Insulin adsorption into porous charged membranes: Effect of the electrostatic interaction

Abstract

Insulin adsorption into a series of porous charged membranes was investigated by batch adsorption experiments, and the experimental results were analyzed by the homogeneous diffusion model. The membranes used in this study were prepared by pore-surface modification of porous poly(acrylonitrile) (PAN) membranes by grafting with weak acidic and basic functional groups. The amount of insulin adsorbed into the membrane was determined from the material balance of insulin. The insulin partition coefficient K between the membrane and solution was estimated from the equilibrium adsorption amount, and the effective diffusion coefficient D was estimated by matching the model with the experimental data as a fitting parameter. The dependence of K and D on the charge properties of the insulin and membrane is observed and discussed. The partition coefficient K increased when the insulin and the membrane carried opposite charges, on the other hand, the effective diffusion coefficient D was reduced. These results indicate that the electrostatic interaction between the insulin and the membranes played an important role in the insulin adsorption.

Insulin transport across porous charged membranes: Effect of the electrostatic interaction

“…Additionally, there is another possibility that the electrostatic attraction between the insulin and membrane changed the diffusion pattern of the insulin within the pores. 30,31 The determined values of k and D from the calculation of the diffusion characteristics are comparable to those obtained from the calculation of the adsorption kinetics, 6 as shown in the parenthesis of Table 2. The k and D values obtained in the present study seem to be reasonable when compared to the reported data of other proteins, such as BSA and lysozyme, 1,29,[32][33][34] which are of the order 10 À7 -10 À10 m/s and 10 À11 -10 À14 m 2 /s, respectively.…”

“…6 As is described that k reveals the effect of the boundary layer between the membrane and solution. The decrease in k may be ascribed to the change in the boundary layer (increased thickness 27 or changed structure 28 ), because the insulin concentration near the membrane surface is expected to be much higher than that in the bulk when the insulin and membrane carries opposite charge.…”

“…Same as the model we used for the calculation of insulin adsorption kinetics, 6 we assume that at a relatively high buffer concentration, the diffusion potential generated in the transport process can be neglected, 19 and the effect of the membrane pore restriction is included in the effective diffusion coefficient D, the diffusion of insulin within the membrane (x direction) can then be described by the Fick's second law…”

“…6 The known amount of freeze-dried test membrane was first immersed in the buffer solution for one day, and then was introduced to the glass vessel containing 10 mL of insulin buffer solution (initial concentration: 0.22 mg/mL) at 37 C. The solution was measured by a UV-vis spectrophotometer (U-2000, Hitachi, Japan) at 276 nm, and its concentration was calculated from the absorption intensity by the calibration curves. The adsorbed amount of insulin into the membrane was estimated from the decrease of the insulin concentration in the solution based on insulin mass conservation.…”

“…5 Generally, oppositely charged molecules can be favorably partitioned into the charged materials as a result of electrostatic interaction, 6,7 but the permeability sometime shows complex tendency. Stroeve coworkers 8,9 investigated the transport properties of bovine serum albumin (BSA) and bovine hemoglobin (BHb) through nanoporous membranes modified with self-assembled monolayers of functionalized thiols.…”