Cubic Iron Core-Shell Nanoparticles Functionalized to Obtain High-Performance MRI Contrast Agents.

Nanoparticles with SiO2 coating were synthesized to have a cubic iron core. These were found to have saturation magnetization very close to the highest possible value of any iron-containing nanoparticles and the bulk iron saturation magnetization. The in vitro toxicology studies show that they are highly biocompatible and possess better MRI contrast agent potential than iron oxide NPs.

Neurotrophic Factors in Parkinson's Disease: Clinical Trials, Open Challenges and Nanoparticle-Mediated Delivery to the Brain.

Neurotrophic factors (NTFs) are small secreted proteins that support the development, maturation and survival of neurons. NTFs injected into the brain rescue and regenerate certain neuronal populations lost in neurodegenerative diseases, demonstrating the potential of NTFs to cure the diseases rather than simply alleviating the symptoms. NTFs (as the vast majority of molecules) do not pass through the blood-brain barrier (BBB) and therefore, are delivered directly into the brain of patients using costly and risky intracranial surgery. The delivery efficacy and poor diffusion of some NTFs inside the brain are considered the major problems behind their modest effects in clinical trials. Thus, there is a great need for NTFs to be delivered systemically thereby avoiding intracranial surgery. Nanoparticles (NPs), particles with the size dimensions of 1-100 nm, can be used to stabilize NTFs and facilitate their transport through the BBB. Several studies have shown that NTFs can be loaded into or attached onto NPs, administered systemically and transported to the brain. To improve the NP-mediated NTF delivery through the BBB, the surface of NPs can be functionalized with specific ligands such as transferrin, insulin, lactoferrin, apolipoproteins, antibodies or short peptides that will be recognized and internalized by the respective receptors on brain endothelial cells. In this review, we elaborate on the most suitable NTF delivery methods and envision "ideal" NTF for Parkinson's disease (PD) and clinical trial thereof. We shortly summarize clinical trials of four NTFs, glial cell line-derived neurotrophic factor (GDNF), neurturin (NRTN), platelet-derived growth factor (PDGF-BB), and cerebral dopamine neurotrophic factor (CDNF), that were tested in PD patients, focusing mainly on GDNF and CDNF. We summarize current possibilities of NP-mediated delivery of NTFs to the brain and discuss whether NPs have impact in improving the properties of NTFs and delivery across the BBB. Emerging delivery approaches and future directions of NTF-based nanomedicine are also discussed.

Small-Molecule Inhibitors of the RNA M6A Demethylases FTO Potently Support the Survival of Dopamine Neurons.

The fat mass and obesity-associated protein (FTO), an RNA N6-methyladenosine (m6A) demethylase, is an important regulator of central nervous system development, neuronal signaling and disease. We present here the target-tailored development and biological characterization of small-molecule inhibitors of FTO. The active compounds were identified using high-throughput molecular docking and molecular dynamics screening of the ZINC compound library. In FTO binding and activity-inhibition assays the two best inhibitors demonstrated Kd = 185 nM; IC50 = 1.46 µM (compound 2) and Kd = 337 nM; IC50 = 28.9 µM (compound 3). Importantly, the treatment of mouse midbrain dopaminergic neurons with the compounds promoted cellular survival and rescued them from growth factor deprivation induced apoptosis already at nanomolar concentrations. Moreover, both the best inhibitors demonstrated good blood-brain-barrier penetration in the model system, 31.7% and 30.8%, respectively. The FTO inhibitors demonstrated increased potency as compared to our recently developed ALKBH5 m6A demethylase inhibitors in protecting dopamine neurons. Inhibition of m6A RNA demethylation by small-molecule drugs, as presented here, has therapeutic potential and provides tools for the identification of disease-modifying m6A RNAs in neurogenesis and neuroregeneration. Further refinement of the lead compounds identified in this study can also lead to unprecedented breakthroughs in the treatment of neurodegenerative diseases.

Macrophage sensing of single-walled carbon nanotubes via Toll-like receptors.

Carbon-based nanomaterials including carbon nanotubes (CNTs) have been shown to trigger inflammation. However, how these materials are 'sensed' by immune cells is not known. Here we compared the effects of two carbon-based nanomaterials, single-walled CNTs (SWCNTs) and graphene oxide (GO), on primary human monocyte-derived macrophages. Genome-wide transcriptomics assessment was performed at sub-cytotoxic doses. Pathway analysis of the microarray data revealed pronounced effects on chemokine-encoding genes in macrophages exposed to SWCNTs, but not in response to GO, and these results were validated by multiplex array-based cytokine and chemokine profiling. Conditioned medium from SWCNT-exposed cells acted as a chemoattractant for dendritic cells. Chemokine secretion was reduced upon inhibition of NF-κB, as predicted by upstream regulator analysis of the transcriptomics data, and Toll-like receptors (TLRs) and their adaptor molecule, MyD88 were shown to be important for CCL5 secretion. Moreover, a specific role for TLR2/4 was confirmed by using reporter cell lines. Computational studies to elucidate how SWCNTs may interact with TLR4 in the absence of a protein corona suggested that binding is guided mainly by hydrophobic interactions. Taken together, these results imply that CNTs may be 'sensed' as pathogens by immune cells.

Macrophage activation status determines the internalization of mesoporous silica particles of different sizes: Exploring the role of different pattern recognition receptors.

