A Study of Human Scleral Permeability using Organ Culture

PURPOSE: To measure the scleral permeability according to the time and regional differences using organ-cultured scleral tissues. METHODS: After measuring hydration and cell viability, scleral permeability was measured using a Ussing apparatus and rhodamine-dextran polymers. Organ-cultured scleral tissues are incubated for 1, 2, and 3 days and its permeability was measured in each quadrant. RESULTS: There are no significant difference in hydration and viability between the organ-cultured sclera and fresh sclera. Increases in permeability are greater with the 10 kDa dextran than with the 40 or 70 kDa dextran, however the scleral permeability did not change significantly with time (p>0.05) nor with regional difference (p>0.05). CONCLUSIONS: The scleral permeability decreased with increased molecular weight of tracers but did not change according to the time- and regional differences.

Experimental Transscleral Ocular Drug Delivery: Use of Pluronic F-127 Gel and Fibrin Glue as a Sustained Release System

PURPOSE: The purpose of this study was to evaluate the effect of two sustained release systems (Pluronic F-127 gel and Fibrin glue) on the diffusion of dexamethasone across the human sclera. METHODS: Scleral sections excised from moist-chamber-stored human globes were mounted in a perfusion chamber that can create transscleral pressure. In the sustained release study, sample (100 muL) of 3H-dexamethasone in Pluronic F-127 gel or Fibrin glue was added to the episcleral side of the tissue, while BSS plusR was perfused across the uveal side at an transscleral pressure of 15 mmHg. Perfusate fractions were collected and measured using scintillation spectrometry and scleral permeability was calculated. RESULTS: The apparent permeability constants of the human sclera to 3H-dexamethasone in BSS plus(R) (the control value), Pluronic F-127 gel, and Fibrin glue were 1.15+/-0.11x10(-5) cm/s (n=5), 1.49+/-0.33x10-6 cm/s (n=5), and 7.32+/-0.98x10(-6) cm/s (n=7), respectively. The permeability values of Pluronic F-127 gel and Fibrin glue were relatively lower than the control value. Pluronic F-127 gel and Fibrin glue showed a uniform sustained release characteristic during a 24-hour period. The cumulative release rates of dexamethasone through the human sclera from BSS plus(R) (the control value), Pluronic F-127 gel, and Fibrin glue were 84.0+/-1.5% (n=5), 29.3+/-5.8% (n=5), and 61.5+/-5.9% (n=4) at 20 hours, respectively. There were significant differences in the human scleral permeability constants and cumulative release rates among the three vehicles (p<0.0001). CONCLUSIONS: Pluronic F-127 gel and Fibrin glue provided a slow, uniform sustained release during a 24- hour period. This study established a strong possibility of the new transscleral drug delivery in vitro using the sustained release systems of Pluronic F-127 gel and Fibrin glue. This may be a good experimental tool in the future development of a practical drug delivery system across the sclera for the treatment of a variety of chorioretinal disorders.