Publications by authors named "Marina Resmini"

43 Publications

Simultaneous Quantification of Antioxidants Paraxanthine and Caffeine in Human Saliva by Electrochemical Sensing for CYP1A2 Phenotyping.

Antioxidants (Basel) 2020 Dec 24;10(1). Epub 2020 Dec 24.

Department of Chemistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, including caffeine, which is transformed into paraxanthine, its main primary metabolite. Both molecules are known for their antioxidant and pro-oxidant characteristics, and the paraxanthine-to-caffeine molar ratio is a widely accepted metric for CYP1A2 phenotyping, to optimize dose-response effects in individual patients. We developed a simple, cheap and fast electrochemical based method for the simultaneous quantification of paraxanthine and caffeine in human saliva, by differential pulse voltammetry, using an anodically pretreated glassy carbon electrode. Cyclic voltammetry experiments revealed for the first time that the oxidation of paraxanthine is diffusion controlled with an irreversible peak at ca. +1.24 V (vs. Ag/AgCl) in a 0.1 M HSO solution, and that the mechanism occurs via the transfer of two electrons and two protons. The simultaneous quantification of paraxanthine and caffeine was demonstrated in 0.1 M HSO and spiked human saliva samples. In the latter case, limits of detection of 2.89 μM for paraxanthine and 5.80 μM for caffeine were obtained, respectively. The sensor is reliable, providing a relative standard deviation within 7% ( = 6). Potential applicability of the sensing platform was demonstrated by running a small scale trial on five healthy volunteers, with simultaneous quantification by differential pulse voltammetry (DPV) of paraxanthine and caffeine in saliva samples collected at 1, 3 and 6 h postdose administration. The results were validated by ultra-high pressure liquid chromatography and shown to have a high correlation factor (r = 0.994).
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http://dx.doi.org/10.3390/antiox10010010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823619PMC
December 2020

Systematic Analysis of the Relative Abundance of Polymers Occurring as Microplastics in Freshwaters and Estuaries.

Int J Environ Res Public Health 2020 12 12;17(24). Epub 2020 Dec 12.

Department of Chemistry, School of Biological and Chemical Science, Queen Mary University of London, London E1 4NS, UK.

Despite growing interest in the environmental impact of microplastics, a standardized characterization method is not available. We carried out a systematic analysis of reliable global data detailing the relative abundance of polymers in freshwaters and estuaries. The polymers were identified according to seven main categories: polyethylene terephthalate, polyethylene, polyvinyl chloride, polypropylene, polystyrene, polyurethane and a final category of miscellaneous plastic. The results show that microplastics comprised of polyvinyl chloride and polyurethane are significantly less abundant than would be expected based on global production, possibly due to their use. This has implications for models of microplastic release into the environment based on production and fate. When analysed by matrix (water, sediment or biota) distinct profiles were obtained for each category. Polyethylene, polypropylene and polystyrene were more abundant in sediment than in biota, while miscellaneous plastics was more frequent in biota. The data suggest that environmental sorting of microplastic particles, influenced by physical, chemical and biological processes, may play a key role in environmental impact, although partitioning among matrices based on density was not realized. The distinct profile of microplastics in biota raises an important question regarding potential selectivity in uptake by organisms, highlighting the priority for more and better-informed laboratory exposure studies.
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http://dx.doi.org/10.3390/ijerph17249304DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7764371PMC
December 2020

Influence of Buffers, Ionic Strength, and pH on the Volume Phase Transition Behavior of Acrylamide-Based Nanogels.

Polymers (Basel) 2020 Nov 4;12(11). Epub 2020 Nov 4.

