A new approach for heparin standardization: combination of scanning UV spectroscopy, nuclear magnetic resonance and principal component analysis

Preanalytical Quality Evaluation of Citrate Evacuated Blood Collection Tubes-Ultraviolet Molecular Absorption Spectrometry Confronted with Ion Chromatography

We previously enabled a direct insight into the quality of citrate anticoagulant tubes before their intended use for specimen collection by introducing an easy-to-perform UV spectrometric method for citrate determination on a purified water model. The results revealed differences between the tubes of three producers, Greiner BIO-ONE (A), LT Burnik (B), and BD (C). It became apparent that tubes C contain an additive, which absorbs light in the ultraviolet range and prevents reliable evaluation of citrate anticoagulant concentration with the suggested method. In this research, we re-evaluate the quality of citrate-evacuated blood collection tubes by complementing UV spectrometry with ion chromatography. (1) Comparable results were obtained for tubes B at 220 nm. (2) Citrate concentrations determined with ion chromatography were lower for tubes A and C. Chromatograms reveal additional peaks for both. (3) Influences of heparin on absorption spectra and chromatograms of citrate were studied. Some similarities with the shape of the anticoagulant spectra of tubes A and C were observed, and the lithium heparin peak in chromatograms is close to them, but a confident judgment was not possible. (4) Contamination of anticoagulant solution with potassium, magnesium, and calcium was confirmed for all the brands, and contamination with lithium for B and C.

New anti-angiogenic compound based on chemically modified heparin

PURPOSE

The purpose of this study was to measure the anti-angiogenic effect of N-desulfated Re-N-acetylated, a chemically modified heparin (mHep).

METHODS

In vitro assays (cell tube formation, viability, proliferation, and migration) with endothelial cells were performed after 24 h of treatment with mHep at 10, 100, and 1000 ng/mL or saline. In vivo tests were performed after laser-induced choroidal neovascularization (CNV) in rats, followed by an intravitreal injection (5 µL) of mHep (10, 100, 1000 ng/mL) or balanced salt solution. Immunofluorescence analysis of the CNV was performed after 14 days.

RESULTS

mHep produced a statistically significant reduction in cell proliferation, tube formation, and migration, without cell viability changes when compared to saline. Mean measures of CNV area were 54.84 × 10⁶ pixels/mm (± 12.41 × 10⁶), 58.77 × 10⁶ pixels/mm (± 17.52 × 10⁶), and 59.42 × 10⁶ pixels/mm (± 17.33 × 10⁶) in groups 100, 1000, and 10,000 ng/mL, respectively, while in the control group, mean area was 72.23 × 10⁶ (± 16.51 × 10⁶). The P value was 0.0065. Perimeter analysis also demonstrated statistical significance (P = 0.0235) with the mean measure of 93.55 × 10⁴, 94.23 × 10⁴, and 102 × 10⁴ in the 100 ng/mL, 1000 ng/mL, and control groups, respectively.

CONCLUSIONS

These results suggest that mHep N-DRN is a potent anti-angiogenic, anti-proliferative, and anti-migratory compound with negligible anticoagulant or hemorrhagic action and no cytotoxicity for retina cells. This compound may serve as a candidate for treating choroidal neovascularization.

Dual inhibition of factor XIIa and factor XIa as a therapeutic approach for safe thromboprotection

Clinical practice shows that a critical unmet need in the field of medical device-associated thrombosis prevention is the availability of an anticoagulant therapy without hemorrhagic risk. In the quest for new drugs that are at least as effective as those currently available, while avoiding bleeding complications, molecules that target nearly every step of the coagulation pathway have been developed. Among these molecules, inhibitors of factor XII (FXII) or factor XI (FXI) are promising alternatives as deficiencies in these factors protect against thrombosis without causing spontaneous hemorrhage, as revealed by epidemiological and preclinical data. Ixodes ricinus-contact phase inhibitor (Ir-CPI), a new anticoagulant candidate with an innovative mechanism of action could be this ideal anticoagulant agent for safe prevention from clotting on medical devices. This protein, which selectively binds to FXIIa, FXIa, and plasma kallikrein and inhibits the reciprocal activation of FXII, prekallikrein, and FXI in human plasma, was shown to prevent thrombosis in an ovine cardiopulmonary bypass system associated with cardiac surgeries. Furthermore, as opposed to unfractionated heparin, Ir-CPI appears to be devoid of bleeding risk. This review outlines the rationale for targeting upstream coagulation factors in order to prevent medical device-associated thrombosis; examines the novel approaches under development; and focuses on Ir-CPI, which shows promising properties in the field of thrombosis prevention.

