Luminescent composites of poly(methylmethacrylate) (PMMA) and nanophosphors (Zn sub(2)SiO sub(4):Mn super(2+), Zn sub(2)SiO sub(4):Eu super(3+)) were prepared by dispersion casting method. It was ...found that nanoparticles embedded in PMMA matrix preserve their typical phosphorescence emission. The influence of Zn sub(2)SiO sub(4) nanofillers on thermal properties of PMMA was also investigated. A shift towards higher glass transition temperatures and slight improvements in thermal stability of the nanocomposites compared to pure PMMA were observed and are discussed herein.
Abstract Because of the ability to induce cell death in certain conditions, the fullerenes (C60 ) are potential anticancer and toxic agents. The colloidal suspension of crystalline C60 (nano-C60 , n ...C60 ) is extremely toxic, but the mechanisms of its cytotoxicity are not completely understood. By combining experimental analysis and mathematical modelling, we investigate the requirements for the reactive oxygen species (ROS)-mediated cytotoxicity of different n C60 suspensions, prepared by solvent exchange method in tetrahydrofuran (THF/ n C60 ) and ethanol (EtOH/ n C60 ), or by extended mixing in water (aqu/ n C60 ). With regard to their capacity to generate ROS and cause mitochondrial depolarization followed by necrotic cell death, the n C60 suspensions are ranked in the following order: THF/ n C60 >EtOH/ n C60 >aqu/ n C60 . Mathematical modelling of singlet oxygen (1 O2 ) generation indicates that the1 O2 -quenching power (THF/ n C60 <EtOH/ n C60 <aqu/ n C60 ) of the solvent intercalated in the fullerene crystals determines their ability to produce ROS and cause cell damage. These data could have important implications for toxicology and biomedical application of colloidal fullerenes.
Whitening‐dependent changes of fluorescence of extracted human teeth Pereira Sanchez, Natalie; Aleksic, Aleksandar; Dramicanin, Miroslav ...
Journal of esthetic and restorative dentistry,
September/October 2017, 2017-Sep, 2017-09-00, 20170901, Letnik:
29, Številka:
5
Journal Article
Recenzirano
Objective
To evaluate in vitro the fluorescence properties of extracted human teeth whitened with 40% hydrogen peroxide.
Materials and Methods
A total of 28 extracted human teeth were pumiced for 1 ...minute using a low‐speed dental handpiece and a disposable rubber cup. Pre‐whitening fluorescence measurements (T0), maximum excitation (Exmax), maximum emission (Emmax), and maximum intensity (Imax108), were performed using a spectrofluorometer. After T0 measurements, the teeth were whitened using the in‐office method with 40% hydrogen peroxide, three times for 20 minutes. The fluorescence parameters were measured under the same conditions 7 and 14 days after bleaching (T1 and T2, respectively).
Results
Exmax exhibited a broader range 7 days after whitening and decreased after 14 days. The Emmax and Imax108 displayed a narrower range after whitening. The mean Exmax differed significantly between the time points (F = 20.09. P < .001). The corresponding analysis for the mean Emmax differed significantly between the time points (F = 16.69, P < .001). The same was true for the mean Imax108 (F = 9.69, P < .001).
Conclusions
Within the limitations of this study, whitening provoked statistically significant changes in fluorescence of the intact teeth in vitro.
Clinical significance
The appearance of human teeth and dental materials and their changes upon aging and exposure to different agents (staining, whitening) is a topic of great relevance to esthetic dentistry. While some appearance parameters, such as color, translucency, and gloss, have been thoroughly studied, fluorescence and its influence on overall tooth appearance is still not well understood, yet it has influenced the development of fluorescence emitting restorative materials.
The results of synthesis and characterization of single wall carbon nanotubes functionalized by hydroxyethyl cellulose have been presented. The properties of pristine and modified single wall carbon ...nanotubes have been compared by different techniques: thermo-gravimetric analysis, Raman spectroscopy, Fourier transform infrared and UV-Vis-NIR spectroscopy. Raman analysis reveals that smaller amount of hydroxyethyl cellulose is required for functionalization of metallic single wall carbon nanotubes compared to semiconducting ones. FTIR analysis has shown the presence of hydroxyethyl groups which is strong evidence for nanotube modification.
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