Christopher P. Marquis

Cytotoxic origin of copper(II) oxide nanoparticles: Comparative studies with micron-sized particles, leachate, and metal salts

The work investigates the source of toxicity of copper oxide nanoparticles (CuO NPs) with respect to its leaching characteristic and speciation. Complexation-mediated leaching of CuO NPs by amino acids was identified as the source of toxicity toward Escherichia coli, the model microorganism used in the current study. The leached copper-peptide complex induces a multiple-fold increase in intracellular reactive oxygen species generation and reduces the fractions of viable cells, resulting in the overall inhibition of biomass growth. The cytotoxicity of the complex leachate is however different from that of equivalent soluble copper salts (nitrates and sulfates). A pH-dependent copper speciation during the addition of copper salts gives rise to uncoordinated copper ions, which in turn result in greater toxicity and cell lysis, the latter of which was not observed for CuO NPs even at comparable pH. Since leaching did not occur with micrometer-sized CuO, no cytotoxicty effect was observed, thus highlighting the prominence of materials toxicity at the nanoscale.

Reversible Antimicrobial Photoswitching in Nanosilver

Nanosilver has emerged as one of the most commercialized nanomaterials, particularly as antimicrobial agents with interesting applications such as wound dressings, textiles, water and air purification, self-sterilizing polymer films, and bone implants. In comparison to bulk counterparts, nanosilver exhibits superior antimicrobial activity toward various microorganisms. Its reactivity is in part driven by a high specific surface area and enhanced surface electronic effects. Incorporation of silver nanoparticles into bacteria was recognized by the surface and intracellular uptake of Escherichia coli, which potentially results in the binding of silver to sulfur-containing membranes and cytoplasmic proteins. Exposure of E. coli and Staphylococcus aureus to dissolved silver ions affects the DNA replication ability as well as inactivates the expression of ribosomal subunit proteins and enzymes vital for adenosine 50-triphosphate (ATP) production. Microscopic studies revealed the condensation and concentration of DNA in the center of the cell and detachment of the cytoplasm membrane from the cell wall upon treatment with silver ions. It was further reported recently that the antimicrobial mechanism of silver nanoparticles was related to protein/membrane damage of E. coli but not to DNA damage. While the antimicrobial effect of nanosilver is widely recognized and has triggered extensive research interest, the ‘‘tuning’’ of its antimicrobial activity, to the best of our knowledge, has never been reported. This is important especially for applications involving direct antimicrobial interactions with human cells such as those in self-sterilizing

The TGF-β superfamily cytokine, MIC-1/GDF15: A pleotrophic cytokine with roles in inflammation, cancer and metabolism

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) is associated with cardiovascular disease, inflammation, body weight regulation and cancer. Its serum levels facilitate the diagnosis and prognosis of cancer and vascular disease. Furthermore, its serum levels are a powerful predictor of all-cause mortality, suggesting a fundamental role in biological processes associated with ageing. In cancer, the data available suggest that MIC-1/GDF15 is antitumorigenic, but this may not always be the case as disease progresses. Cancer promoting effects of MIC-1/GDF15 may be due, in part, to effects on antitumour immunity. This is suggested by the anti-inflammatory and immunosuppressive properties of MIC-1/GDF15 in animal models of atherosclerosis and rheumatoid arthritis. Furthermore, in late-stage cancer, large amounts of MIC-1/GDF15 in the circulation suppress appetite and mediate cancer anorexia/cachexia, which can be reversed by monoclonal antibodies in animals. Available data suggest MIC-1/GDF15 may be an important molecule mediating the interplay between cancer, obesity and chronic inflammation.

Macrophage inhibitory cytokine-1 (MIC-1/GDF15): a new marker of all-cause mortality.

