Publications by authors named "Marc Walker"

63 Publications

Introducing affinity and selectivity into galectin-targeting nanoparticles with fluorinated glycan ligands.

Chem Sci 2020 Nov 16;12(3):905-910. Epub 2020 Nov 16.

Department of Chemistry, University of Warwick CV4 7AL UK

Galectins are potential biomarkers and therapeutic targets. However, galectins display broad affinity towards β-galactosides meaning glycan-based (nano)biosensors lack the required selectivity and affinity. Using a polymer-stabilized nanoparticle biosensing platform, we herein demonstrate that the specificity of immobilised lacto--biose towards galectins can be 'turned on/off' by using site-specific glycan fluorination and in some cases reversal of specificity can be achieved. The panel of fluoro-glycans were obtained by a chemoenzymatic approach, exploiting BiGalK and BiGalHexNAcP enzymes from which are shown to tolerate fluorinated glycans, introducing structural diversity which would be very laborious by chemical methods alone. These results demonstrate that integrating non-natural, fluorinated glycans into nanomaterials can encode unprecedented selectivity with potential applications in biosensing.
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http://dx.doi.org/10.1039/d0sc05360kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179109PMC
November 2020

Rapidly self-deoxygenating controlled radical polymerization in water disproportionation of Cu(i).

Chem Sci 2020 May 5;11(20):5257-5266. Epub 2020 May 5.

University of Warwick, Department of Chemistry Library Road Coventry CV4 7AL UK

Rapidly Cu-RDRP in aqueous media is investigated. The disproportionation of Cu(i)/MeTren in water towards Cu(ii) and highly reactive Cu(0) leads to O-free reaction environments within the first seconds of the reaction, even when the reaction takes place in the open-air. By leveraging this significantly fast O-reducing activity of the disproportionation reaction, a range of well-defined water-soluble polymers with narrow dispersity are attained in a few minutes or less. This methodology provides the ability to prepare block copolymers sequential monomer addition with little evidence for chain termination over the lifetime of the polymerization and allows for the synthesis of star-shaped polymers with the use of multi-functional initiators. The mechanism of is elucidated with the use of various characterization tools, and the species that participate in the rapid oxygen consumption is identified and discussed in detail.
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http://dx.doi.org/10.1039/d0sc01512aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159280PMC
May 2020

The polymeric glyco-linker controls the signal outputs for plasmonic gold nanorod biosensors due to biocorona formation.

Nanoscale 2021 Jun;13(24):10837-10848

Health Unit, Flemish Institute for Technological Research (VITO), Boeretang 200, Mol, BE-2400, Belgium.

Gold nanorods (GNRs) are a promising platform for nanoplasmonic biosensing. The localised surface plasmon resonance (LSPR) peak of GNRs is located in the near-infrared optical window and is sensitive to local binding events, enabling label-free detection of biomarkers in complex biological fluids. A key challenge in the development of such sensors is achieving target affinity and selectivity, while both minimizing non-specific binding and maintaining colloidal stability. Herein, we reveal how GNRs decorated with galactosamine-terminated polymer ligands display significantly different binding responses in buffer compared to serum, due to biocorona formation, and how biocorona displacement due to lectin binding plays a key role in their optical responses. GNRs were coated with either poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) or poly(N-hydroxyethyl acrylamide) (PHEA) prepared via reversible addition-fragmentation chain-transfer (RAFT) polymerisation and end-functionalised with galactosamine (Gal) as the lectin-targeting unit. In buffer Gal-PHEA-coated GNRs aggregated upon soybean agglutinin (SBA) addition, whereas Gal-PHPMA-coated GNRs exhibited a red-shift of the LSPR spectrum without aggregation. In contrast, when incubated in serum Gal-PHPMA-coated nanorods showed no binding response, while Gal-PHEA GNRs exhibited a dose-dependent blue-shift of the LSPR peak, which is the opposite direction (red-shift) to what was observed in buffer. This differential behaviour was attributed to biocorona formation onto both polymer-coated GNRs, shown by differential centrifugal sedimentation and nanoparticle tracking analysis. Upon addition of SBA to the Gal-PHEA coated nanorods, signal was generated due to displacement of weakly-bound biocorona components by lectin binding. However, in the case of Gal-PHPMA which had a thicker corona, attributed to lower polymer grafting densities, addition of SBA did not lead to biocorona displacement and there was no signal output. These results show that plasmonic optical responses in complex biological media can be significantly affected by biocorona formation, and that biocorona formation itself does not prevent sensing so long as its exact nature (e.g. 'hard versus soft') is tuned.
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http://dx.doi.org/10.1039/d1nr01548fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8223873PMC
June 2021

Differential Pulley Release in Trigger Finger: A Prospective, Randomized Clinical Trial.

Hand (N Y) 2021 Mar 1:1558944721994231. Epub 2021 Mar 1.

Yale University, New Haven, CT, USA.

Background: The palmar aponeurosis or "A0 pulley" may play a role in trigger finger pathology. This study assesses the involvement of the A0 pulley in patients receiving trigger finger release.

Methods: This single-surgeon, prospective, randomized clinical trial was conducted among consenting patients with symptomatic trigger finger. Intraoperative coin toss was used to randomize initial release of either the A0 or A1 pulley. Following release, active flexion and extension of the affected digit were examined. The remaining pulley was then released in sequence, and clinical trigger status was recorded.

