THERMAL CONTROL OF DRUG-RELEASE BY A RESPONSIVE ION TRACK MEMBRANE OBSERVED BY RADIO TRACER FLOW DIALYSIS

The combination of a responsive hydrogel with a rigid porous supportin g structure yields a membrane with high mechanical strength and high o n-off-permeability ratio. A membrane consisting of an ion track filter with a thermally responsive lining was prepared by penetrating a 19 m u m thick foil of poly(ethylene terephthalate) (PET) with swift heavy ions at a fluence of 5.10(5) ions/cm(2) followed by etching of the ion tracks to generate an ion track filter with 2.9 mu m pore diameter, o nto which a thin layer of poly(N-isopropylacrylamide) (NIPAAm) hydroge l was grafted. It was revealed that the mass flow of various molecules (water, chloride(-), choline(+), insulin, and albumin) through the me mbrane could be thermally controlled. The on-off-permeability ratio ra nged between 3 and 10 increasing with molecular weight. Over a storage time of 5 months the permeabilities varied up to a factor of 2.6, whi le the on-off-permeability ratio and temperature sensitivity remained practically constant. (C) 1998 Elsevier Science B.V.