Scandium calix[n]arenes (n = 4, 6, 8): structural, cytotoxicity and ring opening polymerization studies.

Interaction of [Sc(OR)3] (R = iPr or triflate) with p-tert-butylcalix[n]arenes, where n = 4, 6, or 8, affords a number of intriguing structural motifs, which are relatively non-toxic (cytotoxicity evaluated against cell lines HCT116 and HT-29) and a number were capable of the ring opening polymerization (ROP) of cyclohexene oxide.

Behavioral deficits and neural damage of Caenorhabditis elegans induced by three rare earth elements.

Rare earth elements (REEs) are widely used in industry, agriculture, medicine and daily life in recent years. However, environmental and health risks of REEs are still poorly understood. In this study, neurotoxicity of trichloride neodymium, praseodymium and scandium were evaluated using nematode Caenorhabditis elegans as the assay system. Median lethal concentrations (48 h) were 99.9, 157.2 and 106.4 mg/L for NdCl3, PrCl3 and ScCl3, respectively. Sublethal dose (10-30 mg/L) of these trichloride salts significantly inhibited body length of nematodes. Three REEs resulted in significant declines in locomotor frequency of body bending, head thrashing and pharyngeal pumping. In addition, mean speed and wavelength of crawling movement were significantly reduced after chronic exposure. Using transgenic nematodes, we found NdCl3, PrCl3 and ScCl3 resulted in loss of dendrite and soma of neurons, and induced down-expression of dat-1::GFP and unc-47::GFP. It indicates that REEs can lead to damage of dopaminergic and GABAergic neurons. Our data suggest that exposure to REEs may cause neurotoxicity of inducing behavioral deficits and neural damage. These findings provide useful information for understanding health risk of REE materials.

Urinary monitoring of exposure to yttrium, scandium, and europium in male Wistar rats.

On the assumption that rare earth elements (REEs) are nontoxic, they are being utilized as replacements of toxic heavy metals in novel technological applications. However, REEs are not entirely innocuous, and their impact on health is still uncertain. In the past decade, our laboratory has studied the urinary excretion of REEs in male Wistar rats given chlorides of europium, scandium, and yttrium solutions by one-shot intraperitoneal injection or oral dose. The present paper describes three experiments for the suitability and appropriateness of a method to use urine for biological monitoring of exposure to these REEs. The concentrations of REEs were determined in cumulative urine samples taken at 0-24 h by inductively coupled plasma atomic emission spectroscopy, showing that the urinary excretion of REEs is <2 %. Rare earth elements form colloidal conjugates in the bloodstream, which make high REEs accumulation in the reticuloendothelial system and glomeruli and low urinary excretion. The high sensitivity of inductively coupled plasma-argon emission spectrometry analytical methods, with detection limits of <2 µg/L, makes urine a comprehensive assessment tool that reflects REE exposure. The analytical method and animal experimental model described in this study will be of great importance and encourage further discussion for future studies.

Urinary scandium as predictor of exposure: effects of scandium chloride hexahydrate on renal function in rats.

Some of the rare earth elements such as Sc are believed to be non-toxic and, at present, are widely utilized for the replacement of toxic heavy metals in technological applications, but they are not entirely free of toxicity, with hidden potential health risks. In this animal experiment, we report the urinary scandium (Sc) excretion rate and nephrotoxiciy in male Wistar rats. For this purpose, the rats were given a single dose of a solution of scandium chloride by intraperitoneal injection. The Sc excretion (U-Sc) was determined in 24-h urine samples by inductively coupled plasma-argon emission spectrometry along with the Sc nephrotoxicity, urine volume (UV), creatinine (Crt), beta-2-microglobulin (beta2-MG) and N-acetyl-beta-D-glucosaminidase (NAG). A dose-dependent Sc excretion of 0.0063% (r = 0.97) via 24-h urine was confirmed. The administration of Sc induced a significant decrease of UV and Crt and a significant increase of NAG and beta2-MG. These results suggest that U-Sc can be a useful tool for monitoring Sc exposure. The formation of Sc colloidal conjugates that deposit in glomeruli may be the cause of a reduction of the glomerular filtration rate. We propose that the analytical method and results described in this study will be of great importance for future toxicological studies on Sc exposure.

Scandia--a potential biomaterial?

Biocompatibility is a pre-requisite for all biomaterials used for medical application. During the last two decades significant advances have been made in the development of novel materials and selection and use of these materials has been directly dependent upon their biocompatibility. Several materials containing calcium or titanium cations demonstrate biocompatibility and are routinely used in various forms within the human body. Due to its position in the periodic table, scandium in the form of its oxide scandia (Sc(2)O(3)) was studied as the first stage of a wider exploration of the biocompatibility of ceramics. A commercial human osteoblast-like cell line (HOS TE 85) was used to study the biocompatibility of both sintered and abraded scandia surfaces. Scanning electron microscopy was used to examine cell adhesion, the MTT assay was used to measure cell metabolic function and the alamarBlue for the assessment of proliferation. Although the results are only preliminary findings, qualitative observations showed that both sintered and abraded surfaces favoured cell adhesion to the same extent. Quantitatively, a significant increase in cell proliferation was observed on Sc(2)O(3) compared to Thermanox, tissue culture control. Furthermore, Sc(2)O(3) has been shown to be non-toxic, able to be maintain cell viability and support cell growth and proliferation.