Results: Thirty fingers from 24 patients were released; 17 fingers received A0 release first, and 13 received A1 release. Following initial A0 release, 8 fingers (47%) demonstrated complete resolution of symptoms, 4 (24%) demonstrated improvement but incomplete resolution of triggering, and 5 (29.4%) demonstrated no improvement. Following initial A1 release, 6 fingers (46%) demonstrated complete resolution, 3 (23%) demonstrated improvement but incomplete resolution of triggering, and 4 (31%) demonstrated no improvement. All patients demonstrated complete resolution after surgical release of both sites. Neither initial A1 release nor initial A0 release was statistically associated with complete, incomplete, or failed symptom resolution.

Conclusions: These data implicate the A0 pulley as the primary cause of 31% to 47% of trigger fingers in our study. Although larger trials are needed to validate these results, our study suggests that release of both A0 and A1 pulleys may offer greater symptom resolution than release of the A1 pulley alone.
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http://dx.doi.org/10.1177/1558944721994231DOI Listing
March 2021

Tuning morphology, surface, and nanocrystallinity of rare earth vanadates by one-pot colloidal conversion of hydroxycarbonates.

Nanoscale 2021 Mar 25;13(9):4931-4945. Epub 2021 Feb 25.

Department of Inorganic Chemistry, Institute of Chemistry, University of Campinas (Unicamp), PO Box 6154, 13083-970 Campinas, SP, Brazil.

We show that particle size, morphology, nanocrystallinity, surface area, and defect density of (Y,Eu)VO structures can be tuned by one-pot colloidal conversion of rare earth hydroxycarbonates in water/ethylene glycol (EG) suspensions. Using small angle X-ray scattering, transmission electron microscopy and dynamic light scattering, we show how volume fractions of EG direct the amorphous to crystalline conversion at 1 atm/95 °C by controlling size and aggregation of hydroxycarbonate precursors. A template effect due to a Kirkendall-type conversion occurs for low EG contents, yielding solids with high densities of oxygen defects, as demonstrated by O uptakes in thermogravimetry and X-ray photoelectron spectroscopy profiles. Starting from small and aggregated hydroxycarbonates high-porosity (Y,Eu)VO nanoparticles were produced with expanded unit cells and short-range (<100 Å) crystalline ordering. We explored the effects of synthesis on the textural, microstructure, and defects of (Y,Eu)VO solids, which were further correlated to the spectroscopic profiles of Eu-activated samples. We show that the ratios between EuD internal quantum yields and particle diameters can be directly correlated to the particle surface areas, opening new perspectives for theoretical detailing of f-f luminescence in YVO solids, and enabling accurate tuning of structure and applicability of colloidal vanadate nanoparticles for sensing and catalysis applications.
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http://dx.doi.org/10.1039/d0nr07902bDOI Listing
March 2021

Cu(III)-bis-thiolato complex forms an unusual mono-thiolato Cu(III)-peroxido adduct.

Chem Commun (Camb) 2021 Jan;57(1):69-72

School of Engineering, University of Warwick, Gibbet Hill Road, Coventry CV4 7Al, UK.

The stable complex [bis(toluene-3,4-dithiolato)copper(iii)][NEt3H] has been synthesised and characterised as a square-planar Cu(iii) complex by X-ray photoelectron spectroscopy, cyclic voltammetry and DFT calculations. Intriguingly, when fragmented in FTICR-MS, an unusual [(toluene-3,4-dithiolate)Cu(iii)(peroxide)]- complex is formed by reaction with oxygen. Natural 1,2-dithiolenes known to bind molybdenum might stabilise Cu(iii) in vivo.
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http://dx.doi.org/10.1039/d0cc06921cDOI Listing
January 2021

Versailles Project on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray photoelectron spectroscopy instruments using low-density polyethylene.

J Vac Sci Technol A 2020 Dec 23;38(6):063208. Epub 2020 Nov 23.

Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 44-46, 12203 Berlin, Germany.

We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of ∼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are ∼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are ∼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration.
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http://dx.doi.org/10.1116/6.0000577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7688089PMC
December 2020

The SARS-COV-2 Spike Protein Binds Sialic Acids and Enables Rapid Detection in a Lateral Flow Point of Care Diagnostic Device.

ACS Cent Sci 2020 Nov 23;6(11):2046-2052. Epub 2020 Sep 23.

Department of Chemistry, University of Warwick, Coventry, CV4 7AL, U.K.

There is an urgent need to understand the behavior of the novel coronavirus (SARS-COV-2), which is the causative agent of COVID-19, and to develop point-of-care diagnostics. Here, a glyconanoparticle platform is used to discover that -acetyl neuraminic acid has affinity toward the SARS-COV-2 spike glycoprotein, demonstrating its glycan-binding function. Optimization of the particle size and coating enabled detection of the spike glycoprotein in lateral flow and showed selectivity over the SARS-COV-1 spike protein. Using a virus-like particle and a pseudotyped lentivirus model, paper-based lateral flow detection was demonstrated in under 30 min, showing the potential of this system as a low-cost detection platform.
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http://dx.doi.org/10.1021/acscentsci.0c00855DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7523238PMC
November 2020

Protecting Group Free Synthesis of Glyconanoparticles Using Amino-Oxy-Terminated Polymer Ligands.

Bioconjug Chem 2020 10 21;31(10):2392-2403. Epub 2020 Sep 21.

