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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231 results found

Gomez-Gonzalez MA, Koronfel MA, Pullin H, Parker JE, Quinn PD, Inverno MD, Scott TB, Xie F, Voulvoulis N, Yallop ML, Ryan MP, Porter AEet al., 2021, Nanoscale chemical imaging of nanoparticles under real-world wastewater treatment conditions, Advanced Sustainable Systems, ISSN: 2366-7486

Understanding nanomaterial transformations within wastewater treatment plants is an important step to better predict their potential impact on the environment. Here, spatially resolved, in situ nano-X-ray fluorescence microscopy is applied to directly observe nanometer-scale dissolution, morphological, and chemical evolution of individual and aggregated ZnO nanorods in complex “real-world” conditions: influent water and primary sludge collected from a municipal wastewater system. A complete transformation of isolated ZnO nanorods into ZnS occurs after only 1 hour in influent water, but larger aggregates of the ZnO nanorods transform only partially, with small contributions of ZnS and Zn-phosphate (Zn3(PO4)2) species, after 3 hours. Transformation of aggregates of the ZnO nanorods toward mixed ZnS, Zn adsorbed to Fe-oxyhydroxides, and a large contribution of Zn3(PO4)2 phases are observed during their incubation in primary sludge for 3 hours. Discrete, isolated ZnO regions are imaged with unprecedented spatial resolution, revealing their incipient transformation toward Zn3(PO4)2. Passivation by transformation(s) into mixtures of less soluble phases may influence the subsequent bioreactivity of these nanomaterials. This work emphasizes the importance of imaging the nanoscale chemistry of mixtures of nanoparticles in highly complex, heterogeneous semi-solid matrices for improved prediction of their impacts on treatment processes, and potential environmental toxicity following release.

Journal article

Yadegari H, Koronfel MA, Wang K, Thornton DB, Stephens IEL, Molteni C, Haynes PD, Ryan MPet al., 2021, Operando measurement of layer breathing modes in lithiated graphite, ACS Energy Letters, Vol: 6, Pages: 1633-1638, ISSN: 2380-8195

Despite their ubiquitous usage and increasing societal dependence on Li-ion batteries, there remains a lack of detailed empirical evidence of Li intercalation/deintercalation into graphite even though this process dictates the performance, longevity, and safety of the system. Here, we report direct detection and dissociation of specific crystallographic phases in the lithiated graphite, which form through a stepwise staging process. Using operando measurements, LiC18, LiC12, and LiC6 phases are observed via distinct low-frequency Raman features, which are the result of displacement of the graphite lattice by induced local strain. Density functional theory calculations confirm the nature of the Raman-active vibrational modes, to the layer breathing modes (LBMs) of the lithiated graphite. The new findings indicate graphene-like characteristics in the lithiated graphite under the deep charged condition due to the imposed strain by the inserted Li. Moreover, our approach also provides a simple experimental tool to measure induced strain in the graphite structure under full intercalation conditions.

Journal article

Alzahabi KH, Usmani O, Georgiou TK, Ryan MP, Robertson BD, Tetley TD, Porter AEet al., 2020, Approaches to treating tuberculosis by encapsulating metal ions and anti-mycobacterial drugs utilizing nano- and microparticle technologies, Emerging Topics in Life Sciences, Vol: 4, Pages: 581-600, ISSN: 2397-8554

Tuberculosis (TB) is caused by a bacterial infection that affects a number of human organs, primarily the lungs, but also the liver, spleen, and spine, causing key symptoms of fever, fatigue, and persistent cough, and if not treated properly, can be fatal. Every year, 10 million individuals become ill with active TB resulting with a mortality approximating 1.5 million. Current treatment guidelines recommend oral administration of a combination of first-line anti-TB drugs for at least 6 months. While efficacious under optimum conditions, ‘Directly Observed Therapy Short-course’ (DOTS) is not without problems. The long treatment time and poor pharmacokinetics, alongside drug side effects lead to poor patient compliance and has accelerated the emergence of multi-drug resistant (MDR) organisms. All this, combined with the limited number of newly discovered TB drugs to treat MDR-TB and shorten standard therapy time, has highlighted the need for new targeted drug delivery systems. In this respect, there has been recent focus on micro- and nano-particle technologies to prepare organic or/and metal particles loaded with TB drugs to enhance their efficacy by targeted delivery via the inhaled route. In this review, we provide a brief overview of the current epidemiology of TB, and risk factors for progression of latent stage tuberculosis (LTBI) to the active TB. We identify current TB treatment regimens, newly discovered TB drugs, and identify studies that have used micro- or nano-particles technologies to design a reliable inhalation drug delivery system to treat TB more effectively.

