Marco Laurenti

McGill University, Montréal, Quebec, Canada

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Publications (13)50.91 Total impact

  • 07/2015; 2(7):075002. DOI:10.1088/2053-1591/2/7/075002
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    ABSTRACT: In this work we present a novel method to produce thermo-responsive, monodisperse microgels, which display temperature dependent photoluminescence. The system is based on bimetallic cores of Au@Ag encapsulated within thermo-responsive poly(N-Isopropylacrylamide) (PNIPAM) microgels and coated with a photoluminescent polymer (poly[2-(3-thienyl)ethoxy-4-butylsulfonate] (PTEBS) by Layer-by-Layer (LBL) technique. The electromagnetic radiation used to excite the PTEBS induces a local electromagnetic field on the surface of the bimetallic cores that enhances the excitation and emission rates of the PTEBS, yielding a metal enhanced fluorescence (MEF). This effect was studied as a function of the bimetallic core size and the separation distance between the PTEBS and the bimetallic cores. Our results permit evaluating for the first time the effect that the metallic core size of colloidal particles exert on the MEF, and prove the relevance of the metallic cores to extend the effect far away from the metallic surface.
    Langmuir 12/2014; 30(51). DOI:10.1021/la503864f · 4.46 Impact Factor
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    ABSTRACT: Multifunctional, biocompatible, and brush-grafted poly(ethylene glycol)/poly(ε-caprolactone) (PEG/PCL) nanoparticles have been synthesized, characterized, and used as vehicles for transporting hydrophobic substances in water. For anchoring the polymer mixed brushes, we used magnetic-silica particles of 40 nm diameter produced by the reverse microemulsion method. The surface of the silica particle was functionalized with biocompatible polymer brushes, which were synthesized by the combination of “grafting to” and “grafting from” techniques. PEG was immobilized on the particles surface, by “grafting to,” whereas PCL was growth by ROP using the “grafting from” approach. By varying the synthetic conditions, it was possible to control the amount of PCL anchored on the surface of the nanoparticles and consequently the PEG/PCL ratio, which is a vital parameter connected with the arrangement of the polymer brushes as well as the hydrophobic/hydrophilic balance of the particles. Thus, adjusting the PEG/PCL ratio, it was possible to obtain a system formed by PEG and PCL chains grafted on the particle's surface that collapsed in segregated domains depending on the solvent used. For instance, the nanoparticles are colloidally stable in water due to the PEG domains and at the same time are able to transport, entrapped within the PCL portion, highly water-insoluble drugs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014
    Journal of Polymer Science Part A Polymer Chemistry 10/2014; 52(20). DOI:10.1002/pola.27338 · 3.11 Impact Factor
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    ABSTRACT: The synthesis of temperature-responsive microgels of poly(N-isopropylacrylamide) (PNIPAM) was first reported in 1986 and, since then, there have been hundreds of publications describing the preparation, characterization and applications of these systems. This paper reviews the developments concerning the study of the structure of PNIPAM-based microgels performed over the last years using small angle neutron scattering (SANS) and also the investigations of the polymer-chain dynamics within the microgels carried out with incoherent elastic and quasielastic neutron scattering, and pulse field gradient nuclear magnetic resonance (PFG-NMR) techniques. Furthermore, the self-diffusion coefficient of the water molecules within the microgel, determined by means of solvent relaxation NMR, is also discussed as a function of the polymer volume fraction of the microgels.
    Advances in Colloid and Interface Science 11/2013; 205. DOI:10.1016/j.cis.2013.11.001 · 7.78 Impact Factor
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    ABSTRACT: In this work, we present a suitable methodology to produce magnetically recoverable bioreactors based on enzymes, which are covalently attached on the surface of iron oxide@silica nanoparticles. In order to produce this system, iron oxide clusters with a mean diameter of 68nm were covered with silica. This strategy yields spherical γ-Fe2O3@SiO2 cluster@shell nanoparticles with a mean diameter of 200nm which present magnetic responsiveness and enhanced stability. The surface of these nanoparticles was modified into two steps with the aim to obtain carboxylic functional groups, which were activated to react with the enzyme glucose oxidase (GOx) that was thus immobilized on the surface of the nanoparticles. The objective of this chemistry at the nanoparticles interface is to produce magnetic-responsive bioreactors. The enzymatic activity was evaluated by using the recoverable bioreactors as part of an amperometric biosensor. These measurements allowed determining the stability, catalytic activity and the amount of enzyme immobilized on the surface of the nanoparticles. Furthermore, the functionalized nanoparticles can be recovered by applying an external magnetic field, which allows them to be employed in chemical processes where the recovery of the biocatalyst is important.