Department of Chemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

The use of covalently crosslinked nanogels for applications in biology and medicine is dependent on their properties and characteristics, which often change because of the biological media involved. Understanding the role of salts, ionic strength and pH in altering specific properties is key to progress in this area. We studied the effect of both chemical structure and media environment on the thermoresponsive behavior of nanogels. A small library of methylenebisacrylamide (MBA) crosslinked nanogels were prepared using -isopropylacrylamide (NIPAM) or -propylacrylamide (NPAM), in combination with functional monomers -hydroxyethylacrylamide (HEAM) and -acryloyl-l-proline (APrOH). The thermoresponsive properties of nanogels were evaluated in phosphate buffer, tris-acetate buffer and Ringer HEPES, with varying concentrations and ionic strengths. The presence of ions facilitates the phase separation of nanogels, and this "salting-out" effect strongly depends on the electrolyte concentration as well as the specificity of individual anions, e.g., their positions in the Hofmeister series. A subtle change in the chemical structure of the side chain of the monomer from NIPAM to NPAM leads to a reduction of the volume phase transition temperature (VPTT) value by ~10 °C. The addition of hydrophilic comonomers such as HEAM, on the other hand, causes a ~20 °C shift in VPTT to higher values. The data highlight the significant role played by the chemical structure of the monomers used, with hydrophobicity and rigidity closely interlinked in determining thermoresponsive behavior. Furthermore, the volume phase transition temperature (VPTT) of nanogels copolymerized with ionizable APrOH comonomer can be tailored by changes in the pH of buffer solutions. This temperature-controlled phase transition is driven by intricate interplay involving the entropy of mixing, electrostatic interactions, conformational transitions, and structural rigidity. These results highlight the importance of understanding the physiochemical properties and behavior of covalently crosslinked nanogels in a biological environment prior to their applications in life-science, such as temperature/pH-triggered drug delivery systems.
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http://dx.doi.org/10.3390/polym12112590DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7694245PMC
November 2020

Fluorescent Imprinted Nanoparticles for the Effective Monitoring of Irinotecan in Human Plasma.

Nanomaterials (Basel) 2020 Aug 29;10(9). Epub 2020 Aug 29.

Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy.

Fluorescent, imprinted nanosized polymers for the detection of irinotecan have been synthesised using a napthalimide polymerisable derivative (2-allyl-6-[2-(aminoethyl)-amino] napthalimide) as functional monomer. The imprinted polymers contain ethylene glycol dimethacrylate (EGDMA) as a cross-linker and were prepared by high dilution radical polymerisation in dimethylsulphoxide (DMSO). The material was able to rebind irinotecan up to 18 nmol/mg with good specificity. Fluorescence emission at 525 nm (excitation at 448 nm) was quenched by increasing concentrations of irinotecan via a static mechanism and also in analytically useful environments as mixtures of human plasma and organic solvents. This allowed the direct detection of irinotecan (in the 10 nM-30 µM range) in human plasma treated with acetonitrile; the limit of detection (LOD) was 9.4 nM, with within-run variability of 10% and day-to-day variability of 13%.
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http://dx.doi.org/10.3390/nano10091707DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7558923PMC
August 2020

Towards point of care systems for the therapeutic drug monitoring of imatinib.

Anal Bioanal Chem 2020 Sep 12;412(24):5925-5933. Epub 2020 Mar 12.

School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

Therapeutic drug monitoring is used in the clinical setting in the optimisation of dosages to overcome inter-patient pharmacokinetic variability, increasing efficacy whilst reducing toxicity. Imatinib is a tyrosine kinase inhibitor, displaying large variations in plasma concentrations that impact therapeutic success. As a result, imatinib has been the focus in the development of innovative techniques, aimed at its quantification in plasma. Liquid chromatography coupled with tandem mass spectrometry is currently the gold standard; however, cost and availability of the equipment limit its wider application in clinical settings. Recent advances in the field have shown Raman spectroscopy and electrochemistry to be key techniques for the development of promising analytical tools. This article reviews the latest advances towards less costly, more portable solutions that can be used at the point of care. Graphical abstract.
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http://dx.doi.org/10.1007/s00216-020-02545-4DOI Listing
September 2020

Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO Evolution and Quantification.

Int J Mol Sci 2020 Feb 11;21(4). Epub 2020 Feb 11.

School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, UK.

The environmental accumulation of plastics worldwide is a consequence of the durability of the material. Alternative polymers, marketed as biodegradable, present a potential solution to mitigate their ecological damage. However, understanding of biodegradability has been hindered by a lack of reproducible testing methods. We developed a novel method to evaluate the biodegradability of plastic samples based on the monitoring of bacterial respiration in aqueous media via the quantification of CO produced, where the only carbon source available is from the polymer. and were used as model organisms for soil and marine systems, respectively. Our results demonstrate that this approach is reproducible and can be used with a variety of plastics, allowing comparison of the relative biodegradability of the different materials. In the case of low-density polyethylene, the study demonstrated a clear correlation between the molecular weight of the sample and CO released, taken as a measure of biodegradability.
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http://dx.doi.org/10.3390/ijms21041176DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072786PMC
February 2020

Dietary Antioxidants in Coffee Leaves: Impact of Botanical Origin and Maturity on Chlorogenic Acids and Xanthones.

Antioxidants (Basel) 2019 Dec 20;9(1). Epub 2019 Dec 20.