Journal article

Michaeloudes C, Seiffert J, Chen S, Ruenraroengsak P, Bey L, Theodorou IG, Ryan M, Cui X, Zhang J, Shaffer M, Tetley T, Porter AE, Chung KFet al., 2020, Effect of silver nanospheres and nanowires on human airway smooth muscle cells: role of sulfidation, Nanoscale Advances, Vol: 2, Pages: 5635-5647, ISSN: 2516-0230

Background: The toxicity of inhaled silver nanoparticles on contractile and pro-inflammatory airway smooth muscle cells (ASMCs) that control airway calibre is unknown. We explored the oxidative activities and sulfidation processes of the toxic-inflammatory response. Method: Silver nanospheres (AgNSs) of 20 nm and 50 nm diameter and silver nanowires (AgNWs), short S-AgNWs, 1.5 μm and long L-AgNWs, 10 μm, both 72 nm in diameter were manufactured. We measured their effects on cell proliferation, mitochondrial reactive oxygen species (ROS) release and membrane potential, and also performed electron microscopic studies. Main results and findings: The greatest effects were observed for the smallest particles with the highest specific surface area and greatest solubility that were avidly internalised. ASMCs exposed to 20 nm AgNSs (25 μg mL−1) for 72 hours exhibited a significant decrease in DNA incorporation (−72.4%; p < 0.05), whereas neither the 50 nm AgNSs nor the s-AgNWs altered DNA synthesis or viability. There was a small reduction in ASMC proliferation for the smaller AgNS, although Ag+ at 25 μL mL−1 reduced DNA synthesis by 93.3% (p < 0.001). Mitochondrial potential was reduced by both Ag+ (25 μg mL−1) by 47.1% and 20 nm Ag NSs (25 μg mL−1) by 40.1% (*both at p < 0.05), but was not affected by 50 nm AgNSs and the AgNWs. None of the samples showed a change in ROS toxicity. However, malondialdehyde release, associated with greater total ROS, was observed for all AgNPs, to an extent following the geometric size (20 nm AgNS: 213%, p < 0.01; 50 nm AgNS: 179.5%, p < 0.01 and L-AgNWs by 156.2%, p < 0.05). The antioxidant, N-acetylcysteine, prevented the reduction in mitochondrial potential caused by 20 nm AgNSs. The smaller nanostructures were internalised and dissolved within the ASMCs with the formation of non-reactive silver sulphide (Ag2S) on their surface, but with very little uptake of L-AgNWs. When A

Journal article

Chen S, Greasley SL, Ong ZY, Naruphontjirakul P, Page SJ, Hanna J, Redpath AN, Tsigkou O, Rankin S, Ryan MP, Porter AE, Jones JRet al., 2020, Biodegradable zinc-containing mesoporous silica nanoparticles for cancer therapy, Materials Today, Vol: 6, Pages: 1-11, ISSN: 1369-7021

Triple-negative breast cancers are extremely aggressive with limited treatment options because of the reduced response of the cancerous cells to hormonal therapy. Here, monodispersed zinc-containing mesoporous silica nanoparticles (MSNPs-Zn) were produced as a tuneable biodegradable platform for delivery of therapeutic zinc ions into cells. We demonstrate that the nanoparticles were internalized by cells, and a therapeutic dose window was identified in which the MSNPs-Zn were toxic to breast cancer cells but not to healthy epithelial (MCF-10a) cells or to murine macrophages. A significant reduction in the viability of triple negative MDA-MB-231 and MCF-7 (ER+) breast cancer cells was seen following 24 h exposure to MSNPs-Zn. The more aggressive MDA-MB-231 cells, with higher metastatic potential, were more sensitive to MSNPs-Zn than the MCF-7 cells. MSNPs-Zn underwent biodegradation inside the cells, becoming hollow structures, as imaged by high-resolution transmission electron microscopy. The mesoporous silica nanoparticles provide a biodegradable vehicle for therapeutic ion release inside cells.

Journal article

Antonio EN, Wicking C, Filip S, Ryan MP, Heutz Set al., 2020, Role of iron speciation in oxidation and deposition at the hexadecane-iron interface, ACS Applied Materials and Interfaces, Vol: 12, Pages: 19140-19152, ISSN: 1944-8244

Interactions between iron surfaces and hydrocarbons are the basis for a wide range of materials synthesis processes and novel applications, including sensing. However, in diesel engines these interactions can lead to deposit formation that reduces performance, lowers efficiency, and increases emissions. Here, we present a global study to understand deposition at iron-hexadecane interfaces. We use a combination of spectroscopy, microscopy, and mass spectrometry to investigate surface reactions, bulk chemistry, and deposition processes. A dynamic equilibrium between the oxidation products, both at the surface and in solution, determines the deposition at the surface. Considering the solution and the surface in parallel, we find that the iron speciation affects the morphology, composition, and quantity of the deposit at the surface, as well as the oxidation of hexadecane. Fe(II) and Fe(III) both promote the decomposition of peroxides-intermediates in the oxidation of hexadecane-but through noncatalytic and catalytic mechanisms, respectively. In contrast, Fe(0) is proposed to initiate hexadecane autoxidation during its oxidation to Fe(III). We find that in all cases, the surfaces exclusively contain Fe(III) following heat treatment with hexadecane. Upon subsequent exposure at room temperature, Fe(III) species are found to promote oxidation; this finding is particularly concerning for hybrid vehicles where longer time periods are expected between engine operation. Our work provides a foundation for the development of strategies that disrupt the role of iron in the degradation of hexadecane to ultimately reduce oxidation and deposition in diesel engines.

