Surface engineerings of polyacrylonitrile-based asymmetric membranes towards biomedical applications: An overview

Polyacrylonitrile (PAN) membranes have attracted much attention due to a variety of excellent characteristics, which include thermal stability and tolerance to most solvents, atmosphere, bacteria and photo irradiation. Therefore, their exploitation also covers many fields, like pervaporation, water treatment, enzyme immobilization, and hemodialysis. However, the relative poor hydrophilicity and biocompatibility get the membranes susceptible to protein adsorption and cell adhesion that may cause biofouling and immunoreactions, especially when the membranes are used in blood-related systems. This review presents various surface engineerings for PAN-based membranes, which mainly refers to grafting polymerization (also known as “grafting-from” method), partially hydrolysis, macromolecule immobilization (also known as “grafting-to” method), and enzyme immobilization. To render the membrane surface with biocompatibility for hemodialysis, the concept of mimicking the outer surface of cells is critical. For example, biomacromolecules such as chitosan, heparin or insulin can be tethered on the PAN-based membranes to improve their surface hemocompatibility remarkably. In addition, one of the potential applications of PAN-based membranes is as enzyme immobilization supports. Over 15 relative literatures are listed and briefly discussed with different enzymes, modified supports, and coupling methods. However, the application trial for these enzyme-immobilized membranes is still elementary.