Department of Chemistry, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

Natural polyphenols are important dietary antioxidants that significantly benefit human health. Coffee and tea have been shown to largely contribute to the dietary intake of these antioxidants in several populations. More recently, the use of coffee leaves to produce tea has become a potential commercial target, therefore prompting studies on the quantification of polyphenols in coffee leaves. In this study a variety of coffee leaf species, at different development stages, were analyzed using ultra-high pressure liquid chromatography. The results demonstrate that both the botanical origin of the samples and their maturity influence significantly the concentration of the antioxidants; for total chlorogenic acids a two-fold difference was found between different species and up to a three-fold variation was observed between young and mature leaves. Furthermore, the range of concentrations of chlorogenic acids in young leaves (35.7-80.8 mg/g of dry matter) were found to be comparable to the one reported for green coffee beans. The results provide important data from which potential new commercial products can be developed.
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http://dx.doi.org/10.3390/antiox9010006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7023256PMC
December 2019

Covalently Crosslinked Nanogels: An NMR Study of the Effect of Monomer Reactivity on Composition and Structure.

Polymers (Basel) 2019 Feb 18;11(2). Epub 2019 Feb 18.

Department of Chemistry and Biochemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

Covalently crosslinked nanogels are widely explored as drug delivery systems and sensors. Radical polymerization provides a simple, inexpensive, and broadly applicable approach for their preparation, although the random nature of the reaction requires careful study of the final chemical composition. We demonstrate how the different reactivities of the monomers influence the total degree of incorporation into the polymer matrix and the role played by the experimental parameters in maximizing polymerization efficiency. Nanogels based on -isopropylacrylamide, --propylacrylamide, and acrylamide crosslinked with -methylenebisacrylamide were included in this study, in combination with functional monomers -acryloyl-l-proline, 2-acrylamido-2-methyl-1-propanesulfonic acid, and 4-vinyl-1-imidazole. Total monomer concentration and initiator quantities are determining parameters for maximizing monomer conversions and chemical yields. The results show that the introduction of functional monomers, changes in the chemical structure of the polymerizable unit, and the addition of templating molecules can all have an effect on the polymerization kinetics. This can significantly impact the final composition of the matrices and their chemical structure, which in turn influence the morphology and properties of the nanogels.
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http://dx.doi.org/10.3390/polym11020353DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419204PMC
February 2019

Prediction of self-assembly of adenosine analogues in solution: a computational approach validated by isothermal titration calorimetry.

Phys Chem Chem Phys 2019 Feb;21(8):4258-4267

School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

The recent discovery of the role of adenosine-analogues as neuroprotectants and cognitive enhancers has sparked interest in these molecules as new therapeutic drugs. Understanding the behavior of these molecules in solution and predicting their ability to self-assemble will accelerate new discoveries. We propose a computational approach based on density functional theory, a polarizable continuum solvation description of the aqueous environment, and an efficient search procedure to probe the potential energy surface, to determine the structure and thermodynamic stability of molecular clusters of adenosine analogues in solution, using caffeine as a model. The method was validated as a tool for the prediction of the impact of small structural variations on self-assembly using paraxanthine. The computational results were supported by isothermal titration calorimetry experiments. The thermodynamic parameters enabled the quantification of the actual percentage of dimer present in solution as a function of concentration. The data suggest that both caffeine and paraxanthine are present at concentrations comparable to the ones found in biological samples.
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http://dx.doi.org/10.1039/c8cp05647aDOI Listing
February 2019

Interactions of NIPAM nanogels with model lipid multi-bilayers: A neutron reflectivity study.

J Colloid Interface Sci 2019 Feb 28;536:598-608. Epub 2018 Oct 28.

Department of Chemistry, Queen Mary, University of London, Joseph Priestley Building, Mile End Road, London E1 4NS, United Kingdom. Electronic address:

In dermal drug delivery, the influence of the chemical structure of the carriers on their penetration mechanisms is not yet fully understood. This is a key requirement in order to design highly efficient delivery systems. In this study, neutron reflectivity is used to provide insights into the interactions between thermoresponsive N-isopropylacrylamide based nanogels, cross-linked with 10%, 20% and 30% N,N'-methylenebisacrylamide, and skin lipid multi-bilayers models. Ceramide lipid multi-bilayers and ceramide/cholesterol/behenic acid mixed lipid multi-bilayers were used for this work. The results indicated that in both multi-bilayers the lipids were depleted by the nanogels mainly through hydrophobic interactions. The ability of nanogels to associate with skin lipids to form water-dispersible complexes was found to be a function of the percentage cross-linker. An enhanced depletion of lipids was further observed in the presence of benzyl alcohol, a well-known skin penetration enhancer.
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http://dx.doi.org/10.1016/j.jcis.2018.10.086DOI Listing
February 2019

Biocompatible Phenylboronic-Acid-Capped ZnS Nanocrystals Designed As Caps in Mesoporous Silica Hybrid Materials for on-Demand pH-Triggered Release In Cancer Cells.

