Encapsulation of low molecular weight heparins: Influence on the anti-Xa/anti-IIa ratio

Comparative Assessment of APTT Reagents for Evaluating Anticoagulant Sensitivity of Fucosylated Glycosaminoglycans (FGs) Derived from Sea Cucumbers

Fucosylated glycosaminoglycans (FGs) derived from sea cucumbers exhibit potent intrinsic Xase (iXase) inhibition, anticoagulation, and antithrombosis. Plasma activated partial thromboplastin time (APTT), a widely used screening test worldwide, is crucial for evaluating anticoagulant efficacy. However, the applicability of these commercially available APTT reagents for assessing anticoagulation of FGs remains unreported. In this study, we investigated the disparity between ellagic acid and colloidal silica APTT reagents in evaluating anticoagulation of dHG-5 and dHLFG-4, two depolymerized FGs, and elucidated the underlying rationale. The results demonstrated that dHG-5 and dHLFG-4 exhibited heightened sensitivity to the ellagic acid APTT reagent both in vitro and in vivo, and did not significantly affect the activation of APTT reagents for plasma. In addition, both ellagic acid and colloidal silica APTT reagents inhibited the anti-iXase of dHG-5 and dHLFG-4, and the inhibition of the ellagic acid APTT reagent was less pronounced compared to the colloidal silica APTT reagent. These findings suggest that the reduced impact of the ellagic acid APTT reagent on the anti-iXase activity of dHG-5 and dHLFG-4 is responsible for the increased sensitivity in plasma APTT analysis. This study offers valuable insights into the characteristics of two APTT reagents applied for assessing the anticoagulant activity of FG-related compounds.

Low-Molecular-Weight Heparins: Reduced Size Particulate Systems for Improved Therapeutic Outcomes

A wide range of diseases have been treated using low-molecular-weight heparins (LMWHs), the drug of choice for anticoagulation. Owing to their better pharmacokinetic features compared to those of unfractionated heparin (uFH), several systems incorporating LMWHs have been investigated to deliver and improve their therapeutic outcomes, especially through development of their micro- and nano-particles. This review article describes current perspectives on the fabrication, characterization, and application of LMWHs-loaded micro- and nano-particles to achieve ameliorated bioavailability. The valuable applications of LMWH will continue to encourage researchers to identify efficient delivery systems that have specific release characteristics and ameliorated bioavailability, overcoming the challenges presented by biological obstructions and the physicochemical properties of LMWHs.

Investigation of cationized triblock and diblock poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers for oral delivery of enoxaparin: In vitro approach

In this study, poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers grafted with a cationic ligand, propargyltrimethyl ammonium iodide (PTA), to fabricate the cationized triblock (P(CatCLCL)₂-PEG) and diblock (P(CatCLCL)-mPEG) copolymers were investigated their potential use for oral delivery of enoxaparin (ENX). Influences of various PTA contents and different structures of the copolymers on molecular characteristics, ENX encapsulation, particle characteristics, and capability of drug transport across Caco-2 cells were elucidated. The results showed that P(CatCLCL)₂-PEG and P(CatCLCL)-mPEG copolymers self-aggregated and encapsulated ENX into spherical particles of ∼200-450nm. The increasing amount of PTA on the copolymers increased encapsulation efficiency of over 90%. The ENX release from both types of the cationized copolymer particles was pH-dependent which was retarded at pH 1.2 and accelerated at pH 7.4, supporting the drug protection in the acidic environment and possible release in the blood circulation. The toxicity of ENX-loaded particles on Caco-2 cells decreased when decreasing the amount of PTA. The triblock and diblock particles dramatically enhanced ENX uptake and transport across Caco-2 cells as compared to the ENX solution. However, the different structures of the copolymers slightly affected ENX transport. These results suggested that P(CatCLCL)₂-PEG and P(CatCLCL)-mPEG copolymers would be potential carriers for oral delivery of ENX.

