Assessment of preservative efficacy of sodium N-hydroxymethylglicinate (NIG) in drug delivery formulations for ophthalmic use

Different drug delivery systems, namely polymeric nanoparticles (NP), nanostructured lipid nanoparticles (NLC), and in situ gelling polymeric solutions (Gel), containing sodium N-hydroxymethylglycinate (NIG) at 0.002% (w/v) as a preservative agent were prepared as sterile formulations and characterized. The study aimed at verifying the maintenance over time of sterility conditions of these polymeric and colloidal systems, after exposure to environmental contamination. It is in fact known that many preservatives can interact with drugs and other additives in a formulation, or be adsorbed on the surface of plastic containers. The same phenomenon might occur when the formulation contains nanosized (colloidal) lipid or polymeric matters. Our experimental findings confirmed the capacity of NIG to keep the sterility of both fresh and packaged nanoparticulate or polymeric systems.