Imperial College London

ProfessorMaryRyan

Faculty of EngineeringDepartment of Materials

Vice-Dean (Research), Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6755m.p.ryan

 
 
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Location

 

B338Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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222 results found

Pramana SS, Cavallaro A, Qi J, Nicklin CL, Ryan MP, Skinner SJet al., 2017, Understanding surface structure and chemistry of single crystal lanthanum aluminate, Scientific Reports, Vol: 7, ISSN: 2045-2322

The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600°C) and chamber pressure of 10-10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10-6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

Journal article

Gonzalez Carter DA, Leo BF, Ruenraroengsak P, Chen S, Goode A, Theodorou I, Chung KF, Carzaniga R, Shaffer M, Dexter D, Ryan M, Porter Aet al., 2017, Silver nanoparticles reduce brain inflammation and related neurotoxicity through induction of H2S-synthesizing enzymes, Scientific Reports, Vol: 7, ISSN: 2045-2322

Silver nanoparticles (AgNP) are known to penetrate into the brain and cause neuronal death. However, there is a paucity in studies examining the effect of AgNP on the resident immune cells of the brain, microglia. Given microglia are implicated in neurodegenerative disorders such as Parkinson’s disease (PD), it is important to examine how AgNPs affect microglial inflammation to fully assess AgNP neurotoxicity. In addition, understanding AgNP processing by microglia will allow better prediction of their long term bioreactivity. In the present study, the in vitro uptake and intracellular transformation of citrate-capped AgNPs by microglia, as well as their effects on microglial inflammation and related neurotoxicity were examined. Analytical microscopy demonstrated internalization and dissolution of AgNPs within microglia and formation of non-reactive silver sulphide (Ag2S) on the surface of AgNPs. Furthermore, AgNP-treatment up-regulated microglial expression of the hydrogen sulphide (H2S)-synthesizing enzyme cystathionine-γ-lyase (CSE). In addition, AgNPs showed significant anti-inflammatory effects, reducing lipopolysaccharide (LPS)-stimulated ROS, nitric oxide and TNFα production, which translated into reduced microglial toxicity towards dopaminergic neurons. Hence, the present results indicate that intracellular Ag2S formation, resulting from CSE-mediated H2S production in microglia, sequesters Ag+ ions released from AgNPs, significantly limiting their toxicity, concomitantly reducing microglial inflammation and related neurotoxicity.

Journal article

Chung KF, Seiffert J, Chen S, Theodorou IG, Goode AE, Leo BF, McGilvery CM, Hussain F, Wiegman C, Rossios C, Zhu J, Gong J, Tariq F, Yufit V, Monteith AJ, Hashimoto T, Skepper JN, Ryan MP, Zhang J, Tetley TD, Porter AEet al., 2017, Inactivation, clearance, and functional effects of lung-instilled short and long silver nanowires in rats, ACS Nano, Vol: 11, Pages: 2652-2664, ISSN: 1936-086X

There is a potential for silver nanowires (AgNWs) to be inhaled, but there is little information on their health effects and their chemical transformation inside the lungs in vivo. We studied the effects of short (S-AgNWs; 1.5 μm) and long (L-AgNWs; 10 μm) nanowires instilled into the lungs of Sprague–Dawley rats. S- and L-AgNWs were phagocytosed and degraded by macrophages; there was no frustrated phagocytosis. Interestingly, both AgNWs were internalized in alveolar epithelial cells, with precipitation of Ag2S on their surface as secondary Ag2S nanoparticles. Quantitative serial block face three-dimensional scanning electron microscopy showed a small, but significant, reduction of NW lengths inside alveolar epithelial cells. AgNWs were also present in the lung subpleural space where L-AgNWs exposure resulted in more Ag+ve macrophages situated within the pleura and subpleural alveoli, compared with the S-AgNWs exposure. For both AgNWs, there was lung inflammation at day 1, disappearing by day 21, but in bronchoalveolar lavage fluid (BALF), L-AgNWs caused a delayed neutrophilic and macrophagic inflammation, while S-AgNWs caused only acute transient neutrophilia. Surfactant protein D (SP-D) levels in BALF increased after S- and L-AgNWs exposure at day 7. L-AgNWs induced MIP-1α and S-AgNWs induced IL-18 at day 1. Large airway bronchial responsiveness to acetylcholine increased following L-AgNWs, but not S-AgNWs, exposure. The attenuated response to AgNW instillation may be due to silver inactivation after precipitation of Ag2S with limited dissolution. Our findings have important consequences for the safety of silver-based technologies to human health.

Journal article

Calderon L, Han TT, McGilvery CM, Yang L, Subramaniam P, Lee K-B, Schwander S, Tetley TD, Georgopoulos PG, Ryan M, Porter AE, Smith R, Chung KF, Lioy PJ, Zhang J, Mainelis Get al., 2017, Release of airborne particles and Ag and Zn compounds from nanotechnology-enabled consumer sprays: Implications for inhalation exposure, ATMOSPHERIC ENVIRONMENT, Vol: 155, Pages: 85-96, ISSN: 1352-2310

