Topical use of coenzyme Q10-loaded liposomes coated with trimethyl chitosan: tolerance, precorneal retention and anti-cataract effect.

The effects of the molecular weight (MW) and concentration of trimethyl chitosan (TMC) on the characteristics of Coenzyme Q10-loaded liposomes coated with trimethyl chitosan were investigated while the efficacy of the antioxidant Coenzyme Q10 in delaying selenite-induced cataract was assessed. The existence of a thick polymer layer on the surface of the liposomes nanoparticle system was affirmed by transmission electron microscopy (TEM) analysis and the changes in particle size distribution and zeta potential. The entrapment efficiency was almost the same as when the polymer was added to liposomes.The Draize test and histological analysis demonstrated the excellent ocular tolerance of TMC for topical administration. Gamma scintigraphic data clearly showed that the drug elimination of polymer-coated liposomes is significantly slower than the radiolabelled solution used as a control. An almost 4.8-fold increase in the precorneal residence time was achieved in the presence of TMC with a higher Mw compared with the control group. Furthermore, the anti-cataract effect was evaluated by morphological examination and analysis of biochemical changes. Coenzyme Q10 exhibited a markedly anti-cataract effect with the percentage of lens opacity being about 53% at the final examination. The mean activities of superoxide dismutase and reduced glutathione were significantly higher in the Coenzyme Q10-treated group than in the cataract model group, while malondialdehyde was significantly lower. In conclusion,the physical properties and precorneal retention time of liposomes could be modified with TMC and ophthalmic instillation of Coenzyme Q10 is able to retard selenite-induced cataract formation.