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Reduction of free radicals and endotoxin by conjugated linoleic acid loaded in an in situ-synthesized poly(N-isopropyl acrylamide) thin layer



A thin layer of poly(N-isopropyl acrylamide) (pNIPAAm) was synthesized in situ on the surface of hydrolyzed polyacrylonitrile (PAN) membrane. This thin layer exhibited both pH response due to the poly(acrylic acid) moiety and temperature response due to the pNIPAAm moiety. The swelling behavior of the membranes was evaluated under various temperatures and pH. The curve of the swelling ratio for the PAN-NIPAAm showed a lower critical solution temperature. Then, conjugated linoleic acid (CLA) was loaded into the pNIPAAm layer. The effects of CLA on the blood coagulation and oxidative stress were evaluated with the use of human blood. The level of reactive oxygen species (ROS) was measured by the chemiluminescence (CL) method to evaluate the oxidative stress. Furthermore, the removal of bacterial endotoxin (lipopolysaccharide) by CLA-loaded PAN-NIPAAm was measured with enzyme-linked immunosorbent assay. The results show that the LCST swelling curve was at 37°C. PNIPAAm chains form expanded structures under 37°C. At temperatures greater than 37°C, however, the chains form compact structures by dehydration. This makes PNIPAAM membrane due to rapid hydration and dehydration changes of the polymer chain. In addition, the swelling ratio increased by 71% when the pH increased from 5 to 10. The concentration of LPS can be reduced by CLA-loaded PAN-NIPAAm 2.1 and 1.2 times of that by unmodified PAN and PAN-NIPAAm membranes, respectively. In addition, the level of ROS against CLA-loaded PAN-NIPAAm was reduced significantly than that against unmodified PAN and PAN-NIPAAm. Therefore CLA-loaded PAN-NIPAAm membrane could offer protection for patients against oxidative stress and could also inhibit lipopolysaccharide for clinical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009