Cytotoxicity of titanium dioxide nanoparticles in mouse fibroblast cells.

Nanotitanium dioxide (TiO2) is an important industrial material that is widely used as an additive in cosmetics, pharmaceuticals, and food colorants. Although the small size of the TiO2 nanoparticle is useful in various applications, the biosafety of this material needs to be evaluated. In this study, mouse fibroblast (L929) cells were used to evaluate the cytotoxicity of different concentrations (3-600 microg/mL) of homogeneous and weakly aggregated TiO2 nanoparticles in aqueous solution. The L929 cells became round and even shrank as the concentration of TiO2 nanoparticles increased. Moreover, TiO2 nanoparticle-treated cells had condensed fragmented chromatin or were directly necrosed, as observed by acridine orange (AO) staining. The transmission electron microscopy (TEM) analysis showed that in cells cultured in a medium containing 300 microg/mL TiO2, the number of lysosomes increased, and some cytoplasmic organelles were damaged. In addition, there was a significant increase in oxidative stress at higher TiO2 nanoparticle concentrations (>60 microg/mL). As the concentration of TiO2 nanoparticles increased in the culture medium, the levels of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) increased, while those of methyl tetrazolium cytotoxicity (MTT), glutathione (GSH), and superoxide dismutase (SOD) decreased. A possible mechanism for the cytotoxicity of TiO2 nanoparticles is also discussed.

Hybrid effects of zirconia nanoparticles with aluminum borate whiskers on mechanical properties of denture base resin PMMA.

The aim of this study was to investigate the hybrid effects of ZrO2 nanoparticles (nano-ZrO2) and aluminum borate whiskers (ABWs) on flexural strength and surface hardness of denture base resin, polymethyl methacrylate (PMMA). Both nano-ZrO2 and ABWs were modified by silane coupling agent (Z6030) before being mixed with PMMA. Various amounts of silanized nano-ZrO2 and ABWs were mixed with PMMA to prepare ZrO2-ABW/PMMA composites. Flexural strength and surface hardness were evaluated using three- point bending test and Vickers hardness test respectively. Fractured surfaces were also observed by scanning electron microscopy (SEM). The mechanical behaviors of silanized ZrO2-ABW/PMMA composites were significantly improved. Flexural strength reached a maximum value of 108.01 ± 5.54 MPa when 2 wt% of nano-ZrO2 was mixed with ABWs at a ZrO2/ABW ratio of 1:2, amounting to an increase of 52% when compared with pure PMMA. Surface hardness achieved a maximum value of 22.50 ± 0.86 MPa when 3 wt% of nano-ZrO2 was mixed with ABWs at the same ZrO2/ABW ratio, which was an increase of 27% when compared with pure PMMA.

[Effect of nano ZrO2 on flexural strength and surface hardness of polymethylmethacrylate].

PURPOSE: To study the effect of polymethylmethacrylate(PMMA's) mechanical properties reinforced by nano ZrO(2) particles with different filling amounts. METHODS: The nano ZrO(2) particles were surface-treated by silane coupling agent(Z-6030) in 1.5wt% ratio, the untreated particles were regarded as the control group. The modified nano ZrO(2) particles were mixed with the PMMA powders in proportion of 0.5%,1%,1.5%,2%,2.5%,3% and 3.5%, respectively.Then the nano ZrO(2) /PMMA composites were synthesized. The specimens were examined by Vickers hardness test and three-point bending test, the surface of fracture was observed by SEM.All data were analyzed with ANOVA test by SAS 6.12 software package. RESULTS: Fourier transform infrared(FTIR) spectroscopy showed that the silane coupling agent linked to the nano ZrO(2) particles' surface after treating,the Vickers hardness was highest when the adding amount of nano ZrO(2) particles was 1.5% and 2%(P<0.05).The flexural strength of nano ZrO(2)/PMMA composites in the proportion of 1.5% was the highest(P<0.05). SEM indicated that the ductile fracture existed on the surface of fracture. CONCLUSIONS: The silane coupling agent can enhance the bonding strength of nano ZrO(2) particles and the PMMA matrix, the PMMA's mechanical properties could be improved by adding the nano ZrO(2) particle in an appropriate proportion. 1.5% and 2% of nano ZrO(2) particles render the nanocomposite the maximal Vickers hardness, while 1.5% ZrO(2) nanoparticles render the nanocomposite the maximal flexural strength.

[The effect of different dispersive methods on flexural strength nano-ZrO(2) reinforced denture polymethyl methacrylate].

PURPOSE: To study the effect of different dispersive methods on flexural strength of nano-ZrO(2)/polymethl methacrylate(PMMA) composite samples. METHODS: The nanometer ZrO2 particles which were modified by coupling agent Z-6030 were mixed to PMMA as the filler materials (3%) by means of handle disperse, ball milling disperse and ultrasonic wet disperse, respectively. Pure PMMA was used as blank control .With reference to the standard of ISO-1567:1999, standard samples were made and tested by three-point bending test. Then the data of flexural strength of the four groups were analyzed statistically with SAS 6.12 software package for one-way ANOVA(Newman-Keuls test). And the optimized synthesis way of the PMMA composite materials was selected. RESULTS: The flexural strength of the ball milling group and the ultrasonic group were significantly higher than the handle group and blank group(P<0.05), with an increase of 17%,10% compared with the blank group. There was no significant difference between the ball milling group and the ultrasonic group (P>0.05). CONCLUSION: Dispersal ways have effect on the flexural strength of PMMA composite materials which are filled with ZrO(2) particles.

[Influence of different amount of silane coupling agent on the flexural strength of PMMA/nanometer ZrO2 composites].

PURPOSE: To study the influence of different amount of silane coupling agent Z-6030 on the flexural strength of PMMA/nanometer ZrO(2) composites. METHODS: Nanometer ZrO(2) particles were modified by silane coupling agent Z-6030 with different percentages.In situ polymerization method was used to combine PMMA/ nanometer ZrO(2) composites of denture base plate. With reference to the standard of ISO1567:1999, standard samples of the experimental group were made. PMMA II type powder and PMMA II type liquor were used,which was not added nanometer ZrO(2) and silane coupling agent to make the standard samples of common denture base plate. PMMA II type powder and PMMA II type liquor were used,which was added nanometer ZrO(2) unmodified by silane coupling agent to make the standard samples of the control group. The data of flexural strength of the base plate materials were tested with three-point bending test. One-way ANOVA was adopted to analyze the data using SAS 6.12 software package. RESULTS: When the percentage of silane coupling agent Z-6030 was 3.5%,the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate was strongest, which was significantly higher than that of the common denture base plate group,the control group,2.0% group,4.0% group,4.5% group and 5.0% group(P<0.05). 0.5% group,1.0% group,1.5% group,2.5% group,3.0% group and 3.5% group had no significant difference with each other(P>0.05). 0.5% group,1.0% group,1.5% group,2.0% group,2.5% group,3.0% group,4.0% group,4.5% group,5.0% group,the common denture base plate group and the control group had no significant difference with each other(P>0.05). CONCLUSION: Using proper percentage of silane coupling agent Z-6030 can improve the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate. This study showed that the best range of the percentage of silane coupling agent Z-6030 was 3.5%.