Preparation and characterization of low-molecular-weight heparin/protamine nanoparticles (LMW-H/P NPs) as FGF-2 carrier

We produced low-molecular-weight heparin/protamine nanoparticles (LMW-H/P NPs) as a carrier for heparin-binding growth factors, such as fibroblast growth factor-2 (FGF-2). A mixture of low-molecular-weight heparin (MW: about 5000 Da, 6.4 mg/mL) and protamine (MW: about 3000 Da, 10 mg/mL) at a ratio of 7:3 (vol:vol) yields a dispersion of microparticles (1-6 microm in diameter). In this study, diluted low-molecular-weight heparin solution in saline (0.32 mg/mL) mixed with diluted protamine (0.5 mg/mL) at a ratio at 7:3 (vol:vol) resulted in soluble nanoparticles (112.5 +/- 46.1 nm in diameter). The generated NPs could be then stabilized by adding 2 mg/mL dextran (MW: 178-217 kDa) and remained soluble after lyophilization of dialyzed LMW-H/P NP solution. We then evaluated the capacity of LMW-H/P NPs to protect activity of FGF-2. Interaction between FGF-2 and LMW-H/P NPs substantially prolonged the biological half-life of FGF-2. Furthermore, FGF-2 molecules were protected from inactivation by heat and proteolysis in the presence of LMW-H/P NPs.