Glycomaterials display enhanced binding affinity to carbohydrate-binding proteins due to the nonlinear enhancement associated with the cluster glycoside effect. Gold nanoparticles bearing glycans have attracted significant interest in particular. This is due to their versatility, their highly tunable gold cores (size and shape), and their application in biosensors and diagnostic tools. However, conjugating glycans onto these materials can be challenging, necessitating either multiple protecting group manipulations or the use of only simple glycans. This results in limited structural diversity compared to glycoarrays which can include hundreds of glycans. Here we report a method to generate glyconanoparticles from unprotected glycans by conjugation to polymer tethers bearing terminal amino-oxy groups, which are then immobilized onto gold nanoparticles. Using an isotope-labeled glycan, the efficiency of this reaction was probed in detail to confirm conjugation, with 25% of end-groups being functionalized, predominantly in the ring-closed form. Facile post-glycosylation purification is achieved by simple centrifugation/washing cycles to remove excess glycan and polymer. This streamlined synthetic approach may be particularly useful for the preparation of glyconanoparticle libraries using automation, to identify hits to be taken forward using more conventional synthetic methods. Exemplar lectin-binding studies were undertaken to confirm the availability of the glycans for binding and show this is a powerful tool for rapid assessment of multivalent glycan binding.
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http://dx.doi.org/10.1021/acs.bioconjchem.0c00465DOI Listing
October 2020

Correlating the Local Electrocatalytic Activity of Amorphous Molybdenum Sulfide Thin Films with Microscopic Composition, Structure, and Porosity.

ACS Appl Mater Interfaces 2020 Sep 15;12(39):44307-44316. Epub 2020 Sep 15.

Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.

Thin-film electrodes, produced by coating a conductive support with a thin layer (nanometer to micrometer) of active material, retain the unique properties of nanomaterials (., activity, surface area, conductivity, .) while being economically scalable, making them highly desirable as electrocatalysts. Despite the ever-increasing methods of thin-film deposition (., wet chemical synthesis, electrodeposition, chemical vapor deposition, .), there is insufficient understanding on the nanoscale electrochemical activity of these materials in relation to structure/composition, particularly for those that lack long-range order (., amorphous thin-film materials). In this work, scanning electrochemical cell microscopy (SECCM) is deployed in tandem with complementary, colocated compositional/structural analysis to understand the microscopic factors governing the electrochemical activity of amorphous molybdenum sulfide (a-MoS) thin films, a promising class of hydrogen evolution reaction (HER) catalyst. The a-MoS thin films, produced under ambient conditions by electrodeposition, possess spatially heterogeneous electrocatalytic activity on the tens-of-micrometer scale, which is not attributable to microscopic variations in elemental composition or chemical structure (., Mo and/or S bonding environments), shown through colocated, local energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. A new SECCM protocol is implemented to directly correlate electrochemical activity to the electrochemical surface area (ECSA) in a single measurement, revealing that the spatially heterogeneous HER response of a-MoS is predominantly attributable to variations in the nanoscale porosity of the thin film, with surface roughness ruled out as a major contributing factor by complementary atomic force microscopy (AFM). As microscopic composition, structure, and porosity (ECSA) are all critical factors dictating the functional properties of nanostructured materials in electrocatalysis and beyond (., battery materials, electrochemical sensors, .), this work further cements SECCM as a premier tool for structure-function studies in (electro)materials science.
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http://dx.doi.org/10.1021/acsami.0c11759DOI Listing
September 2020

Nanozeolite ZSM-5 electrolyte additive for long life sodium-ion batteries.

Chem Commun (Camb) 2020 Oct;56(78):11609-11612

School of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT, UK.

A novel low cost sodium-ion battery electrolyte additive ZSM-5 nanozeolite, which improves cycle life, is demonstrated in a Na-ion cell. The addition of this zeolitic small molecule scavenger removes electrolyte decomposition products, and has beneficial properties compared to traditional organic additives such as fluoroethylene carbonate (FEC). Capacity retention after 480 cycles improves from 40% (none) compared to 62% (ZSM-5). This is due to the enhanced interface stability over the cell life-time, as shown by XPS.
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http://dx.doi.org/10.1039/d0cc03976dDOI Listing
October 2020

Atomic level termination for passivation and functionalisation of silicon surfaces.

Nanoscale 2020 Aug;12(33):17332-17341

School of Engineering, University of Warwick, Coventry, CV4 7AL, UK.

Chemical treatments play an essential role in the formation of high quality interfaces between materials, including in semiconductor devices, and in the functionalisation of surfaces. We have investigated the effects of hydrogen and fluorine termination of (100)-orientation silicon surfaces over a range of length scales. At the centimetre scale, lifetime measurements show clean silicon surfaces can be temporarily passivated by a short treatment in both HF(2%) : HCl(2%) and HF(50%) solutions. The lifetime, and hence surface passivation, becomes better with immersion time in the former, and worse with immersion time in the latter. At the nanometre scale, X-ray photoelectron spectroscopy and atomic force microscopy show treatment with strong HF solutions results in a roughened fluorine-terminated surface. Subsequent superacid-derived surface passivation on different chemically treated surfaces shows considerably better passivation on surfaces treated with HF(2%) : HCl(2%) compared to HF. Lifetime data are modelled to understand the termination in terms of chemical and field effect passivation at the centimetre scale. Surfaces passivated with Al2O3 grown by atomic layer deposition behave similarly when either HF(2%) : HCl(2%) or HF(50%) are used as a pre-treatment, possibly because of the thin silicon dioxide interlayer which subsequently forms. Our study highlights that chemical pre-treatments can be extremely important in the creation of high quality functionalised surfaces.
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http://dx.doi.org/10.1039/d0nr03860aDOI Listing
August 2020

Acral Lentiginous Melanoma: Do Surgical Approach and Sentinel Lymph Node Biopsy Matter?

