Ce-doped MgO films on AZ31 alloy substrate for biomedical applications: preparation, characterization and testing

Magnesium ions, MgO nanoparticles and thin films, magnesium alloys and cerium compounds are materials intensively studied due to their corrosion protection, antibacterial and pharmacological properties. In this work, we have designed, prepared and investigated, novel thin films of MgO doped with cerium, deposited on Mg alloy (AZ31) for temporary implants, in order to enhance their life time. More precisely, we report on microstructure and corrosion behavior of MgO pure and doped with 0.1 at % Ce films, fabricated by sol-gel route coupled with spin-coating technique, on AZ31 alloy substrate. A modified sol-gel method that start from magnesium acetylacetonate, cerium nitrate and 2-methoxyethanol (as a stabilizer for the sol) was been used successfully for cerium doped MgO sol precursor preparation. The structure and morphology of the surface of the coatings, before and after immersion for 7-30 d in Hank's solution at 37 °C, were characterized by x-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscopy and Fourier infrared transmittance spectrum (FT-IR). A comparison between the corrosion protection of undoped MgO and MgO doped with 0.1 at % Ce coatings on the AZ31 alloy substrate is performed by electrochemical tests and immersion tests using open circuit potential and electrochemical impedance spectroscopy in Hank's solution, at 37 °C. The electrochemical results showed that the protection of the AZ31 alloy substrate against corrosion was better with the doped with 0.1 at % Ce MgO film deposited than with pure MgO coting. The investigations of the films after immersion in Hank's solution, at 37 °C, for 7, 21 and 30 d indicated that the grown layer on the film is bone like apatite that suggests a good bioactivity of 0.1 at % Ce-doped MgO coating. Our work demonstrates that the performance corrosion protection of the biodegradable magnesium alloys used for orthopedic applications, in simulated physiological environments (Hank and Ringer) can be enhanced through coating with Ce3+doped MgO sol-gel thin film.

Lead-Free BNT-BT0.08/CoFe2O4 Core-Shell Nanostructures with Potential Multifunctional Applications

Herein we report on novel multiferroic core–shell nanostructures of cobalt ferrite (CoFe₂O₄)–bismuth, sodium titanate doped with barium titanate (BNT–BT_0.08), prepared by a two–step wet chemical procedure, using the sol–gel technique. The fraction of CoFe₂O₄ was varied from 1:0.5 to 1:1.5 = BNT–BT_0.08/CoFe₂O₄ (molar ratio). X–ray diffraction confirmed the presence of both the spinel CoFe₂O₄ and the perovskite Bi_0.5Na_0.5TiO₃ phases. Scanning electron microscopy analysis indicated that the diameter of the core–shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two–phase composite nanostructures consisting of a BNT–BT_0.08 core surrounded by a CoFe₂O₄ shell with an average thickness of 4–7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT–BT_0.08/CoFe₂O₄ composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe₂O₄ semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mössbauer measurements have shown no change in the valence of the Fe³⁺, Co²⁺, Bi³⁺ and Ti⁴⁺ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT–BT_0.08/CoFe₂O₄ core–shell composite potentially suitable for magnetoelectric applications.

Combined use of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy for estimating incipient phase separation in lead titanate-based multiferroics

The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O3 (x = 0.00, 0.03, 0.04, 0.05) by means of a combination of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy. We found that Fe ions are substituted as Fe3+ at Ti sites and preferentially exhibit pentahedral coordination, whereas Ti ions have coexisting valences of Ti4+/Ti3+. Fe3+ ions are preferentially ordered in clusters, and there exists a transition temperature TC1, below which phase separation occurs between a tetragonal phase T1 free of magnetic clusters and a cubic phase, and a lower transition temperature TC2, below which the cubic phase rich in magnetic clusters is transformed into a tetragonal phase T2. The phase separation persists at the nanoscale level down to room temperature and is visible in HRTEM images as a mixing of nanodomains with different tetragonality ratios. This phase separation was observed over the whole studied concentration range of xFe values. It occurs progressively with the value of xFe, and the transition temperature TC2 decreases with the concentration from about 620 K (xFe = 0.03) to about 600 K (xFe = 0.05), while TC1 remains nearly constant.

Clinical Relevance of Tumor Ploidy and Micronucleus Formation for Oral Cavity Cancer

Aims and Background

To study the clinical relevance of tumor ploidy and micronucleus formation as prognostic factors.

Methods and Study Design

Twenty-eight patients with squamous cell carcinoma of the oral cavity were treated with primary radiochemotherapy consisting of irradiation up to 70 Gy in combination with cisplatin. Cell cycle distribution, micronucleus formation and ploidy were evaluated by flow cytometry of biopsies taken before treatment and after irradiation to 10 Gy (5 × 2 Gy). Sexteen out of 28 patients relapsed after a minimum follow-up period of two years.

Results

Flow cytometry of the recurrence biopsy showed hyperpentaploid (5c exceeding) cells in 13/16 (81%) of the relapsed patients. In 7 patients the hyperploid clone was not present in the flow cytometry of the primary tumors. Ploidy could retrospectively be determined also by image cytometry in archival tumor material of the pretreatment specimens. Patients with a level below 100 5c cells per 10,000 cell nuclei were shown to have a significantly better prognosis than patients with more than 100 hyperpentaploid tumor cells. The micronucleus formation was 2-5 times higher in tumors showing a good response to treatment than in carcinomas relapsing within two years.