Macrophage inhibitory cytokine‐1 (MIC‐1/GDF15) is a member of the TGF‐b superfamily, previously studied in cancer and inflammation. In addition to regulating body weight, MIC‐1/GDF15 may be used to predict mortality and/or disease course in cancer, cardiovascular disease (CVD), chronic renal and heart failure, as well as pulmonary embolism. These data suggested that MIC‐1/GDF15 may be a marker of all‐cause mortality. To determine whether serum MIC‐1/GDF15 estimation is a predictor of all‐cause mortality, we examined a cohort of 876 male subjects aged 35–80 years, selected from the Swedish Population Registry, and followed them for overall mortality. Serum MIC‐1/GDF15 levels were determined for all subjects from samples taken at study entry. A second (independent) cohort of 324 same‐sex twins (69% female) from the Swedish Twin Registry was similarly examined. All the twins had telomere length measured and 183 had serum levels of interleukin 6 (IL‐6) and C‐reactive protein (CRP) available. Patients were followed for up to 14 years and had cause‐specific and all‐cause mortality determined. Serum MIC‐1/GDF15 levels predicted mortality in the all‐male cohort with an adjusted odds ratio (OR) of death of 3.38 (95%CI 1.38–8.26). This finding was validated in the twin cohort. Serum MIC‐1/GDF15 remained an independent predictor of mortality when further adjusted for telomere length, IL‐6 and CRP. Additionally, serum MIC‐1/GDF15 levels were directly correlated with survival time independently of genetic background. Serum MIC‐1/GDF15 is a novel predictor of all‐cause mortality.

Effects of Serum Adsorption on Cellular Uptake Profile and Consequent Impact of Titanium Dioxide Nanoparticles on Human Lung Cell Lines

Exposure to fetal bovine serum (FBS) is shown herein to reduce the aggregate size of titanium dioxide (TiO(2)) nanoparticles, affecting uptake and consequent effect on A549 and H1299 human lung cell lines. Initially, the cellular uptake of the FBS-treated TiO(2) was lower than that of non-FBS-treated TiO(2). Expulsion of particles was then observed, followed by a second phase of uptake of FBS-treated TiO(2), resulting in an increase in the cellular content of FBS-treated TiO(2), eventually exceeding the amount by cells exposed to non-FBS-treated TiO(2). Surface adsorbed vitronectin and the clathrin-mediated endocytosis pathway were shown to regulate the uptake of TiO(2) into A549 cells, while the endocytosis mechanism responsible remains elusive for H1299. Intriguingly, nystatin treatment was shown to have the unexpected effect of increasing nanoparticle uptake into the A549 cells via an alternate endocytic pathway. The surface adsorbed serum components were found to provide some protection from the cytotoxic effect of endocytosed TiO(2) nanoparticles.

Assembly of Polyethylenimine-Based Magnetic Iron Oxide Vectors: Insights into Gene Delivery

The use of a nonviral magnetic vector, comprised of magnetic iron oxide nanoparticles (MNP), polyethylenimine (PEI), and plasmid DNA, for transfection of BHK21 cells under a magnetic field is presented. Four different vector configurations were studied by systematically varying the mixing order of MNP, PEI, and DNA. The assembly of the vector has significant effects on its vector size, surface charge, cellular uptake, and level of gene expression. Mixing MNP with PEI first improved MNP stability, giving a narrow aggregate size distribution and positive surface charge at physiological pH, which in turn facilitated DNA binding onto MNP. The presence of serum in culture media improves vector dispersion and alters the surface charge of all vectors to negative charge, indicating serum protein adsorption. Cellular uptake was greater for larger vectors than the smaller vectors due to enhanced gravitational and magnetic aided sedimentation onto the cells. High MNP uptake by the cells, however, does not inevitably lead to increase gene expression efficiency. It can be shown that besides vector uptake, gene expression is affected by extracellular factors such as premature DNA release from MNP and DNA degradation by serum as well as intracellular factors such as vector lysosomal degradation, inability of DNA to detach from MNP, and cytotoxic effects of MNP at high uptake. Some of these extra- and intracellular properties are shown to be mediated by the presence of PEI.

Nanoparticle–protein corona complexes govern the biological fates and functions of nanoparticles

Upon contact with plasma or other protein-containing biological fluids, the surface of nanoparticles is immediately decorated with proteins forming a biologically active protein corona. The biological fates and functions of nanoparticles are determined by physiological responses toward these nanoparticle-protein corona complexes as the effective biological unit of nanoparticles. In this article, we review representative studies on the effects of particle physicochemical characteristics along with the protein profiles in the biological medium on the formation of protein corona and importantly, how the dynamic nature and protein fingerprints of the formed corona govern the biological responses toward nanoparticles. The biological effects arising from the presence of protein corona can be both beneficial and unfavourable to the biomedical applications of nanoparticles. The protein corona-cell interactions open up the feasibility of targeted delivery and cell-specific uptake of therapeutic nanoparticles and in other circumstances, engineering of nanoparticles as adjuvants for vaccine development as well as mitigation of the unintentional cytotoxic effects of nanoparticles. On the other hand, the protein corona-cell interactions could induce rapid clearance of nanoparticles from in vivo circulation as well as activating unwanted inflammatory responses. Taken together, the knowledge on the formation and biological effects of protein corona enables tailored tuning of the physicochemical characteristics of nanoparticles, unique to their intended biological activity.