ACS Appl Mater Interfaces 2018 Oct 1;10(40):34029-34038. Epub 2018 Oct 1.

Institute of Polymer Chemistry (ICP), Johannes Kepler University Linz , Altenberger Strasse 69 , Linz 4040 , Austria.

Biocompatible ZnS-based nanocrystals capped with 4-mercaptophenylboronic acid ([email protected]) have been size-designed as excellent pH-responsive gatekeepers on mesoporous silica nanoparticles (MSNs), which encapsulate fluorophore safranin O (S2-Saf) or anticancer drug epirubicin hydrochloride (S2-Epi) for delivery applications in cancer cells. In this novel hybrid system, the gate mechanism consists of reversible pH-sensitive boronate ester moieties linking the nanocrystals directly to the alcohol groups from silica surface scaffold, avoiding tedious intermediate functionalization steps. The ∼3 nm size of the [email protected] nanocrystals was tailored to allow efficient sealing of the pore voids and achieve a "zero premature cargo release" at neutral pH (7.4). The system selectively released the cargo in acidic conditions (pH 5.4 and 3.0) because of the hydrolysis of the boronate esters, which unblocked the pore voids. Delivery of the cargo by off-on cycles was demonstrated by changes in pH from 7.4 to 3.0, showing its potential pH-switching behavior. Cellular uptake of these nanocarriers within human cervix adenocarcinoma (HeLa) cells was achieved and the controlled release of the chemotherapeutic drug epirubicin was shown to occur within the endogenous endosomal/lysosomal acidified cancer cell microenvironment and further diffused into the cytosol. Cytotoxicity tests done on the mesoporous support without cargo and covalently linked with [email protected] nanocrystals as caps were negative, suggesting that the proposed system is biocompatible and can be considered as a very promising drug nanocarrier.
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http://dx.doi.org/10.1021/acsami.8b13698DOI Listing
October 2018

Bare carbon electrodes as simple and efficient sensors for the quantification of caffeine in commercial beverages.

R Soc Open Sci 2018 May 2;5(5):172146. Epub 2018 May 2.

Institute of Analytical Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, Bratislava 812 37, Slovak Republic.

Food quality control is a mandatory task in the food industry and relies on the availability of simple, cost-effective and stable sensing platforms. In the present work, the applicability of bare glassy carbon electrodes for routine analysis of food samples was evaluated as a valid alternative to chromatographic techniques, using caffeine as test analyte. A number of experimental parameters were optimized and a differential pulse voltammetry was applied for quantification experiments. The detection limit was found to be 2 × 10 M (3σ criterion) and repeatability was evaluated by the relative standard deviation of 4.5%. The influence of sugars, and compounds structurally related to caffeine on the current response of caffeine was evaluated and found to have no significant influence on the electrode performance. The suitability of bare carbon electrodes for routine analysis was successfully demonstrated by quantifying caffeine content in seven commercially available drinks and the results were validated using a standard ultra-high performance liquid chromatography method. This work demonstrates that bare glassy carbon electrodes are a simple, reliable and cost-effective platform for rapid analysis of targets such as caffeine in commercial products and they represent therefore a competitive alternative to the existing analytical methodologies for routine food analysis.
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http://dx.doi.org/10.1098/rsos.172146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5990824PMC
May 2018

Interaction of thermal responsive NIPAM nanogels with model lipid monolayers at the air-water interface.

J Colloid Interface Sci 2018 Jun 17;519:97-106. Epub 2018 Feb 17.