Plast Reconstr Surg Glob Open 2020 Mar 25;8(3):e2698. Epub 2020 Mar 25.

Division of Surgical Oncology, Department of Surgery, Oregon Health & Science University, Portland, Ore.

Management of acral lentiginous melanoma (ALM) remains controversial. Traditionally, ALM was managed with digit amputation (DA), resulting in significant morbidity, but recent evidence has advocated for digit sparing management. Furthermore, the significance of nodal metastasis for ALM is not well reported. The aims of this study were to determine if surgical approach for primary ALM impacts outcomes and to evaluate the predictive value of nodal status for ALM.

Methods: Patients with localized ALM diagnosed from 1982 to 2017 were retrospectively identified. Clinicopathologic characteristics were correlated with surgical approach, nodal metastasis, overall survival, and recurrence-free survival.

Results: There were 47 patients with ALM. Median age was 59 years, and median thickness was 3 mm. 51% of patients underwent wide local excision (WLE), 27.9% underwent DA, and 20.9% underwent partial digit amputation (PDA). ALM on the hand versus foot (OR: 12.7, 95%, confidence interval (CI), 2.0-80.1; = 0.007) and subungual versus nonsubungual location (OR: 28.0, 95% confidence interval, 2.7-295.7; = 0.006) were significantly associated with surgical approach (DA and PDA versus WLE). There were no significant differences in overall survival or recurrence-free survival between DA, PDA, or WLE cases ( = 0.481 and = 0.778, respectively). There were no significant differences in overall survival or recurrence-free survival based on nodal status ( = 0.562 and = 0.136, respectively).

Conclusions: No significant differences in overall survival or recurrence-free survival were seen between ALM patients treated with DA, PDA, and WLE. Given these results, PDA or WLE may be options in select patients with digital ALM; however, careful consideration must be taken when deciding on the surgical approach.
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http://dx.doi.org/10.1097/GOX.0000000000002698DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7253243PMC
March 2020

Polymer-Stabilized Sialylated Nanoparticles: Synthesis, Optimization, and Differential Binding to Influenza Hemagglutinins.

Biomacromolecules 2020 04 31;21(4):1604-1612. Epub 2020 Mar 31.

Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.

During influenza infection, hemagglutinins (HAs) on the viral surface bind to sialic acids on the host cell's surface. While all HAs bind sialic acids, human influenza targets terminal α2,6 sialic acids and avian influenza targets α2,3 sialic acids. For interspecies transmission (zoonosis), HA must mutate to adapt to these differences. Here, multivalent gold nanoparticles bearing either α2,6- or α2,3-sialyllactosamine have been developed to interrogate a panel of HAs from pathogenic human, low pathogenic avian, and other species' influenza. This method exploits the benefits of multivalent glycan presentation compared to monovalent presentation to increase affinity and investigate how multivalency affects selectivity. Using a library-orientated approach, parameters including polymer coating and core diameter were optimized for maximal binding and specificity were probed using galactosylated particles and a panel of biophysical techniques [ultraviolet-visible spectroscopy, dynamic light scattering, and biolayer interferometry]. The optimized particles were then functionalized with sialyllactosamine and their binding analyzed against a panel of HAs derived from pathogenic influenza strains including low pathogenic avian strains. This showed significant specificity crossover, which is not observed in monovalent formats, with binding of avian HAs to human sialic acids and in agreement with alternate assay formats. These results demonstrate that precise multivalent presentation is essential to dissect the interactions of HAs and may aid the discovery of tools for disease and zoonosis transmission.
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http://dx.doi.org/10.1021/acs.biomac.0c00179DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7173702PMC
April 2020

Structures of mixed manganese ruthenium oxides (MnRu)O crystallised under acidic hydrothermal conditions.

Dalton Trans 2020 Feb;49(8):2661-2670

Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK.

A synthesis method for the preparation of mixed manganese-ruthenium oxides is presented along with a detailed characterisation of the solids produced. The use of 1 M aqueous sulfuric acid mediates the redox reaction between KRuO4, KMnO4 and Mn2+ to form ternary oxides. At reaction temperature of 100 °C the products are mixtures of α-MnO2 (hollandite-type) and β-MnO2 (rutile-type), with some evidence of Ru incorporation in each from their expanded unit cell volumes. At reaction temperature of 200 °C solid-solutions β-Mn1-xRuxO2 are formed and materials with x ≤ 0.6 have been studied. The amount of Ru included in the oxide is greater than expected from the ratio of metals used in the synthesis, as determined by elemental analysis, implying that some Mn remains unreacted in solution. Powder X-ray diffraction (XRD) shows that while the unit cell volume expands in a linear manner, following Vegard's law, the tetragonal lattice parameters, and the a/c ratio, do not follow the extrapolated trends: this anisotropic behaviour is consistent with the different local coordination of the metals in the end members. Powder XRD patterns show increased peak broadening with increasing ruthenium content, which is corroborated by electron microscopy that shows nanocrystalline material. X-ray absorption near-edge spectra show that the average oxidation state of Mn in the solid solutions is reduced below +4 while that of Ru is increased above +4, suggesting some redistribution of charge. Analysis of the extended X-ray absorption fine structure provides complementary local structural information, confirming the formation of a solid solution, while X-ray photoelectron spectroscopy shows that the surface oxidation states of both Ru and Mn are on average lower than +4, suggesting a disordered surface layer may be present in the materials.
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http://dx.doi.org/10.1039/c9dt04156gDOI Listing
February 2020

"Tuning aggregative versus non-aggregative lectin binding with glycosylated nanoparticles by the nature of the polymer ligand".

