Development of solid lipid nanoparticles and nanostructured lipid carriers containing amphotericin B

Abstract

Amphotericin B (AmB) is one of the most effective systemic antifungal agents, but its use is circumscribed by the dose-limiting toxicity of the conventional micellar dispersion formulation, Fungizone®. To lower its toxicity, AmB incorporated into aqueous dispersion of lipid nanoparticles was proposed. The paper describes the development of two types of lipid nanoparticles. Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) made from glyceryl behenate (GB) and glyceryl palmitostearate (GP) were prepared by either hot high pressure homogenization (HPH) or warm microemulsion (WME) techniques in order to evaluate the physical stability of these particles, as well as the chemical stability of drug during storage at 4°C for 3 months. NLC differed from SLN by the presence of liquid lipid (glyceryl tricaprylate/caprate) in the lipid matrix. The results indicated that these two lipid nanoparticles could be colloidal carriers for intravenous therapy. The optimized AmB-SLN formulations had an average diameter less than 300 nm, exhibited monodispersity and carried a negative charge. The AmB content was rapidly degraded when using tween 80 or cremophor EL as stabilizers. The best formulation of SLN dispersion prepared by HPH method consisted of 3% GP and 2% poloxamer 407 (P407), while the best formulation of SLN formulation prepared by WME method consisted of 10% GP, 20% cremophor RH40 and 20% glycerin. Lyophilized AmB-loaded SLN was not success possible due to incomplete lyophilization process. Entrapment efficiency of AmB was improved by blending small amounts of liquid oils with solid lipids. A significant increase in the encapsulation efficacy of NLC containing P407 was noted when compared to that of SLN formulation. In addition, the application of lecithin in the SLN dispersions could increase the amount of drug into the particles. The 1H-NMR data indicated the formation of oil clusters within the solid nanoparticles or the presence between the solid platelet and the surfactant layer. Both AmB-SLN and AmB-NLC formulation have less aggregated species and hemolytic response than Fungizone® indicating that lipid nanoparticles could reduce its toxicity. The release profiles of AmB formulations depended on its aggregated form and entrapment efficiency. Furthermore, the formulation containing 5% AmB showed a drug release by a biphasic profile. For in vitro antifungal testing, all of the selected AmB formulations were equal and more effective than both AmB itself and Fungizone®. It was demonstrated by IR spectra that there was no chemical reaction occurred between AmB and other components. The DSC, HSM, X-ray diffractograms showed that AmB in lipid matrix was in either molecularly dispersed or amorphous form except the formulation containing 5% drug loading.