Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

The choice of the intervention in the surgical treatment of nontoxic diffuse multinodular goiter

The choice between sub-total (STT) and total (TT) thyroidectomy in surgical management of multinodular goitre should be based on the disease pathophysiology and the critical review of short and long-term results of these treatments. In order to make a comparative evaluation the authors carried out a retrospective analysis on a series of patients operated from 1970 to 1993 and on the results of a 16.3 years mean follow-up. Of 551 patients operated on the thyroid gland, 389 (70.6%) affected by multinodular goitre were considered. 340 were female and 49 male (39 years medium age). 341 (87.6%) underwent STT and 48 (12.4%) TT. Post-operative opotherapy was adjusted according to hormonal assays. Post-operative vocal cord motility and calcemia were assessed. A routine endocrinological follow-up protocol has been carried out on all patients since 1980. Transitory vocal cord palsy and hypocalcemia were significantly more frequent in TT, while permanent damage was not. Of 40 TT (complete 5 years mean follow-up, 97.5% of the patients reached euthyroidism with replacement therapy. Of 189 STT (complete 16.3 years mean follow-up), 61.4% of the patients received opotherapy. A recurrent goitre was ascertained in 39.1% of the total (73.3% in the patients not receiving opotherapy) and operated in 16.2% of the cases. According to the authors their results support the choice of TT as it matches the rationale of surgical treatment of multinodular non-toxic goitre based on the pathophysiology of the disease. Moreover it allows easy achievement of euthyroidism avoiding goitre relapse and subsequently re-operation, with an incidence of permanent recurrent nerve palsy and hypoparathyroidism not significantly different from that after STT

Spark plasma sintering of cryomilled CoNiCrAlY powders

The influence of a cryomilling treatment in liquid N2 on the characteristics of Co-32Ni-21Cr-8Al-0.5Y powders is first investigated in this work. The cryogenic process is then followed by a consolidation step performed using Spark Plasma Sintering. Different morphology, particle size increase, crystallite size decrease down to nanometric level and higher sinterability are the most important changes observed in CoNiCrAlY powders after cryomilling. Correspondingly, a relatively finer micro structure is obtained in SPSed samples. Moreover, if samples obtained starting from cryomilled powders are exposed to an oxidizing environment at high temperature, a protective a-Al203 layer is produced on their external surface, while the formation of undesired unstable oxides is hindered. This result seems promising with the final aim of increasing high-temperature oxidation resistance in TBC of gas turbine engines

Spark Plasma Sintering Processing for the Evaluation of Cryomilled CoNiCrAlY Alloys for High Temperature Applications in Oxidizing Environment

The aim of this work is to investigate the use of Spark Plasma Sintering (SPS) as a rapid and efficient approach to evaluate possible benefits deriving from cryogenic mechano-treatments of MCrAlY systems for high temperature applications in oxidizing conditions. Specifically, following our previous investigation, the influence of cryomilling on Co–32Ni–21Cr–8Al–0.5Y (wt.%) alloy characteristics is systematically analyzed in this work. It is shown that mechanical milling in liquid N2 produces morphology changes, particle size increase, crystallite size decrease down to nanometric level (about 20 nm sized) and the formation of oxide nanodispersoids in the processed powders. These features are found to be responsible for the significant influence of the cryogenic treatment on the sintering behavior of resulting powders. Specifically, the densification process is progressively favoured if cryomilling intensity does not exceed a certain level. In contrast, powders sintering becomes relatively more difficult with severely milled powders. It is shown that a significant microstructure refinement (down to 350 ± 150 grain sized) is obtained in SPSed samples prepared from cryomilled powders. When cryomilled CoNiCrAlY SPSed specimens are exposed to an oxidizing environment at 1100 °C, an α-Al2O3 layer tends to be selectively produced on their external surface, thus limiting the formation of less protective mixed oxides observed when the unmilled system is oxidized under the same condition. Al depletion from the bulk of the sample is correspondingly reduced. Therefore, the obtained results provide a useful contribution for the identification of the optimal cryomilling conditions leading to high-temperature oxidation resistance improvement in thermal barrier coatings of gas turbine engines