Molecular bases of an alternative dual-enzyme system for light color acclimation of marine Synechococcus cyanobacteria.

Marine Synechococcus cyanobacteria owe their ubiquity in part to the wide pigment diversity of their light-harvesting complexes. In open ocean waters, cells predominantly possess sophisticated antennae with rods composed of phycocyanin and two types of phycoerythrins (PEI and PEII). Some strains are specialized for harvesting either green or blue light, while others can dynamically modify their light absorption spectrum to match the dominant ambient color. This process, called type IV chromatic acclimation (CA4), has been linked to the presence of a small genomic island occurring in two configurations (CA4-A and CA4-B). While the CA4-A process has been partially characterized, the CA4-B process has remained an enigma. Here we characterize the function of two members of the phycobilin lyase E/F clan, MpeW and MpeQ, in Synechococcus sp. strain A15-62 and demonstrate their critical role in CA4-B. While MpeW, encoded in the CA4-B island and up-regulated in green light, attaches the green light-absorbing chromophore phycoerythrobilin to cysteine-83 of the PEII α-subunit in green light, MpeQ binds phycoerythrobilin and isomerizes it into the blue light-absorbing phycourobilin at the same site in blue light, reversing the relationship of MpeZ and MpeY in the CA4-A strain RS9916. Our data thus reveal key molecular differences between the two types of chromatic acclimaters, both highly abundant but occupying distinct complementary ecological niches in the ocean. They also support an evolutionary scenario whereby CA4-B island acquisition allowed former blue light specialists to become chromatic acclimaters, while former green light specialists would have acquired this capacity by gaining a CA4-A island.

Cu-doped TiO2 nanoparticles improve local antitumor immune activation and optimize dendritic cell vaccine strategies.

Nanoparticle-mediated cancer immunotherapy holds great promise, but more efforts are needed to obtain nanoformulations that result in a full scale activation of innate and adaptive immune components that specifically target the tumors. We generated a series of copper-doped TiO2 nanoparticles in order to tune the kinetics and full extent of Cu2+ ion release from the remnant TiO2 nanocrystals. Fine-tuning nanoparticle properties resulted in a formulation of 33% Cu-doped TiO2 which enabled short-lived hyperactivation of dendritic cells and hereby promoted immunotherapy. The nanoparticles result in highly efficient activation of dendritic cells ex vivo, which upon transplantation in tumor bearing mice, exceeded the therapeutic outcomes obtained with classically stimulated dendritic cells. Efficacious but simple nanomaterials that can promote dendritic cancer cell vaccination strategies open up new avenues for improved immunotherapy and human health.

Interplay between differentially expressed enzymes contributes to light color acclimation in marine Synechococcus.

Marine Synechococcus, a globally important group of cyanobacteria, thrives in various light niches in part due to its varied photosynthetic light-harvesting pigments. Many Synechococcus strains use a process known as chromatic acclimation to optimize the ratio of two chromophores, green-light-absorbing phycoerythrobilin (PEB) and blue-light-absorbing phycourobilin (PUB), within their light-harvesting complexes. A full mechanistic understanding of how Synechococcus cells tune their PEB to PUB ratio during chromatic acclimation has not yet been obtained. Here, we show that interplay between two enzymes named MpeY and MpeZ controls differential PEB and PUB covalent attachment to the same cysteine residue. MpeY attaches PEB to the light-harvesting protein MpeA in green light, while MpeZ attaches PUB to MpeA in blue light. We demonstrate that the ratio of mpeY to mpeZ mRNA determines if PEB or PUB is attached. Additionally, strains encoding only MpeY or MpeZ do not acclimate. Examination of strains of Synechococcus isolated from across the globe indicates that the interplay between MpeY and MpeZ uncovered here is a critical feature of chromatic acclimation for marine Synechococcus worldwide.

Metal Sulfide Nanoparticles: Precursor Chemistry.

