This study deals with the morphofunctional influence of 72 h exposure to a 6 mT static magnetic field (SMF) during differentiation induced by 50 ng/ml 12-O-tetradecanoyl-13-phorbol acetate (TPA) in human leukaemia U937 cells. The cell morphology of U937 cells was investigated by optic and electron microscopy. Specific antibodies and/or molecules were used to label CD11c, CD14, phosphatidylserine, F-actin and to investigate the distribution and activity of lysosomes, mitochondria and SER. [Ca(2+)](i) was evaluated with a spectrophotometer. The degree of differentiation in SMF-exposed cells was lower than that of non-exposed cells, the difference being exposure time-dependent. SMF-exposed cells showed cell shape and F-actin modification, inhibition of cell attachment, appearance of membrane roughness and large blebs and impaired expression of specific macrophagic markers on the cell surface. The intracellular localization of SER and lysosomes was only partially affected by exposure. A significant localization of mitochondria with an intact membrane potential at the cell periphery in non-exposed, TPA-stimulated cells was observed; conversely, in the presence of SMF, mitochondria were mainly localised near the nucleus. In no case did SMF exposure affect cell viability. The sharp intracellular increase of [Ca(2+)](i) could be one of the causes of the above-described changes.

A surprising and unexpected biomineralization process was observed during toxicological assessment of carbon nanoparticles on Paracentrotus lividus (sea urchin) pluteus larvae. The larvae activate a process of defense against external material, by incorporating the nanoparticles into microstructures of aragonite similarly to pearl oysters. Aiming at a better understanding of this phenomenon, the larvae were exposed to increasing concentrations of carbon nanoparticles and the biomineralization products were analyzed by electron microscopy, x-ray diffraction and Raman spectroscopy. In order to evaluate the possible influence of Sp-CyP-1 expression on this biomineralization process by larvae, analyses of gene expression (Sp-CyP-1) and calcein labeling were performed. Overall, we report experimental evidence about the capability of carbon nanoparticles to induce an increment of Sp-CyP-1 expression with the consequent activation of a biomineralization process leading to the production of a new pearl-like biomaterial never previously observed in sea urchins.

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The in vitro effects of polyalkyl-imide hydrogel (PAI) containing 96% pyrogen-free water on the viability, apoptosis, cell shape and metabolic activities of murine 3T3 and human Detroit 555 fibroblasts were investigated. Analysis of the viscous-elastic properties and the ultrastructure of PAI, performed by rheometer and AFM respectively, showed that the material has the typical characteristics of hydrogel, including a three-dimensional configuration of molecules arranged in a regular network with many discrete caveolae where most of the water is captured. Hydrogel biocompatibility was found to be high for both cell lines, with some differences. Cell viability decreased more in 3T3 cells than Detroit 550 fibroblasts when cultured in the presence of 100 mg/ml hydrogel but not at concentrations of 25 and 50 mg/ml hydrogel. The period of incubation with PAI (24 and 48 h) only partially affected cell viability. Apoptosis, most likely due to cells' inability to adhere to the polymer, was the only type of cell death observed. Fibroblasts grown in the presence of polymer were always metabolically active since they continued to synthesize collagen. In conclusion, PAI hydrogel, even at high concentrations, was biocompatible for both fibroblasts, but in particular for human cells, thus encouraging its use as a dermal filler.