Validity of Three-Dimensional Tortuous Pore Structure and Fouling of Hemoconcentration Capillary Membrane Using the Tortuous Pore Diffusion Model and Scanning Probe Microscopy

Abstract

Hemoconcentration membranes used in cardiopulmonary bypass require a pore structure design with high pure water permeability, which does not allow excessive protein adsorption and useful protein loss. However, studies on hemoconcentration membranes have not been conducted yet. The purpose of this study was to analyze three-dimensional pore structures and protein fouling before and after blood contact with capillary membranes using the tortuous pore diffusion model and a scanning probe microscope system. We examined two commercially available capillary membranes of similar polymer composition that are successfully used in hemoconcentration clinically. Assuming the conditions of actual use in cardiopulmonary bypass, bovine blood was perfused inside the lumens of these membranes. Pure water permeability before and after bovine blood perfusion was measured using dead-end filtration. The scanning probe microscopy system was used for analysis. High-resolution three-dimensional pore structures on the inner surface of the membranes were observed before blood contact. On the other hand, many pore structures after blood contact could not be observed due to protein fouling. The pore diameters calculated by the tortuous pore diffusion model and scanning probe microscopy were mostly similar and could be validated reciprocally. Achievable pure water permeabilities showed no difference, despite protein fouling on the pore inlets (membrane surface). In addition, low values of albumin sieving coefficient are attributable to protein fouling that occurs on the membrane surface. Therefore, it is essential to design the membrane structure that provides the appropriate control of fouling. The characteristics of the hemoconcentration membranes examined in this study are suitable for clinical use.

Electron Microscopic Confirmation of Anisotropic Pore Characteristics for ECMO Membranes Theoretically Validating the Risk of SARS-CoV-2 Permeation

“…The method reported in our previous study [ 15 , 16 ] was employed to observe the inner and outer surfaces of hollow fiber membranes.…”

“…For a comparative verification against the SPM, followed by the design validation, we used a FE-SEM (JSM-7610F, Jeol Ltd., Tokyo, Japan) to observe the inner and outer surfaces of the hollow fiber membranes at an accelerating voltage of 1.5 kV, a working distance of 4.5 mm, and an emission current of 47.2 μA [ 16 ]. No conductive treatment with Au or C was applied.…”

“…The objective of this study is to clarify the pore structure of ECMO membranes by using our approach for analyzing membrane pore structures by scanning probe microscope (SPM) and field emission scanning electron microscope (FE-SEM) [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Then, the permeability of SARS-CoV-2 through the membrane is evaluated using the steric exclusion model and hindered diffusion model, which are simple permeation theories in membrane science.…”

Newly Developed Pediatric Membrane Oxygenator that Suppresses Excessive Pressure Drop in Cardiopulmonary Bypass and Extracorporeal Membrane Oxygenation (ECMO)

“…Figure 16 shows the observations of the inner lumen and outer surfaces of the capillary membrane of Sample A for reference. The method reported in our previous study [31] was employed to observe the inner lumen and outer surfaces of the capillary membranes using a field emission scanning electron microscope (FE-SEM) (JSM-7610F, Jeol Ltd., Tokyo, Japan) at an accelerating voltage of 1.5 kV and an emission current of 47.2 µA Membranes 2020, 10, 362 25 of 28 gradually replaced with plasma (the pores are gradually filled with plasma) over time, resulting in the permeation of plasma into a hollow fiber membrane lumen. Therefore, it is useful to design a pore size and pore structure on the outer side of a membrane such that plasma does not reach the membrane thickness.…”

“…Figure 16 shows the observations of the inner lumen and outer surfaces of the capillary membrane of Sample A for reference. The method reported in our previous study [ 31 ] was employed to observe the inner lumen and outer surfaces of the capillary membranes using a field emission scanning electron microscope (FE-SEM) (JSM-7610F, Jeol Ltd., Tokyo, Japan) at an accelerating voltage of 1.5 kV and an emission current of 47.2 µA…”