Development of hydrophilic gels containing coenzyme Q-loaded liposomes: characterization, stability and rheology measurements.

Objective: The aim of this study was to develop, characterize and evaluate stability of a gel containing coenzyme Q (Q)-loaded liposomes, and enhance the stability of Q in the nanocarrier-containing gel compared to the conventional gel.

Methods: Q-loaded liposome dispersions prepared from unsaturated or saturated lecithin, were characterized for particle size, polydispersity index (PDI), zeta-potential, pH value, oxidation index, Q-content and morphology, and incorporated into carbomer gel. Liposome gels and liposome-free gel were analyzed for flow properties, pH values, Q-content, and liposomes size and PDI (liposome gels), 48 h after preparation and in predetermined time intervals during 6 months storage at different temperatures in order to predict their long term stability.

Results: Liposomes were of small particle size, homogeneous, negatively charged, and their incorporation into gel did not significantly change (p > .05) their particle size and PDI. All gels revealed non-Newtonian, shear-thinning plastic flow behavior during storage with no marked changes in rheological parameters. Storage of gels did not significantly influence the pH value (p > .05), while it significantly decreased Q-content (p < .05). Q was significantly more (p < .05) stable in liposome gel containing unsaturated lecithin liposomes (G1) than in gel containing saturated lecithin liposomes (G2) and liposome-free gel (G3).

Conclusions: Q-loaded liposome gel G1 was the optimal formulation, since during storage at different temperatures, it did not show significant increase in liposome size and PDI, it provided significantly higher stability for Q than other gels and its pH value was suitable for skin application. Due to limited Q-stability it should be stored at 4 °C.