The present work exploits Ti sheets and TiO 2 nanotube (TNT) layers and their surface modifications for the proliferation of different cells. Ti sheets with a native oxide layer, Ti sheets with a crystalline thermal oxide layer, and two kinds of TNT layers (prepared via electrochemical anodization) with a defined inner diameter of 12 and 15 nm were used as substrates. A part of the Ti sheets and the TNT layers was additionally coated by thin TiO 2 coatings using atomic layer deposition (ALD). An increase in cell growth of WI-38 fibroblasts (>50%), MG-63 osteoblasts (>30%), and SH-SY5Y neuroblasts (>30%) was observed for all materials coated by five cycles ALD compared to their uncoated counterparts. The additional ALD TiO 2 coatings changed the surface composition of all materials but preserved their original structure and protected them from unwanted crystallization and shape changes. The presented approach of mild surface modification by ALD has a significant effect on the materials' biocompatibility and is promising toward application in implant materials.

Background: Copper-containing biomaterials are increasingly applied for bone regeneration due to their pro-angiogenetic, pro-osteogenetic and antimicrobial properties. Therefore, the effect of Cu2+ on osteoclasts, which play a major role in bone remodeling was studied in detail. Methods: Human primary osteoclasts, differentiated from human monocytes were differentiated or cultivated in the presence of Cu2+. Osteoclast formation and activity were analyzed by measurement of osteoclast-specific enzyme activities, gene expression analysis and resorption assays. Furthermore, the glutathione levels of the cells were checked to evaluate oxidative stress induced by Cu2+. Results: Up to 8 µM Cu2+ did not induce cytotoxic effects. Activity of tartrate-resistant acid phosphatase (TRAP) was significantly increased, while other osteoclast specific enzyme activities were not affected. However, gene expression of TRAP was not upregulated. Resorptive activity of osteoclasts towards dentin was not changed in the presence of 8 µM Cu2+ but decreased in the presence of extracellular bone matrix. When Cu2+ was added to mature osteoclasts TRAP activity was not increased and resorption decreased only moderately. The glutathione level of both differentiating and mature osteoclasts was significantly decreased in the presence of Cu2+. Conclusions: Differentiating and mature osteoclasts react differently to Cu2+. High TRAP activities are not necessarily related to high resorption.

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Purpose Titanium dioxide nanoparticles, 25 nm in size of crystallites (TiO 2 P25), are among the most produced nanomaterials worldwide. The broad use of TiO 2 P25 in material science has implied a request to evaluate their biological effects, especially in the lungs. Hence, the pulmonary A549 cell line has been used to estimate the effects of TiO 2 P25. However, the reports have provided dissimilar results on caused toxicity. Surprisingly, the physicochemical factors influencing TiO 2 P25 action in biological models have not been evaluated in most reports. Thus, the objective of the present study is to characterize the preparation of TiO 2 P25 for biological testing in A549 cells and to evaluate their biological effects. Methods We determined the size and crystallinity of TiO 2 P25. We used four techniques for TiO 2 P25 dispersion. We estimated the colloid stability of TiO 2 P25 in distilled water, isotonic NaCl solution, and cell culture medium. We applied the optimal dispersion conditions for testing the biological effects of TiO 2 P25 (0–100 µg.mL −1 ) in A549 cells using biochemical assays (dehydrogenase activity, glutathione levels) and microscopy. Results We found that the use of fetal bovine serum in culture medium is essential to maintain sufficient colloid stability of dispersed TiO 2 P25. Under these conditions, TiO 2 P25 were unable to induce a significant impairment of A549 cells according to the results of biochemical and microscopy evaluations. When the defined parameters for the use of TiO 2 P25 in A549 cells were met, similar results on the biological effects of TiO 2 P25 were obtained in two independent cell laboratories. Conclusion We optimized the experimental conditions of TiO 2 P25 preparation for toxicity testing in A549 cells. The results presented here on TiO 2 P25-induced cellular effects are reproducible. Therefore, our results can be helpful for other researchers using TiO 2 P25 as a reference material.