Fascination with and the need for evermore increasing efficiency, power, or strength have been the cornerstones for developing new materials and methods for their creation. Higher solar cell conversion efficiencies, increased battery storage power, and lightweight strong materials are some that have been at the forefront of attention for these efforts. Materials created for most applications start as simple chemical compounds. A study of how these chemicals have been used in the past can be used to create new materials and new methods of production. Herein, a class of materials that are valuable in a multitude of applications, metal sulfide nanoparticles, are examined, along with how they are being produced and how new methods can be established that will help to standardize and increase production capabilities. Precursor-solvent combinations that can be used to create metal sulfide nanoparticles in the gas phase are also explored.

Iron-Doping of Copper Oxide Nanoparticles Lowers Their Toxic Potential on C6 Glioma Cells.

Copper oxide nanoparticles (CuO-NPs) are well known for their cytotoxicity which in part has been attributed to the release of copper ions from CuO-NPs. As iron-doping has been reported to reduce the susceptibility of CuO-NPs to dissolution, we have compared pure CuO-NPs and CuO-NPs that had been doped with 10% iron (CuO-Fe-NPs) for copper release and for their toxic potential on C6 glioma cells. Physicochemical characterization revealed that dimercaptosuccinate (DMSA)-coated CuO-NPs and CuO-Fe-NPs did not differ in their size or zeta potential. However, the redox activity and liberation of copper ions from CuO-Fe-NPs was substantially slower compared to that from CuO-NPs, as demonstrated by cyclic voltammetry and by the photometric quantification of the copper ion-bathocuproine complex, respectively. Exposure of C6 cells to these NPs caused an almost identical cellular copper accumulation and each of the two types of NPs induced ROS production and cell toxicity. However, the time- and concentration-dependent loss in cell viability was more severe for cells that had been treated with CuO-NPs compared to cells exposed to CuO-Fe-NPs. Copper accumulation and toxicity after exposure to either CuO-NPs or CuO-Fe-NPs was prevented in the presence of copper chelators, while neutralization of the lysosomal pH by bafilomycin A1 prevented toxicity without affecting cellular copper accumulation or ROS production. These data demonstrate that iron-doping does not affect cellular accumulation of CuO-NPs and suggests that the intracellular liberation of copper ions from CuO-NPs is slowed by the iron doping, which in turn lowers the cell toxic potential of iron-doped CuO-NPs.

The gas-phase formation of tin dioxide nanoparticles in single droplet combustion and flame spray pyrolysis.

Tin dioxide (SnO2) nanoparticles synthesized via flame spray pyrolysis (FSP) have promising applications for gas sensors. The formation of SnO2 nanoparticles in the gas-phase has been investigated using single droplet combustion and FSP. Precursor solutions of Tin (II) 2-ethylhexanoate dissolved in Xylene with varying Sn concentrations were selected as the precursor-solvent system. The selected precursor-solvent system has its stability and ability to synthesize homogeneous nanoparticles, compared to metal nitrate based precursor solutions. The precursor-solvent system was studied using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and thermogravimetric analysis (TGA). The SnO2 nanoparticles were characterized using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). Droplet surface micro-explosions were observed during the single droplet combustion of the precursor solutions. It is because of the heterogeneous vapor-phase nucleation, which is beneath the liquid droplet surface and caused by precursor thermal decomposition. The results show that the size of nanoparticles obtained both from FSP and single droplet combustion increases with increasing metal-precursor concentration. The TEM images of the particles from such droplet combustion reveal two types of nanoparticles with different sizes and morphologies. The current work provides fundamental understanding of precursor decomposition and particle formation during single droplet combustion, which help in-depth understanding of the flame spray pyrolysis.

Model-Based Nanoengineered Pharmacokinetics of Iron-Doped Copper Oxide for Nanomedical Applications.

