The nonlinear relationship between concentration of analyte and its permeability coefficient in ocular tissues

Monitoring and quantifying the permeability of different drugs and chemical solutions through ocular tissues is of great importance due to its potential use in pharmacological research. In this study, Optical Coherence Tomography, a relatively new innovation in biomedical imaging was used for the functional imaging of glucose diffusion in the sclera of the eye. The permeability coefficient for different glucose concentrations was quantified non-destructively in order to compare the effect of glucose concentration on its rate of diffusion. In these in vitro experiments, fresh New Zealand white rabbit eyes were imaged during the diffusion of different glucose concentrations (10, 15, 20, and 25%). The nonlinearity of the permeability coefficient in the tissue with differing glucose concentrations was evident. The results suggest an inversely proportional relationship between the permeability coefficient and the glucose concentration in epithelial tissues. The permeability coefficient of glucose declined from (1.67 ± 0.17) × 10^-5 cm/sec to (5.08 ± 0.23) × 10^-6 cm/sec for the 10% and 25% glucose solutions, respectively. Furthermore, the nonlinear relationship between the permeability rate and the concentration of hyperosmotic solutions demonstrated in this study could be further utilized in numerous scientific and clinical fields such as optical clearing of tissues and noninvasive diagnosis of eye diseases.