The increasing prevalence and use of nanotechnology-enabled consumer products have increased potential consumer exposures to nanoparticles; however, there is still a lack of data characterizing such consumer exposure. The research reported here investigated near-field airborne exposures due to the use of 13 silver (Ag)-based and 5 zinc (Zn)-based consumer sprays. The products were sprayed into a specially designed glove box, and all products were applied with equal spraying duration and frequency. Size distribution and concentration of the released particles were assessed using a Scanning Mobility Particle Sizer and an Aerodynamic Particle Sizer. Inductively coupled plasma mass spectrometry (ICP-MS) was used to investigate the presence of metals in all investigated products. Spray liquids and airborne particles from select products were examined using transmission electron microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS). We found that all sprays produced airborne particles ranging in size from nano-sized particles (<100 nm) to coarse particles (>2.5 μm); however, there was a substantial variation in the released particle concentration depending on a product. The total aerosol mass concentration was dominated by the presence of coarse particles, and it ranged from ∼30 μg/m3 to ∼30,000 μg/m3. The TEM verified the presence of nanoparticles and their agglomerates in liquid and airborne states. The products were found to contain not only Ag and Zn compounds - as advertised on the product labeling - but also a variety of other metals including lithium, strontium, barium, lead, manganese and others. The results presented here can be used as input to model population exposures as well as form a basis for human health effects studies due to the use nanotechnology-enabled products.

Journal article

Gonzalez Arellano DL, Bhamrah Harley J, Yang J, Gilchrist JB, McComb, Ryan MP, Heutz SEMet al., 2017, Room temperature routes towards the creation of zinc oxide films from molecular precursors, ACS Omega, Vol: 2, Pages: 98-104, ISSN: 2470-1343

The advent of “flexible” electronics on plastic substrates with low melting points requires the development of thin film deposition techniques that operate at low temperatures. This is easily achieved with vacuum or solution-processed molecular or polymeric semiconductors, but oxide materials remain a significant challenge. Here we show that zinc oxide (ZnO) can be prepared using only room-temperature processes, using the molecular thin film precursor zinc phthalocyanine (ZnPc), followed by vacuum ultra-violet light treatment to elicit degradation of the organic components and transformation of the deposited film to oxide material. The degradation mechanism was assessed by studying the influence of the atmosphere during the reaction: it was particularly sensitive to oxygen pressure in the chamber and optimal degradation conditions were established as 3 mbar with 40% oxygen in nitrogen. The morphology of the film was relatively unchanged during the reaction, but detailed analysis of itscomposition using both scanning transmission electron microscopy (STEM) and secondary ion mass spectrometry (SIMS) revealed that a 40 nm thick layer containingZnO results from the 100 nm thick precursor after complete reaction. Our methodology represents a simple route for the fabrication of oxides and multilayer structuresthat can be easily integrated into current molecular thin film growth setups,without the need for a high temperature step.

Journal article

Hassan Sk M, Abdullah AM, Ko M, Laycock N, Ingham B, Ryan MP, Williams DEet al., 2017, Effect of Cr/Mo on the protectiveness of corrosion scales on carbon steel in sweet medium under high flow regime, Pages: 509-517, ISSN: 1938-6737

© The Electrochemical Society. We investigate the effects of Cr/Mo micro-alloying of plain carbon steel on the corrosion behaviour and scale protectiveness in CO 2 saturated (sweet) brine (0.5 M NaCl) environment, under hydrodynamic conditions, at 80 o C in a slightly acidic environment (pH 6.6). Potentiostatic current transients indicate positive effects of Cr/Mo micro-alloying on an individual as well as synergistic level of the alloyents. Increase in Cr/Mo content appears to reduce the overall current passing through corrosion scale and encourage faster crystallization. SEM images suggest that Cr/Mo micro-alloying induced formation of thinner scale with better protectiveness. From the mechanistic perspective, we suggest that the addition of small amounts of Cr/Mo modulates the current due to dissolution of iron, as well as the current due to growth of a crystalline layer, by modifying the local environment at the steel surface. Modeling of the hypothesis is currently in progress.

Conference paper

Pang J, Theodorou I, Centeno A, Petrov P, Alford N, Ryan M, Xie Fet al., 2016, Gold nanodisc arrays as near infrared metal-enhanced fluorescence platforms with tuneable enhancement factors, Journal of Materials Chemistry C, Vol: 5, Pages: 917-925, ISSN: 2050-7534

Metal enhanced fluorescence (MEF) is a physical effect through which the near-field interaction of fluorophores with metallic nanoparticles can lead to large fluorescence enhancement. MEF can be exploited in many fluorescence-based biomedical applications, with potentially significant improvement in detection sensitivity and contrast enhancement. Offering lower autofluorescence and minimal photoinduced damage, the development of effective and multifunctional MEF platforms in the near-infrared (NIR) region, is particularly desirable. In this work, the enhancement of NIR fluorescence caused by interaction with regular arrays of cylindrical gold (Au) nanoparticles (nanodiscs), fabricated through nanosphere lithography, is reported. Significant MEF of up to 235 times is obtained, with tuneable enhancement factors. The effect of array structure on fluorescence enhancement is investigated by semi-quantitatively de-convoluting excitation enhancement from emission enhancement, and modelling the local electric field enhancement. By considering arrays of Au nanodiscs with the same extinction maximum, it is shown that the excitation enhancement, due to increased electric field, is not significantly different for the particle sizes and separation distances considered. Rather, it is seen that the emission from the fluorophore is strongly enhanced, and is dependent on the topography, in particular particle size. The results show that the structural characteristics of Au nanodisc arrays can be manipulated to tune their enhancement factor, and hence their sensitivity.