STATEMENT OF SIGNIFICANCE

The anionic drugs such as proteins, peptides or polysaccharides are generally administered via invasive route causing patient incompliance and high cost of hospitalization. The development of biomaterials for non-invasive delivery of those drugs has gained much attention, especially for oral delivery. However, they have limitation due to non-biocompatibility and poor drug bioavailability. In this study, the novel poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers grafted with propargyltrimethyl ammonium iodide, a small cationic ligand, were introduced to use as a carrier for oral delivery of enoxaparin, a highly negatively charged drug. The study showed that these cationized copolymers could achieve high enoxaparin entrapment efficiency, protect drug release in an acidic environment and enhance enoxaparin permeability across Caco-2 cells, the intestinal cell model. These characteristics of the cationized copolymers make them a potential candidate for oral delivery of anionic drugs for biomaterial applications.

Family of Bioactive Heparin-Coated Iron Oxide Nanoparticles with Positive Contrast in Magnetic Resonance Imaging for Specific Biomedical Applications

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH) are well-known for their anticoagulant properties. There is also currently a growing interest in using LMWH in targeted cancer therapy. In particular, several types inhibit heparanase, a key enzyme overexpressed in the tumor microenvironment that promotes angiogenesis progression and metastasis spreading. Here, we propose iron oxide nanoparticles (HEP-IONP) coated with different heparins of distinct anticoagulant/anti-heparanase activity ratios and suitable for positive contrast in magnetic resonance imaging. As a proof of concept, magnetic resonance angiography (MRA) was conducted in mice up to 3 h after intravenous administration. This new IONP-based positive contrast appropriate for clinic together with the long vascular circulating times can enable innovative theranostic applications if combined with the various bioactivities of the heparins. Indeed, we showed, using advanced in vitro tests, how HEP-IONP anticoagulant or anti-heparanase activities were maintained depending on the heparin species used for the coating. Overall, the study allowed presenting an IONP coated with a commercial LMWH (Lovenox) suggested as a theranostic translational probe for MRA diagnostic and treatment of thrombosis, and an antitumor IONP coated with a specific depolymerized heparin to be used in targeted therapy and diagnostic modalities.

Development and characterization of polymer lipid hybrid nanoparticles for oral delivery of LMWH

The present study aimed to develop an improved oral delivery system for low-molecular-weight heparin (LMWH), novel polymer lipid hybrid nanoparticles were developed. LMWH loaded chitosan polymer lipid hybrid nanoparticles (LMWH-CS-PLNs) were developed using double emulsification and solvent evaporation method. The performance of developed formulations was evaluated by using in vitro and in vivo behavior, such as drug release studies, in vitro permeation study, in vivo venous thrombolytic study, in vitro uptake studies by using intestinal epithelium resembling Caco-2 cell lines. The new CS-PLNs might provide an effective strategy for oral delivery of LMWH with improved encapsulation efficiency as compared to CS-NPs and SA-LNPs.

Aerosolizable modified-release particles of montelukast improve retention and availability of the drug in the lungs

Montelukast, a cysteinyl leukotriene receptor antagonist available as oral tablets, is used as a second-line therapy in asthma. In this study, we sought to enhance the availability of montelukast in the lungs by encapsulating the drug in poly (lactide-co-glycolic acid)-based (PLGA) respirable large porous particles. We determined the oral and lung specific availability of montelukast by assessing metabolic stability of the drug in the lung and liver homogenates, respectively. We similarly measured the oral and inhalational bioavailability by monitoring the pharmacokinetics and disposition of the drug in live animals. After preparing montelukast-loaded particles with various polymers, in the absence or presence of polyethylenimine (PEI-1), we characterized the particles for physical-chemical properties, entrapment efficiency, in vitro release, uptake by alveolar macrophages, deposition in the lungs, and safety after pulmonary administration. When incubated in lung or liver homogenates, the amount of intact drug in the lung homogenates was greater than that in the liver homogenates. Likewise, the extent of montelukast absorption via the lungs was greater than that via the oral route. Compared with smaller non-porous particles, large porous particles (PEI-1) were taken up by the alveolar macrophages at a lesser extent but deposited in the lungs at a greater extent. The levels of injury markers in the bronchoalveolar lavage fluid (BALF), collected from rat lungs treated with PEI-1, were no different from that in BALF collected from saline treated rats. Overall, the retention time and concentration of montelukast in the lungs can be increased by formulating the drug in large porous particles of PLGA.

