Response of monocyte-derived dendritic cells to rapidly solidified nickel-titanium ribbons with shape memory properties.

Ni-Ti Shape Memory Alloys (SMAs) have attracted considerable attention as biomaterials for medical devices. However, the biocompatibility of Ni-Ti SMAs is often unsatisfactory due to their poor surface structure. Here we prepared Rapidly Solidified (RS) Ni-Ti SMA ribbons by melt-spinning and their surface was characterised by Auger-electron spectroscopy, X-ray photoelectron spectrometry and scanning electron microscopy. The biocompatibility of the produced ribbons and their immunomodulatory properties were studied on human monocyte-derived dendritic cells (MoDCs). We showed that melt-spinning of Ni-Ti SMAs can form a thin homogenous oxide layer, which improves their corrosion resistance and subsequent toxicity to MoDCs. Ni-Ti RS ribbons stimulated the maturation of MoDCs, as detected by changes in the cells' morphology and increased expression of HLA-DR, CD86, CD40 and CD83 molecules. However, Ni-Ti RS ribbons enhanced the tolerogenic properties of immature MoDCs, which produced higher levels of IL-10 and IL-27, driving the differentiation of IL-10- and TGF-ß-producing CD4+T cells. On the other hand, in the presence of lipopolysaccharide, an important pro-inflammatory biomolecule, Ni-Ti RS ribbons enhanced the allostimulatory and Th1 polarising capacity of MoDCs, whereas the production of Th2 and Th17 cytokines was down-regulated. In conclusion, Ni-Ti RS ribbons possess substantial immunomodulatory properties on MoDCs. These findings might be clinically relevant, because implanted Ni-Ti SMA devices can induce both desired and adverse effects on the immune system, depending on the microenvironmental stimuli.

Cytotoxicity of gold nanoparticles prepared by ultrasonic spray pyrolysis.

The aim of this work was to study the cytotoxicity of different fractions of gold nanoparticles prepared by ultrasonic spray pyrolysis from gold scrap. The target cells were rat thymocytes, as a type of nonproliferating cells, and L929 mouse fibroblasts, as a type of continuous proliferating cells. Fractions 1 and 2, composed of pure gold nanoparticles, as determined by scanning electron microscopy with a combination of energy dispersive X-ray analysis, were nontoxic for thymocytes, but reduced moderately the proliferative activity of L929 cells. The inhibitory effect of fraction 2, containing particles smaller in size than fraction 1, was stronger. Fraction 3, composed of Au and up to 3% Cu was noncytotoxic for thymocytes, but was cytotoxic for L929 cells. Fraction 4, composed of Au and Ag nanoparticles, and fraction 5, composed of Au together with Cu, Ni, Zn, Fe, and In were cytotoxic for both thymocytes and L929 cells. These results suggest that USP enables the synthesis of pure gold nanoparticles with controlled size, even from gold scrap. However, microstructural analyses and biocompatibility testing are necessary for their proper selection from more cytotoxic gold nanoparticles, contaminated with other elements of gold alloys.