Department of Chemistry and Biochemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK. Electronic address:

Understanding the interaction of nanoparticles (NP) with ceramide lipids is important in developing strategies to overcome the formidable obstacle that is skin. This paper presents studies of interactions between N-isopropylacrylamide nanogels, crosslinked with 30% N,N'-methylenebisacrylamide, and model ceramide lipid monolayers at the air-water interface as a function of temperature. In the case of the mixed ceramide/cholesterol/behenic acid monolayer, the interaction of nanogels with the ceramide was strongly mediated by the fatty acids. This interaction between nanogels and monolayer components is dominated by hydrophobic-hydrophobic binding. The data show the important intermediary role of the fatty acid in facilitating transmembrane transport. For a pure ceramide lipid monolayer, the neutron reflectivity (NR), Brewster angle microscopy (BAM) and surface pressure results showed a lipid-nanogel complex formation and the subsequent depletion/solubilisation of the lipids from the interface when the area per molecule for the lipid was increased from 42 to 44 Å.
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http://dx.doi.org/10.1016/j.jcis.2018.02.050DOI Listing
June 2018

Adsorption versus aggregation of NIPAM nanogels: new insight into their behaviour at the air/water interface as a function of concentration.

Phys Chem Chem Phys 2017 Jul;19(26):17173-17179

Department of Chemistry and Biochemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

We have used neutron reflectivity (NR) measurements in combination with dynamic light scattering (DLS), surface tension and ellipsometry, to study the adsorption behaviour at the air/water interface of N-isopropylacrylamide-based nanogels as a function of concentration. The data provide clear evidence that the nanogels are adsorbed at the interface in a strongly deformed shape and forming a multi-layer where the thickness increases with nanogel concentration in the bulk. The combination of surface characterisation techniques and bulk studies indicate that interfacial film formation is preferred over bulk aggregation. This observation at the air/water interface supports the Derjaguin prediction, that a sphere's interaction with a plane (the thick adsorbed nanogel layer at interface) is much larger than nanogel-nanogel (sphere-sphere) association in the bulk. These findings, in particular the changes in conformations and the thick layer adsorption at the interface as a function of concentration, impact significantly on a number of applications for which nanogels are currently being investigated. These results contribute to the understanding of the behaviour of soft colloids at the interfaces.
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http://dx.doi.org/10.1039/c7cp02979aDOI Listing
July 2017

Fluorescent molecularly imprinted nanogels for the detection of anticancer drugs in human plasma.

Biosens Bioelectron 2016 Dec 26;86:913-919. Epub 2016 Jul 26.

Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Italy. Electronic address:

Several fluorescent molecularly imprinted nanogels for the detection of the anticancer drug sunitinib were synthesized and characterized. A selection of functional monomers based on different aminoacids and coumarin allowed isolation of polymers with very good rebinding properties and sensitivities. The direct detection of sunitinib in human plasma was successfully demonstrated by fluorescence quenching of the coumarin-based nanogels. The plasma sample simply diluted in DMSO allowed the recovery of various amounts of sunitib, as determined by an averaged calibration curve. The LOD was 400nM, with within-run variability <9%, day to day variability <5%, and good accuracy in the recovery of sunitinib from spiked samples.
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http://dx.doi.org/10.1016/j.bios.2016.07.087DOI Listing
December 2016

Molecularly Imprinted Polymer Coated Quantum Dots for Multiplexed Cell Targeting and Imaging.

Angew Chem Int Ed Engl 2016 07 30;55(29):8244-8. Epub 2016 May 30.

Sorbonne Universités, Université de Technologie de Compiègne, CNRS Enzyme and Cell Engineering Laboratory, Rue Roger Couttolenc, CS 60319, 60203, Compiègne Cedex, France.

Advanced tools for cell imaging are of great interest for the detection, localization, and quantification of molecular biomarkers of cancer or infection. We describe a novel photopolymerization method to coat quantum dots (QDs) with polymer shells, in particular, molecularly imprinted polymers (MIPs), by using the visible light emitted from QDs excited by UV light. Fluorescent core-shell particles specifically recognizing glucuronic acid (GlcA) or N-acetylneuraminic acid (NANA) were prepared. Simultaneous multiplexed labeling of human keratinocytes with green QDs conjugated with MIP-GlcA and red QDs conjugated with MIP-NANA was demonstrated by fluorescence imaging. The specificity of binding was verified with a non-imprinted control polymer and by enzymatic cleavage of the terminal GlcA and NANA moieties. The coating strategy is potentially a generic method for the functionalization of QDs to address a much wider range of biocompatibility and biorecognition issues.
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http://dx.doi.org/10.1002/anie.201601122DOI Listing
July 2016

The 'Leaky Pipeline'.

Authors:
Marina Resmini

Chemistry 2016 Mar 16;22(11):3533-4. Epub 2016 Feb 16.

