Relationship of Stokes Radius to the Rate of Diffusion across Bruch's Membrane

Abstract

Flux was dependent on the direction of the concentration gradient and the R(S) of the individual tracers. We have successfully demonstrated that quantitative gel exclusion chromatography can be used to follow diffusion of a mixture of tracers across BM/Ch, and that we can measure flux across BM/Ch preparations with an exposed surface area as small as 1.8 mm(2).

Evaluation of protein drug stability with vitreous humor in a novel ex-vivo intraocular model

“…However, these mathematical models only provide limited information about the diffusivity, and do not consider or discuss the stability and interactions of proteins/excipients with the VH components. Additionally, a number of reports describing in-vivo and ex-vivo transport experiments on the diffusion behavior of small and large molecules in the direction of VH to choroid [19][20][21][22] as well as choroid to VH [23] are available. However, ex-vivo transport experiments are limited in the duration of the experiment to a few hours only, in order to maintain tissue integrity (retina/choroid).…”

Mutant Fibulin-3 Causes Proteoglycan Accumulation and Impaired Diffusion Across Bruch's Membrane

“…41 Here we used this system to measure differences in the diffusion of four molecules through Bruch's membrane of 9- and 18-month-old Efemp1 +/+ , Efemp1 ki/ki , and Efemp1 −/− mice in the BrM to Ch direction. We established a concentration gradient of all four molecules across BrM/Ch and applied Fick's first law to calculate the flux and permeability coefficient of each molecule as described previously.…”

“…The BrM/Ch-X-ray film “sandwich” was mounted, separating the two chambers with only the 1.0-mm diameter circle of BrM/Ch allowing communication between them. Four molecules with different R s were selected for their ability to separate cleanly by gel exclusion chromatography 41 : cytosine (molecular weight [MW] = 110.1, R s < 1.0 nm; Sigma-Aldrich Corp.), RNase A (MW = 13,700, R s = 1.72 nm; Teknova, Hollister, CA, USA), human serum albumin (MW = 66,382, R s = 3.55 nm; EMD Chemicals, Gibbstown, NJ, USA), and horse spleen ferritin (MW = 450,000, R s = 6.15 nm; EMD Chemicals). A mixture of these molecules dissolved in PBS with 1 mM MgCl, and 0.1 mM CaCl 2 (PBS-CM) was added to the reservoir on the BrM side of the tissue with only PBS-CM on the Ch side.…”

“… 40 We have previously established a method to study globular protein and small molecule diffusion across Bruch's membrane by simultaneously measuring the flux of multiple molecules with different R s using quantitative gel exclusion chromatography. 41 Coupling this method with a modified Ussing chamber has allowed us to study diffusion across very small pieces (1.8 mm 2 ) of isolated Bruch's membrane/choroid (BrM/Ch). 41 In this study, we used this system to examine Bruch's membrane's diffusion properties in Efemp1 ki/ki and Efemp1 −/− mice.…”

“… 41 Coupling this method with a modified Ussing chamber has allowed us to study diffusion across very small pieces (1.8 mm 2 ) of isolated Bruch's membrane/choroid (BrM/Ch). 41 In this study, we used this system to examine Bruch's membrane's diffusion properties in Efemp1 ki/ki and Efemp1 −/− mice.…”