The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. As low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purposes (carrier and drug) with a direct chemical composition-biological functionality relationship. Model-based dissolution kinetics of CuO NPs in the cellular interior at post-exposure conditions were controlled through Fe-doping for intra/extra cellular Cu2+ and biological outcome. Through controlled ion release and reactions taking place in the cellular interior, tumors could be treated selectively, in vitro and in vivo. Locally administered NPs enabled tumor cells apoptosis and stimulated systemic anti-cancer immune responses. We clearly show therapeutic effects without tumor cells relapse post-treatment with 6 % Fe-doped CuO NPs combined with myeloid-derived suppressor cell silencing.

Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate.

The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode-particle collision method and cyclic voltammetry, respectively. The influence of Cl- and NO3- anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single-particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal-based nanoparticles in general, and copper-based nanoparticles in particular, are discussed.

The impact of nanoparticle-driven lysosomal alkalinization on cellular functionality.

BACKGROUND: The biomedical use of nanosized materials is rapidly gaining interest, which drives the quest to elucidate the behavior of nanoparticles (NPs) in a biological environment. Apart from causing direct cell death, NPs can affect cellular wellbeing through a wide range of more subtle processes that are often overlooked. Here, we aimed to study the effect of two biomedically interesting NP types on cellular wellbeing. RESULTS: In the present work, gold and SiO2 NPs of similar size and surface charge are used and their interactions with cultured cells is studied. Initial screening shows that at subcytotoxic conditions gold NPs induces cytoskeletal aberrations while SiO2 NPs do not. However, these transformations are only transient. In-depth investigation reveals that Au NPs reduce lysosomal activity by alkalinization of the lysosomal lumen. This leads to an accumulation of autophagosomes, resulting in a reduced cellular degradative capacity and less efficient clearance of damaged mitochondria. The autophagosome accumulation induces Rac and Cdc42 activity, and at a later stage activates RhoA. These transient cellular changes also affect cell functionality, where Au NP-labelled cells display significantly impeded cell migration and invasion. CONCLUSIONS: These data highlight the importance of in-depth understanding of bio-nano interactions to elucidate how one biological parameter (impact on cellular degradation) can induce a cascade of different effects that may have significant implications on the further use of labeled cells.

An Integrated Data-Driven Strategy for Safe-by-Design Nanoparticles: The FP7 MODERN Project.

The development and implementation of safe-by-design strategies is key for the safe development of future generations of nanotechnology enabled products. The safety testing of the huge variety of nanomaterials that can be synthetized is unfeasible due to time and cost constraints. Computational modeling facilitates the implementation of alternative testing strategies in a time and cost effective way. The development of predictive nanotoxicology models requires the use of high quality experimental data on the structure, physicochemical properties and bioactivity of nanomaterials. The FP7 Project MODERN has developed and evaluated the main components of a computational framework for the evaluation of the environmental and health impacts of nanoparticles. This chapter describes each of the elements of the framework including aspects related to data generation, management and integration; development of nanodescriptors; establishment of nanostructure-activity relationships; identification of nanoparticle categories; hazard ranking and risk assessment.

Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP).

Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications.

Toxicity of metal oxide nanoparticles in Escherichia coli correlates with conduction band and hydration energies.

Metal oxide nanoparticles (MOx NPs) are used for a host of applications, such as electronics, cosmetics, construction, and medicine, and as a result, the safety of these materials to humans and the environment is of considerable interest. A prior study of 24 MOx NPs in mammalian cells revealed that some of these materials show hazard potential. Here, we report the growth inhibitory effects of the same series of MOx NPs in the bacterium Escherichia coli and show that toxicity trends observed in E. coli parallel those seen previously in mammalian cells. Of the 24 materials studied, only ZnO, CuO, CoO, Mn2O3, Co3O4, Ni2O3, and Cr2O3 were found to exert significant growth inhibitory effects; these effects were found to relate to membrane damage and oxidative stress responses in minimal trophic media. A correlation of the toxicological data with physicochemical parameters of MOx NPs revealed that the probability of a MOx NP being toxic increases as the hydration enthalpy becomes less negative and as the conduction band energy approaches those of biological molecules. These observations are consistent with prior results observed in mammalian cells, revealing that mechanisms of toxicity of MOx NPs are consistent across two very different taxa. These results suggest that studying nanotoxicity in E. coli may help to predict toxicity patterns in higher organisms.