Journal article

Simoes TA, Bryant MG, Brown AP, Milne SJ, Ryan M, Neville A, Brydson Ret al., 2016, Evidence for the dissolution of molybdenum during tribocorrosion of CoCrMo hip implants in the presence of serum protein., Acta Biomater, Vol: 45, Pages: 410-418

We have characterized CoCrMo, Metal-on-Metal (MoM) implant, wear debris particles and their dissolution following cycling in a hip simulator, and have related the results to the tribocorrosion of synthetic wear debris produced by milling CoCrMo powders in solutions representative of environments in the human body. Importantly, we have employed a modified ICP-MS sample preparation procedure to measure the release of ions from CoCrMo alloys during wear simulation in different media; this involved use of nano-porous ultrafilters which allowed complete separation of particles from free ions and complexes in solution. As a result, we present a new perspective on the release of metal ions and formation of metal complexes from CoCrMo implants. The new methodology enables the mass balance of ions relative to complexes and particles during tribocorrosion in hip simulators to be determined. A much higher release of molybdenum ions relative to cobalt and chromium has been measured. The molybdenum dissolution was enhanced by the presence of bovine serum albumin (BSA), possibly due to the formation of metal-protein complexes. Overall, we believe that the results could have significant implications for the analysis and interpretation of metal ion levels in fluids extracted from hip arthroplasty patients; we suggest that metal levels, including molybdenum, be analysed in these fluids using the protocol described here. STATEMENT OF SIGNIFICANCE: We have developed an important new protocol for the analysis of metal ion levels in fluids extracted from hip implant patients and also hip simulators. Using this procedure, we present a new perspective on the release of metal ions from CoCrMo alloy implants, revealing significantly lower levels of metal ion release during tribocorrosion in hip simulators than previously thought, combined with the release of much higher percentages of molybdenum ions relative to cobalt and chromium. This work is of relevance, both from the perspective of th

Journal article

Sweeney S, Hu S, Ruenraroengsak P, Chen S, Gow A, Schwander S, Zhang JJ, Chung KF, Ryan MP, Porter AE, Shaffer MS, Tetley TDet al., 2016, Carboxylation of multiwalled carbon nanotubes reduces their toxicity in primary human alveolar macrophages, Environmental Science: Nano, Vol: 3, Pages: 1340-1350, ISSN: 2051-8153

Surface functionalisation of multiwalled carbon nanotubes (MWCNT) is commonly used to facilitate their various and diverse applications. Inhaled nanomaterials, such as MWCNTs, have a high deposition rate in the alveolar units of the deep lung, where alveolar macrophages (AM) provide the front line of cellular immune defence by removing foreign matter (microbes, particles etc.). The toxicity of MWCNTs (with or without functionalisation) towards primary human AMs is not known. We investigated the physicochemical characteristics and toxicity of two MWCNT materials: acid purified ‘Purified-MWCNT’ and concentrated acid functionalised ‘COOH-MWCNT’. We hypothesised that the bioreactivity with primary human AM would differ between the materials. Full characterisation of the MWCNTs revealed that –COOH functionalisation yielded shorter MWCNTs, accompanied by a greater occurrence of framework defects, in comparison to Purified-MWCNT. In agreement with our hypothesis that the bioreactivity would differ, Purified-MWCNT were significantly more toxic as measured by reduced cell viability and increased inflammatory mediator release. For example, IL-1β and IL-8 release by AMs significantly increased 3.5- and 2.4-fold, respectively (P < 0.05), 24 hours after treatment with Purified-MWCNT. In contrast, IL-1β and IL-8 release by AMs did not significantly change 24 hours after treatment with COOH-MWCNT. We determined that the mechanism of this toxicity is likely due to activation of the inflammasome, as lipopolysaccharide priming of primary human AMs was necessary to see the inflammatory response and this was accompanied by lysosomal disruption and increased generation of reactive oxygen species. This study contributes further to our understanding of the effects of MWCNTs and surface modification on highly relevant human lung AMs; the findings have important implications for the manufacture, application and use of MWCNTs. In particular, this is

Journal article

Zhang JJ, Lee KB, He L, Seiffert J, Subramaniam P, Yang L, Chen S, Maguire P, Mainelis G, Schwander S, Tetley T, Porter A, Ryan M, Shaffer M, Hu S, Gong J, Chung KFet al., 2016, Effects of a nanoceria fuel additive on the physicochemical properties of diesel exhaust particles., Environmental Science: Processes & Impacts, Vol: 18, Pages: 1333-1342, ISSN: 2050-7887

