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

Kiyotaka Sakai,Hiroki Yoshimoto,Makoto Fukuda,Hitoshi Saomoto

doi:10.3390/membranes10110315

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.

Highlights

Hemoconcentration membranes used in extracorporeal circulatory surgeries require a membrane pore structure design with a high pure water permeability, which does not allow useful proteins such as albumin to leak out [1,2]
Clear 3D pore structures and fiber structures made of polymer particles were observed before blood contact, and the pore diameter could be measured from this using the scanning probe microscopy (SPM) line analysis (Figure 2(a1–a3) and Figure 3(a1–a3))
On the contrary, regarding the ultrafiltration membrane with high pure water permeability (Lp ) after blood contact, the pores seemed to be covered by a protein adsorption layer; clear pores could not be observed (Figure 2(b1–d3))

Summary

Introduction

Hemoconcentration membranes used in extracorporeal circulatory surgeries require a membrane pore structure design with a high pure water permeability, which does not allow useful proteins such as albumin to leak out [1,2]. The most serious dysfunction of a hemoconcentrator is abnormally decreased pure water permeability due to protein fouling on a membrane surface. If critical protein fouling occurs, pure water permeability decreases, so the circuit including a hemoconcentrator must be replaced. Membranes 2020, 10, x FOR PEER REVIEW during the extracorporeal cardiopulmonary bypass (CPB) surgery. During this replacement, the CPB surgery is interrupted. This isHowever, a serious accident puts the patient’s lifemembranes in danger.

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