Gold nanoparticles are widely used in biomedical imaging and diagnostic tests. Based on their established use in the laboratory and the chemical stability of Au(0), gold nanoparticles were expected to be safe. The recent literature, however, contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background a systematic study of water-soluble gold nanoparticles stabilized by triphenylphosphine derivatives ranging in size from 0.8 to 15 nm is made. The cytotoxicity of these particles in four cell lines representing major functional cell types with barrier and phagocyte function are tested. Connective tissue fibroblasts, epithelial cells, macrophages, and melanoma cells prove most sensitive to gold particles 1.4 nm in size, which results in IC(50) values ranging from 30 to 56 microM depending on the particular 1.4-nm Au compound-cell line combination. In contrast, gold particles 15 nm in size and Tauredon (gold thiomalate) are nontoxic at up to 60-fold and 100-fold higher concentrations, respectively. The cellular response is size dependent, in that 1.4-nm particles cause predominantly rapid cell death by necrosis within 12 h while closely related particles 1.2 nm in diameter effect predominantly programmed cell death by apoptosis.

As a cofactor in numerous enzymatic reactions, magnesium fulfils various intracellular physiological functions. Thus, imbalance in magnesium status—primarily hypomagnesaemia as it is seen more often than hypermagnesaemia—might result in unwanted neuromuscular, cardiac or nervous disorders. Measuring total serum magnesium is a feasible and affordable way to monitor changes in magnesium status, although it does not necessarily reflect total body magnesium content. The following review focuses on the natural occurrence of magnesium and its physiological function. The absorption and excretion of magnesium as well as hypo- and hypermagnesaemia will be addressed.

Abstract. Patients with ESRD have a high circulating calcium (Ca) ϫ phosphate (P) product and develop extensive vascular calcification that may contribute to their high cardiovascular morbidity. However, the cellular mechanisms underlying vascular calcification in this context are poorly understood. In an in vitro model, elevated Ca or P induced human vascular smooth muscle cell (VSMC) calcification independently and synergistically, a process that was potently inhibited by serum. Calcification was initiated by release from living VSMC of membrane-bound matrix vesicles (MV) and also by apoptotic bodies from dying cells. Vesicles released by VSMC after prolonged exposure to Ca and P contained preformed basic calcium phosphate and calcified extensively. However, vesicles released in the presence of serum did not contain basic calcium phosphate, co-purified with the mineralization inhibitor fetuin-A and calcified minimally. Importantly, MV released under normal physiologic conditions did not calcify, and VSMC were also able to inhibit the spontaneous precipitation of Ca and P in solution. The potent mineralization inhibitor matrix Gla protein was found to be present in MV, and pretreatment of VSMC with warfarin markedly enhanced vesicle calcification. These data suggest that in the context of raised Ca and P, vascular calcification is a modifiable, cell-mediated process regulated by vesicle release. These vesicles contain mineralization inhibitors derived from VSMC and serum, and perturbation of the production or function of these inhibitors would lead to accelerated vascular calcification.Patients with ESRD develop extensive medial calcification, or Monckeberg's sclerosis, that causes increased arterial stiffness and contributes to the high cardiovascular mortality (1,2). Calciphylaxis is an increasingly common and life-threatening form of calcification characterized by destructive calcification in the media of subcutaneous arterioles, leading to occlusion and subsequent widespread tissue necrosis (2,3). The precise pathophysiology of vascular calcification in ESRD is unknown, but risk factors include age, hypertension, time on dialysis, and, most significant, abnormalities in calcium (Ca) and phosphate (P) metabolism (4,5). Normal serum concentrations of Ca and inorganic P ions are metastable with respect to basic calcium phosphate (BCP; a mixture of octacalcium phosphate, dicalcium phosphate dihydrate, and apatite) precipitation but can support growth of nascent crystals. In ESRD, systemic Ca and inorganic P concentrations typically exceed 2.4 and 2.0 mM, respectively (4). Consequently, calcification in ESRD has traditionally been ascribed to supersaturation and subsequent precipitation of mineral ions. This has led to therapeutic measures to reduce the Ca/P product aimed mostly at reduction of P.Recent studies have shown that vascular calcification is a regulated process similar to bone formation (6,7). VSMC in the normal artery wall constitutively express potent inhibitors of calcification, such as matrix Gla ...

Gold nanoparticles (AuNPs) are generally considered nontoxic, similar to bulk gold, which is inert and biocompatible. AuNPs of diameter 1.4 nm capped with triphenylphosphine monosulfonate (TPPMS), Au1.4MS, are much more cytotoxic than 15-nm nanoparticles (Au15MS) of similar chemical composition. Here, major cell-death pathways are studied and it is determined that the cytotoxicity is caused by oxidative stress. Indicators of oxidative stress, reactive oxygen species (ROS), mitochondrial potential and integrity, and mitochondrial substrate reduction are all compromised. Genome-wide expression profiling using DNA gene arrays indicates robust upregulation of stress-related genes after 6 and 12 h of incubation with a 2 x IC50 concentration of Au1.4MS but not with Au15MS nanoparticles. The caspase inhibitor Z-VAD-fmk does not rescue the cells, which suggests that necrosis, not apoptosis, is the predominant pathway at this concentration. Pretreatment of the nanoparticles with reducing agents/antioxidants N-acetylcysteine, glutathione, and TPPMS reduces the toxicity of Au1.4MS. AuNPs of similar size but capped with glutathione (Au1.1GSH) likewise do not induce oxidative stress. Besides the size dependency of AuNP toxicity, ligand chemistry is a critical parameter determining the degree of cytotoxicity. AuNP exposure most likely causes oxidative stress that is amplified by mitochondrial damage. Au1.4MS nanoparticle cytotoxicity is associated with oxidative stress, endogenous ROS production, and depletion of the intracellular antioxidant pool.

Genetic evidence from mutant mice suggests that ␣ 2 -HS glycoprotein/fetuin-A (Ahsg) is a systemic inhibitor of precipitation of basic calcium phosphate preventing unwanted calcification. Using electron microscopy and dynamic light scattering, we demonstrate that precipitation inhibition by Ahsg is caused by the transient formation of soluble, colloidal spheres, containing Ahsg, calcium, and phosphate. These "calciprotein particles" of 30 -150 nm in diameter are initially amorphous and soluble but turn progressively more crystalline and insoluble in a time-and temperature-dependent fashion. Solubilization in Ahsg-containing calciprotein particles provides a novel conceptual framework to explain how insoluble calcium precipitates may be transported and removed in the bodies of mammals. Mutational analysis showed that the basic calcium phosphate precipitation inhibition activity resides in the amino-terminal cystatin-like domain D1 of Ahsg. A structure-function analysis of wild type and mutant forms of cystatin-like domains from Ahsg, full-length fetuin-B, histidine-rich glycoprotein, and kininogen demonstrated that Ahsg domain D1 is most efficient in inhibiting basic calcium phosphate precipitation. The computer-modeled domain structures suggest that a dense array of acidic residues on an extended ␤-sheet of the cystatin-like domain Ahsg-D1 mediates efficient inhibition.