Quality Control of Heparin Injections: Comparison of Four Established Methods

Heparin is an anticoagulant medication that is usually injected subcutaneously. The quality of a set of commercial heparin injections from different producers was examined by NMR, IR, UV-Vis spectroscopies and potentiometric multisensor system. The type of raw material regarding heparin animal origin and producer, heparin molecular weight and activity values were derived based on the non-targeted analysis of 1H NMR fingerprints. DOSY NMR spectroscopy was additionally used to study homogeneity and additives profile. UV-Vis and IR, being cheaper than NMR, combined with multivariate statistics were successfully applied to study excipients composition as well as semi-estimation of activity values. Potentiometric multisensor measurements were found to be an important additional source of information about inorganic composition of finished heparin formulations. All investigated instrumental techniques are useful for finished heparin injections and should be selected according to availability as well as the information and confidence required for a specific sample.

Recent advances in biotechnology for heparin and heparan sulfate analysis

Heparan sulfate (HS) is a class of linear, sulfated, anionic polysaccharides, called glycosaminoglycans (GAGs), which present on the mammalian cell surfaces and extracellular matrix. HS GAGs display a wide range of critical biological functions, particularly in cell signaling. HS is composed of repeating units of 1 → 4 glucosidically linked uronic acid and glucosamine residues. Heparin, a pharmacologically important version of HS, having higher sulfation and a higher content of iduronic acid than HS, is a widely used clinical anticoagulant. However, due to their heterogeneity and complex structure, HS and heparin are very challenging to analyze, limiting biological studies and even resulting in safety concerns in their therapeutic application. Therefore, reliable methods of structural analysis of HS and heparin are critically needed. In addition to the structural analysis of heparin, its concentration in blood needs to be closely monitored to avoid complications such as thrombocytopenia or hemorrhage caused by heparin overdose. This review summarizes the progress in biotechnological approaches in the structural characterization of HS and heparin over the past decade and includes the development of the ultrasensitive approaches for detection and measurement in biological samples.

Tools for the Quality Control of Pharmaceutical Heparin

Heparin is a vital pharmaceutical anticoagulant drug and remains one of the few naturally sourced pharmaceutical agents used clinically. Heparin possesses a structural order with up to four levels of complexity. These levels are subject to change based on the animal or even tissue sources that they are extracted from, while higher levels are believed to be entirely dynamic and a product of their surrounding environments, including bound proteins and associated cations. In 2008, heparin sources were subject to a major contamination with a deadly compound-an over-sulphated chondroitin sulphate polysaccharide-that resulted in excess of 100 deaths within North America alone. In consideration of this, an arsenal of methods to screen for heparin contamination have been applied, based primarily on the detection of over-sulphated chondroitin sulphate. The targeted nature of these screening methods, for this specific contaminant, may leave contamination by other entities poorly protected against, but novel approaches, including library-based chemometric analysis in concert with a variety of spectroscopic methods, could be of great importance in combating future, potential threats.

Chondroitin-Sulfate-A-Coated Magnetite Nanoparticles: Synthesis, Characterization and Testing to Predict Their Colloidal Behavior in Biological Milieu

Biopolymer coated magnetite nanoparticles (MNPs) are suitable to fabricate biocompatible magnetic fluid (MF). Their comprehensive characterization, however, is a necessary step to assess whether bioapplications are feasible before expensive in vitro and in vivo tests. The MNPs were prepared by co-precipitation, and after careful purification, they were coated by chondroitin-sulfate-A (CSA). CSA exhibits high affinity adsorption to MNPs (H-type isotherm). We could only make stable MF of CSA coated MNPs (CSA@MNPs) under accurate conditions. The CSA@MNP was characterized by TEM (size ~10 nm) and VSM (saturation magnetization ~57 emu/g). Inner-sphere metal–carboxylate complex formation between CSA and MNP was proved by FTIR-ATR and XPS. Electrophoresis and DLS measurements show that the CSA@MNPs at CSA-loading > 0.2 mmol/g were stable at pH > 4. The salt tolerance of the product improved up to ~0.5 M NaCl at pH~6.3. Under favorable redox conditions, no iron leaching from the magnetic core was detected by ICP measurements. Thus, the characterization predicts both chemical and colloidal stability of CSA@MNPs in biological milieu regarding its pH and salt concentration. MTT assays showed no significant impact of CSA@MNP on the proliferation of A431 cells. According to these facts, the CSA@MNPs have a great potential in biocompatible MF preparation for medical applications.