Polyethylenimine based magnetic iron-oxide vector: the effect of vector component assembly on cellular entry mechanism, intracellular localization, and cellular viability.

The order of assembly of a magnetic nanoparticle (MNP) vector comprised of the same components (MNP, PEI, and plasmid DNA) on entry mechanism, intracellular localization, and viability of BHK21 cells was investigated. Cellular uptake measurements under four different uptake inhibiting conditions, such as low temperature, depleted cellular ATP, nystatin treatment, and hypertonic environment, show that the cellular entry mechanism of the MNP vector was mediated via clathrin endocytosis. Despite different vector component assembly, all MNP vectors were taken up by the cells through the same mechanism. Labeling and intracellular tracking of the MNP vectors using epi-fluorescence and confocal laser scanning microscopy showed localization of MNP vector within the lysosomes when DNA was assembled on the outer layer of vector. Conversely, when PEI was on the surface of the vector, such that it enclosed both magnetic nanoparticles and the DNA, vector localization in the cell nucleus was observed. The microscopy results demonstrated that the configuration of the MNP vectors dictate the vectors final intracellular target location, and thus the efficiency of transfection. The cellular viability assessment using three different assays further showed that the cellular viability of MNP vector was dose-dependent and varied with the assembly of vector component. All viability assays found negligible toxicity when DNA was on the outer layer of MNP vector except at the highest vector loading. In contrast, attachment of PEI on MNP vector surface induced a significant decrease in cellular viability, due to the ability of PEI on the MNP vector to rupture the lysosomal vesicles.

Cereulide, the emetic toxin of Bacillus cereus, is putatively a product of nonribosomal peptide synthesis

Aims:  To determine if cereulide, the emetic toxin produced by Bacillus cereus, is produced by a nonribosomal peptide synthetase (NRPS).

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) and mortality in end-stage renal disease

BACKGROUND Elevated macrophage inhibitory cytokine-1 (MIC-1/GDF15) levels in serum mediate anorexia and weight loss in some cancer patients and similarly elevated levels occur in chronic kidney disease (CKD). Serum MIC-1/GDF15 is also elevated in chronic inflammatory diseases and predicts atherosclerotic events independently of traditional risk factors. The relationship between chronic inflammation, decreasing body mass index (BMI) and increased mortality in CKD is not well understood and is being actively investigated. MIC-1/GDF15 may link these features of CKD. METHODS Cohorts of incident dialysis patients from Sweden (n = 98) and prevalent hemodialysis patients from the USA (n = 381) had serum MIC-1/GDF15, C-reactive protein (CRP) levels and BMI measured at study entry. Additional surrogate markers of nutritional adequacy, body composition and inflammation were assessed in Swedish patients. Patients were followed for all-cause mortality. RESULTS In the Swedish cohort, serum MIC-1/GDF15 was associated with decreasing BMI, measures of nutrition and markers of oxidative stress and inflammation. Additionally, high serum MIC-1/GDF15 levels identified patients with evidence of protein-energy wasting who died in the first 3 years of dialysis. The ability of serum MIC-1/GDF15 to predict mortality in the first 3 years of dialysis was confirmed in the USA cohort. In both cohorts, serum MIC-1/GDF15 level was an independent marker of mortality when adjusted for age, CRP, BMI, history of diabetes mellitus and/or cardiovascular disease and glomerular filtration rate or length of time on dialysis at study entry. CONCLUSIONS MIC-1/GDF15 is a novel independent serum marker of mortality in CKD capable of significantly improving the mortality prediction of other established markers. MIC-1/GDF15 may mediate protein-energy wasting in CKD and represent a novel therapeutic target for this fatal complication.