Objectives This study aimed to synthesize nanocrystals (NCs) of zinc oxide (ZnO) and calcium ion (Ca 2+ )-doped ZnO with different percentages of calcium oxide (CaO), to evaluate cytotoxicity and to assess the effects of the most promising NCs on cytotoxicity depending on lipopolysaccharide (LPS) stimulation. Materials and Methods Nanomaterials were synthesized (ZnO and ZnO:xCa, x = 0.7; 1.0; 5.0; 9.0) and characterized using X-ray diffractometry, scanning electron microscopy, and methylene blue degradation. SAOS-2 and RAW 264.7 were treated with NCs, and evaluated for viability using the MTT assay. NCs with lower cytotoxicity were maintained in contact with LPS-stimulated (+LPS) and nonstimulated (−LPS) human dental pulp cells (hDPCs). Cell viability, nitric oxide (NO), and reactive oxygen species (ROS) production were evaluated. Cells kept in culture medium or LPS served as negative and positive controls, respectively. One-way analysis of variance and the Dunnett test (α = 0.05) were used for statistical testing. Results ZnO:0.7Ca and ZnO:1.0Ca at 10 µg/mL were not cytotoxic to SAOS-2 and RAW 264.7. +LPS and −LPS hDPCs treated with ZnO, ZnO:0.7Ca, and ZnO:1.0Ca presented similar NO production to negative control ( p > 0.05) and lower production compared to positive control ( p < 0.05). All NCs showed reduced ROS production compared with the positive control group both in +LPS and −LPS cells ( p < 0.05). Conclusions NCs were successfully synthesized. ZnO, ZnO:0.7Ca and ZnO:1.0Ca presented the highest percentages of cell viability, decreased ROS and NO production in +LPS cells, and maintenance of NO production at basal levels.

The aim of this study was to assess the ability of red light emitting diodes (LED) to modulate oxidative stress in human dental pulp fibroblasts (HDPFs) when different irradiation parameters are employed. Cells from primary teeth were seeded (100,000 cells/well) in 24-well plates in culture medium (DMEM). At 24 h after incubation, the culture medium was replaced with DMEM containing 10 μg/mL lipopolysaccharide (LPS). Thereafter, the cells were irradiated (LED 630 nm, 0.04 W/cm 2 and 0.08 W/cm 2 ) at 0 J/cm 2 (control group), 4 J/cm 2 , 15 J/cm 2 , and 30 J/cm 2 ; and their viability (MTT assay), number (Trypan Blue), synthesis of nitric oxide (NO) (Griess reagent), and reactive oxygen species (ROS) (fluorescence probe, DCFH-DA) were assessed. The Kruskal-Wallis and Mann-Whitney statistical tests using Bonferroni correction were employed (significance level of 5%). Compared to that in control fibroblasts, increased viability was observed in HDPFs exposed to LPS and irradiated with 15 J/cm 2 and 30 J/cm 2 at 0.04 W/cm 2 and 4 J/cm 2 and 15 J/cm 2 at 0.08 W/cm 2 (p < 0.05). Exposure to 4 J/cm 2 at 0.04 W/cm 2 and 15 J/cm 2 and 30 J/cm 2 at 0.08 W/cm 2 modulated the oxidative stress in cells relative to that observed in non-irradiated LPS-treated pulp cells (p < 0.05). It was concluded that the irradiation strategies of using red LED with radiant exposures of 15 J/cm 2 and 30 J/cm 2 at 0.04 W/cm 2 and 15 J/cm 2 at 0.08 W/cm 2 were the best parameters to decrease NO and ROS concentration and to stimulate viability of HDPFs exposed to LPS challenge.

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