Influence of magnetite incorporation into chitosan on the adsorption of the methotrexate and in vitro cytotoxicity.

Emerging pollutants are a group of substances involved in environmental contamination resulting mostly from incomplete drug metabolism, associated with inadequate disposal and ineffective effluent treatment techniques. Methotrexate (MTX), for instance, is excreted at high concentrations in unchanged form through the urine. Although the MTX is still effective in cancer and autoimmune disease treatment, this drug shows the ability of bioaccumulation and toxicity to the organism. Thus, the present work aimed to evaluate the adsorption of the MTX drug onto magnetic nanocomposites containing different amounts of incorporated magnetite (1:1, 1:5, and 1:10 wt%), combining the theoretical-experimental study as well as the in vitro cytotoxicity. Moreover, equilibrium studies (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Hill, Redlich-Peterson, and Sips), kinetic (PFO, PSO, and IPD), and thermodynamic (ΔG°, ΔH°, and ΔS°) were used to describe the experimental data, and ab initio simulations were employed in the theoretical study. Magnetic nanocomposites were synthesized by the co-precipitation method using only FeCl2 as the iron precursor. Adsorbents were characterized by FTIR, XRD, Raman, SEM-EDS, BET, and VSM analysis. Meanwhile, cytotoxic effects on L929 and A375 cell lines were evaluated through MTT, NR, and LDH assays. The adsorption of the MTX was carried out in a typical batch system, exploring the different experimental conditions. The theoretical study suggests the occurrence of chemisorption between CS·Fe3O4-MTX. The maximum adsorption capacity of MTX was 285.92 mg g-1, using 0.125 g L-1 of CS·Fe3O4 1:1, with an initial concentration of the MTX (50 mg L-1), pH 4.0 at 293 ± 1.00 K. The best adjustment of equilibrium and kinetic data were the Sips (low values for statistical errors) and PSO (qe = 96.73 mg g-1) models, respectively. Thermodynamic study shows that the adsorption occurred spontaneously (ΔG° < 0), with exothermic (ΔH° = - 4698.89 kJ mol-1) and random at the solid-solution interface (ΔS° = 1,476,022.00 kJ mol-1 k-1) behavior. Finally, the in vitro study shows that magnetic nanomaterials exhibit higher cytotoxicity in melanoma cells. Therefore, the magnetic nanocomposite reveals to be not only an excellent tool for water remediation studies but also a promising platform for drug delivery.

Surface treatments and its effects on the fatigue behavior of a 5% mol yttria partially stabilized zirconia material.

This study evaluated the effect of distinct surface treatments on the fatigue behavior (biaxial flexural fatigue testing) and surface characteristics (topography and roughness) of a 5% mol yttria partially stabilized zirconia ceramic (5Y-PSZ). Disc-shaped specimens of 5Y-PSZ (IPS e.max ZirCAD MT Multi) were manufactured (ISO 6872-2015) and allocated into six groups (n = 15) considering the following surface treatments: Ctrl - no-treatment; GLZ - low-fusing porcelain glaze application; SNF - 5 nm SiO2 nanofilm; AlOx - aluminum oxide particle air-abrasion; SiC - silica-coated aluminum oxide particles (silica-coating); and 7%Si - 7% silica-coated aluminum oxide particles (silica-coating). The biaxial flexural fatigue tests were performed by the step-stress method (20Hz for 10,000 cycles) with a step increment of 50N starting at 100N and proceeding until failure detection. The samples were tested with the treated surface facing down (tensile stress side). Topography, fractography, roughness, and phase content assessments of treated specimens were performed. GLZ group presented the highest fatigue behavior, while AlOx presented the lowest performance, and was only similar to SiC and 7%Si. Ctrl and SNF presented intermediary fatigue behavior, and were also similar to SiC and 7%Si. GLZ promoted a rougher surface, Ctrl and SNF had the lowest roughness, while the air-abrasion groups presented intermediary roughness. No m-phase content was detected (only t and c phases were detected). In conclusion, the application of a thin-layer of low-fusing porcelain glaze, the deposition of silica nanofilms and the air-abrasion with silica-coated alumina particles had no detrimental effect on the fatigue behavior of the 5Y-PSZ, while the air-abrasion with alumina particles damaged the fatigue outcomes.

Fatigue performance of fully-stabilized zirconia polycrystals monolithic restorations: The effects of surface treatments at the bonding surface.

This study evaluated the distinct conditioning effect of the intaglio surface of bonded fully-stabilized zirconia (FSZ) simplified restorations on the mechanical fatigue behavior of the set prior to and after aging. Ceramic disc shaped specimens (Ø= 10 mm and 1 mm thick) were randomly allocated into 14 groups considering: "surface treatments" (Ctrl: no-treatment; PM: universal primer; GLZ: low-fusing porcelain glaze; SNF: 5 nm SiO2 nanofilm deposition; AlOx: air-abrasion with aluminum oxide; SiC: air-abrasion with silica-coated aluminum oxide; 7%Si: air-abrasion with 7% silica-coated aluminum oxide); and "aging" (baseline: 24 h at 37 °C in water; or aged: 90 days at 37 °C in water + 12,000 thermal cycles). The discs were treated, luted with resin cement onto the dentin analog, subjected to aging or not, and then tested under a step-stress fatigue test at 20 Hz, 10,000 cycles/step, step-size of 100N starting at 200N, and proceeding until failure detection. Fractographic, topographic, surface roughness, contact angle, and atomic force microscopy analyzes were performed. The surface treatments at baseline led to statistically similar fatigue failure loads (953N-1313N), except for GLZ (1313N), which was significantly higher than 7%Si (953 N). Meanwhile, Ctrl had 40% pre-test failures (debonding) after aging, and therefore the worst fatigue performance (notable decrease in fatigue results), while all the other groups presented superior and statistically similar fatigue behavior (973-1271N). In fact, when considering baseline Vs aging conditions, stable fatigue results could only be noted when using surface treatments. In conclusion, internal surface treatments of FSZ ceramic restorations are mandatory for fatigue behavior stability after aging the restorative set, while non-treatment induced unstable results.