Journal article

Hadden JHL, Ryan MP, Riley DJ, 2020, Is nickel hydroxide charging only skin-deep?, ACS Applied Energy Materials, Vol: 3, Pages: 2803-2810, ISSN: 2574-0962

The depth of charging in Ni(OH)2-coated electrodes treated with paraffin wax to remove porosity has been investigated using time-of-flight secondary-ion mass spectrometry after charging and discharging in deuterated solvent at pH 14. The proportion of deuterium uptake was found to be dependent on the number of charge/discharge cycles, showing that the measured deuterium signal was indeed dependent on the electrochemical redox activity of the sample. Sputter craters were characterized using atomic force microscopy to find the sputter rate. This then allowed the maximum depth of charging to be found to be approximately 20 nm. This confirmed a surface “skin” in which charging occurs with the rest of the bulk inactive.

Journal article

Rodrigues RL, Xie F, Porter AE, Ryan MPet al., 2020, Geometry-induced protein reorientation on the spikes of plasmonic gold nanostars, NANOSCALE ADVANCES, Vol: 2, Pages: 1144-1151, ISSN: 2516-0230

Journal article

Guo L, Lovell E, Tang Q, Boldrin DC, Tang CC, Day SJ, Cohen LF, Ryan MPet al., 2020, Fine control of Curie temperature of magnetocaloric alloys La(Fe,Co,Si)(13) using electrolytic hydriding, Scripta Materialia, Vol: 175, Pages: 33-37, ISSN: 1359-6462

This work demonstrates precision control of hydrogen content in La(Fe,Co,Si)13Hδ for the development of environmentally friendly magnetocaloric-based cooling technologies, using an electrolytic hydriding technique. We show the Curie temperature, a critical parameter which directly governs the temperature window of effective cooling, can be varied easily and reproducibly in 1 K steps within the range 274 K to 402 K. Importantly, both partially (up to 10%) and fully hydrided compositions retain favorable entropy change values comparable to that of the base composition. Crucially, we show in these second-order phase transition compounds, partial hydriding is stable and not susceptible against phase separation.

Journal article

Parra-Puerto A, Ng KL, Fahy K, Goode AE, Ryan MP, Kucernak Aet al., 2019, Supported transition metal phosphides: Activity survey for HER, ORR, OER and corrosion resistance in acid and alkaline electrolytes, ACS Catalysis, Vol: 9, Pages: 11515-11529, ISSN: 2155-5435

Carbon supported MxPy (M = Ni, Co, W, Cr and Mo) were prepared via pyrolysis using a very simple and scalable method utilizing non-toxic metal and phosphorous precursors. The electrochemical hydrogen evolution (HER), oxygen reduction (ORR), and oxygen evolution (OER) reactions and corrosion resistance under both acid and alkaline conditions were examined for all these catalysts and compared to the benchmark catalysts Pt/C (HER/ORR) and IrO2(OER). The highest activities were found in alkaline solutions for Co2P for HER and ORR and Ni2P for OER. Good activity for these was also found in acid for some of these reactions, although the catalysts suffered from susceptibility to corrosion. Co2P was further studied in an alkaline environment as it shows high catalytic activity towards the oxygen reduction reaction (ORR) without significant hysteresis. The onset potential (at 0.5 mA cm-2) obtained was 0.8 V and a Tafel slope value of 38 mV dec-1 with a maximum kinetic mass activity of 2870 A gCo-1 at 0.7 V (RHE). Utilising high resolution transmission electron microscopy (HRTEM) it is possible to observe high-surface area needle-like single crystal cobalt oxide structures on the surfaces of the Co2P particles at the beginning of the ORR. Hence the high rates of initial corrosion of the Co2P identified appear to be associated with the dissolution and precipitation of Cobalt oxide on the particle surface. The as-synthesised Co2P/C also shows good performance in an 8-hour stability test for the Oxygen Evolution Reaction (OER), carried out at 1.6 V vs. RHE in alkaline conditions, with negligible drop in current density over time. Interestingly, in an acidic environment the catalyst is very active towards 2-electron- oxygen reduction leading to H2O2 with high selectivity (85%). It is intriguing that the pH dependence on this catalyst towards the ORR is similar to that seen for gold.

