Vitamin C as a shelf-life extender in liposomes

Abstract The objective of this study was to evaluate the influence of vitamin C (VC) on the stability of stored liposomes under different climatic conditions. Liposomal formulations containing 1 mg/mL of VC (LIP-VC) and blank formulations (LIP-B) were prepared by the reverse-phase evaporation method. After preparation, they were characterized according to their refractive index, average vesicle diameter, polydispersity index (PDI), zeta potential, pH, content, encapsulation efficiency (EE%), morphology, stability and antioxidant activity. For stability, LIP-VC and LIP-B were stored in different climatic conditions (4 °C, 25 °C and 40 °C) for 30 days. The LIP-VC presented 1.3365 refractive index, 161 nm of mean diameter, 0.231 PDI, -7.3 mV zeta potential, 3.2 pH, 19.4% EE%, spherical morphology, 1 mg/mL of VC content, and antioxidant activity of 12 and 11.4 μmol of TE/mL for the radical DPPH and ABTS+, respectively. During stability, the LIP-B stored in 40 °C showed an instability in the parameters: PDI, vesicle size and zeta potential after 15 days, while the LIP-VC remained stable in its size and PDI for 30 days. After that, it is shown that VC can be used as an antioxidant and stabilizer in liposomes to increase the stability and shelf-life of vesicles.

Protective effect of guarana-loaded liposomes on hemolytic activity.

Paullinia cupana var. sorbilis (Mart.) Ducke, popularly known as guarana, is one of the most promising plants in Brazilian flora and has attracted considerable interest from the scientific community owing to its numerous therapeutic activities and less side effects. Hence, using nanotechnology is a viable alternative to primarily improve the physicochemical characteristics and bioavailability of guarana. The objective of the present study was to develop, characterize, and evaluate the stability of liposomes containing guarana powder and to evaluate their antioxidant and hemolytic activity in vitro. Three different concentrations of guarana powder and two methods of liposome preparation were tested. Liposomes were developed and characterized, and their stability was analyzed by evaluating physicochemical parameters. Hemolytic activity of guarana liposomal formulation (G-Lip) was compared with that of guarana in its free form (FG) and of liposome without guarana (W-Lip). Red blood cells from rats were exposed to these different formulations dissolved in phosphate buffer solution (PBS; pH 7.4). The best stability was achieved for the formulation containing 1 mg mL-1 guarana powder produced by the reverse phase evaporation method. FG showed dose-dependent antioxidant activity, which was maintained in G-Lip. W-Lip showed high hemolytic activity in PBS at pH 7.4 possibly because of the presence of polysorbate 80, and on addition of guarana to these structures, the hemolytic process was reversed. The same protective effect was observed for FG. It is believed that the complex structure of guarana, primarily the presence of polyphenols, exerts a powerful antioxidant action, helping to protect erythrocytes.