestion by different combinations of heparinases. In this work, orthogonal chromatographic approaches including SAX, SEC-MS and 2D-LC-MS were applied to qualitatively and quantitatively analyze the heparinase released LR-terminals. The disaccharides next to LR are those ones with low or non-sulfation, UA-GlcNAc and UA-GlcNAc6S, and then they are extended with the highly sulfated disaccharides, IdoA2S-GlcNS and IdoA2S-GlcNS6S. It is suggested that the sulfo transferases did not work at the sugar residues next to LR terminal, especially the 2-O-sulfo and N-sulfo transferases, which could be affected by steric hindrance from LR, when heparin is biosynthesized. This conclusion will be theoretical fundamental to help us understand heparin's structure deeper. The methods provided in this work could be potential ways to control heparin's quality and monitor the production processes of heparin properly.