Biomimetic Solid Lipid Nanoparticles for Oral Bioavailability Enhancement of Low Molecular Weight Heparin and Its Lipid Conjugates: In Vitro and in Vivo Evaluation

Abstract

Low molecular weight heparin (LMWH) is an anionic oligosaccharide macromolecule, which is commonly administered via parenteral routes for the treatment of vascular disorders like deep vein thrombosis (DVT) and pulmonary embolism (PE). Oral heparin delivery can tremendously improve the treatment of such disorders but is restricted due to its large size and anionic character. The present investigation describes synthesis of LMWH-lipid conjugates and their encapsulation in phosphatidylcholine stabilized biomimetic solid lipid nanoparticles (SLNs) for LMWH's oral bioavailability enhancement. Briefly, LMWH was conjugated with different saturated lipids of varying chain length (stearic acid, palmitic acid and myristic acid) using carbodiimide chemistry. The conjugation was confirmed with IR and (1)H NMR spectroscopy. The LMWH-lipid conjugate loaded SLNs were characterized for various parameters like shape, size, zeta potential, entrapment efficiency and in vitro release behavior in different simulated GIT pH mediums. The GIT toxicity of LMWH-lipid conjugate loaded SLNs to different tissues of intestinal epithelium was observed using H&E staining followed by microscopic observation at cellular level. The LMWH-lipid conjugate loaded SLNs were found to be safe for oral administration. The plasma concentration of LMWH was estimated using anti-FXa chromogenic assay. A significantly higher bioavailability (p < 0.05) of LMWH was observed using LMWH-lipid conjugates loaded SLNs in comparison to LMWH loaded SLNs and free LMWH. The order of different conjugates in bioavailability enhancement was LMWH-stearic acid > LMWH-palmitic acid > LMWH-myristic acid. This strategy holds promise for future applications of oral delivery of LMWH conjugates in the form of SLNs particularly for the treatment of cardiovascular disease like DVT and PE.

Strategies to Overcome Heparins’ Low Oral Bioavailability

“…Lipids and deoxycholic acid (DOCA) ( Figure 3 ) have been proven to be suitable choices for conjugation with heparins [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. As they are naturally occurring substances, the administration of these conjugates may involve few toxic effects [ 32 ].…”

Low molecular weight heparins for current and future uses: approaches for micro- and nano-particulate delivery

“…Strategies for oral delivery of LMWHs through the use of nanoparticulate carriers are also based on enhancement of bioadhesion and adsorption to gastro-intestinal tissues, modification of tight junctions and protection against acidic pH of the stomach. Paliwal et al (2011) synthesized LMWH-lipid conjugates, which were then encapsulated in phosphatidylcholine-stabilized solid lipid nanoparticles (SLNs) for enhancement of LMWH's oral bioavailability. The chylomicron mimicking biocompatible lipid-based carrier systems improved oral BAV of the therapeutic molecule by following a transcellular mechanism of lipid transport through intestinal lymphatics.…”

“…The chylomicron mimicking biocompatible lipid-based carrier systems improved oral BAV of the therapeutic molecule by following a transcellular mechanism of lipid transport through intestinal lymphatics. Prepared SLNs were found to be free of any gastro-intestinal toxicity and a maximum overall BAV (relative to IV LMWH) of 57% (Paliwal et al, 2011).…”

Cardiovascular therapy through nanotechnology – how far are we still from bedside?

“…In terms of patients' acceptance, the best delivery route is usually represented by oral administration, however, few vasculoprotective nanoparticle formulations are thus far available in this form [e.g., PLGA-curcumin (166,167), heparinloaded nanoparticles (168,169)]. Parenteral administration evades the problems related to gastrointestinal route, i.e., the poor absorption, gastrointestinal intolerance and/ or non-compliance associated with oral preparations.…”