Diclofenac sustained release from sterilised soft contact lens materials using an optimised layer-by-layer coating

A layer-by-layer (LbL) coating was designed using ionic polysaccharides (chitosan, sodium alginate, sodium hyaluronate) and genipin (crosslinker), to sustain the release of diclofenac sodium salt (DCF) from soft contact lens (SCL) materials. The coating was hydrophilic, biocompatible, non-toxic, reduced bacterial growth and had minor effects on the physical properties of the material, such as wettability, ionic permeability, refractive index and transmittance, which remained within the recommended values for SCLs. The coating was applied on a silicone-based hydrogel and on commercial SofLens and Purevision SCLs. The coating attenuated the initial drug burst and extended the therapeutic period for, at least, two weeks. Relevantly, the problems of sterilizing drug loaded SCLs coated with biopolymers, using classic methods that involve high temperature or radiation, were successfully solved through high hydrostatic pressure (HHP) sterilization.