Nanoceria (i.e., CeO2 nanoparticles) fuel additives have been used in Europe and elsewhere to improve fuel efficiency. Previously we have shown that the use of a commercial fuel additive Envirox™ in a diesel-powered electricity generator reduced emissions of diesel exhaust particle (DEP) mass and other pollutants. However, such additives are currently not permitted for use in on-road vehicles in North America, largely due to limited data on the potential health impact. In this study, we characterized a variety of physicochemical properties of DEPs emitted from the same engine. Our methods include novel techniques such as Raman spectrometry for analyzing particle surface structure and an assay for DEP oxidative potential. Results show that with increasing Envirox™ concentrations in the fuel (0×, 0.1×, 1×, and 10× of manufacturer recommended 0.5 mL Envirox™ per liter fuel), DEP sizes decreased from 194.6 ± 20.1 to 116.3 ± 14.8 nm; the zeta potential changed from -28.4 mV to -22.65 mV; DEP carbon content decreased from 91.8% to 79.4%; cerium and nitrogen contents increased from 0.3% to 6.5% and 0.2% to 0.6%, respectively; the ratio of organic carbon (OC) to elemental carbon (EC) increased from 22.9% to 38.7%; and the ratio of the disordered carbon structure to the ordered carbon structure (graphitized carbon) in DEPs decreased. Compared to DEPs emitted from 0×, 0.1×, and 1× fuels, DEPs from the 10× fuel had a lower oxidative potential likely due to the increased ceria content because pure ceria nanoparticles exhibited the lowest oxidative potential compared to all the DEPs. Since the physicochemical parameters tested here are among the determinants of particle toxicity, our findings imply that adding ceria nanoparticles into diesel may alter the toxicity of DEPs. The findings from the present study, hence, can help future studies that will examine the impact of nanoceria additives on DEP to

Journal article

Podhorska L, Delcassian D, Goode AE, Agyei M, McComb DW, Ryan MP, Dunlop IEet al., 2016, Mechanisms of polymer-templated nanoparticle synthesis: contrasting ZnS and Au, Langmuir, Vol: 32, Pages: 9216-9222, ISSN: 0743-7463

We combine solution small-angle X-ray scattering (SAXS) and high-resolution analytical transmission electron microscopy (ATEM) to gain a full mechanistic understanding of substructure formation in nanoparticles templated by block copolymer reverse micelles, specifically poly(styrene)-block-poly(2-vinyl pyridine). We report a novel substructure for micelle-templated ZnS nanoparticles, in which small crystallites (~4 nm) exist within a larger (~20 nm) amorphous organic-inorganic hybrid matrix. The formation of this complex structure is explained via SAXS measurements that characterize in situ for the first time the intermediate state of the metal-loaded micelle core: Zn2+ ions are distributed throughout the micelle core, which solidifies as a unit on sulfidation. The nanoparticle size is thus determined by the radius of the metal-loaded core, rather than the quantity of available metal ions. This mechanism leads to particle size counter-intuitively decreasing with increasing metal content, based on the modified interactions of the metal-complexed monomers in direct contrast to gold nanoparticles templated by the same polymer.

Journal article

Theodorou IG, Ruenraroengsak P, Gow A, Schwander S, Zhang JJ, Chung KF, Tetley TD, Ryan MP, Porter AEet al., 2016, Effect of pulmonary surfactant on the dissolution, stability and uptake of zinc oxide nanowires by human respiratory epithelial cells., Nanotoxicology, Vol: 10, Pages: 1351-1362, ISSN: 1743-5404

Inhaled nanoparticles (NPs) have high-deposition rates in the alveolar region of the lung but the effects of pulmonary surfactant (PS) on nanoparticle bioreactivity are unclear. Here, the impact of PS on the stability and dissolution of ZnO nanowires (ZnONWs) was investigated, and linked with their bioreactivity in vitro with human alveolar epithelial type 1-like cells (TT1). Pre-incubation of ZnONWs with Curosurf® (a natural porcine PS) decreased their dissolution at acidic pH, through the formation of a phospholipid corona. Confocal live cell microscopy confirmed that Curosurf® lowered intracellular dissolution, thus delaying the onset of cell death compared to bare ZnONWs. Despite reducing dissolution, Curosurf® significantly increased the uptake of ZnONWs within TT1 cells, ultimately increasing their toxicity after 24 h. Although serum improved ZnONW dispersion in suspension similar to Curosurf®, it had no effect on ZnONW internalization and toxicity, indicating a unique role of PS in promoting particle uptake. In the absence of PS, ZnONW length had no effect on dissolution kinetics or degree of cellular toxicity, indicating a less important role of length in determining ZnONW bioreactivity. This work provides unique findings on the effects of PS on the stability and toxicity of ZnONWs, which could be important in the study of pulmonary toxicity and epithelial-endothelial translocation of nanoparticles in general.

Journal article

Seiffert J, Buckley A, Leo B, Zhu J, Hussain F, Guo C, Warren J, Hodgson A, Gong J, Ryan M, Zhang J, Porter A, Tetley T, Gow A, Smith R, Dai R, Martin NG, Chung KFet al., 2016, Pulmonary effects of inhalation of spark-generated silver nanoparticles in Brown-Norway and Sprague-Dawley rats, Respiratory Research, Vol: 17, ISSN: 1465-993X