J Mater Chem B 2020 01 28;8(1):136-145. Epub 2019 Nov 28.

Department of Chemistry, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, UK. and Warwick Medical School, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, UK.

Glycan-lectin interactions drive a diverse range of biological signaling and recognition processes. The display of glycans in multivalent format enables their intrinsically weak binding affinity to lectins to be overcome by the cluster glycoside effect, which results in a non-linear increase in binding affinity. As many lectins have multiple binding sites, upon interaction with glycosylated nanomaterials either aggregation or surface binding without aggregation can occur. Depending on the application area, either one of these responses are desirable (or undesirable) but methods to tune the aggregation state, independently from the overall extent/affinity of binding are currently missing. Herein, we use gold nanoparticles decorated with galactose-terminated polymer ligands, obtained by photo-initiated RAFT polymerization to ensure high end-group fidelity, to show the dramatic impact on agglutination behaviour due to the chemistry of the polymer linker. Poly(N-hydroxyethyl acrylamide) (PHEA)-coated gold nanoparticles, a polymer widely used as a non-ionic stabilizer, showed preference for aggregation with lectins compared to poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA)-coated nanoparticles which retained colloidal stability, across a wide range of polymer lengths and particle core sizes. Using biolayer interferometry, it was observed that both coatings gave rise to similar binding affinity and hence provided conclusive evidence that aggregation rate alone cannot be used to measure affinity between nanoparticle systems with different stabilizing linkers. This is significant, as turbidimetry is widely used to demonstrate glycomaterial activity, although this work shows the most aggregating may not be the most avid, when comparing different polymer backbones/coating. Overall, our findings underline the potential of PHPMA as the coating of choice for applications where aggregation upon lectin binding would be problematic, such as in vivo imaging or drug delivery.
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http://dx.doi.org/10.1039/c9tb02004gDOI Listing
January 2020

Work function of GaAs(hkl) and its modification using PEI: mechanisms and substrate dependence.

Phys Chem Chem Phys 2019 Nov 1;21(44):24666-24673. Epub 2019 Nov 1.

Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.

Spin-coating of poly(ethylenimine) (PEI) has been used to reduce the work function of GaAs (001), (110), (111)A and (111)B. The magnitude of the reduction immediately after coating varies significantly from 0.51 eV to 0.69 eV and depends on the surface crystal face, on the GaAs bulk doping and on the atomic termination of the GaAs. For all samples, the work function reduction shrinks in ambient air over the first 20 hours after spin coating, but reductions around 0.2-0.3 eV persist after 1 year of storage in air. Core-level photoemission of thin film PEI degradation in air is consistent with a two-stage reaction with CO and HO previously proposed in carbon capture studies. The total surface dipole from PEI coating is consistent with a combination of internal neutral amine dipole and an interface dipole whose magnitude depends on the surface termination. The contact potential difference measured by Kelvin probe force microscopy on a cleaved GaAs heterostructure is smaller on p-doped regions. This can be explained by surface doping due to the PEI, which increases the band bending on p-doped GaAs where Fermi level pinning is weak. Both surface doping and surface dipole should be accounted for when considering the effect of PEI coated on a semiconductor surface.
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http://dx.doi.org/10.1039/c9cp04490fDOI Listing
November 2019

Site-specific conjugation of antifreeze proteins onto polymer-stabilized nanoparticles.

Polym Chem 2019 Jun 31;10(23):2986-2990. Epub 2019 Jan 31.

Department of Chemistry , University of Warwick , Coventry , CV4 7AL , UK . Email:

Antifreeze proteins (AFPs) have many potential applications, ranging from cryobiology to aerospace, if they can be incorporated into materials. Here, a range of engineered AFP mutants were prepared and site-specifically conjugated onto RAFT polymer-stabilized gold nanoparticles to generate new hybrid multivalent ice growth inhibitors. Only the SNAP-tagged AFPs lead to potent 'antifreeze' active nanomaterials with His-Tag capture resulting in no activity, showing the mode of conjugation is essential. This versatile strategy will enable the development of multivalent AFPs for translational and fundamental studies.
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http://dx.doi.org/10.1039/c8py01719kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6592154PMC
June 2019

Synthesis of Pd/Ru Bimetallic Nanoparticles by and Potential as a Catalyst for Upgrading 5-Hydroxymethyl Furfural Into Liquid Fuel Precursors.

Front Microbiol 2019 20;10:1276. Epub 2019 Jun 20.

School of Biosciences, University of Birmingham, Birmingham, United Kingdom.