Department of Chemistry and Biochemistry, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

Gender bias is widespread and needs to be acknowledged and addressed by the scientific community. In this Guest Editorial, M. Resmini, Professor of Materials Chemistry at the Queen Mary University of London, describes how supervisors can play an important role in addressing the ‘leaky pipeline′, namely, the progressive loss of capable women from STEM disciplines.
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http://dx.doi.org/10.1002/chem.201600292DOI Listing
March 2016

Smart coumarin-tagged imprinted polymers for the rapid detection of tamoxifen.

Anal Bioanal Chem 2016 Mar 9;408(7):1855-61. Epub 2016 Feb 9.

Department of Chemistry, SBCS, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

A signalling molecularly imprinted polymer was synthesised for easy detection of tamoxifen and its metabolites. 6-Vinylcoumarin-4-carboxylic acid (VCC) was synthesised from 4-bromophenol to give a fluorescent monomer, designed to switch off upon binding of tamoxifen. Clomiphene, a chlorinated analogue, was used as the template for the imprinting, and its ability to quench the coumarin fluorescence when used in a 1:1 ratio was demonstrated. Tamoxifen and 4-hydroxytamoxifen were also shown to quench coumarin fluorescence. Imprinted and non-imprinted polymers were synthesised using VCC, methacrylic acid as a backbone monomer and ethylene glycol dimethacrylate as cross-linker, and were ground and sieved to particle sizes ranging between 45 and 25 μm. Rebinding experiments demonstrate that the imprinted polymer shows very strong affinity for both clomiphene and tamoxifen, while the non-imprinted polymer shows negligible rebinding. The fluorescence of the imprinted polymer is quenched by clomiphene, tamoxifen and 4-hydroxytamoxifen. The switch off in fluorescence of the imprinted polymer under these conditions could also be detected under a UV lamp with the naked eye, making this matrix suitable for applications when coupled with a sample preparation system.
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http://dx.doi.org/10.1007/s00216-015-9296-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4759217PMC
March 2016

Smart nanogels at the air/water interface: structural studies by neutron reflectivity.

Nanoscale 2016 Mar;8(9):4951-60

Department of Chemistry, SBCS, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

The development of effective transdermal drug delivery systems based on nanosized polymers requires a better understanding of the behaviour of such nanomaterials at interfaces. N-Isopropylacrylamide-based nanogels synthesized with different percentages of N,N'-methylenebisacrylamide as cross-linker, ranging from 10 to 30%, were characterized at physiological temperature at the air/water interface, using neutron reflectivity (NR), with isotopic contrast variation, and surface tension measurements; this allowed us to resolve the adsorbed amount and the volume fraction of nanogels at the interface. A large conformational change for the nanogels results in strong deformations at the interface. As the percentage of cross-linker incorporated in the nanogels becomes higher, more rigid matrices are obtained, although less deformed, and the amount of adsorbed nanogels is increased. The data provide the first experimental evidence of structural changes of nanogels as a function of the degree of cross-linking at the air/water interface.
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http://dx.doi.org/10.1039/c5nr07538fDOI Listing
March 2016

Incorporation of Cobalt-Cyclen Complexes into Templated Nanogels Results in Enhanced Activity.

Chemistry 2016 Mar 10;22(11):3764-74. Epub 2015 Dec 10.

Department of Chemistry and Biochemistry, School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

Recent advances in nanomaterials have identified nanogels as an excellent matrix for novel biomimetic catalysts using the molecular imprinting approach. Polymerisable Co-cyclen complexes with phosphonate and carbonate templates have been prepared, fully characterised and used to obtain nanogels that show high activity and turnover with low catalytic load, compared to the free complex, in the hydrolysis of 4-nitrophenyl phosphate, a nerve agent simulant. This work demonstrates that the chemical structure of the template has an impact on the coordination geometry and oxidation state of the metal centre in the polymerisable complex resulting in very significant changes in the catalytic properties of the polymeric matrix. Both pseudo-octahedral cobalt(III) and trigonal-bipyramidal cobalt(II) structures have been used for the synthesis of imprinted nanogels, and the catalytic data demonstrate that: i) the imprinted nanogels can be used in 15 % load and show turnover; ii) the structural differences in the polymeric matrices resulting from the imprinting approach with different templates are responsible for the molecular recognition capabilities and the catalytic activity. Nanogel P1, imprinted with the carbonate template, shows >50 % higher catalytic activity than P2 imprinted with the phosphonate.
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http://dx.doi.org/10.1002/chem.201503946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4797703PMC
March 2016

Smart Polymeric Nanoparticles as Emerging Tools for Imaging--The Parallel Evolution of Materials.

