Effect of chromium oxide (III) nanoparticles on the production of reactive oxygen species and photosystem II activity in the green alga Chlamydomonas reinhardtii

Nanoparticles as contrast agents for brain nuclear magnetic resonance imaging in Alzheimer's disease diagnosis

Nuclear Magnetic Resonance Imaging (MRI) of amyloid plaques is a powerful non-invasive approach for the early and accurate diagnosis of Alzheimer's disease (AD) along with clinical observations of behavioral changes and cognitive impairment. The present article aims at giving a critical and comprehensive review of recent advances in the development of nanoparticle-based contrast agents for brain MRI. Nanoparticles considered for the MRI of AD must comply with a highly stringent set of requirements including low toxicity and the ability to cross the blood-brain-barrier. In addition, to reach an optimal signal-to-noise ratio, they must exhibit a specific ability to target amyloid plaques, which can be achieved by grafting antibodies, peptides or small molecules. Finally, we propose to consider new directions for the future of MRI in the context of Alzheimer's disease, in particular by enhancing the performances of contrast agents and by including therapeutic functionalities following a theranostic strategy.

Engineered nano particles: Nature, behavior, and effect on the environment

Increased application of engineered nano particles (ENPs) in production of various appliances and consumer items is increasing their presence in the natural environment. Although a wide variety of nano particles (NPs) are ubiquitously dispersed in ecosystems, risk assessment guidelines to describe their ageing, direct exposure, and long-term accumulation characteristics are poorly developed. In this review, we describe what is known about the life cycle of ENPs and their impact on natural systems and examine if there is a cohesive relationship between their transformation processes and bio-accessibility in various food chains. Different environmental stressors influence the fate of these particles in the environment. Composition of solid media, pore size, solution chemistry, mineral composition, presence of natural organic matter, and fluid velocity are some environmental stressors that influence the transformation, transport, and mobility of nano particles. Transformed nano particles can reduce cell viability, growth and morphology, enhance oxidative stress, and damage DNA in living organisms.

Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii

Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer ⁵¹Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1h and 72h of exposure to 100nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23±12% after 1h and 37±7% after 72h) and cytosolic heat-stable proteins and peptides (39±18% after 1h and 35±3% after 72h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28kDa) appeared after 1h of exposure for both Cr species. After 72h another biomolecule of lower molecular weight (∼0.7kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the first time, that both Cr(III) and Cr(VI) have similar fate within algal cells, supporting the tenet that a unique redox form occurs within cells.