Journal article

Scatigno GG, Dong P, Ryan MP, Wenman MRet al., 2019, The effect of salt loading on chloride-induced stress corrosion cracking of 304L austenitic stainless steel under atmospheric conditions, Materialia, Vol: 8, Pages: 1-11, ISSN: 2589-1529

The effect of salt loading on chloride-induced stress corrosion cracking in 304 L was studied at atmospheric pressure. Stress relieved samples were uniaxially pre-strained to 5% and were loaded with nine levels of MgCl2, investigating Cl− deposition levels from 1.7 × 10−4 to 3.1 x 10−2 g cm−2. Samples were subject to 60 MPa stress, 90 °C at 70% relative humidity, for 480 h. A direct correlation between chloride deposition and the density of cracking and corrosion was observed between 5.7 × 10−4 and 1.96 × 10−2 g cm−2. Crack propagation rates were constant between salt loadings of 5.7 × 10−4 and 2.4 × 10−2 g cm−2 at 1–2 µm h−1.

Journal article

Gomez-Gonzalez MA, Koronfel MA, Goode AE, Al-Ejji M, Voulvoulis N, Parker JE, Quinn PD, Scott TB, Xie F, Yallop ML, Porter AE, Ryan MPet al., 2019, Spatially resolved dissolution and speciation changes of ZnO nanorods during short-term in situ incubation in a simulated wastewater environment, ACS Nano, Vol: 13, Pages: 11049-11061, ISSN: 1936-0851

Zinc oxide engineered nanomaterials (ZnO ENMs) are used in a variety of applications worldwide due to their optoelectronic and antibacterial properties with potential contaminant risk to the environment following their disposal. One of the main potential pathways for ZnO nanomaterials to reach the environment is via urban wastewater treatment plants. So far there is no technique that can provide spatiotemporal nanoscale information about the rates and mechanisms by which the individual nanoparticles transform. Fundamental knowledge of how the surface chemistry of individual particles change, and the heterogeneity of transformations within the system, will reveal the critical physicochemical properties determining environmental damage and deactivation. We applied a methodology based on spatially resolved in situ X-ray fluorescence microscopy (XFM), allowing observation of real-time dissolution and morphological and chemical evolution of synthetic template-grown ZnO nanorods (∼725 nm length, ∼140 nm diameter). Core-shell ZnO-ZnS nanostructures were formed rapidly within 1 h, and significant amounts of ZnS species were generated, with a corresponding depletion of ZnO after 3 h. Diffuse nanoparticles of ZnS, Zn3(PO4)2, and Zn adsorbed to Fe-oxyhydroxides were also imaged in some nonsterically impeded regions after 3 h. The formation of diffuse nanoparticles was affected by ongoing ZnO dissolution (quantified by inductively coupled plasma mass spectrometry) and the humic acid content in the simulated sludge. Complementary ex situ X-ray absorption spectroscopy and scanning electron microscopy confirmed a significant decrease in the ZnO contribution over time. Application of time-resolved XFM enables predictions about the rates at which ZnO nanomaterials transform during their first stages of the wastewater treatment process.

Journal article

Gu Y, Li J, Wang L, Xie M, Wu X, Xie F, Ryan MPet al., 2019, Template-Free Cu Electrodeposition to Prepare Cu-Micro-Brush Electrodes for Electrochemical CO2 Reduction, CHEMISTRYSELECT, Vol: 4, Pages: 10995-11001, ISSN: 2365-6549

Journal article

Leo BF, Fearn S, Gonzalez-Carter D, Theodorou I, Ruenraroengsak P, Goode A, Mcphail D, Dexter DT, Shaffer MSP, Chung KF, Porter AE, Ryan MPet al., 2019, Label-free TOF-SIMS imaging of sulfur producing enzymes inside microglia cells following exposure to silver nanowires, Analytical Chemistry, Vol: 91, Pages: 11098-11107, ISSN: 0003-2700

There are no methods sensitive enough to detect enzymes within cells, without the use of analyte labelling. Here we show that it is possible to detect protein ion signals of three different H2S-synthesizing enzymes inside microglia after pre-treatment with silver nanowires (AgNW) using time of flight-secondary ion mass spectrometry (TOF-SIMS). Protein fragment ions, including the fragment of amino acid (C4H8N+ - 70 amu), fragments of the sulfur producing cystathionine-containing enzymes and the Ag+ ion signal could be detected without the use of any labels; the cells were mapped using the C4H8N+ amino acid fragment. Scanning electron microscopy imaging and energy dispersive x-ray chemical analysis showed that the AgNWs were inside the same cells imaged by TOF-SIMS and transformed chemically into crystalline Ag2S within cells in which the sulfur producing proteins were detected. The presence of these sulfur producing cystathionine-containing enzymes within the cells was confirmed by Western Blots and confocal microscopy images of fluorescently labelled antibodies against the sulfur producing enzymes. Label-free ToF-SIMS is very promising for the label-free identification of H2S-contributing enzymes and their cellular localization in biological systems. The technique could in future be used to identify which of these enzymes are most contributory.

