SURFACE HEPARINIZATION OF POLYPROPYLENE MICROPOROUS MEMBRANES FOR SELECTIVE ADSORPTION OF LOW-DENSITY LIPOPROTEIN

Abstract

To endow polypropylene microporous membrane(PPMM) with adsorption selectivity to low-density lipoprotein(LDL),a versatile method was developed to covalently immobilize heparin on the PPMM surface.This was achieved by grafting acrylic acid(AA) on the PPMM surface by UV irradiation,and subsequent chemical binding of heparin with ethylenediamine as a spacer.The membrane surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The hydrophilicity and blood compatibility of the PPMM surface were improved obviously by the surface heparinization.Water contact angle of the membrane surface was decreased from(138±7.2)° for the nascent PPMM to(35.1±2.7)° for the heparinized PPMM with 7.39 μg/cm2 heparin.An enzyme-linked immunosorbent assay(ELISA) was employed to analyze the adsorption of the LDL on the nascent and heparinized PPMMs.It was found that the surface heparinization greatly enhanced the adsorption of LDL both from single protein solution and binary protein solution containing human serum albumin(HSA),and the heparinized PPMM could selectively adsorb LDL from binary protein solution.In addition,the adsorbed LDL could be desorbed from the heparinized PPMM with sodium chloride solution,which indicated the adsorption was of reversibility.