BackgroundThe increasing use of silver nanoparticles (AgNPs) in consumer products is concerning. Weexamined the potential toxic effects when inhaled in Brown-Norway (BN) rats with a preinflammatorystate compared to Sprague-Dawley (SD) rats.MethodsWe determined the effect of AgNPs generated from a spark generator (mass concentration:600-800 µg/mm3; mean diameter: 13-16 nm; total lung doses: 8 [Low] and 26-28 [High] µg)inhaled by the nasal route in both rat strains. Rats were sacrificed at day 1 and day 7 afterexposure and measurement of lung function.ResultsIn both strains, there was an increase in neutrophils in bronchoalveolar lavage (BAL) fluid at24 hours at the high dose, with concomitant eosinophilia in BN rats. While BAL inflammatorycells were mostly normalised by Day 7, lung inflammation scores remained increasedalthough not the tissue eosinophil scores. Total protein levels were elevated at both lungdoses in both strains. There was an increase in BAL IL-1β, KC, IL-17, CCL2 and CCL3 levels inboth strains at Day 1, mostly at high dose. Phospholipid levels were increased at the highdose in SD rats at Day 1 and 7, while in BN rats, this was only seen at Day 1; surfactantprotein D levels decreased at day 7 at the high dose in SD rats, but was increased at Day 1 atthe low dose in BN rats. There was a transient increase in central airway resistance and intissue elastance in BN rats at Day 1 but not in SD rats. Positive silver-staining was seenparticularly in lung tissue macrophages in a dose and time-dependent response in bothstrains, maximal by day 7. Lung silver levels were relatively higher in BN rat and present atday 7 in both strains.ConclusionsPresence of cellular inflammation and increasing silver-positive macrophages in lungs at day7, associated with significant levels of lung silver indicate that lung toxicity is persistent evenwith the absence of airway luminal inflammation at that time-point. The higher levels andpersistence of lung silve

Journal article

Theodorou IG, Jawad Z, Qin H, Aboagye EO, Porter A, Ryan M, Xie Fet al., 2016, Significant metal enhanced fluorescence of Ag2S quantum dots in the second near-infrared window, Nanoscale, Vol: 8, Pages: 12869-12873, ISSN: 2040-3372

The amplification of light in NIR-II from Ag2S QDs via metal enhanced fluorescence (MEF) is reported for the first time. Significant fluorescence enhancement of over 100 times for Ag2S QDs deposited on Au-nanostructured arrays, paves the way for novel sensing and imaging applications based on Ag2S QDs, with improved detection sensitivity and contrast enhancement.

Journal article

Othman BA, Greenwood C, Abuelela AF, Bharath AA, Chen S, Theodorou I, Douglas T, Uchida M, Ryan M, Merzaban JS, Porter AEet al., 2016, Targeted Cancer Therapy: Correlative Light-Electron Microscopy Shows RGD-Targeted ZnO Nanoparticles Dissolve in the Intracellular Environment of Triple Negative Breast Cancer Cells and Cause Apoptosis with Intratumor Heterogeneity (Adv. Healthcare Mater. 11/2016)., Advanced Healthcare Materials, Vol: 5, Pages: 1248-1248, ISSN: 2192-2640

On page 1310 J. S. Merzaban, A. E. Porter, and co-workers present fluorescently labeled RGD-targeted ZnO nanoparticles (NPs; green) for the targeted delivery of cytotoxic ZnO to integrin αvβ3 receptors expressed on triple negative breast cancer cells. Correlative light-electron microscopy shows that NPs dissolve into ionic Zn(2+) (blue) upon uptake and cause apoptosis (red) with intra-tumor heterogeneity, thereby providing a possible strategy for targeted breast cancer therapy. Cover design by Ivan Gromicho.

Journal article

Scatigno GG, Ryan MP, Giuliani F, Wenman MRet al., 2016, The effect of prior cold work on the chloride stress corrosion cracking of 304L austenitic stainless steel under atmospheric conditions, Materials Science and Engineering: A, Vol: 668, Pages: 20-29, ISSN: 0921-5093

A systematic study of the effect of cold work (CW) on chloride-induced stress corrosion cracking (SCC) in 304L stainless steel was performed. CW between 0% and 40% was applied prior to corrosion of specimens at 75 °C and 70% relative humidity, for 500 h, using MgCl2 (at atmospheric pressure). Samples cracked most readily between 0.5% and 5% CW; at 20% and above no cracks were present. Additionally, above 5% CW, some specific orientation relationships become evident, with cracks primarily aligned along <111> parallel to the transverse direction. The results suggest that at levels of CW >20%, the synergistic effect of micro-mechanisms may hinder SCC in this system.

Journal article

Sweeney S, Leo BF, Chen S, Abraham-Thomas N, Thorley AJ, Gow A, Schwander S, Zhang JJ, Shaffer MS, Chung KF, Ryan MP, Porter AE, Tetley TDet al., 2016, Pulmonary surfactant mitigates silver nanoparticle toxicity in human alveolar type-I-like epithelial cells., Colloids and Surfaces B - Biointerfaces, Vol: 145, Pages: 167-175, ISSN: 1873-4367

Accompanying increased commercial applications and production of silver nanomaterials is an increased probability of human exposure, with inhalation a key route. Nanomaterials that deposit in the pulmonary alveolar region following inhalation will interact firstly with pulmonary surfactant before they interact with the alveolar epithelium. It is therefore critical to understand the effects of human pulmonary surfactant when evaluating the inhalation toxicity of silver nanoparticles. In this study, we evaluated the toxicity of AgNPs on human alveolar type-I-like epithelial (TT1) cells in the absence and presence of Curosurf(®) (a natural pulmonary surfactant substitute), hypothesising that the pulmonary surfactant would act to modify toxicity. We demonstrated that 20nm citrate-capped AgNPs induce toxicity in human alveolar type I-like epithelial cells and, in agreement with our hypothesis, that pulmonary surfactant acts to mitigate this toxicity, possibly through reducing AgNP dissolution into cytotoxic Ag(+) ions. For example, IL-6 and IL-8 release by TT1 cells significantly increased 10.7- and 35-fold, respectively (P<0.01), 24h after treatment with 25μg/ml AgNPs. In contrast, following pre-incubation of AgNPs with Curosurf(®), this effect was almost completely abolished. We further determined that the mechanism of this toxicity is likely associated with Ag(+) ion release and lysosomal disruption, but not with increased reactive oxygen species generation. This study provides a critical understanding of the toxicity of AgNPs in target human alveolar type-I-like epithelial cells and the role of pulmonary surfactant in mitigating this toxicity. The observations reported have important implications for the manufacture and application of AgNPs, in particular for applications involving use of aerosolised AgNPs.