cells support the nucleation and growth of ruthenium and ruthenium-palladium nanoparticles (Bio-Ru and Bio-Pd/Ru NPs). We report a method for the synthesis of these monometallic and bimetallic NPs and their application in the catalytic upgrading of 5-hydroxymethyl furfural (5-HMF) to 2,5 dimethylfuran (DMF). Examination using high resolution transmission electron microscopy with energy dispersive X-ray microanalysis (EDX) and high angle annular dark field (HAADF) showed Ru NPs located mainly at the cell surface using Ru(III) alone but small intracellular Ru-NPs (size ∼1-2 nm) were visible only in cells that had been pre-"seeded" with Pd(0) (5 wt%) and loaded with equimolar Ru. Pd(0) NPs were distributed between the cytoplasm and cell surface. Cells bearing 5% Pd/5% Ru showed some co-localization of Pd and Ru but chance associations were not ruled out. Cells loaded to 5 wt% Pd/20 wt% Ru showed evidence of core-shell structures (Ru core, Pd shell). Examination of this cell surface material using X-ray photoelectron spectroscopy (XPS) showed Pd(0) and Pd(II) and Ru(IV) and Ru(III), with confirmation by analysis of bulk material using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses. Both Bio-Ru NPs and Bio-Pd/Ru NPs were active in the conversion of 5-HMF into 2,5-DMF but commercial Ru on carbon catalyst outperformed 5 wt% bio-Ru by fourfold. While 5 wt% Pd/20 wt% Ru achieved 20% yield of DMF the performance of the 5 wt% Pd/5 wt% Ru bio-catalyst was higher and comparable to the commercial 5 wt% Ru/C catalyst in a test reaction using commercial 5-HMF (>50% selectivity). 5-HMF was prepared by thermochemical hydrolysis of starch and cellulose with solvent extraction of 5-HMF into methyltetrahydrofuran (MTHF). Here, with MTHF as the reaction solvent the commercial Ru/C catalyst had little activity (100% conversion, negligible selectivity to DMF) whereas the 5 wt% Pd/5 wt% Ru bio-bimetallic gave 100% conversion and 14% selectivity to DMF from material extracted from hydrolyzates. The results indicate a potential green method for realizing increased energy potential from biomass wastes as well as showing a bio-based pathway to manufacturing a scarcely described bimetallic material.
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http://dx.doi.org/10.3389/fmicb.2019.01276DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6595500PMC
June 2019

Upconversion of Cellulosic Waste Into a Potential "Drop in Fuel" via Novel Catalyst Generated Using and a Consortium of Acidophilic Sulfidogens.

Front Microbiol 2019 10;10:970. Epub 2019 May 10.

School of Biosciences, University of Birmingham, Birmingham, United Kingdom.

Biogas-energy is marginally profitable against the "parasitic" energy demands of processing biomass. Biogas involves microbial fermentation of feedstock hydrolyzate generated enzymatically or thermochemically. The latter also produces 5-hydroxymethyl furfural (5-HMF) which can be catalytically upgraded to 2, 5-dimethyl furan (DMF), a "drop in fuel." An integrated process is proposed with side-stream upgrading into DMF to mitigate the "parasitic" energy demand. 5-HMF was upgraded using bacterially-supported Pd/Ru catalysts. Purpose-growth of bacteria adds additional process costs; Pd/Ru catalysts biofabricated using the sulfate-reducing bacterium (SRB) were compared to those generated from a waste consortium of acidophilic sulfidogens (CAS). Methyl tetrahydrofuran (MTHF) was used as the extraction-reaction solvent to compare the use of bio-metallic Pd/Ru catalysts to upgrade 5-HMF to DMF from starch and cellulose hydrolyzates. MTHF extracted up to 65% of the 5-HMF, delivering solutions, respectively, containing 8.8 and 2.2 g 5-HMF/L MTHF. Commercial 5% (wt/wt) Ru-carbon catalyst upgraded 5-HMF from pure solution but it was ineffective against the hydrolyzates. Both types of bacterial catalyst (5wt%Pd/3-5wt% Ru) achieved this, bio-Pd/Ru on the CAS delivering the highest conversion yields. The yield of 5-HMF from starch-cellulose thermal treatment to 2,5 DMF was 224 and 127 g DMF/kg extracted 5-HMF, respectively, for CAS and catalysts, which would provide additional energy of 2.1 and 1.2 kWh/kg extracted 5-HMF. The CAS comprised a mixed population with three patterns of metallic nanoparticle (NP) deposition. Types I and II showed cell surface-localization of the Pd/Ru while type III localized NPs throughout the cell surface and cytoplasm. No metallic patterning in the NPs was shown via elemental mapping using energy dispersive X-ray microanalysis but co-localization with sulfur was observed. Analysis of the cell surfaces of the bulk populations by X-ray photoelectron spectroscopy confirmed the higher S content of the CAS bacteria as compared to and also the presence of Pd-S as well as Ru-S compounds and hence a mixed deposit of PdS, Pd(0), and Ru in the form of various +3, +4, and +6 oxidation states. The results are discussed in the context of recently-reported controlled palladium sulfide ensembles for an improved hydrogenation catalyst.
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http://dx.doi.org/10.3389/fmicb.2019.00970DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6523789PMC
May 2019

Novel catalytically active Pd/Ru bimetallic nanoparticles synthesized by Bacillus benzeovorans.

Sci Rep 2019 03 18;9(1):4715. Epub 2019 Mar 18.

School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.

Bacillus benzeovorans assisted and supported growth of ruthenium (bio-Ru) and palladium/ruthenium ([email protected]) [email protected] nanoparticles (NPs) as bio-derived catalysts. Characterization of the bio-NPs using various electron microscopy techniques and high-angle annular dark field (HAADF) analysis confirmed two NP populations (1-2 nm and 5-8 nm), with [email protected] in the latter. The Pd/Ru NP lattice fringes, 0.231 nm, corresponded to the (110) plane of RuO While surface characterization using X-ray photoelectron spectroscopy (XPS) showed the presence of Pd(0), Pd(II), Ru(III) and Ru(VI), X-ray absorption (XAS) studies of the bulk material confirmed the Pd speciation (Pd(0) and Pd(II)- corresponding to PdO), and identified Ru as Ru(III) and Ru(IV). The absence of Ru-Ru or Ru-Pd peaks indicated Ru only exists in oxide forms (RuO and RuOH), which are surface-localized. X ray diffraction (XRD) patterns did not identify Pd-Ru alloying. Preliminary catalytic studies explored the conversion of 5-hydroxymethyl furfural (5-HMF) to the fuel precursor 2,5-dimethyl furan (2,5-DMF). Both high-loading (9.7 wt.% Pd, 6 wt.% Ru) and low-loading (2.4 wt.% Pd, 2 wt.% Ru) bio-derived catalysts demonstrated high conversion efficiencies (~95%) and selectivity of ~63% (~20% better than bio-Ru NPs) and 58%, respectively. These materials show promising future scope as efficient low-cost biofuel catalysts.
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http://dx.doi.org/10.1038/s41598-019-40312-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6423089PMC
March 2019

