Characterization of silicone pressure-sensitive adhesive episcleral implant for drug delivery

Abstract

The development of an effective sustained ocular drug delivery system remains a challenging task. The objective of the present study was to characterize a silicone pressure sensitive adhesive (PSA) episcleral implant system for transscleral drug delivery. Silicone PSA implants for dexamethasone, atenolol, and bovine serum albumin (BSA) were prepared at different polymer-to-drug mass ratios. Implant adhesion to human cadaver sclera was measured. Drug release experiments were conducted in well-stirred containers in vitro. The results were then analyzed using a pharmacokinetic model and in vitro–in vivo data comparison from previous studies. The silicone PSA episcleral implants in the present study had an average diameter of 3.5 mm and a thickness of 0.8 mm. Drug release from the silicone PSA implants was influenced by drug solubility, implant polymer content, and implant coating. Drug release from the implants was observed to follow the receding boundary release mechanism and was solubility dependent with the higher water solubility drug showing higher release rate than the low-solubility drug. Increasing polymer content in the implants led to a significant decrease in the drug release rate. Coated implants reduced the initial burst effect and provided lower release rates than the uncoated implants. These implants provided sustained drug release that could last up to several months in vitro and demonstrated the potential to offer drug delivery for chronic ocular diseases via the transscleral route.

• Controlled release
• episcleral implant
• macromolecules
• silicone adhesive
• transscleral delivery

Acknowledgements

The authors thank Gaurav Tolia for his help in the preparation of the silicone PSA implants and Dr Jinsong Hao for helpful discussion. The authors acknowledge Advanced Materials Characterization Center at the University of Cincinnati for their assistance in the SEM study.

Declaration of interest

The authors report that they have no conflicts of interest. The authors acknowledge the use of tissues procured by the National Disease Research Interchange (NDRI) with the support from NIH Grant 5 U42 RR006042.