Continuous supercritical CO2 assisted process for the production of nano-niosomes loaded with a second-generation antibiotic for ocular therapy

Nano-niosomes were produced by a continuous supercritical CO2 assisted process. Operating at 100 bar and 40 ◦C, different Span® 80 to Tween® 80 wt ratios and two surfactant to cholesterol molar ratios were tested. The 90/10 Span® 80 to Tween® 80 ratio produced the right formulation to obtain spherical and stable niosomes, with a mean diameter of 145 ± 52 nm. Adding cholesterol to niosome formulations, a general slight increase in vesicles mean size was observed and also a larger tendency to their aggregation. Ofloxacin was selected as a model drug to be loaded into nano-niosomes; the largest encapsulation efficiency of 78% and a prolonged drug release up to 5 h were measured when the 90/10 Span® 80 to Tween® 80 ratio was used in the starting formulation, in which also cholesterol, at a surfactant to cholesterol molar ratio equal to 4, was added.