Polypropylene grafted with NIPAAm and APMA for creating hemocompatible surfaces that load/elute nalidixic acid

Polypropylene (PP) films grafted with N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were tested as components of medical devices able to load and to sustain the release of the antimicrobial agent nalidixic acid. A pre-irradiation method was applied for grafting PP films with two NIPAAm:APMA weight ratios and to various extents. The grafting composition was analyzed recording FTIR-ATR spectra. PP-g-(1NIPAAm-r-0.5APMA) exhibited the temperature-responsiveness of PNIPAAm, while the grafting with a greater content in APMA led to that PP-g-(1NIPAAm-r-1APMA) remained highly swollen at 37 °C. The greater the content in APMA on the PP surface, the higher the amount of nalidixic acid loaded (up to 0.036 mg/cm2) and the slower the release rate in phosphate buffer pH 7.4. Coating with carboxymethyl-dextran (CM-dextran) of some drug-loaded films led to minor drug unloading while remarkably high amounts of dextran were deposited (up to 0.50 mg/cm2). This coating did not significantly modify the drug release rate neither the hemocompatibility of the PP-g-(NIPAAm-r-APMA) films, which was per se very good. Drug-loaded films remarkably inhibited the growth of Escherichia coli in in vitro microbiological tests.