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Nanosphere-encapsulated drugs offer a means to overcome many drug delivery limitations by localizing the site of delivery and providing controlled release. This research details the synthesis and encapsulation of ciprofloxacin in pullulan-polycaprolactone (PCL) core shell nanospheres and the characterization of these materials by 1H-NMR, UV spectroscopy, dynamic light scattering (DLS) and scanning electron microscopy (SEM).1H-NMR results confirm that the pullulan-PCL grafted copolymer was successfully synthesized. UV spectroscopy showed that the ciprofloxacin loaded nanospheres contain 35-40% ciprofloxacin by weight. DLS and SEM results indicate that the loaded nanospheres are spherical in shape and approximately 142+/-12 nm in size. Under in vitro test conditions, approximately 20% of the ciprofloxacin is released in the first 4 hours, with additional release over 10 days. The nanoparticles demonstrate bioactivity against Escheria coli and do not affect the proliferation of two human cell lines. These results demonstrate the potential of pullulan-PCL core-shell nanospheres as delivery vehicles of hydrophobic drugs, including antibiotics for localized treatments applicable to a wide-range of human bacterial infections.

The wear of polyethylene in bovine serum was evaluated as a function of load and molecular weight. The range and distribution of contact loadings simulated those which exist in currently available total hip and total knee prostheses. The wear increased exponentially with load at constant molecular weight. An increasing molecular weight parametrically displaced the exponential curve to higher loads, lowering the overall rate. It is proposed that the behavior of these materials be described in terms of a critical pressure-velocity product although the specific mechanisms for wear acceleration are not known in this case.

The resistance to sliding wear was measured in bovine serum for two polyethylenes with molecular weights of about 10(5) and 10(6) that had been irradiated in air and nitrogen with gamma-ray dosages up to 20 Mrad. Molecular weight measurements were performed after irradiation as well. Wear generally increased with dosage and contact stress, becoming measurable in many cases only after a critical dose (or stress) was exceeded. The most significant effect noted was that the irradiation changed the pressure dependence of the wear rate. Thus, whether or not a sterilizing (or resterilizing) dose will measurably increase the wear depends on the contact stress and, therefore, on the specific application. The increase in wear rate appeared to be due to a combination of scission and oxidation, suggesting the practical advisability of radiation sterilization under an inert atmosphere, as confirmed by comparative measurements at the higher dosages.