The Effect of Autologous Fat Grafting on Edema and Ecchymoses in Primary Open Rhinoplasty.

Aesthet Surg J 2020 03;40(4):359-366

Division of Plastic Surgery, Department of Surgery, Yale University School of Medicine, New Haven, CT.

Background: Autologous fat is a safe and effective soft tissue filler. Recent evidence also suggests improved wound healing and immune modulation with fat grafting.

Objectives: The aim of this study was to describe a novel technique utilizing fat grafting during primary open rhinoplasty. We hypothesize a more rapid resolution of bruising and edema.

Methods: Patients who underwent rhinoplasty were reviewed and compared by presence or absence of concurrent fat grafting. Three-dimensional images were analyzed employing Mirror (Vectra, Canfield Scientific, NJ). Ecchymoses were outlined utilizing a magnetic lasso followed by an area measurement. Volumetric edema measurements were also taken and assessed. Edema and ecchymosis were measured at 2 and 6 weeks postoperatively. Statistical significance was defined as P < 0.05.

Results: Sixty-two patients were included. Thirty-three patients (53.2%) received autologous fat grafting and 29 (46.8%) did not. Age, gender, surgical approach, and osteotomy distribution were similar between the groups. The fat grafted group showed 7.29 cm2 fewer ecchymoses (P < 0.001) and 0.73 cc less edema (P = 0.68) in the early postoperative interval. Six weeks postoperatively, the fat grafted group showed 1 cc less edema (P = 0.36) with negligible differences in bruising.

Conclusions: Autologous fat grafting is a useful adjunct to rhinoplasty and is associated with significantly fewer ecchymoses in the acute postoperative period.

Level Of Evidence: 4:
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http://dx.doi.org/10.1093/asj/sjz075DOI Listing
March 2020

Covalent Attachment of Fibronectin onto Emulsion-Templated Porous Polymer Scaffolds Enhances Human Endometrial Stromal Cell Adhesion, Infiltration, and Function.

Macromol Biosci 2019 02 13;19(2):e1800351. Epub 2018 Dec 13.

S. A. Richardson, Dr. A. M. Eissa, Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.

A novel strategy for the surface functionalization of emulsion-templated highly porous (polyHIPE) materials as well as its application to in vitro 3D cell culture is presented. A heterobifunctional linker that consists of an amine-reactive N-hydroxysuccinimide ester and a photoactivatable nitrophenyl azide, N-sulfosuccinimidyl-6-(4'-azido-2'-nitrophenylamino)hexanoate (sulfo-SANPAH), is utilized to functionalize polyHIPE surfaces. The ability to conjugate a range of compounds (6-aminofluorescein, heptafluorobutylamine, poly(ethylene glycol) bis-amine, and fibronectin) to the polyHIPE surface is demonstrated using fluorescence imaging, FTIR spectroscopy, and X-ray photoelectron spectroscopy. Compared to other existing surface functionalization methods for polyHIPE materials, this approach is facile, efficient, versatile, and benign. It can also be used to attach biomolecules to polyHIPE surfaces including cell adhesion-promoting extracellular matrix proteins. Cell culture experiments demonstrated that the fibronectin-conjugated polyHIPE scaffolds improve the adhesion and function of primary human endometrial stromal cells. It is believed that this approach can be employed to produce the next generation of polyHIPE scaffolds with tailored surface functionality, enhancing their application in 3D cell culture and tissue engineering whilst broadening the scope of applications to a wider range of cell types.
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http://dx.doi.org/10.1002/mabi.201800351DOI Listing
February 2019

Electromagnetic Functionalization of Wide-Bandgap Dielectric Oxides by Boron Interstitial Doping.

Adv Mater 2018 Sep 21;30(39):e1802025. Epub 2018 Aug 21.

Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.

A surge in interest of oxide-based materials is testimony for their potential utility in a wide array of device applications and offers a fascinating landscape for tuning the functional properties through a variety of physical and chemical parameters. In particular, selective electronic/defect doping has been demonstrated to be vital in tailoring novel functionalities, not existing in the bulk host oxides. Here, an extraordinary interstitial doping effect is demonstrated centered around a light element, boron (B). The host matrix is a novel composite system, made from discrete bulk LaAlO :LaBO compounds. The findings show a spontaneous ordering of the interstitial B cations within the host LaAlO lattices, and subsequent spin-polarized charge injection into the neighboring cations. This leads to a series of remarkable cation-dominated electrical switching and high-temperature ferromagnetism. Hence, the induced interstitial doping serves to transform a nonmagnetic insulating bulk oxide into a ferromagnetic ionic-electronic conductor. This unique interstitial B doping effect upon its control is proposed to be as a general route for extracting/modifying multifunctional properties in bulk oxides utilized in energy and spin-based applications.
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http://dx.doi.org/10.1002/adma.201802025DOI Listing
September 2018

Multivalent Presentation of Ice Recrystallization Inhibiting Polymers on Nanoparticles Retains Activity.

