Drug permeation through temperature-sensitive membranes prepared from poly(vinylidene fluoride) with grafted poly(N-isopropylacrylamide) chains

Abstract

Temperature-responsive copolymers, poly(vinylidene fluoride)-graft-poly(N- isopropylacrylamide) (PVDF-g-PNIPAAM), were synthesized by thermally-induced graft copolymerization of N-isopropylacrylamide (NIPAAM) with the ozone-pretreated PVDF. Temperature-sensitive microfiltration membranes were then prepared from the PVDF-g-PNIPAAM copolymers by phase inversion. The chemical structure and composition of the PVDF-g-PNIPAAM copolymers were characterized by FT-IR spectroscopy and elemental analysis. X-ray photoelectron spectroscopy (XPS) analyses of the membranes revealed a substantial surface enrichment in grafted NIPAAM polymer. The pore sizes of the PVDF-g-PNIPAAM membranes were measured using a Coulter® Porometer. The temperature-dependent swelling behavior of the membranes in aqueous solution was studied by atomic force microscope (AFM) and water retention behavior. Increasing the surface graft concentration of the membrane resulted in a higher degree of temperature-sensitive swelling. The copolymer membranes also exhibited reversible temperature-dependent permeability to calcein and fluorescein isothiocyanate (FITC)-dextran in phosphate buffer solutions (pH 7.4), with the most drastic change in permeability being observed in the temperature range between 27 and 32°C. © 2004 Elsevier B.V. All rights reserved.