Journal article

Ruenraroengsak P, Kiryushko D, Theodorou IG, Klosowski MM, Taylor ER, Niriella T, Palmieri C, Yagüe E, Ryan MP, Coombes RC, Xie F, Porter AEet al., 2019, Frizzled-7-targeted delivery of zinc oxide nanoparticles to drug-resistant breast cancer cells, Nanoscale, Vol: 11, Pages: 12858-12870, ISSN: 2040-3364

There is a need for novel strategies to treat aggressive breast cancer subtypes and overcome drug resistance. ZnO nanoparticles (NPs) have potential in cancer therapy due to their ability to potently and selectively induce cancer cell apoptosis. Here, we tested the in vitro chemotherapeutic efficacy of ZnONPs loaded via a mesoporous silica nanolayer (MSN) towards drug-sensitive breast cancer cells (MCF-7: estrogen receptor-positive, CAL51: triple-negative) and their drug-resistant counterparts (MCF-7TX, CALDOX). ZnO-MSNs were coated on to gold nanostars (AuNSs) for future imaging capabilities in the NIR-II range. Electron and confocal microscopy showed that MSN-ZnO-AuNSs accumulated close to the plasma membrane and were internalized by cells. High-resolution electron microscopy showed that MSN coating degraded outside the cells, releasing ZnONPs that interacted with cell membranes. MSN-ZnO-AuNSs efficiently reduced the viability of all cell lines, and CAL51/CALDOX cells were more susceptible than MCF7/MCF-7-TX cells. MSN-ZnO-AuNSs were then conjugated with the antibody to Frizzled-7 (FZD-7), the receptor upregulated by several breast cancer cells. We used the disulphide (S-S) linker that could be cleaved with a high concentration of glutathione normally observed within cancer cells, releasing Zn2+ into the cytoplasm. FZD-7 targeting resulted in approximately three-fold amplified toxicity of MSN-ZnO-AuNSs towards the MCF-7TX drug-resistant cell line with the highest FZD-7 expression. This study shows that ZnO-MSs are promising tools to treat triple-negative and drug-resistant breast cancers and highlights the potential clinical utility of FZD-7 for delivery of nanomedicines and imaging probes specifically to these cancer types.

Journal article

Pang JS, Theodorou IG, Centeno A, Petrov PK, Alford NM, Ryan MP, Xie Fet al., 2019, Tunable three-dimensional plasmonic arrays for large near-infrared fluorescence enhancement, ACS Applied Materials and Interfaces, Vol: 11, Pages: 23083-23092, ISSN: 1944-8244

Metal-enhanced fluorescence (MEF), resulting from the near-field interaction of fluorophores with metallic nanostructures, has emerged as a powerful tool for dramatically improving the performance of fluorescence-based biomedical applications. Allowing for lower autofluorescence and minimal photoinduced damage, the development of multifunctional and multiplexed MEF platforms in the near-infrared (NIR) windows is particularly desirable. Here, a low-cost fabrication method based on nanosphere lithography is applied to produce tunable three-dimensional (3D) gold (Au) nanohole–disc arrays (Au-NHDAs). The arrays consist of nanoscale glass pillars atop nanoholes in a Au thin film: the top surfaces of the pillars are Au-covered (effectively nanodiscs), and small Au nanoparticles (nanodots) are located on the sidewalls of the pillars. This 3D hole–disc (and possibly nanodot) construct is critical to the properties of the device. The versatility of our approach is illustrated through the production of uniform and highly reproducible Au-NHDAs with controlled structural properties and tunable optical features in the NIR windows. Au-NHDAs allow for a very large NIR fluorescence enhancement (more than 400 times), which is attributed to the 3D plasmonic structure of the arrays that allows strong surface plasmon polariton and localized surface plasmon resonance coupling through glass nanogaps. By considering arrays with the same resonance peak and the same nanodisc separation distance, we show that the enhancement factor varies with nanodisc diameter. Using computational electromagnetic modeling, the electric field enhancement at 790 nm was calculated to provide insights into excitation enhancement, which occurs due to an increase in the intensity of the electric field. Fluorescence lifetime measurements indicate that the total fluorescence enhancement may depend on controlling excitation enhancement and therefore the array morphology. Our findings provide important in

Journal article

Sk MH, Qi J, Al-Qahtani N, Abdullah AM, Laycock N, Ryan MP, Williams DEet al., 2019, Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel (vol 166, C3233, 2019), JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: X3-X3, ISSN: 0013-4651