Crude Heparin Preparations Unveil the Presence of Structurally Diverse Oversulfated Contaminants

Nowadays, pharmaceutical heparin is purified from porcine and bovine intestinal mucosa. In the past decade there has been an ongoing concern about the safety of heparin, since in 2008, adverse effects associated with the presence of an oversulfated chondroitin sulfate (OSCS) were observed in preparations of pharmaceutical porcine heparin, which led to the death of patients, causing a global public health crisis. However, it has not been clarified whether OSCS has been added to the purified heparin preparation, or whether it has already been introduced during the production of the raw heparin. Using a combination of different analytical methods, we investigate both crude and final heparin products and we are able to demonstrate that the sulfated contaminants are intentionally introduced in the initial steps of heparin preparation. Furthermore, the results show that the oversulfated compounds are not structurally homogeneous. In addition, we show that these contaminants are able to bind to cells in using well known heparin binding sites. Together, the data highlights the importance of heparin quality control even at the initial stages of its production.

Anti-Thrombin, Anti-Adhesive, Anti-Migratory, and Anti-Proliferative Activities of Sulfated Galactans from the Tropical Green Seaweed, Udotea flabellum

In this study, sulfated polysaccharide-rich extracts were isolated from 22 tropical seaweeds (4 red, 11 brown, and 7 green) found in northeastern Brazil, and evaluated for the role of anticoagulant agents. Fifteen of the extracts showed anticoagulant activity, including all the extracts from green seaweeds. Udoteaflabellum (a green seaweed) extract was the most potent, requiring an amount of only 3 µg to double the plasma coagulation time in the activated partial thromboplastin time test. A similar result was obtained with 1 µg of heparin. Two sulfated homogalactans with anticoagulant activity, F-I (130 kDa) and F-II (75 kDa), were isolated from this extract using several bio-guided purification steps. Their anticoagulant activity, as well as properties related to antitumor activity (anti-proliferative, anti-adhesive, and anti-migratory), were accessed. Their anticoagulant activities were close to that of heparin. We found that F-I and F-II (0.5–10 μg/mL) were not able to directly inhibit thrombin. In the presence of anti-thrombin, F-I (0.5 μg/mL) was more effective than heparin (0.5 μg/mL) in inhibiting thrombin, while F-II showed similar effects as heparin. F-I and F-II also inhibited B16-F10 (murine melanoma cells) adhesion, migration, and proliferation on a fibronectin-coated surface, but not on laminin- or collagen I-coated surfaces. Except for the antiproliferative activity, the other effects of F-I and F-II were eliminated upon their desulfation (~50%), indicating that the degree of sulfation is not as important for F-I and F-II anti-proliferative activity as the sulfation position. Taken together, the results provide strong evidence for the potential utility of sulfated galactans from U.flabellum, making these compounds an interesting option for future investigations that aim to design new anticoagulant/antitumor agents.

Baccharis dracunculifolia-based mouthrinse alters the exopolysaccharide structure in cariogenic biofilms

Baccharis dracunculifolia is a native plant from Brazil with antimicrobial activity. The purpose of this study was to investigate whether a B. dracunculifolia-based mouthrinse (Bd) changes the structure of insoluble exopolysaccharides (IEPS) in Streptococcus mutans UA159 cariogenic biofilm. Biofilms were grown on glass slides and treated with Bd, its vehicle (VC), chlorhexidine digluconate (CHX), or saline solution (NaCl). Among the treatments, only CHX significantly reduced the biofilm biomass and bacterial viability (p<0.05). Gas chromatography-mass spectrometry and nuclear magnetic resonance analyses revealed that IEPS from the four biofilm samples were α- glucans containing different proportions of (1→6) and (1→3) glycosidic linkages. The structural differences among the four IEPS were compared by principal component analysis (PCA). PCA analysis indicated that IEPS from VC- and NaCl-treated biofilms were structurally similar to each other. Compared with the control, IEPS from Bd- and CHX-treated biofilms were structurally different and had distinct chemical profiles. In summary, the fact that Bd changed the IEPS chemical composition indicates that this mouthrinse may affect the cariogenic properties of the S. mutans biofilm formed.

Re-visiting the structure of heparin

The sulfated polysaccharide heparin has been used as a life-saving anticoagulant in clinics well before its detailed structure was known. This mini-review is a survey of the evolution in the discovery of the primary and secondary structure of heparin. Highlights in this history include elucidation and synthesis of the specific sequence that binds to antithrombin, the development of low-molecular-weight heparins currently used as antithrombotic drugs, and the most promising start of chemo-enzymatic synthesis. Special emphasis is given to peculiar conformational properties contributing to interaction with proteins that modulate different biological properties.