Mesoporous silica-based particles are promising candidates for biomedical applications. Here, we address the importance of macrophage activation status for internalization of AMS6 (approx. 200 nm in diameter) versus AMS8 (approx. 2 µm) mesoporous silica particles and the role of different phagocytosis receptors for particle uptake. To this end, FITC-conjugated silica particles were used. AMS8 were found to be non-cytotoxic both for M-CSF-stimulated (anti-inflammatory) and GM-CSF-stimulated (pro-inflammatory) macrophages, whereas AMS6 exhibited cytotoxicity towards M-CSF-stimulated, but not GM-CSF-stimulated macrophages; this toxicity was, however, mitigated in the presence of serum. AMS8 triggered the secretion of pro-inflammatory cytokines in M-CSF-activated cells. Class A scavenger receptor (SR-A) expression was noted in both M-CSF and GM-CSF-stimulated macrophages, although the expression was higher in the former case, and gene silencing of SR-A resulted in a decreased uptake of AMS6 in the absence of serum. GM-CSF-stimulated macrophages expressed higher levels of the mannose receptor CD206 compared to M-CSF-stimulated cells, and uptake of AMS6, but not AMS8, was reduced following the downregulation of CD206 in GM-CSF-stimulated cells; particle uptake was also suppressed by mannan, a competitive ligand. These studies demonstrate that macrophage activation status is an important determinant of particle uptake and provide evidence for a role of different macrophage receptors for cell uptake of silica particles.

Pan-European inter-laboratory studies on a panel of in vitro cytotoxicity and pro-inflammation assays for nanoparticles.

The rapid development of nanotechnologies and increased production and use of nanomaterials raise concerns about their potential toxic effects for human health and environment. To evaluate the biological effects of nanomaterials, a set of reliable and reproducible methods and development of standard operating procedures (SOPs) is required. In the framework of the European FP7 NanoValid project, three different cell viability assays (MTS, ATP content, and caspase-3/7 activity) with different readouts (absorbance, luminescence and fluorescence) and two immune assays (ELISA of pro-inflammatory cytokines IL1-ß and TNF-α) were evaluated by inter-laboratory comparison. The aim was to determine the suitability and reliability of these assays for nanosafety assessment. Studies on silver and copper oxide nanoparticles (NPs) were performed, and SOPs for particle handling, cell culture, and in vitro assays were established or adapted. These SOPs give precise descriptions of assay procedures, cell culture/seeding conditions, NPs/positive control preparation and dilutions, experimental well plate preparation, and evaluation of NPs interference. The following conclusions can be highlighted from the pan-European inter-laboratory studies: Testing of NPs interference with the toxicity assays should always be conducted. Interference tests should be designed as close as possible to the cell exposure conditions. ATP and MTS assays gave consistent toxicity results with low inter-laboratory variability using Ag and CuO NPs and different cell lines and therefore, could be recommended for further validation and standardization. High inter-laboratory variability was observed for Caspase 3/7 assay and ELISA for IL1-ß and TNF-α measurements.

Environmental hazard of oil shale combustion fly ash.

The combined chemical and ecotoxicological characterization of oil shale combustion fly ash was performed. Ash was sampled from the most distant point of the ash-separation systems of the Balti and Eesti Thermal Power Plants in North-Eastern Estonia. The fly ash proved potentially hazardous for tested aquatic organisms and high alkalinity of the leachates (pH>10) is apparently the key factor determining its toxicity. The leachates were not genotoxic in the Ames assay. Also, the analysis showed that despite long-term intensive oil-shale combustion accompanied by considerable fly ash emissions has not led to significant soil contamination by hazardous trace elements in North-Eastern Estonia. Comparative study of the fly ash originating from the 'new' circulating fluidized bed (CFB) combustion technology and the 'old' pulverized-fired (PF) one showed that CFB fly ash was less toxic than PF fly ash. Thus, complete transfer to the 'new' technology will reduce (i) atmospheric emission of hazardous trace elements and (ii) fly ash toxicity to aquatic organisms as compared with the 'old' technology.

Effects of rhamnolipids from Pseudomonas aeruginosa DS10-129 on luminescent bacteria: toxicity and modulation of cadmium bioavailability.

In this study, the mixture of mono- and di-rhamnolipids produced by Pseudomonas aeruginosa DS10-129 was characterized for its toxicity and modulatory effects on Cd availability to different bacteria. Gram-negative naturally bioluminescent Vibrio fischeri and recombinant bioluminescent Pseudomonas fluorescens, P. aeruginosa, Escherichia coli, and Gram-positive Bacillus subtilis were used as model organisms. Rhamnolipids reduced the bioluminescence of these bacteria in less than a second of exposure even in relatively low concentrations (30-min EC(50) 45-167 mg l(-1)). Toxicity of Cd to Gram-negative bacteria (30-min EC(50) values 0.16 mg l(-1) for E. coli, 0.96 mg l(-1) for P. fluorescens, and 4.4 mg l(-1) for V. fischeri) was remarkably (up to 10-fold) reduced in the presence of 50 mg l(-1) rhamnolipids. Interestingly, the toxicity of Cd to Gram-positive B. subtilis (30-min EC(50) value 0.49 mg l(-1)) was not affected by rhamnolipids. Rhamnolipids had an effect on desorption of Cd from soil: 40 mg l(-1) rhamnolipids increased the water-extracted fraction of Cd twice compared with untreated control. However, this additionally desorbed fraction of Cd remained bound with rhamnolipids and was not available to bacteria. Hence, in carefully chosen concentrations (still effectively complexing heavy metals but not yet toxic to soil bacteria), rhamnolipids could be applied in remediation of polluted areas.