Crown Ether-Functionalized Polyethersulfone Membranes with Potential Applications in Hemodialysis

Abstract

Polyethersulfone (PES) is one of the most used synthetic polymers for the production of hemodialysis membranes, due to its appropriate features, such as biocompatibility, high permeability for low-molecular-weight proteins, high endotoxin retention ability, and resistance to sterilization processes. However, there is room for improvement regarding their anticoagulant properties when coming into contact with blood. In the present study, commercial PES membranes were plasma-treated and then chemically modified with crown ether, an organic compound that could interfere with the coagulation cascade by complexating Ca²⁺ in the blood. The physico-chemical and morphological characteristics of the membranes were determined by FT-IR, XPS, TGA, SEM, and CT analyses, while their efficiency in retaining calcium ions was evaluated via ICP-MS. The results revealed that plasma treatment with a mixture of argon and ammonia was the most effective in generating nitrogen-containing surface functional groups and that these moieties can be successfully used for the covalent functionalization of the membranes. Also, the Ca²⁺ retention ability of the PES membranes was improved by up to 30% after chemical modification with 4'-aminobenzo-15-crown-5 ether.

Keywords: crown ether; hemodialysis; polyethersulfone.

Figure 1

Proposed reaction mechanism for the functionalization of PES with cyanuric chloride and 4′-aminobenzo-15-crown-5 ether.

Figure 2

ATR FT-IR spectra of the neat and plasma-treated PES membranes.

Figure 3

Survey XPS spectra of the neat and plasma-treated PES membranes.

Figure 4

High-resolution N 1s spectrum obtained for the M3 sample—amine (blue line), amide (red line) and imine (green line).

Figure 5

CT images obtained for the neat (M0), argon/ammonia (M3), and argon (M7) plasma-treated membranes. The scale bar represents 50 μm.

Figure 6

ATR FT-IR spectra of the plasma-treated PES membranes modified with cyanuric chloride (a) and 4′-aminobenzo-15-crown-5 ether (b).

Figure 7

XPS spectra of the chemically modified membranes.

Figure 8

High-resolution C 1s spectra obtained for fPES-CN (a) and fPES-CN-AB15C5 (b) membranes.

Figure 9

SEM images of the chemically modified PES membranes.

Figure 10

TGA and DTG curves obtained for the neat (a) and chemically modified PES membranes ((b)—fPES-CN and (c)—fPES-CN-AB15C5).

Figure 11

The percentages of calcium ions retained by the neat, plasma-treated, and chemically modified PES membranes.