Chemical reduction of carboxyl groups in heparin abolishes its vasodilatory activity

Previous studies have shown that heparin induces vascular relaxation via integrin-dependent nitric oxide (NO)-mediated activation of the muscarinic receptor. The aim of this study was to identify the structural features of heparin that are necessary for the induction of vasodilatation. To address this issue, we tested heparin from various sources for their vasodilatation activities in the rat aorta ring. Structural and chemical characteristics of heparin, such as its molecular weight and substitution pattern, did not show a direct correlation with the vasodilation activity. Principal component analysis (PCA) of circular dichroism (CD), (1)H-nuclear magnetic resonance (NMR) and vasodilation activity measurements confirmed that there is no direct relationship between the physico-chemical nature and vasodilation activity of the tested heparin samples. To further understand these observations, unfractionated heparin (UFH) from bovine intestinal mucosa, which showed the highest relaxation effect, was chemically modified. Interestingly, non-specific O- and N-desulfation of heparin reduced its anticoagulant, antithrombotic, and antihemostatic activities, but had no effect on its ability to induce vasodilation. On the other hand, chemical reduction of the carboxyl groups abolished heparin-induced vasodilation and reduced the affinity of heparin toward the extracellular matrix (ECM). In addition, dextran and dextran sulfate (linear non-sulfated and highly sulfated polysaccharides, respectively) did not induce significant relaxation, showing that the vasodilation activity of polysaccharides is neither charge-dependent nor backbone unspecific. Our results suggest that desulfated heparin molecules may be used as vasoactive agents due to their low side effects.

Antiproliferative activity of fucan nanogel

Sulfated fucans comprise families of polydisperse natural polysaccharides based on sulfated L-fucose. Our aim was to investigate whether fucan nanogel induces cell-specific responses. To that end, a non toxic fucan extracted from Spatoglossum schröederi was chemically modified by grafting hexadecylamine to the polymer hydrophilic backbone. The resulting modified material (SNFuc) formed nanosized particles. The degree of substitution with hydrophobic chains was close to 100%, as estimated by elemental analysis. SNFfuc in aqueous media had a mean diameter of 123 nm and zeta potential of -38.3 ± 0.74 mV, as measured by dynamic light scattering. Nanoparticles conserved their size for up to 70 days. SNFuc cytotoxicity was determined using the MTT assay after culturing different cell lines for 24 h. Tumor-cell (HepG2, 786, H-S5) proliferation was inhibited by 2.0%-43.7% at nanogel concentrations of 0.05-0.5 mg/mL and rabbit aorta endothelial cells (RAEC) non-tumor cell line proliferation displayed inhibition of 8.0%-22.0%. On the other hand, nanogel improved Chinese hamster ovary (CHO) and monocyte macrophage cell (RAW) non-tumor cell line proliferation in the same concentration range. The antiproliferative effect against tumor cells was also confirmed using the BrdU test. Flow cytometric analysis revealed that the fucan nanogel inhibited 786 cell proliferation through caspase and caspase-independent mechanisms. In addition, SNFuc blocks 786 cell passages in the S and G2-M phases of the cell cycle.

A robust method to quantify low molecular weight contaminants in heparin: detection of tris(2-n-butoxyethyl) phosphate

Recently, oversulfated chondroitin sulfate (OSCS) was identified in contaminated heparin preparations, which were linked to several adverse clinical events and deaths. Orthogonal analytical techniques, namely nuclear magnetic resonance (NMR) and capillary electrophoresis (CE), have since been applied by several authors for the evaluation of heparin purity and safety. NMR identification and quantification of residual solvents and non-volatile low molecular contaminants with USP acceptance levels of toxicity was achieved 40-fold faster than the traditional GC-headspace technique, which takes ~120 min against ~3 min to obtain a (1)H NMR spectrum with a signal/noise ratio of at least 1000/1. The procedure allowed detection of Class 1 residual solvents at 2 ppm and quantification was possible above 10 ppm. 2D NMR techniques (edited-HSQC (1)H/(13)C) permitted visualization of otherwise masked EDTA signals at 3.68/59.7 ppm and 3.34/53.5 ppm, which may be overlapping mononuclear heparin signals, or those of ethanol and methanol. Detailed NMR and ESI-MS/MS studies revealed a hitherto unknown contaminant, tris(2-n-butoxyethyl) phosphate (TBEP), which has potential health risks.