Langmuir 2019 06 22;35(23):7347-7353. Epub 2018 Aug 22.

Department of Chemistry , University of Warwick , Coventry CV4 7AL , United Kingdom.

Poly(vinyl alcohol) (PVA) has emerged as the most potent mimic of antifreeze (glyco)proteins ice recrystallization inhibition (IRI) activity, despite its lack of structural similarities and flexible, rather than rigid, backbone. The precise spacing of hydroxyl groups is hypothesized to enable PVA to recognize the prism planes of ice but not the basal plane, due to hydroxyl pattern matching of the ice surface giving rise to the macroscopic activity. Here, well-defined PVA derived from reversible addition-fragmentation chain-transfer (RAFT) polymerization is immobilized onto gold nanoparticles to enable the impact of nanoscale assembly and confinement on the observed IRI activity. Unlike previous reports using star-branched or bottle-brush PVAs, the nanoparticle-PVA retains all IRI activity compared to polymers in solution. Evidence is presented to show that this is due to the low grafting densities on the particle surface meaning the chains are free to explore the ice faces, rather than being constrained as in star-branched polymers. These results demonstrate a route to develop more functional IRI's and inclusion of metallic particle cores for imaging and associated applications in cryobiology.
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http://dx.doi.org/10.1021/acs.langmuir.8b01952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6354916PMC
June 2019

Three-dimensional Analysis of How Radiation Affects Deep Inferior Epigastric Perforator (DIEP) Flap Volume, Projection, and Position in Breast Cancer Reconstruction.

Ann Plast Surg 2018 08;81(2):235-239

Department of Radiation Oncology, Yale University School of Medicine, New Haven, CT.

Background: The deep inferior epigastric perforator (DIEP) flap has gained popularity for autologous free flap breast reconstruction. Historically, patients receiving post mastectomy radiation therapy (PMRT) were not candidates for immediate autologous reconstruction due to concerns for flap volume depletion, fat necrosis, and flap failure. However, this literature is anecdotal and lacks case controls. We objectively analyzed the effects radiation imparts on immediate DIEP flap reconstruction using 3-dimensional software and inherent controls.

Methods: We performed a cohort study on breast cancer patients who underwent immediate bilateral DIEP flap reconstructions followed by PMRT between 2005 and 2014. Exclusion criteria included patients less than 6 months from PMRT completion and bilateral PMRT. Three-dimensional photographs were analyzed using Geomagic (Rock Hill, SC) software to compare flap position, projection, and volume between the irradiated and nonirradiated reconstructed breasts. Breast Q survey evaluated patients' satisfaction.

Results: Eleven patients met inclusion criteria. Average time from PMRT completion to photo acquisition was 1.93 years. There was no statistical difference in average volume or projection in the irradiated versus nonirradiated side (P = 0.087 and P = 0.176, respectively). However, position of the irradiated flaps was significantly higher on the chest wall compared to controls (mean difference, 1.325 cm; P < 0.004).

Conclusions: Three-dimensional analysis exhibited no statistical differences in projection or volume between irradiated DIEP flaps and nonirradiated controls. However, irradiated DIEP flaps were positioned higher on the chest wall, similar to observations in irradiated tissue expanders/implants. Patients were satisfied as measured by Breast Q. Immediate bilateral DIEP flap reconstructions can safely be performed with PMRT with satisfactory results.
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http://dx.doi.org/10.1097/SAP.0000000000001462DOI Listing
August 2018

The Hand Surgeon Consultation Improves Patient Knowledge in a Hand Surgery Mission to Honduras.

J Hand Surg Asian Pac Vol 2018 Mar;23(1):11-17

* Section of Plastic Surgery, Yale University School of Medicine, New Haven, CT, USA.

Background: The purpose of this study was to assess impact of the surgeon consultation and informed consent process on patient education in an international hand surgery mission compared with a US academic hand surgery practice. These two groups were selected to evaluate communication difficulties in a surgical mission setting compared with standard of care in a high-income country.

Methods: A multi-part survey was administered to patients presenting to a hand surgery mission during March 2012 and new patients of a university hand center in a 3-month period during 2011. Surveys were administered prior to and following surgeon consultation with one fellowship-trained hand surgeon. The survey assessed knowledge of basic hand anatomy, physiology, disease, individual diagnosis, and surgical risks.

Results: 71 patients participated in the study (university n=36, mission n=35). Pre-consultation quiz score averaged 58% in the university group versus 27% in the mission group. Post-consultation quiz scores averaged 62% in the university group versus 40% in the mission group. Only the mission group's quiz score increase was statistically significant. 93% of the university group reported learning about their condition and diagnosis, but only 40% demonstrated correct insight into their diagnosis. In the mission group, 73% reported learning about their condition and diagnosis while 53% demonstrated correct insight into their diagnosis. Although all consultations involved discussion of surgical risks, only 62% of the university group and 52% of the mission group recalled discussing surgical risks.

Conclusions: The hand surgeon consultation was more effective in improving hand knowledge in the surgery mission group compared to in a university hand practice. This suggests that the surgeon consultation should be pursued despite communication barriers in surgical missions. However, the discrepancy between patient perception of knowledge gains and correct insight into diagnosis, and the deficit of patient retention of surgical risks need to be improved.
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http://dx.doi.org/10.1142/S2424835518500017DOI Listing
March 2018
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