Journal article

Sk MH, Qi J, Abdullah AM, Laycock N, Ryan MP, Williams DEet al., 2019, Effect of Trace H2S on the Scale Formation Behavior in a Predominant CO2 Environment under Hydrodynamic Control: Role of Cr/Mo Micro-Alloying in Plain Carbon Steel, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: C3233-C3240, ISSN: 0013-4651

Journal article

Koronfel MA, Goode AE, Gomez-Gonzalez MA, Nelson Weker J, Simões TA, Brydson R, Quinn P, Toney MF, Hart A, Porter AE, Ryan MPet al., 2019, Chemical Evolution of CoCrMo Wear Particles: an In-Situ Characterisation Study, The Journal of Physical Chemistry C, ISSN: 1932-7447

Journal article

Hadden JHL, Ryan MP, Riley DJ, 2019, Examining the charging behaviour of nickel hydroxide nanomaterials, Electrochemistry Communications, Vol: 101, Pages: 47-51, ISSN: 1388-2481

To investigate the depth of charging at the material surface, batches of nickel hydroxide nanoparticles were hydrothermally synthesised in the range 3–450 nm. Any surfactant added was removed post synthesis using ozone. The capacity per gram (Cs) increased and the capacity per unit area (CA) was constant with decreasing particle size down to 20 nm. Further reduction in particle size resulted in a decrease in both CS and CA, suggesting the Ni(OH)2 is charged to a depth in the order of 10 nm at the charging rate studied. The results obtained have implications in the design of Ni(OH)2 electrodes in charge storage applications.

Journal article

Guo L, Lovell E, Wilson N, Burdett P, Cohen LF, Ryan MPet al., 2019, The electrochemical behaviour of magnetocaloric alloys La(Fe,Mn,Si)13Hx under magnetic field conditions, Chemical Communications, Vol: 55, Pages: 3642-3645, ISSN: 1359-7345

The degradation mechanism of La(Fe,Mn,Si)13Hx has been examined under conditions representative of the complex operating parameters of a refrigeration cycle. The magnetic field effects are found to be dominated by magneto-transport and are most significant when the material is in its paramagnetic state - resulting in significantly accelerated corrosion rates.

Journal article

Theodorou I, Ruenraroengsak P, Carter D, Jiang Q, Yague E, Aboagye E, Coombes RC, Porter AE, Ryan M, Xie Fet al., 2019, Towards multiplexed near-infrared cellular imaging using gold nanostar arrays with tunable fluorescence enhancement, Nanoscale, Vol: 11, Pages: 2079-2088, ISSN: 2040-3364

Sensitive detection of disease biomarkers expressed by human cells is critical to the development of novel diagnostic and therapeutic methods. Here we report that plasmonic arrays based on gold nanostar (AuNS) monolayers enable up to 19-fold fluorescence enhancement for cellular imaging in the near-infrared (NIR) biological window, allowing the application of low quantum yield fluorophores for sensitive cellular imaging. The high fluorescence enhancement together with low autofluorescence interference in this wavelength range enable higher signal-to-noise ratio compared to other diagnostic modalities. Using AuNSs of different geometries and therefore controllable electric field enhancement, cellular imaging with tunable enhancement factors is achieved, which may be useful for the development of multicolour and multiplexed platforms for a panel of biomarkers, allowing to distinguish different subcell populations at the single cell level. Finally, the uptake of AuNSs within HeLa cells and their high biocompatibility, pave the way for novel high-performance in vitro and in vivo diagnostic platforms.

Journal article

Theodorou I, Jiang Q, Malms L, Xie X, Coombes RC, Aboagye E, Porter AE, Ryan M, Xie Fet al., 2018, Fluorescence enhancement from single gold nanostars: towards ultra-bright emission in the first and second near-infrared biological windows, Nanoscale, Vol: 10, Pages: 15854-15864, ISSN: 2040-3364

Gold nanostars (AuNSs) are promising agents for the development of high-performance diagnostic devices, by enabling metal enhanced fluorescence (MEF) in the physiological near-infrared (NIR) and second near-infrared (NIR-II) windows. The local electric field near their sharp tips and between their branches can be enhanced by several orders of magnitude, holding great promise for large fluorescence enhancements from single AuNS particles, rather than relying on interparticle coupling in nanoparticle substrates. Here, guided by electric field simulations, two different types of AuNSs with controlled morphologies and plasmonic responses in the NIR and NIR-II regions are used to investigate the mechanism of MEF from colloidal AuNSs. Fluorophore conjugation to AuNSs allows significant fluorescence enhancement of up to 30 times in the NIR window, and up to 4-fold enhancement in the NIR-II region. Together with other inherent advantages of AuNSs, including their multispike morphology offering easy access to cell membranes and their large surface area providing flexible multifunctionality, AuNS are promising for the development of in vivo imaging applications. Using time-resolved fluorescence measurements to deconvolute semi-quantitatively excitation enhancement from emission enhancement, we show that a combination of enhanced excitation and an increased radiative decay rate, both contribute to the observed large enhancement. In accordance to our electric field modelling, however, excitation enhancement is the component that varies most with particle morphology. These findings provide important insights into the mechanism of MEF from AuNSs, and can be used to further guide particle design for high contrast enhancement, enabling the development of MEF biodetection technologies.