Effect of trivalent metal ions on phase separation and membrane lipid packing: role in lipid peroxidation.

The capacity of Al3+-related cations (Sc3+, Ga3+, In3+, Be2+, Y3+, and La3+) to promote membrane rigidification and lateral phase separation was evaluated in liposomes containing zwitterionic (phosphatidylcholine, PC) and negatively charged (phosphatidylserine, PS) phospholipids. These effects were correlated with the capacity of the ions to stimulate Fe2+-supported lipid peroxidation. A13+, Sc3+, Ga3+, In3+, Be2+, Y3+, and La3+ (50-200 microM) increased the order parameter of the fluorescent probe 1,3-diphenylhexatriene incorporated in PC:PS membranes. In addition, the electron paramagnetic resonance spectra of spin-labeled fatty acids indicated a reduction in lipid motion induced by Sc3+, Y3+, and La3+. The effect was found to extend down to carbon 16 on the acyl chain. The ions (10-200 microM) were also able to induce lateral phase separation, as evaluated from the increase in fluorescence quenching of the probe 2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl-1-hexadec anoyl-sn-glycero-3-phosphocholine. The ability of the ions to alter membrane lipid packing and induce lateral phase separation correlated in a positive manner (r2 = 0.91 and 0.90, respectively) with their capacity to stimulate the production of Fe2+-initiated 2-thiobarbituric-reactive species, a measure of lipid peroxidation. These results show that Al3+-related metal ions cause membrane rigidification and phase separation, which could affect membrane-related processes. The results support the hypothesis that ions without redox capacity can stimulate Fe2+-initiated lipid peroxidation by increasing lipid packing and by promoting the formation of rigid clusters. Both processes will bring phospholipid acyl chains closer together, thus favoring the propagation step of lipid peroxidation.

[Occupational hygiene in production and use of multicomponent metal compounds]. / Gigiena truda pri poluchenii i primenenii mnogokompozitsionnykh soedinenii metallow.

The article deals with results obtained in hygienic evaluation of production and application of new monocrystalline compounds based on cesium, sodium, iodine, lead, scandium, fluorine. The evaluation covered work conditions and health state of those engaged into production of monocrystalline compounds, revealed the main occupational hazards. The experiments determined fundamental toxicometric parameters, studied characteristics of general toxic and specific effects induced by lead fluoride and cesium iodine. The results formed basis for sanitary measures, establishment of MACs for 4 monocrystalline compounds in the air of workplace.

Antibacterial effect of the scandium complex of enterochelin. Studies of the mechanism of action.

There is good evidence to show that ferric enterochelin is an essential growth factor for a number of Gram-negative pathogenic bacteria exposed to the host iron binding proteins, transferrin and lactoferrin. Tests of nineteen complexes of enterochelin as potential antibacterial agents showed that only those containing either indium (In3+) or scandium (Sc3+) inhibited bacterial growth. In this study, further evidence is presented which demonstrates a competition between the Sc3+ and Fe3+ complexes. The uptake of both complexes is energy dependent and is also repressed in iron-replete cells. The Sc3+ complex accumulates within the cells at 20% of the rate of the Fe3+ complex. The main components of the ferric enterochelin transport system are required for the transport of the Sc3+ complex although some Sc3+ appears to enter the cell by another route. The accumulation, within the cell, of 14C-labelled enterochelin complexes depends on the growth medium. The relationship of the size of the metal ion to the biological activity of the complex is discussed and possible mechanisms of action of the Sc3+ complex are considered.

Studies of nutritional safety of some heavy metals in mice.

Heavy metals have been proposed as nutrient markers to allow the accurate determination of the time of passage, nutrient intake, or apparent utilization of multiple nutrients. In order to evaluate possible toxic effects of scandium, chromium, lanthanum, samarium, europium, dysprosium, terbium, thulium, and ytterbium oxides, and barium sulfate upon growth, general development, reproduction, and lactation, mice were fed different levels of these compounds for three generations. The amount of elements fed were 0,110, 100, and 1000 times the use amount. The use amounts were (in ppm2.) : Sc, 0.12; Cr, 0.02; La.0.40;; Sm. 0.80; Eu, 0.036:TB, 1.20; Dy, 1.20; Tm. 0.08; Tb, 0.12; and Ba, 0.008. The use amount was one-fifth of the concentration required for activation analysis. Mortality and morbidity were negligible. No consistent growth rate changes were observed; however, different groups showed different growth rates during different generations. The number of mice born showed no significant differences amoung treatment groups. Survival, growth rate, hematology, morphological development, maturation, reproduction, and lactational performance were comparable in mice fed the different levels of 10 heavy metal oxides to those mice fed the basal diet.