Chemistry 2016 Mar 13;22(11):3612-20. Epub 2015 Nov 13.

Queen Mary University of London, Department of Chemistry, SBCS, Mile End Road, London, E1 4NS, UK.

The field of imaging has developed considerably over the past decade and recent advances in the area of nanotechnology, in particular nanomaterials, have opened new opportunities. Polymeric nanoparticles are particularly interesting and a number of novel materials, characterized by stimuli-responsive characteristics and fluorescent tagging, have allowed visualization, intracellular labeling and real-time tracking. In some of the latest applications the nanoparticles have been used for imagining of tumor cells, both in vivo and ex vivo.
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http://dx.doi.org/10.1002/chem.201502610DOI Listing
March 2016

Molecularly Imprinted Polymers for Catalysis and Synthesis.

Adv Biochem Eng Biotechnol 2015 ;150:107-29

School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK.

The area of biomimetic catalysis based on molecular imprinted polymers has progressed considerably over the last two decades, with research efforts focused on developing catalysts for challenging reactions and on understanding the key factors in template structure and polymer morphology that influence efficiency and selectivity. Recent advances and significant achievements in the field presented in this chapter are organized according to four topics: hydrolytic reactions of challenging substrates, oxidase mimics, metallo-enzyme mimics, and polymers that display unusual reactivity, such as in the case of reactions for which enzymes don't exist, such as Diels-Alder and Kemp elimination. For each theme, significant examples for recent literature are presented and discussed.
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http://dx.doi.org/10.1007/10_2015_319DOI Listing
November 2015

A versatile fiber-optic fluorescence sensor based on molecularly imprinted microstructures polymerized in situ.

Angew Chem Int Ed Engl 2013 Aug 21;52(32):8317-21. Epub 2013 Jun 21.

Université de Technologie de Compiègne, Génie Enzymatique et Cellulaire, Rue Roger Couttolenc, CS60319, 60203 Compiègne, France.

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http://dx.doi.org/10.1002/anie.201301045DOI Listing
August 2013

Protein-size molecularly imprinted polymer nanogels as synthetic antibodies, by localized polymerization with multi-initiators.

Adv Mater 2013 Feb 8;25(7):1048-51. Epub 2012 Nov 8.

UMR CNRS 6022, Compiègne University of Technology, Compiègne, France.

A new approach is proposed for the synthesis of molecularly imprinted polymers (MIPs) (synthetic antibodies) as soluble nanogels with sizes close to the size of real antibodies. To imprint a molecular memory in particles consisting of only a few polymer chains, an initiator carrying multiple iniferter moieties is used. This allows for the simultaneous initiation of several polymer chains, and yields molecularly imprinted nanogels (17 nm, molecular weight (MW) = 97 kDa) with good affinity and selectivity for the target.
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http://dx.doi.org/10.1002/adma.201203400DOI Listing
February 2013

Modulation of imprinting efficiency in nanogels with catalytic activity in the Kemp elimination.

J Mol Recognit 2012 Jun;25(6):352-60

School of Biological and Chemical Sciences, Queen Mary University of London, Mile end road, London E1 4NS, UK.

The interactions between the template and the functional monomer are a key to the formation of cavities in the imprinted nanogels with high molecular recognition properties. Nanogels with enzyme-like activity for the Kemp elimination have been synthesized using 4-vinylpyridine as the functional monomer and indole as the template. The weak hydrogen bond interaction in the complex is shown to be able to induce very distinctive features in the cavities of the imprinted nanogels. The percentage of initiator used in the polymerisation, ranging from 1% to 3%, although it does not have a substantial effect on the catalytic rate, reduces considerably the imprinting efficiency. The alteration of the template/monomer ratio is also investigated, and the data show that there is considerable loss of imprinting efficiency. In terms of substrate selectivity, a number of experiments have been performed using 5-Cl-benzisoxazole as substrate analogue, as well as 5-nitro-indole as template analogue for the preparation of a different set of nanogels. All the kinetic data demonstrate that the chemical structure of the template is key to the molecular recognition properties of the imprinted nanogels that are closely tailored and able to differentiate among small structural changes.
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http://dx.doi.org/10.1002/jmr.2180DOI Listing
June 2012

Molecularly imprinted polymers as biomimetic catalysts.

Authors:
Marina Resmini

Anal Bioanal Chem 2012 Apr 14;402(10):3021-6. Epub 2012 Jan 14.