Development of enoxaparin sodium polymeric microparticles for colon-specific delivery

Background and aims

Recent studies have shown that low molecular weight heparins are effective in the treatment of inflammatory bowel disease. Therefore, there is considerable interest in the development of an oral colonic delivery pharmaceutical system allowing targeted release of heparin in the inflamed tissue. The objective of this study was to prepare microparticles for the oral administration and colonic release of enoxaparin and to evaluate the influence of certain formulation factors on their characteristics.

Methods

Microparticles were prepared by water/oil/water double emulsion technique followed by solvent evaporation. The influence of several formulation factors on the characteristics of microparticles were evaluated. The formulation factors were alginate concentration in the inner aqueous phase, polymer (Eudragit^® FS 30D and Eudragit^® RS PO) concentration in the organic phase and ratios between the two polymers. The microparticles were characterized in terms of morphology, size, entrapment efficiency and enoxaparin release.

Results

The results showed that increasing sodium alginate percentage reduced the encapsulation efficiency of enoxaparin and accelerated enoxaparin release. Regarding the influence of the two polymers, reducing polymer concentration in the organic phase led to a smaller size of microparticles, a lower entrapment efficiency and an important retardation of enoxaparin release. The formulation prepared with Eudragit^® FS 30D limited the release to a maximum of 3% in gastric simulated environment, a specific characteristic of oral systems for colonic delivery, and fulfilled our objective to delay the release.

Conclusions

Microparticles prepared with Eudragit^® FS 30D represent a suitable and potential oral system for the colonic delivery of enoxaparin.

pH-responsive thiolated chitosan nanoparticles for oral low-molecular weight heparin delivery: in vitro and in vivo evaluation

The aim of present study was to investigate a pH-responsive and mucoadhesive nanoparticle system for oral bioavailability enhancement of low-molecular weight heparin (LMWH). The thioglycolic acid (TGA) was first covalently attached to chitosan (CS) with 396.97 ± 54.54 μmol thiol groups per gram of polymer and then the nanoparticles were prepared with thiolated chitosan (TCS) and pH-sensitive polymer hydroxypropyl methylcellulose phthalate (HPMCP) by ionic cross-linking method. The obtained nanoparticles were characterized for the shape, particle size, zeta potential, drug entrapment efficiency and loading capacity. In vitro results revealed the acid stability of pH-responsive nanoparticles, which had a significant control over LMWH release and could effectively protect entrapped drugs in simulated gastric conditions. By the attachment of the thiol ligand, an improvement of permeation-enhancing effect on freshly excised carp intestine (1.86-fold improvement) could be found. The mucoadhesive properties were evaluated using fluorescently labeled TCS or CS nanoparticles. As compared with the controls, a significant improvement of mucoadhesion on rat intestinal mucosa was observed in TCS/HPMCP nanoparticles via confocal laser scanning microscopy. The activated partial thromboplastin time (APTT) was significantly prolonged and an increase in the oral bioavailability of LMWH was turned out to be pronounced after oral delivered LMWH-loaded TCS/HPMCP nanoparticles in rats, which suggested enhanced anticoagulant effects and improved absorption of LMWH. In conclusion, pH-responsive TCS/HPMCP nanoparticles hold promise for oral delivery of LMWH.

Alginate coated chitosan core shell nanoparticles for oral delivery of enoxaparin: in vitro and in vivo assessment

