Complexation of a poly-L-arginine with low molecular weight heparin enhances pulmonary absorption of the drug

Purpose. This study tests the hypothesis that complexation between a cationic polymer, poly-L-arginine (PLA), and an anionic drug, low molecular weight heparin (LMWH), enhances pulmonary absorption and reduces the epithelial toxicity. Materiala and Methods. Enoxaparin, a LMWH, was complexed with PLAs of different molecular weights at varying concentrations. The resulting complexes were characterized by measuring particle size and zeta potential, and by quantitating the interactions between PLA and enoxaparin using an azure A assay. Changes in transepithelial electrical resistance (TEER) and cytotoxicity induced by enoxaparin-PLA complex were investigated in Calu-3 cells. Pulmonary absorption of LMWH was determined by measuring plasma anti-factor Xa levels. A bronchoalveolar lavage (BAL) study was performed to investigate if the PLA-based formulations caused any cellular or biochemical changes in the lungs. Results. The particle size of enoxaparin-PLA complexes decreased and the zeta potential values of the complex became less negative as the concentration of positively charged PLA in the complex increased. In vitro experiments suggest that addition of enoxaparin-PLA complex to the apical side of a polarized cell monolayer results in a significant increase in permeability to C-14-mannitol and a decrease in TEER. Pulmonary formulations of enoxaparin plus 0.0125% or 0.0625% PLA of molecular weight 93 kDa led to a twofold increase in the relative bioavailability of LMWH compared to the control (enoxaparin plus normal saline). The BAL study showed that the enoxaparin-PLA complex formulation did not elicit any significant increases in marker enzyme activities compared to the normal saline-treated or untreated control groups. Conclusion. PLA could be used as a carrier for the pulmonary delivery of LMWH.