Journal article

Qin H, Wu D, Sathian J, Xie X, Ryan M, Xie Fet al., 2018, Tuning the upconversion photoluminescence lifetimes of NaYF4:Yb3+, Er3+ through lanthanide Gd3+ doping, Scientific Reports, Vol: 8, ISSN: 2045-2322

The multiplexing capacity of conventional fluorescence materials are significantly limited by spectral overlap and background interference, mainly due to their short-lived fluorescence lifetimes. Here, we adopt a novel Gd3+ doping strategy in NaYF4 host materials, realized tuning of upconversion photoluminescence (UCPL) lifetimes at selective emissions. Time-correlated single-photon counting (TCSPC), was applied to measure the photoluminescence lifetimes accurately. We demonstrated the large dynamic range of lifetimes of upconversion nanoparticles with good upconversion quantum yields, mainly owing to the dominance of high efficient energy transfer upconversion mechanism. The exceptional tunable properties of upconversion materials allow great potential for them to be utilized in biotechnology and life sciences.

Journal article

Ellis T, Chiappi M, García-Trenco A, Al-Ejji M, Sarkar S, Georgiou TK, Shaffer MSP, Tetley TD, Schwander S, Ryan MP, Porter AEet al., 2018, Multimetallic microparticles increase the potency of rifampicin against intracellular Mycobacterium tuberculosis, ACS Nano, Vol: 12, Pages: 5228-5240, ISSN: 1936-0851

Mycobacterium tuberculosis ( M.tb) has the extraordinary ability to adapt to the administration of antibiotics through the development of resistance mechanisms. By rapidly exporting drugs from within the cytosol, these pathogenic bacteria diminish antibiotic potency and drive the presentation of drug-tolerant tuberculosis (TB). The membrane integrity of M.tb is pivotal in retaining these drug-resistant traits. Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) are established antimicrobial agents that effectively compromise membrane stability, giving rise to increased bacterial permeability to antibiotics. In this work, biodegradable multimetallic microparticles (MMPs), containing Ag NPs and ZnO NPs, were developed for use in pulmonary delivery of antituberculous drugs to the endosomal system of M.tb-infected macrophages. Efficient uptake of MMPs by M.tb-infected THP1 cells was demonstrated using an in vitro macrophage infection model, with direct interaction between MMPs and M.tb visualized with the use of electron FIB-SEM tomography. The release of Ag NPs and ZnO NPs within the macrophage endosomal system increased the potency of the model antibiotic rifampicin by as much as 76%, realized through an increase in membrane disorder of intracellular M.tb. MMPs were effective at independently driving membrane destruction of extracellular bacilli located at the exterior face of THP1 macrophages. This MMP system presents as an effective drug delivery vehicle that could be used for the transport of antituberculous drugs such as rifampicin to infected alveolar macrophages, while increasing drug potency. By increasing M.tb membrane permeability, such a system may prove effectual in improving treatment of drug-susceptible TB in addition to M.tb strains considered drug-resistant.

Journal article

Wang T, Centeno A, Darvill D, Pang J, Ryan MP, Xie Fet al., 2018, Tuneable fluorescence enhancement over nanostructured ZnO arrays with controlled morphology, Physical Chemistry Chemical Physics, Vol: 21, Pages: 14828-14834, ISSN: 1463-9076

Zinc oxide (ZnO) nanorods (NRs) have been demonstrated as a promising platform for enhanced fluorescence-based sensing. It is, however, desirable to achieve a tuneable fluorescence enhancement with these platforms so that the fluorescence output can be adjusted based on the real need. Here we show that the fluorescence enhancement can be tuned by changing the diameter of the ZnO nanorods, simply controlled by potassium chloride (KCl) concentration during synthesis, using arrays of previously developed aligned NRs (a.k.a. aligned NR forests) and nanoflowers (NFs). Combining the experimental results obtained from ZnO nanostructures with controlled morphology and computer-aided verification, we show that the fluorescence enhancement factor increases when ZnO NRs become thicker. The fluorescence enhancement factor of NF arrays is shown to have a much stronger dependency on the rod diameter than that of aligned NR arrays. We prove that the morphology of nanostructures, which can be controlled, can be an important factor for fluorescence enhancement. Our (i) effort towards understanding the structure–property relationships of ZnO nanostructured arrays and (ii) demonstration on tuneable fluorescence enhancement by nanostructure engineering can provide some guidance towards the rational design of future fluorescence amplification platforms potentially for bio-sensing.