PdO doping tunes band-gap energy levels as well as oxidative stress responses to a Co3O4 p-type semiconductor in cells and the lung.

We demonstrate through PdO doping that creation of heterojunctions on Co3O4 nanoparticles can quantitatively adjust band-gap and Fermi energy levels to study the impact of metal oxide nanoparticle semiconductor properties on cellular redox homeostasis and hazard potential. Flame spray pyrolysis (FSP) was used to synthesize a nanoparticle library in which the gradual increase in the PdO content (0-8.9%) allowed electron transfer from Co3O4 to PdO to align Fermi energy levels across the heterojunctions. This alignment was accompanied by free hole accumulation at the Co3O4 interface and production of hydroxyl radicals. Interestingly, there was no concomitant superoxide generation, which could reflect the hole dominance of a p-type semiconductor. Although the electron flux across the heterojunctions induced upward band bending, the E(c) levels of the doped particles showed energy overlap with the biological redox potential (BRP). This allows electron capture from the redox couples that maintain the BRP from -4.12 to -4.84 eV, causing disruption of cellular redox homeostasis and induction of oxidative stress. PdO/Co3O4 nanoparticles showed significant increases in cytotoxicity at 25, 50, 100, and 200 µg/mL, which was enhanced incrementally by PdO doping in BEAS-2B and RAW 264.7 cells. Oxidative stress presented as a tiered cellular response involving superoxide generation, glutathione depletion, cytokine production, and cytotoxicity in epithelial and macrophage cell lines. A progressive series of acute pro-inflammatory effects could also be seen in the lungs of animals exposed to incremental PdO-doped particles. All considered, generation of a combinatorial PdO/Co3O4 nanoparticle library with incremental heterojunction density allowed us to demonstrate the integrated role of E(v), E(c), and E(f) levels in the generation of oxidant injury and inflammation by the p-type semiconductor, Co3O4.

Custom-designed nanomaterial libraries for testing metal oxide toxicity.

Advances in aerosol technology over the past 10 years have enabled the generation and design of ultrafine nanoscale materials for many applications. A key new method is flame spray pyrolysis (FSP), which produces particles by pyrolyzing a precursor solution in the gas phase. FSP is a highly versatile technique for fast, single-step, scalable synthesis of nanoscale materials. New innovations in particle synthesis using FSP technology, including variations in precursor chemistry, have enabled flexible, dry synthesis of loosely agglomerated, highly crystalline ultrafine powders (porosity ≥ 90%) of binary, ternary, and mixed-binary-and-ternary oxides. FSP can fulfill much of the increasing demand, especially in biological applications, for particles with specific material composition, high purity, and high crystallinity. In this Account, we describe a strategy for creating nanoparticle libraries (pure or Fedoped ZnO or TiO2) utilizing FSP and using these libraries to test hypotheses related to the particles' toxicity. Our innovation lies in the overall integration of the knowledge we have developed in the last 5 years in (1) synthesizing nanomaterials to address specific hypotheses, (2) demonstrating the electronic properties that cause the material toxicity, (3) understanding the reaction mechanisms causing the toxicity, and (4) extracting from in vitro testing and in vivo testing in terrestrial and marine organisms the essential properties of safe nanomaterials. On the basis of this acquired knowledge, we further describe how the dissolved metal ion from these materials (Zn²âº in this Account) can effectively bind with different cell constituents, causing toxicity. We use Fe-S protein clusters as an example of the complex chemical reactions taking place after free metal ions migrate into the cells. As a second example, TiO2 is an active material in the UV range that exhibits photocatalytic behavior. The induction of electron-hole (e⁻/h⁺) pairs followed by free radical production is a key mechanism for biological injury. We show that decreasing the bandgap energy increases the phototoxicity in the presence of near-visible light. We present in detail the mechanism of electron transfer in biotic and abiotic systems during light exposure. Through this example we show that FSP is a versatile technique for efficiently designing a homologous library, meaning a library based on a parent oxide doped with different amounts of dopant, and investigating the properties of the resulting compounds. Finally, we describe the future outlook and state-of-the-art of an innovative two-flame system. A double-flame reactor enables independent control over each flame, the nozzle distances and the flame angles for efficient mixing of the particle streams. In addition, it allows for different flame compositions, flame sizes, and multicomponent mixing (a grain-grain heterojunction) during the reaction process.

