Preclinical Safety Testing of Novel Silica Eye Drop as an Ophthalmic Carrier Matrix

Topical eye drops are common for treating eye diseases, often requiring multiple daily doses. Silica Matrix technology enables drug delivery systems that release drugs over time. This study aimed to develop and characterize a silica-based eye drop, as well as a 14-day tolerance and toxicity assessment to evaluate its potential as a drug carrier in ophthalmology. Silica Eye Drop is a silica-based composite containing silica microparticles, made via sol-gel chemistry and spray drying, along with silica hydrogel. The product was terminally sterilised by gamma irradiation and characterised by particle size, silica content, in vitro dissolution time, droplet size, applicability, endotoxin content, sterility, and short-term stability. Four New Zealand rabbits received one drop daily in one eye’s conjunctival sac for 14 days, while the other eye served as a control. During the study, eye conditions, blood chemistry, and postmortem histology were monitored. The final formulation contained 23% (w/w) silica microparticles (average diameter 3.21 μm) and 77% (w/w) silica hydrogel, with 18.2 wt% silica, dissolving in 24 h. The average droplet volume was 31.3 ± 4.4 µl, easily dispensed manually from a single-dose unit with acceptable size variability. A 2-month stability study showed no major changes in product properties. Finally, in the rabbit toxicity study, both the treated and untreated eyes showed similar tolerability levels. The Silica Eye Drop was successfully developed and manufactured. Easy to use with consistent quality, it demonstrated the safety and potential of silica platform technology for a carrier material in topical ophthalmic products. In this study, a novel silica-based eye drop formulation was described and evaluated. Silica microparticles were synthesised and incorporated through a Fill and Finish process, followed by sterilization and characterization for particle size, silica content, dissolution, droplet size, microbiological purity, and short-term stability. In vivo tolerability was assessed in four New Zealand rabbits over 14 days with daily administration. The optimised formulation contained 23% (w/w) silica microparticles and 77% (w/w) silica hydrogel (18.2 wt% silica). Microparticles (D50 = 3.21 μm) fully dissolved within 24 h. No adverse ocular effects occurred, confirming excellent safety, stability, and therapeutic potential. A novel Silica Eye Drop formulation was developed, showing full dissolution in 24 h and good tolerability in rabbits, highlighting its promise for future ocular therapies.