Journal article

Othman BA, Greenwood C, Abuelela AF, Bharath AA, Chen S, Theodorou I, Douglas T, Uchida M, Ryan M, Merzaban JS, Porter AEet al., 2016, Correlative light-electron microscopy shows RGD-targeted ZnO nanoparticles dissolve in the intracellular environment of triple negative breast cancer cells and cause apoptosis with intra-tumor heterogeneity, Advanced Healthcare Materials, Vol: 5, Pages: 1310-1325, ISSN: 2192-2640

ZnO nanoparticles (NPs) are reported to show a high degree of cancer cell selectivity with potential use in cancer imaging and therapy. Questions remain about the mode by which the ZnO NPs cause cell death, whether they exert an intra- or extra-35 cellular effect, and the resistance among different cancer cell types to ZnO NP exposure. The present study quantified the variability between the cellular toxicity, dynamics of cellular uptake and dissolution of bare and RGD (Arg-Gly-Asp)-targeted ZnO NPs by MDA-MB-231 cells. Compared to bare ZnO NPs, RGD-targeting of the ZnO NPs to integrin αvβ3 receptors expressed on MDA-MB-231 cells appeared to increase the toxicity of the ZnO NPs to breast cancer cells at lower doses. Confocal microscopy of live MDA-MB-231 cells confirmed uptake of both classes of ZnO NPs with a commensurate rise in intracellular Zn2+ concentration prior to cell death. The response of the cells within the population to intracellular Zn2+ was highly heterogeneous. In addition, the results emphasize the utility of dynamic and quantitative imaging in understanding cell uptake and processing of targeted therapeutic ZnO NPs at the cellular level by heterogeneous cancer cell populations, which could be crucial for the development of optimized treatment strategies.

Journal article

Goode AE, Porter AE, KÅ‚osowski MM, Ryan MP, Heutz S, McComb DWet al., 2016, Analytical transmission electron microscopy at organic interfaces, Current Opinion in Solid State and Materials Science, Vol: 21, Pages: 55-67, ISSN: 1359-0286

Organic materials are ubiquitous in all aspects of our daily lives. Increasingly there is a need to understand interactions between different organic phases, or between organic and inorganic materials (hybrid interfaces), in order to gain fundamental knowledge about the origin of their structural and functional properties. In order to understand the complex structure–property–processing relationships in (and between) these materials, we need tools that combine high chemical sensitivity with high spatial resolution to allow detailed interfacial characterisation. Analytical transmission electron microscopy (TEM) is a powerful and versatile technique that can fulfil both criteria. However, the application of analytical TEM to organic systems presents some unique challenges, such as low contrast between phases, and electron beam sensitivity. In this review recent analytical TEM approaches to the nanoscale characterisation of two systems will be discussed: the hybrid collagen/mineral interface in bone, and the all-organic donor/acceptor interface in OPV devices.

Journal article

Zhang X, Wu X, Centeno A, Ryan M, alford N, riley D, Xie F, Zhang X, Wu XU, Centeno A, Ryan M, Alford N, Riley D, Xie Fet al., 2016, Significant broadband photocurrent enhancement by Au-CZTS core-shell nanostructured photocathodes, Scientific Reports, Vol: 6, ISSN: 2045-2322

Copper zinc tin sulfide (CZTS) is a promising material for harvesting solar energy due to its abundance and non-toxicity. However, its poor performance hinders their wide application. In this paper gold (Au) nanoparticles are successfully incorporated into CZTS to form Au@CZTS core-shell nanostructures. The photocathode of Au@CZTS nanostructures exhibits enhanced optical absorption characteristics and improved incident photon-to-current efficiency (IPCE) performance. It is demonstrated that using this photocathode there is a significant increase of the power conversion efficiency (PCE) of a photoelectrochemical solar cell of 100% compared to using a CZTS without Au core. More importantly, the PCE of Au@CZTS photocathode improved by 15.8% compared to standard platinum (Pt) counter electrode. The increased efficiency is attributed to plasmon resonance energy transfer (PRET) between the Au nanoparticle core and the CZTS shell at wavelengths shorter than the localized surface plasmon resonance (LSPR) peak of the Au and the semiconductor bandgap.