Flame emission spectroscopy of single droplet micro explosions.

Nanoparticles exhibit superior physical and chemical properties, making them highly desirable for various applications. Flame spray pyrolysis (FSP) is a versatile technique for synthesizing size and composition-controlled metal oxide/sulfide nanoparticles through a gas-phase reaction. To understand the fundamental mechanisms governing nanoparticle formation in FSP, simplified single-droplet experiments have proven to unravel the physicochemical mechanisms of liquid metal precursor combustions. This work introduces a novel method using flame emission spectroscopy and high-speed imaging to analyze combustion species and metal release during metalorganic single droplet combustions, with the example of the 2-ethylhexanoci acid (EHA)-tetrahydrothiophene (THT)-mesitylcopper (MiCu) precursor system. The method enables the tracing of precursor components released from droplet into the flame by spatial and temporal resolved emission tracking from combustion species (OH*, CH*, C2*, CS*, CS2*) and atomic spectral lines (Cu I). The tracking of metal emission enables the direct observation of the particle formation route, offering novel insights into the metalorganic precursor combustions. The findings of this work show a direct correlation between micro-explosions and nanoparticle formation through the gas-to-particle route. The release of copper emissions is observed with the micro-explosion event, marking the micro-explosions as the critical mechanism for the metal release and subsequent nanoparticle formation during the combustion process. The results indicate a metalorganic viscous shell formation (THT + MiCu) leading to the micro explosion. The EHA/THT ratio significantly affects the combustion behavior. Lower ratios lead to a gradual copper release before the micro explosion; higher ratios shorten the copper release and delay the micro explosion - the highest ratio results in two distinct burning stages.

Zebrafish high-throughput screening to study the impact of dissolvable metal oxide nanoparticles on the hatching enzyme, ZHE1.

The zebrafish is emerging as a model organism for the safety assessment and hazard ranking of engineered nanomaterials. In this Communication, the implementation of a roboticized high-throughput screening (HTS) platform with automated image analysis is demonstrated to assess the impact of dissolvable oxide nanoparticles on embryo hatching. It is further demonstrated that this hatching interference is mechanistically linked to an effect on the metalloprotease, ZHE 1, which is responsible for degradation of the chorionic membrane. The data indicate that 4 of 24 metal oxide nanoparticles (CuO, ZnO, Cr2 O3 , and NiO) could interfere with embryo hatching by a chelator-sensitive mechanism that involves ligation of critical histidines in the ZHE1 center by the shed metal ions. A recombinant ZHE1 enzymatic assay is established to demonstrate that the dialysates from the same materials responsible for hatching interference also inhibit ZHE1 activity in a dose-dependent fashion. A peptide-based BLAST search identifies several additional aquatic species that express enzymes with homologous histidine-based catalytic centers, suggesting that the ZHE1 mechanistic paradigm could be used to predict the toxicity of a large number of oxide nanoparticles that pose a hazard to aquatic species.

Fe-doped ZnO nanoparticles: the oxidation number and local charge on iron, studied by 57Fe Mößbauer spectroscopy and DFT calculations.

Iron bru: Fe-doped ZnO may contain Fe(2+) and Fe(3+) species. Whilst Mößbauer spectroscopy can distinguish these sites in pure oxides FeO and Fe(2)O(3), it gives very similar shifts for Fe-doped phases. This result is rationalized by electron redistribution from the dopant site to the crystal matrix. Mößbauer shifts correlate with the local charge on the Fe sites and different dopant sites can be identified by the Mößbauer quadrupole splitting (see figure).