School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

The quest for synthetic biomimetic catalysts able to complement the activity of enzymes has attracted substantial research efforts, and the molecular imprinting approach is one of the attractive techniques that are currently being investigated. In the last 3 years, there has been considerable interest in studying in greater detail the parameters that control and influence the catalytic activity of imprinted polymers and applying molecular imprinting to a wider range of polymeric matrices. This article reports on some of the interesting examples available in the literature regarding the use of metal-containing polymers, microgels and nanogels and thermoresponsive polymers.
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http://dx.doi.org/10.1007/s00216-011-5671-2DOI Listing
April 2012

Identification of interactions involved in the generation of nucleophilic reactivity and of catalytic competence in the catalytic site Cys/His ion pair of papain.

Biochemistry 2011 Dec 17;50(49):10732-42. Epub 2011 Nov 17.

Laboratory of Structural and Mechanistic Enzymology, School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK.

Understanding the roles of noncovalent interactions within the enzyme molecule and between enzyme and substrate or inhibitor is an essential goal of the investigation of active center chemistry and catalytic mechanism. Studies on members of the papain family of cysteine proteinases, particularly papain (EC 3.4.22.2) itself, continue to contribute to this goal. The historic role of the catalytic site Cys/His ion pair now needs to be understood within the context of multiple dynamic phenomena. Movement of Trp177 may be necessary to expose His159 to solvent with consequent decrease in its degree of electrostatic solvation of (Cys25)-S(-). Here we report an investigation of this possibility using computer modeling of quasi-transition states and pH-dependent kinetics using 3,3'-dipyridazinyl disulfide, its n-propyl and phenyl derivatives, and 4,4'-dipyrimidyl disulfide as reactivity probes that differ in the location of potential hydrogen-bonding acceptor atoms. Those interactions that influence ion pair geometry and thereby catalytic competence, including by transmission of the modulatory effect of a remote ionization with pK(a) 4, were identified. A key result is the correlation between the kinetic influence of the modulatory trigger of pK(a) 4 and disruption of the hydrogen bond donated by the indole N-H of Trp177, the hydrophobic shield of the initial "intimate" ion pair. This hydrogen bond is accepted by the amide O of Gln19-a component of the oxyanion hole that binds the tetrahedral species formed from the substrate during the catalytic act. The disruption would be expected to contribute to the mobility of Trp177 and possibly to the effectiveness of the binding of the developing oxyanion.
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http://dx.doi.org/10.1021/bi201207zDOI Listing
December 2011

Tuning molecular recognition in water-soluble nanogels with enzyme-like activity for the kemp elimination.

Chemistry 2011 Sep 18;17(39):11052-9. Epub 2011 Aug 18.

School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK.

The synthesis and characterization of water-soluble imprinted nanogels with enzyme-like activity in the Kemp elimination is reported together with studies that demonstrate how the recognition properties, morphology, and catalytic activity of the nanoparticles can be tuned by the use of surfactants, such as Tween 20. A detailed kinetic investigation is carried out, which shows clear evidence of saturation kinetics and rule out the effects of mass transfer. This is supported by characterization of the polymeric materials that confirms the morphological changes resulting from the use of surfactants. These results provide an important tool for the development of nanoparticle-based, new catalyst-mimicking enzymes.
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http://dx.doi.org/10.1002/chem.201002747DOI Listing
September 2011

Simple spectroscopic method for titration of binding sites in molecularly imprinted nanogels with hydrolase activity.

Biosens Bioelectron 2009 Nov 5;25(3):572-8. Epub 2009 Apr 5.

School of Biological and Chemical Sciences, Walter Besant Building, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.

In this investigation we report the preparation of soluble molecularly imprinted catalytic nanogels with hydrolytic activity. The nanogels were imprinted using a stoichiometric non-covalent approach, employing a phosphate transition state analogue as template and polymerizable tyrosine and arginine units as functional monomers, for catalysis of a carbonate hydrolysis reaction. Full characterization of the rebinding and of the hydrolytic activity was performed, with particular emphasis on a novel titration method developed for the measurement of active site concentrations and the subsequent calculation of accurate catalytic parameters. Considering the features of the template molecule and the functional monomers used, an original method for performing rebinding experiments is described, taking advantage of the change of the visible spectrum evident on binding the sodium salt of the template to the arginine residue present in the nanogel.
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http://dx.doi.org/10.1016/j.bios.2009.03.042DOI Listing
November 2009