The mechanisms underlying the cytotoxic action of pure fullerene suspension (nano-C₆₀) and water-soluble polyhydroxylated fullerene [C₆₀(OH)_n] were investigated. Crystal violet assay for cell viability demonstrated that nano-C₆₀ was at least three orders of magnitude more toxic than C₆₀(OH)_n to mouse L929 fibrosarcoma, rat C6 glioma, and U251 human glioma cell lines. Flow cytometry analysis of cells stained with propidium iodide (PI), PI/annexin V–fluorescein isothiocyanate, or the redox-sensitive dye dihydrorhodamine revealed that nano-C₆₀ caused rapid (observable after few hours), reactive oxygen species (ROS)–associated necrosis characterized by cell membrane damage without DNA fragmentation. In contrast, C₆₀(OH)_n caused delayed, ROS-independent cell death with characteristics of apoptosis, including DNA fragmentation and loss of cell membrane asymmetry in the absence of increased permeability. Accordingly, the antioxidant N-acetylcysteine protected the cell lines from nano-C₆₀ toxicity, but not C₆₀(OH)_n toxicity, while the pan-caspase inhibitor z-VAD-fmk blocked C₆₀(OH)_n-induced apoptosis, but not nano-C₆₀–mediated necrosis. Finally, C₆₀(OH)_n antagonized, while nano-C₆₀ synergized with, the cytotoxic action of oxidative stress–inducing agents hydrogen peroxide and peroxynitrite donor 3-morpholinosydnonimine. Therefore, unlike polyhydroxylated C₆₀ that exerts mainly antioxidant/cytoprotective and only mild ROS-independent pro-apoptotic activity, pure crystalline C₆₀ seems to be endowed with strong pro-oxidant capacity responsible for the rapid necrotic cell death.

The influence of the mechanical activation of ZnO nanoparticle fillers on the structural and electrical properties of the matrix of poly(vinylidenefluoride)–ZnO (PVDF–ZnO) films was investigated. Transmission electron microscopy and scanning electron microscopy analyses showed that mechanical activation in a high energy planetary ball mill reduces the size of ZnO particles. X-ray diffraction and Raman spectroscopy revealed that PVDF crystallized predominantly as the γ -phase. Non-activated ZnO filler reduces the degree of the crystallinity of the matrix and promotes crystallization of α -phase of PVDF in the film, while the fillers activated for 5 and 10 min induce crystallization of β -phase, indicating that mechanical activation of the filler can be used as a general method for fabrication of PVDF composites with increased content of piezoelectric β -phase crystals. Dielectric spectroscopy measurements show that polymer composite with the high content of β -phase (with ZnO filler activated for 5 min) exhibits the highest value of dielectric permittivity in 150–400 K range of temperatures. Kinetic analysis shows combined effects of increased surface area and increased concentration of surface defects on the interactions between polymer chains and activated nanoparticles.

Background/Aim. Dimensional stability and accuracy of an impression after chemical disinfection by immersion in disinfectants are crucial for the accuracy of final prosthetic restorations. The aim of this study was to assess the deformation of addition and condensation silicone impressions after disinfection in antimicrobial solutions. Methods. A total of 120 impressions were made on the model of the upper arch representing three full metal-ceramic crown preparations. Four impression materials were used: two condensation silicones (Oranwash L - Zhermack and Xantopren L Blue - Heraeus Kulzer) and two addition silicones (Elite H-D + regular body - Zhermack and Flexitime correct flow - Heraeus Kulzer). After removal from the model the impressions were immediately immersed in appropriate disinfectant (gluta-raldehyde, benzalkonium chloride - Sterigum and 5.25% NaOCl) for a period of 10 min. The control group consisted of samples that were not treated with disinfectant solution. Consecutive measurements of identical impressions were realized with a Canon G9 (12 megapixels, 2 fps, 6x/24x), and automated with a computer Asus Lamborghini VX-2R Intel C2D 2.4 GHz, by using Remote Capture software package, so that time-depending series of images of the same impression were obtained. Results. The dimensional changes of all the samples were significant both as a function of time and the applied disinfectant. The results show significant differences of the obtained dimensional changes between the group of condensation silicones and the group of addition silicones for the same time, and the same applied disinfectant (p = 0.026, F = 3.95). Conclusion. The greatest dimensional changes of addition and condensation silicone impressions appear in the first hour after their separation from the model.