Targeting an allosteric site in dynamin-related protein 1 to inhibit Fis1-mediated mitochondrial dysfunction.

The large cytosolic GTPase, dynamin-related protein 1 (Drp1), mediates both physiological and pathological mitochondrial fission. Cell stress triggers Drp1 binding to mitochondrial Fis1 and subsequently, mitochondrial fragmentation, ROS production, metabolic collapse, and cell death. Because Drp1 also mediates physiological fission by binding to mitochondrial Mff, therapeutics that inhibit pathological fission should spare physiological mitochondrial fission. P110, a peptide inhibitor of Drp1-Fis1 interaction, reduces pathology in numerous models of neurodegeneration, ischemia, and sepsis without blocking the physiological functions of Drp1. Since peptides have pharmacokinetic limitations, we set out to identify small molecules that mimic P110's benefit. We map the P110-binding site to a switch I-adjacent grove (SWAG) on Drp1. Screening for SWAG-binding small molecules identifies SC9, which mimics P110's benefits in cells and a mouse model of endotoxemia. We suggest that the SWAG-binding small molecules discovered in this study may reduce the burden of Drp1-mediated pathologies and potentially pathologies associated with other members of the GTPase family.

Flame Aerosol Synthesis of Metal Sulfides at High Temperature in Oxygen-Lean Atmosphere.

The development of a novel reactive spray technology based on the well-known gas-phase metal oxide synthesis route provides innumerable opportunities for the production of non-oxide nanoparticles. Among these materials, metal sulfides are expected to have a high impact, especially in the development of electrochemical and photochemical high-surface-area materials. As a proof-of-principle, MnS, CoS, Cu2 S, ZnS, Ag2 S, In2 S3 , SnS, and Bi2 S3 are synthesized in an O2 -lean and sulfur-rich environment. In addition, the formation of Cu2 S in a single-droplet combustion experiment is reported. The multiscale approach combining flame sprays with single-droplet combustion is expected to pave the way toward a fundamental understanding of the gas-phase formation of metal sulfides in the future. The knowledge acquired can open the possibility for the development of a next-generation gas-phase technology facilitating the scalable synthesis of functional binary/ternary metal sulfides.

TiO2 nanoparticles' library toxicity (UV and non-UV exposure) - High-throughput in vivo transcriptomics reveals mechanisms.

The hazards of nanomaterials/nanoparticles (NMs/NPs) are mostly assessed using individual NMs, and a more systematic approach, using many NMs, is needed to evaluate its risks in the environment. Libraries of NMs, with a range of identified different but related characters/descriptors allow the comparison of effects across many NMs. The effects of a custom designed Fe-doped TiO2 NMs library containing 11 NMs was assessed on the soil model Enchytraeus crypticus (Oligochaeta), both with and without UV (standard fluorescent) radiation. Effects were analyzed at organism (phenotypic, survival and reproduction) and gene expression level (transcriptomics, high-throughput 4x44K microarray) to understand the underlying mechanisms. A total of 48 microarrays (20 test conditions) were done plus controls (UV and non-UV). Unique mechanisms induced by TiO2 NPs exposure included the impairment in RNA processing for TiO2_10nm, or deregulated apoptosis for 2%FeTiO2_10nm. Strikingly apparent was the size dependent effects such as induction of reproductive effects via smaller TiO2 NPs (≤12 nm) - embryo interaction, while larger particles (27 nm) caused reproductive effects through different mechanisms. Also, phagocytosis was affected by 12 and 27 nm NPs, but not by ≤11 nm. The organism level study shows the integrated response, i.e. the result after a cascade of events. While uni-cell models offer key mechanistic information, we here deliver a combined biological system level (phenotype and genotype), seldom available, especially for environmental models.