A Comparative Study of Magnetic Properties of Large Diameter Co Nanowires and Nanotubes.

A comparative study of the magnetic properties of the arrays of Co nanowires and nanotubes with large external diameters (180 nm) has been carried out. The nanowires/nanotubes were grown by electrodeposition into the self-assembled pores of anodic alumina membranes. The experimental study of their magnetic behavior was focused on the angular dependence of hysteresis loops and their parameters. In both nanowire and nanotube arrays, from the analysis of experimental data, effective longitudinal magnetic anisotropy is concluded, which is stronger in the case of the nanotube array. In addition, the extremely small remanence observed for all loops indicates the important role played by magnetostatic interactions. Micromagnetic simulations were first performed considering intrinsic shape and magnetocrystalline anisotropy terms, together with an effective easy-plane anisotropy to account for those magnetostatic interactions. A qualitative agreement between experiments and simulations is found despite the complexity introduced by the intrinsic and extrinsic array properties (i.e., large diameters, grain structure, and array configuration). In addition, simulations were also carried out for individual nanowire/nanotube with a particular emphasis to understand their differences at the remanence, due to pure geometry contribution.

Mechanical behavior of yttria-stabilized tetragonal zirconia polycrystalline ceramic after different zirconia surface treatments.

This study investigated the effects of different zirconia surface conditioning methods on the biaxial flexure strength, surface characteristics and fractographic analysis of a Y-TZP ceramic. Disc-shaped specimens were manufactured according to ISO 6872-2008 for biaxial flexure strength testing, and then randomly assigned into seven groups (n=30). Control (CTRL): without treatment; Tribochemical silica coating (TBS): specimens were sandblasted with silica-coated aluminum oxide particles (CoJet-Sand) for 10s; Silica nanofilm (SNF): specimens were silica coated with a 5nm SiO2 nanofilm; and four protocols of low-fusing porcelain glaze (GLZ): etching with 10% hydrofluoric acid gel (HF) for 1min (GLZ1), 5min (GLZ5), 10min (GLZ10) and 15min (GLZ15). Phase transformation, roughness, micro-morphological, flexural analysis tests, and fractographic analyses were performed. X-ray diffraction (XRD) analysis showed that the TBS promoted the highest m-phase content (20.35). However, for the GLZ groups, XRD analysis was not sensitive enough to obtain an accurate reading for phase transformation. The GLZ group had the highest roughness values. The TBS group had the highest characteristic strength (1291.38MPa), followed by SNF (999.26MPa). These results suggest that (TBS) and (SNF) treatments did not reduce the mechanical properties, while (GLZ) led to a degradation in the mechanical properties.

Adhesion to Y-TZP ceramic: study of silica nanofilm coating on the surface of Y-TZP.

This study evaluated the influence of silica-based film coatings on the surface of yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP), in particular on the durability of the bond strength between the ceramic and resin cement. Eighty Y-TZP (In-Ceram YZ, Vita) blocks (4 × 4 × 3 mm) were obtained and divided into four groups according to the surface treatments (n = 20): tribochemical silica coating (TBS; Cojet, 3M/ESPE), 5 nm SiO2 nanofilm and silanization (F-5), 500 nm SiO2 nanofilm and silanization (F-500), and 500 nm SiO2 nanofilm + hydrofluoric-acid-etching + silanization (F-500HF). Specimens of composite resin (3.25 mm in diameter and 3 mm in height) were cemented to Y-TZP blocks using resin cement (Relyx ARC). Half of the specimens from each group were tested 24 h after adhesion (B: baseline condition), and the other half were subjected to aging (A: storage for 90 days and 10,000 thermal cycles). The specimens were subjected to shear testing (SBS) (1 mm/min). After testing, the surfaces were analyzed with a stereomicroscope and scanning electron microscope. Micromorphologic and elemental chemical analyses of the treated Y-TZP surface were made by X-ray energy dispersive spectroscopy. Bond strength data were statistically analyzed by Kruskal-Wallis/Mann-Whitney tests (α = 0.05). The surface treatment showed significant differences for B (p = 0.0001) and A (p = 0.0000) conditions. In both storage conditions, TBS and F-5 groups promoted the significantly highest bond strength. Most of the specimens presented adhesive failure. The X-ray energy dispersive spectroscopy analysis depicted the highest peak of silica in the TBS, F-5, and F-500 groups. The adhesion to zirconia can be improved if the surface receives a 5 nm layer of SiO2 nanofilm or is subjected to sandblasting with silica particles, followed by silanization.