Journal article

Ramadan AJ, Rochford LA, Moffat J, Mulcahy C, Ryan MP, Jones TS, Heutz Set al., 2016, The morphology and structure of vanadyl phthalocyanine thin films on lithium niobate single crystals, Journal of Materials Chemistry C, Vol: 4, Pages: 348-351, ISSN: 2050-7534

The electric field of ferroelectric materials has been used as a driving force to promote molecular adsorption and control the orientation of small dipolar molecules. This approach has not been investigated on larger polyaromatic molecules, such as those used in organic electronic devices, even though the physical and electronic properties of thin films are strongly dependent on molecular structure and orientation, ultimately affecting device performance. Here we investigate the effects of model ferroelectric surfaces on a dipolar organic semiconducting molecule. Thin films of vanadyl phthalocyanine (VOPc) deposited on to (0001) and (2[1 with combining macron][1 with combining macron]0) lithium niobate were subjected to structural and morphological analysis. Whilst thin films could be grown on these surfaces, no obvious change to their structure or morphology was observed suggesting there was no influence of a surface electrical field or surface chemistry on the film structure, and that the substrate is more complex than previously thought.

Journal article

Walker RJ, Pougin A, Oropeza FE, Villar-Garcia IJ, Ryan MP, Strunk J, Payne DJet al., 2016, Surface Termination and CO2 Adsorption onto Bismuth Pyrochlore Oxides, CHEMISTRY OF MATERIALS, Vol: 28, Pages: 90-96, ISSN: 0897-4756

Journal article

Botelho DJ, Leo BF, Massa CB, Sarkar S, Tetley TD, Chung KF, Chen S, Ryan MP, Porter AE, Zhang J, Schwander SK, Gow AJet al., 2016, Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity, NANOTOXICOLOGY, Vol: 10, Pages: 118-127, ISSN: 1743-5390

Journal article

Tay SER, Goode AE, Weker JN, Cruickshank AA, Heutz S, Porter AE, Ryan MP, Toney MFet al., 2015, Direct in situ observation of ZnO nucleation and growth via transmission X-ray microscopy, Nanoscale, Vol: 8, Pages: 1849-1853, ISSN: 2040-3372

The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation.

Journal article

Sarkar S, Leo BF, Carranza C, Chen S, Rivas-Santiago C, Porter AE, Ryan MP, Gow A, Chung KF, Tetley TD, Zhang JJ, Georgopoulos PG, Ohman-Strickland PA, Schwander Set al., 2015, Modulation of human macrophage responses to mycobacterium tuberculosis by silver nanoparticles of different size and surface modification, PLOS One, Vol: 10, ISSN: 1932-6203

Exposure to silver nanoparticles (AgNP) used in consumer products carries potential health risks including increased susceptibility to infectious pathogens. Systematic assessments of antimicrobial macrophage immune responses in the context of AgNP exposure are important because uptake of AgNP by macrophages may lead to alterations of innate immune cell functions. In this study we examined the effects of exposure to AgNP with different particle sizes (20 and 110 nm diameters) and surface chemistry (citrate or polyvinlypyrrolidone capping) on cellular toxicity and innate immune responses against Mycobacterium tuberculosis (M.tb) by human monocyte-derived macrophages (MDM). Exposures of MDM to AgNP significantly reduced cellular viability, increased IL8 and decreased IL10 mRNA expression. Exposure of M.tb-infected MDM to AgNP suppressed M.tb-induced expression of IL1B, IL10, and TNFA mRNA. Furthermore, M.tb-induced IL-1β, a cytokine critical for host resistance to M.tb, was inhibited by AgNP but not by carbon black particles indicating that the observed immunosuppressive effects of AgNP are particle specific. Suppressive effects of AgNP on the M.tb-induced host immune responses were in part due to AgNP-mediated interferences with the TLR signaling pathways that culminate in the activation of the transcription factor NF-κB. AgNP exposure suppressed M.tb-induced expression of a subset of NF-κB mediated genes (CSF2, CSF3, IFNG, IL1A, IL1B, IL6, IL10, TNFA, NFKB1A). In addition, AgNP exposure increased the expression of HSPA1A mRNA and the corresponding stress-induced Hsp72 protein. Up-regulation of Hsp72 by AgNP can suppress M.tb-induced NF-κB activation and host immune responses. The observed ability of AgNP to modulate infectious pathogen-induced immune responses has important public health implications.

Journal article

Goode AE, Gonzalez Carter DA, Motskin M, Pienaar IS, Chen S, Hu S, Ruenraroengsak P, Ryan M, Shaffer MSP, Dexter DT, Porter AEet al., 2015, High resolution and dynamic imaging of biopersistence and bioreactivity of extra and intracellular MWNTs exposed to microglial cells, Biomaterials, Vol: 70, Pages: 57-70, ISSN: 1878-5905

Multi-walled carbon nanotubes (MWNTs) are increasingly being developed both as neuro-therapeutic drug delivery systems to the brain and as neural scaffolds to drive tissue regeneration across lesion sites. MWNTs with different degrees of acid oxidation may have different bioreactivities and propensities to aggregate in the extracellular environment, and both individualised and aggregated MWNTs may be expected to be found in the brain. Before practical application, it is vital to understand how both aggregates and individual MWNTs will interact with local phagocytic immune cells, the microglia, and ultimately to determine their biopersistence in the brain. The processing of extra- and intracellular MWNTs (both pristine and when acid oxidised) by microglia was characterised across multiple length scales by correlating a range of dynamic, quantitative and multi-scale techniques, including: UV-vis spectroscopy, light microscopy, focussed ion beam scanning electron microscopy and transmission electron microscopy. Dynamic, live cell imaging revealed the ability of microglia to break apart and internalise micron-sized extracellular agglomerates of acid oxidised MWNT, but not pristine MWNTs. The total amount of MWNTs internalised by, or strongly bound to, microglia was quantified as a function of time. Neither the significant uptake of oxidised MWNTs, nor the incomplete uptake of pristine MWNTs affected microglial viability, pro-inflammatory cytokine release or nitric oxide production. However, after 24 hrs exposure to pristine MWNTs, a significant increase in the production of reactive oxygen species was observed. Small aggregates and individualised oxidised MWNTs were present in the cytoplasm and vesicles, including within multilaminar bodies, after 72 hours. Some evidence of morphological damage to oxidised MWNT structure was observed including highly disordered graphitic structures, suggesting possible biodegradation. This work demonstrates the utility of dynamic, quant