The objective of present research work was to develop alginate coated chitosan core shell nanoparticles (Alg-CS-NPs) for oral delivery of low molecular weight heparin, enoxaparin. Chitosan nanoparticles (CS-NPs) were synthesized by ionic gelation of chitosan using sodium tripolyphosphate. Core shell nanoparticles were prepared by coating CS-NPs with alginate solution under mild agitation. The Alg-CS-NPs were characterized for surface morphology, surface coating, particle size, polydispersity index, zeta potential, drug loading and entrapment efficiency using SEM, Zeta-sizer, FTIR and DSC techniques. Alginate coating increased the size of optimized chitosan nanoparticles from around 213 nm to about 335 nm as measured by dynamic light scattering in zeta sizer and further confirmed by SEM analysis. The performance of optimized enoxaparin loaded Alg-CS-NPs was evaluated by in vitro drug release studies, in vitro permeation study across intestinal epithelium, in vivo venous thrombosis model, particulate uptake by intestinal epithelium using fluorescence microscopy and pharmacokinetic studies in rats. Coating of alginate over the CS-NPs improved the release profile of enoxaparin from the nanoparticles for successful oral delivery. In vitro permeation studies elucidated that more than 75% enoxaparin permeated across the intestinal epithelium with Alg-CS-NPs. The Alg-CS-NPs significantly increased (p<0.05) the oral bioavailability of enoxaparin in comparison to plain enoxaparin solution as revealed by threefold increase in AUC of plasma drug concentration time curve and around 60% reduction in thrombus formation in rat venous thrombosis model. The core shell Alg-CS-NPs showed promising potential for oral delivery and significantly enhanced the in vivo oral absorption of enoxaparin.

Ultrasonic-assisted preparation of a low molecular weight heparin (LMWH) with anticoagulant activity

Low molecular weight heparin (LMWH) is currently used as an anticoagulant agent and constitutes an alternative to unfractionated heparin, which is the cause of serious adverse drug reaction such as heparin-induced thrombocytopenia (HIT). Commercially available LMWH is produced by enzymatic depolymerization that is costly or by chemical methods that are generally carried out under conditions that could imply side reactions that reduce final product efficiency and yields. In this work, we present the use of a physicochemical method for the production of LMWH. This method consists in the use of hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. LMWH that are produced using this physicochemical method have an average molecular weight and anticoagulant properties (Anti-Xa and Anti-IIa) that are comparable to some of commercial LMWH that are currently used. Ultrasonic-assisted radical depolymerization of heparin leads to products with a remarkably low polydispersity index. Moreover, in comparison to other LMWH such as those produced by enzymatic β-elimination, this physicochemical depolymerization of heparin induces fewer oligosaccharides with less than five monosaccharide units. This contributes to the better preservation of the ATIII pentasaccharide binding sequence, which results in a high Anti-Xa/Anti-IIa ratio (1.86). However, LMWH obtained using this physicochemical method have a lower degree of sulfation than other LMWH, which seems to be the cause of a lower Anti-Xa and Anti-IIa activity (143.62±5.42 and 77.07±4.4, respectively).

Oral delivery of low molecular weight heparin by polyaminomethacrylate coacervates

PURPOSE

Oral bioavailability of low molecular weight heparin (LMWH) can be achieved by several advanced drug delivery approaches. Here, a new preparation method for coacervates (CAs) using non-toxic polyethylene glycol derivates was developed.

METHODS

LMWH were coacervated with polyaminomethacrylates (Eudragit® RL or RS) using polyethylene glycol (PEG) derivatives as non-toxic solvents. CAs were analyzed for their physicochemical properties and pharmacokinetic parameters were determined for different formulations in rabbits.

RESULTS

CAs from both polymer types using various PEGs were of irregular shape and had particle sizes of around 40 μm, encapsulation efficiencies of >90%, and complete LMWH in vitro release was obtained within 2 h. In vivo, oral Absorption at doses of 300 IU/kg was rather low (F < 2.5%) while dose increase resulted in a maximum at 600 IU/kg (FRL: 6.0 ± 1.2%; FRS: 5.8 ± 2.5%) and 1,200 IU/kg did not result in higher bioavailability (FRL: 4.6 ± 0.4%; FRS: 4.1 ± 0.8%). CAs were applicable to various LMWH types where the oral availability decreased in the order fondaparinux>enoxaparin>nadroparin>certoparin depending mainly on the molecular weight.

CONCLUSIONS

CAs prepared by an organic solvent-free method allowed the oral delivery of LMWHs. The therapeutic efficiency and the simple and solvent-free manufacturing process underlines the high potential of this new preparation method.