Journal article

Sk MH, Abdullah AM, Qi J, Ko M, Ingham B, Laycock N, Ryan MP, Williams DEet al., 2018, The effects of Cr/Mo micro-alloying on the corrosion behavior of carbon steel in CO2-saturated (sweet) brine under hydrodynamic control, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 165, Pages: C278-C288, ISSN: 0013-4651

The effects of micro-alloying of plain carbon steel with Cr and Mo on the corrosion behavior in CO2-saturated (sweet) brine (0.5 MNaCl, pH 6.6) environment, under hydrodynamic conditions, at 80◦C were investigated. Crystalline siderite/chukanovite scalesformed on all the alloys. Analysis of potentiostatic current transient data suggest that there exists a synergistic interaction betweenCr and Mo, which induces more rapid crystallization of the scale compared to Mo-free steels. Increasing the Mo content alsosuppressed the transport-dependent dissolution current passing through the initially-present amorphous surface film. TEM imagesof the FIB-sectioned corrosion scales confirm that the corrosion scale formed on 1Cr0.7Mo is comparatively thinner and yet offersgreater protectiveness when compared to the plain carbon steel.

Journal article

Botelho D, Leo BF, Massa C, Sarkar S, Tetley T, Chung KF, Chen S, Ryan MP, Porter A, Atochina-Vasserman EN, Zhang J, Schwander S, Gow AJet al., 2018, Exposure to silver nanospheres leads to altered respiratory mechanics and delayed immune response in an in vivo Murine model, Frontiers in Pharmacology, Vol: 9, ISSN: 1663-9812

Here we examine the organ level toxicology of both carbon black (CB) and silver nanoparticles (AgNP). We aim to determine metal-specific effects to respiratory function, inflammation and potential interactions with lung lining fluid (LLF). C57Bl6/J male mice were intratracheally instilled with saline (control), low (0.05 μg/g) or high (0.5 μg/g) doses of either AgNP or CB 15 nm nanospheres. Lung histology, cytology, surfactant composition and function, inflammatory gene expression, and pulmonary function were measured at 1, 3, and 7 days post-exposure. Acutely, high dose CB resulted in an inflammatory response, increased neutrophilia and cytokine production, without alteration in surfactant composition or respiratory mechanics. Low dose CB had no effect. Neither low nor high dose AgNPs resulted in an acute inflammatory response, but there was an increase in work of breathing. Three days post-exposure with CB, a persistent neutrophilia was noted. High dose AgNP resulted in an elevated number of macrophages and invasion of lymphocytes. Additionally, AgNP treated mice displayed increased expression of IL1B, IL6, CCL2, and IL10. However, there were no significant changes in respiratory mechanics. At day 7, inflammation had resolved in AgNP-treated mice, but tissue stiffness and resistance were significantly decreased, which was accompanied by an increase in surfactant protein D (SP-D) content. These data demonstrate that the presence of metal alters the response of the lung to nanoparticle exposure. AgNP-surfactant interactions may alter respiratory function and result in a delayed immune response, potentially due to modified airway epithelial cell function.

Journal article

Koronfel MA, Goode AE, Weker JN, Tay SER, Stitt CA, Simoes TA, Mosselmans JFW, Quinn P, Brydson R, Hart A, Toney MF, Porter AE, Ryan MPet al., 2018, Understanding the reactivity of CoCrMo-implant wear particles, npj Materials Degradation, Vol: 2, ISSN: 2397-2106

CoCrMo-based metal-on-metal hip implants experienced unexpectedly high failure rates despite the high wear and corrosion resistance of the bulk material. Although they exhibit a lower volumetric wear compared to other implant materials, CoCrMo-based implants produced a significantly larger 'number' of smaller wear particles. CoCrMo is nominally an extremely stable material with high Cr content providing passivity. However, despite the Co:Cr ratio in the original alloy being 2:1; chemical analyses of wear particles from periprosthetic tissue have found the particles to be composed predominately of Cr species, with only trace amounts of Co remaining. Here a correlative spectroscopy and microscopy approach has shown that these particles dissolve via a non-stoichiometric, and geometrically inhomogeneous, mechanism similar to de-alloying. This mechanism is previously unreported for this material and was not apparent in any of the regulatory required tests, suggesting that such tests are insufficiently discriminating.

Journal article

Zhang Y, Cao M, Lv H, Wei J, Gu Y, Liu D, Zhang W, Ryan MP, Wu Xet al., 2018, Electrodeposited nanometer-size IrO2/Ti electrodes with 0.3 mg IrO2 cm(-2) for sludge dewatering electrolysers, ELECTROCHIMICA ACTA, Vol: 265, Pages: 507-513, ISSN: 0013-4686

Journal article

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