Journal article

Ramadan AJ, Rochford LA, Ryan MP, Jones TS, Heutz Set al., 2015, The influence of polar (0001) zinc oxide (ZnO) on the structure and morphology of vanadyl phthalocyanine (VOPc), RSC Advances, Vol: 5, Pages: 65949-65952, ISSN: 2046-2069

Metal oxide thin films are increasingly utilized in small molecular organic photovoltaic devices to facilitate electron transport and injection. Despite this there is little understanding of the influence these layers have on the structure of adjacent organic semiconductor layers. Here we use both O- and Zn- terminated (0001) single crystal zinc oxide (ZnO) as a model system to investigate the effect of a metal oxide surface on the growth of a molecular semiconductor, vanadyl phthalocyanine (VOPc). The surface reconstructions of these model surfaces are determined and the properties of thin films of VOPc deposited atop are investigated. The nature of the bulk truncation of the surface is found to have pronounced effects on both the morphology and crystal structure of these molecular films. This work highlights the importance of considering the effects of the chemical composition and surface termination of metal oxide films on the structure of adjacent molecular semiconductor films.

Journal article

Mukherjee D, Porter A, Ryan M, Schwander S, Chung KF, Tetley T, Zhang J, Georgopoulos Pet al., 2015, Modeling in vivo interactions of engineered nanoparticles in the pulmonary alveolar lining fluid, Nanomaterials, Vol: 5, Pages: 1223-1249, ISSN: 2079-4991

Increasing use of engineered nanomaterials (ENMs) in consumer products may result in widespread human inhalation exposures. Due to their high surface area per unit mass, inhaled ENMs interact with multiple components of the pulmonary system, and these interactions affect their ultimate fate in the body. Modeling of ENM transport and clearance in vivo has traditionally treated tissues as well-mixed compartments, without consideration of nanoscale interaction and transformation mechanisms. ENM agglomeration, dissolution and transport, along with adsorption of biomolecules, such as surfactant lipids and proteins, cause irreversible changes to ENM morphology and surface properties. The model presented in this article quantifies ENM transformation and transport in the alveolar air to liquid interface and estimates eventual alveolar cell dosimetry. This formulation brings together established concepts from colloidal and surface science, physics, and biochemistry to provide a stochastic framework capable of capturing essential in vivo processes in the pulmonary alveolar lining layer. The model has been implemented for in vitro solutions with parameters estimated from relevant published in vitro measurements and has been extended here to in vivo systems simulating human inhalation exposures. Applications are presented for four different ENMs, and relevant kinetic rates are estimated, demonstrating an approach for improving human in vivo pulmonary dosimetry.

Journal article

Munusamy P, Wang C, Engelhard MH, Baer DR, Smith JN, Liu C, Kodali V, Thrall BD, Chen S, Porter AE, Ryan MPet al., 2015, Comparison of 20nm silver nanoparticles synthesized with and without a gold core: Structure, dissolution in cell culture media, and biological impact on macrophages, Biointerphases, Vol: 10, ISSN: 1934-8630

Widespread use of silver nanoparticles raises questions of environmental and biological impact. Many synthesis approaches are used to produce pure silver and silver-shell gold-core particles optimized for specific applications. Since both nanoparticles and silver dissolved from the particles may impact the biological response, it is important to understand the physicochemical characteristics along with the biological impact of nanoparticles produced by different processes. The authors have examined the structure, dissolution, and impact of particle exposure to macrophage cells of two 20 nm silver particles synthesized in different ways, which have different internal structures. The structures were examined by electron microscopy and dissolution measured in Rosewell Park Memorial Institute media with 10% fetal bovine serum. Cytotoxicity and oxidative stress were used to measure biological impact on RAW 264.7 macrophage cells. The particles were polycrystalline, but 20 nm particles grown on gold seed particles had smaller crystallite size with many high-energy grain boundaries and defects, and an apparent higher solubility than 20 nm pure silver particles. Greater oxidative stress and cytotoxicity were observed for 20 nm particles containing the Au core than for 20 nm pure silver particles. A simple dissolution model described the time variation of particle size and dissolved silver for particle loadings larger than 9 μg/ml for the 24-h period characteristic of many in-vitro studies.

Journal article

Theodorou IG, Botelho D, Schwander S, Zhang J, Chung KF, Tetley TD, Shaffer MSP, Gow A, Ryan MP, Porter AEet al., 2015, Static and Dynamic Microscopy of the Chemical Stability and Aggregation State of Silver Nanowires in Components of Murine Pulmonary Surfactant, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 49, Pages: 8048-8056, ISSN: 0013-936X

Journal article

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