Design and in vitro evaluation of doxycycline hyclate niosomes as a potential ocular delivery system.

Niosomes have been considered as promising nanoscale carriers for ocular drug delivery, since they have been shown to increase the bioavailability of various drugs and to improve their efficacy. The main objective of this study was to prepare and characterize niosomes for ocular delivery of doxycycline hyclate. Niosomes were prepared using various surfactants (namely Span 20, Span 60, Span 80, Tween 60) and cholesterol in different molar ratios, using the thin film hydration method followed by multiple membrane extrusion or the reverse-phase evaporation method. In our hands highest entrapment efficiency was encountered with the formulation composed of Span 60 and cholesterol, prepared by the reverse phase evaporation method. Transmission electron microscopy and dynamic light scattering were used to assess the morphology, size and size distribution paterns of prepared niosomes. In vitro release studies showed sustained release of doxycycline from niosomes. After 2 months of storage at 4 °C the doxycycline-loaded niosomes remained physically stable in terms of encapsulation efficiency and particle size. The performed Draize test revealed that the prepared niosomes were well tolerated by the eye. Taken together our findings indicate that niosomes could be considered as a plausible drug delivery platform for for ophthalmic application of doxycycline.