Abstract
Abstract: :
Purpose:To measure the glucose diffusion coefficients of human, bovine, and porcine corneas in vitro. The results of this study would serve as a guide in the development of nutrient–permeable materials for corneal implants. Methods: Diffusion of glucose across human (n = 8), bovine (n = 7), and porcine corneas (n = 8) was measured using a modified blind well chamber apparatus (Boyden chamber). Dialysis membranes (MWCO 14000) (n = 7) and non–porous mylar membranes (n = 7) were used as positive and negative controls, respectively. Corneal and polymer samples were sandwiched between an upper chamber filled with deionized water and a lower chamber filled with a circulating glucose solution maintained at a fixed concentration of 10 mg/mL. Motorized stirring bars were used to mix the solution in the upper chamber in order to prevent boundary layering of glucose. The glucose concentrations of the upper chambers were measured at 30 minute intervals with a FreeStyleTM glucose meter. Diffusion coefficients of glucose for each of the samples were calculated from the glucose flux data using Fick’s law of diffusion. Results:The diffusion coefficient of glucose is highest for human corneas (3.0 ± 0.2 x 10–6 cm2/s) followed by porcine corneas (1.8 ± 0.6 x 10–6 cm2/s) and bovine corneas (1.6 ± 0.1 x 10–6 cm2/s) (P < 0.05). The diffusion coefficients of all tested corneas were significantly higher (P < 0.05) than that of dialysis membrane (3.4 ± 0.2 x 10–7 cm2/s). Conclusions:The glucose diffusion coefficients of human, bovine, and porcine corneas in vitro is on the order of 10–6 cm2/s. Human corneas have the highest permeability to glucose, followed by porcine and bovine corneas. The results of this study provide an index by which polymers can be evaluated for their potential as corneal implant materials based on their permeability to glucose.
Keywords: cornea: basic science • nutritional factors