Conclusions

The 5c-exceeding ratio measured by image cytometry and micronucleus formation proved to be good prognostic parameters for the clinical outcome of patients with locally advanced head and neck carcinomas.

Development and Biocompatibility Evaluation of Photocatalytic TiO₂/Reduced Graphene Oxide-Based Nanoparticles Designed for Self-Cleaning Purposes

Graphene is widely used in nanotechnologies to amplify the photocatalytic activity of TiO₂, but the development of TiO₂/graphene composites imposes the assessment of their risk to human and environmental health. Therefore, reduced graphene oxide was decorated with two types of TiO₂ particles co-doped with 1% iron and nitrogen, one of them being obtained by a simultaneous precipitation of Ti3+ and Fe3+ ions to achieve their uniform distribution, and the other one after a sequential precipitation of these two cations for a higher concentration of iron on the surface. Physico-chemical characterization, photocatalytic efficiency evaluation, antimicrobial analysis and biocompatibility assessment were performed for these TiO₂-based composites. The best photocatalytic efficiency was found for the sample with iron atoms localized at the sample surface. A very good anti-inhibitory activity was obtained for both samples against biofilms of Gram-positive and Gram-negative strains. Exposure of human skin and lung fibroblasts to photocatalysts did not significantly affect cell viability, but analysis of oxidative stress showed increased levels of carbonyl groups and advanced oxidation protein products for both cell lines after 48 h of incubation. Our findings are of major importance by providing useful knowledge for future photocatalytic self-cleaning and biomedical applications of graphene-based materials.

Tofacitinib in the Treatment of Rheumatoid Arthritis and Chronic Plaque Psoriasis

Tofacitinib is an oral immunosuppressant approved for the treatment of rheumatoid arthritis (RA) and is currently undergoing investigation (Phase III trials) for treating chronic plaque psoriasis. Tofacitinib inhibits Janus kinases (JAKs), which are essential for the signaling of multiple inflammatory pathways and have been implicated in the pathogenesis of RA and psoriasis. The efficacy and safety of tofacitinib in the treatment of RA and psoriasis have been demonstrated in Phase III trials. Across all studies, the efficacy of tofacitinib in alleviating symptoms of RA and psoriasis were superior to placebo. Moreover, treatment was generally well-tolerated, with the most frequently reported adverse events, for both RA and psoriasis, being nasopharyngitis and upper respiratory tract infection. As such, tofacitinib proves to be an effective therapeutic option for RA and a promising new therapy for psoriasis.

Characterization of fine grain Ba0.995Y0.005TiO3 ceramics obtained from gel-precursor nanopowder

Using an acetate-alkoxide sol-gel route in which the precursors are barium acetate, yttrium isopropoxide and titanium diisopropoxide bis-acetylacetonate, we prepared a ferroelectric material with the formula: Ba1-xYxTiO3, x = 0.005. SEM analysis showed a polymeric microstructure of the gel due to the chelated titanium alkoxide precursor used as starting materials. The evolution of the structure and microstructure of the precursor gel heated at temperatures up to 1000 degrees C was studied by various techniques. The powder obtained by heating the gel at 1100 degrees C presented a homogeneous structure consisting of submicronic particles (approximately 200 nm). XRD and SAED analyses revealed that Ba0.995Y0.005TiO3 nanocrystals of about 5-10 nm appeared at 600 degrees C, together with BaCO3. The presence of barium carbonate was identified also by IR spectroscopy and thermal analyses. The ceramics obtained from the as-prepared powder presented good dielectric properties (capacitance = 840 pF/dielectric constant = 3860 and dielectric loss (tandelta) = 0.078 at Curie temperatures of 120-121 degrees C).

Synthesis of La and Nb doped PZT powder by the gel-combustion method

Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)]0.9825Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3(-) = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at ≤400 °C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate (Pb2O·CO3) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 °C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3(-) ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3(-) equal to 0.09.

Association of autonomous thyroid adenoma with chronic thyroiditis

Coexistence of an autonomous thyroid adenoma (ATA) with chronic thyroiditis suggests a complex pathogeny pointing to the autonomous character of the nodule and to the presence of immunitary disorders. The rarity of this association and the paucity of data prompted us to present 4 cases of a series of 71 thyroidectomized ATA cases. The rarity of ATA associated with chronic thyroiditis, accumulation of radioiodine under the conditions of euthyroidism only at the adenoma level as well as the possibility for the disease to occur in hypopituitarism, all support the hypothesis of an initial thyreotropic deficiency, with subsequent hyperplasia "of necessity". Later on there is an autonomous hyperfunction increasing pituitary depression, with total extinction of the thyroid tissue outside the adenoma. When the two lesions are associated, we consider that initially there was the TSH-dependent thyroiditis that developed during which, by accidental depression of TSH secretion a local hyperplasia occurs which later becomes autonomous.