Chromatographic study of nucleoside-lipids by RP-UHPLC-DAD/CAD.

Today, one of the most popular strategies in drug delivery is the encapsulation of therapeutic agents in supramolecular nanosystems formed from amphiphilic molecules. Synthetic nucleoside-lipids, composed of one nucleoside and lipidic chains, constitute promising new amphiphilic excipients under research in the field of pharmaceutical and biomedical applications. The aim of this work was to study the chromatographic behavior of these nucleoside-lipids in reversed-phase HPLC to establish appropriate chromatographic conditions for their analysis in drug delivery systems. The effect of the stationary phase, the organic solvent, the pH* values, and pH modifier nature of the mobile phase were studied on retention, peak shape, and detection. Good chromatographic performance was achieved on both Syncronis® C18 and Acquity® BEH C18 with mobile phases composed of MeOH/water, 95:5 (v/v) mixtures at apparent pH above 5. Dual detection by diode array detection (DAD) and charged aerosol detection (CAD) was investigated. CAD signal was found to be dependent on the type of pH modifiers added to the mobile phase. In isocratic elution, the same order of magnitude of CAD responses was obtained for the tested nucleoside-lipids. This study led to suitable chromatographic conditions for purity and stability studies of nucleoside-lipids. The purity of the synthetized molecules was established to be superior to 98%. Different stability in organic solvents was noticed depending on nucleoside-lipid structure. This first study will allow quantitative applications to establish loading ratio and encapsulation yield in future drug delivery systems composed of nucleoside-lipid-based assemblies.

Solid Lipid Nanoparticles for Image-Guided Therapy of Atherosclerosis.

Although the application of nanotechnologies to atherosclerosis remains a young field, novel strategies are needed to address this public health issue. In this context, the magnetic resonance imaging (MRI) approach has been gradually investigated in order to enable image-guided treatments. In this contribution, we report a new approach based on nucleoside-lipids allowing the synthesis of solid lipid nanoparticles (SLN) loaded with iron oxide particles and therapeutic agents. The insertion of nucleoside-lipids allows the formation of stable SLNs loaded with prostacycline (PGI2) able to inhibit platelet aggregation. The new SLNs feature better relaxivity properties in comparison to the clinically used contrast agent Feridex, indicating that SLNs are suitable for image-guided therapy.

Analysis of fatty acid samples by hydrophilic interaction liquid chromatography and charged aerosol detector.

HILIC/CAD techniques were used in analysis of samples containing fatty acids. Amine base column appeared to be the more retentive stationary phase compared to zwitterionic and BEH silica. The retention decreased with pH mobile phases changing from 3 to 5. Acetonitrile and acetone organic modifier were compared. Acetone gave higher eluotropic strength and better peak symmetry whereas acetonitrile led to higher efficiency. The retention decreased when ammonium acetate concentration increased from 5 to 20mM. The use of sub-2µm column did not show flat Van Deemter curves at high flow rates. A rapid separation of PGI2 and its main degradation product, 6-keto prostaglandin F1α was obtained in 1.6min with a Hypersil GOLD, 50mm×2.1mm, 1.9µm with; acetonitrile/acetate ammonium pH 5 at 20mM (85/15; v/v at 0.7ml/min).

Green analytical method development for statin analysis.

Green analytical chemistry method was developed for pravastatin, fluvastatin and atorvastatin analysis. HPLC/DAD method using ethanol-based mobile phase with octadecyl-grafted silica with various grafting and related-column parameters such as particle sizes, core-shell and monolith was studied. Retention, efficiency and detector linearity were optimized. Even for column with particle size under 2 µm, the benefit of keeping efficiency within a large range of flow rate was not obtained with ethanol based mobile phase compared to acetonitrile one. Therefore the strategy to shorten analysis by increasing the flow rate induced decrease of efficiency with ethanol based mobile phase. An ODS-AQ YMC column, 50 mm × 4.6 mm, 3 µm was selected which showed the best compromise between analysis time, statin separation, and efficiency. HPLC conditions were at 1 mL/min, ethanol/formic acid (pH 2.5, 25 mM) (50:50, v/v) and thermostated at 40°C. To reduce solvent consumption for sample preparation, 0.5mg/mL concentration of each statin was found the highest which respected detector linearity. These conditions were validated for each statin for content determination in high concentrated hydro-alcoholic solutions. Solubility higher than 100mg/mL was found for pravastatin and fluvastatin, whereas for atorvastatin calcium salt the maximum concentration was 2mg/mL for hydro-alcoholic binary mixtures between 35% and 55% of ethanol in water. Using atorvastatin instead of its calcium salt, solubility was improved. Highly concentrated solution of statins offered potential fluid for per Buccal Per-Mucous(®) administration with the advantages of rapid and easy passage of drugs.