Characterization of gamma irradiated ethylene-norbornene copolymer using FTIR, UV-Vis and DSC techniques

Due to their new combination of properties and shortage of the experimental data, the radiolysis of a new class of materials, cyclo-olefin copolymers (COC), which are polymerized from norbornene and ethylene using metallocene catalysts, is of great interest to the study of radiation chemistry and physics of polymeric systems. Ethylene-norbornene copolymer, bare and containing 0.45 wt % of the hindered phenolic type of an antioxidant (IRGANOX 1010) was subjected to gamma irradiation (100, 200 and 500 kGy) in the presence of air and in water. The irradiated copolymer was studied using FTIR, UV-vis spectrophotometric and gel content analysis. The insoluble fraction was formed in copolymer irradiated in water with 500 kGy, in bare 36% and in copolymer with an antioxidant 23%. The radiation induced changes in the molecular structure were correlated to the specific heat capacity and the glass transition temperature measured by DSC method

Bioreactor validation and biocompatibility of Ag/poly(N-vinyl-2-pyrrolidone) hydrogel nanocomposites

Silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) nanocomposites containing Ag nanoparticles at different concentrations were synthesized using gamma-irradiation. Cytotoxicity of the obtained nanocomposites was determined by MU assay in monolayer cultures of normal human immunocompetent peripheral blood mononuclear cells (PBMC) that were either non-stimulated or stimulated to proliferate by mitogen phytohemagglutinin (PHA), as well as in human cervix adenocarcinoma cell (HeLa) cultures. Silver release kinetics and mechanical properties of nanocomposites were investigated under bioreactor conditions in the simulated body fluid (SBF) at 37 degrees C. The release of silver was monitored under static conditions, and in two types of bioreactors: perfusion bioreactors and a bioreactor with dynamic compression coupled with SBF perfusion simulating in vivo conditions in articular cartilage. Ag/PVP nanocomposites exhibited slight cytotoxic effects against PBMC at the estimated concentration of 0.4 mu mol dm(-3), with negligible variations observed amongst different cell cultures investigated. Studies of the silver release kinetics indicated internal diffusion as the rate limiting step, determined by statistically comparable results obtained at all investigated conditions. However, silver release rate was slightly higher in the bioreactor with dynamic compression coupled with SBF perfusion as compared to the other two systems indicating the influence of dynamic compression. Modelling of silver release kinetics revealed potentials for optimization of Ag/PVP nanocomposites for particular applications as wound dressings or soft tissue implants