    Colloids and surfaces B: Biointerfaces 10/2013; 114C:11-19. DOI:10.1016/j.colsurfb.2013.09.051 · 4.15 Impact Factor
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    ABSTRACT: UCST-like microgels constituted by chains of poly(acrylic acid) (PAAc) and poly(acrylamide) (PAAm) show an intense swelling behavior when they are heated that is not comparable with the observed in neat poly(acrylamide) neither neat poly(acrylic acid) microgels. In order to figure out the microscopic changes that occur within the microgels, we have used quasielastic neutron scattering (IQNS) and FTIR-ATR techniques in order to study the polymer dynamics and the chemical groups, which are involved along this process. With IQNS we have observed that at 290 K, the co-existence of PAAc and PAAm in the microgels, produced a substantial reduction of the vibrational motion of the polymer chains as well as a reduction of the segmental diffusion coefficient. By contrast when the microgels were heated at 330 K, we observed an increment of the oscillations of the vibrational component as well as a significant increment of the segmental diffusion coefficient. The FTIR-ATR experiments indicated that during the microgel heating, there is a rupture of the intramolecular hydrogen bonds existing between the groups COOH and CONH2 of neighboring polymer chains. This process is reversible and these interactions reappear again when the system is cooled at 290 K, during the collapse of the microgels.
    Polymer 08/2013; 54(18):4963-4971. DOI:10.1016/j.polymer.2013.06.057 · 3.56 Impact Factor
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    ABSTRACT: In this work, we report the synthesis, characterization, and possible application as drug-delivery system magnetically triggered, of hybrid microparticles formed by magnetic nanoparticles embedded within poly(ε-caprolactone). The magnetism of the microparticles permits their localization within the body using magnetic resonance imaging, and the biodegradable polymer layer allows entrapping drugs that can be released when temperature increases. The synthesis of the hybrid material was performed using "grafting from" technique of conveniently modified magnetic nanoparticles. Subsequently, the resulting hybrid nanoparticles were assembled into spherical particles of 138 ± 49 nm via precipitation technique. The produced hybrid material was evaluated as stimuli-responsive drug delivery system in which the release of the drug was triggered by magnetic induction. Furthermore, the microparticles were injected in rats and their localization within the animal was monitored using the local field inhomogeneities generated by the particles. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 05/2013; 101B(4). DOI:10.1002/jbm.b.32792 · 2.76 Impact Factor
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    ABSTRACT: This work reports the synthesis of a new water-soluble conjugated polymer, which interacts specifically with heavy metal ions such as lead and mercury. In order to produce such a material, the fluorescent properties of polythiophene, which constitutes the polymer backbone, were combined with the chelating capacity of meso-2,3-dimercaptosuccinic acid, which forms the side-chain of the conjugated polymer. Thus, the new polymer acts as chemical complexing agent, the fluorescence of which is quenched in the presence of heavy metal ions. A possible explanation of the mechanism of such a variation is also discussed. The system presented is envisaged to be used as a sensor for heavy metal ions that appear as pollutants in the environment.
    Polymer International 05/2013; 62(5):811-816. DOI:10.1002/pi.4369 · 2.41 Impact Factor
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    ABSTRACT: An amphiphilic star shaped block copolymer, based on well known biocompatible components, was synthesized using branched poly(ε-caprolactone) as hydrophobic core and branched poly(ethyleneglycol) as hydrophilic corona. The composition of this macromolecule, based on two well differentiated blocks, conferred amphiphilic behavior to the whole system that acted as driving force for its self-assembling in aqueous media. Depending on the polymer concentration it was possible to obtain different architectures. The TEM micrographs permitted to follow the evolution of the system from single vesicles toward necklace entanglements. In this work, we discuss the mechanism that would be involved in the evolution of the system's morphology as a function of the block copolymer concentration. In addition, the proposed star shaped block copolymer presented good solubilizing properties that were used to disperse in water, poorly soluble molecules such as chlorine-carbazoles, which were used to investigate the suitability of the self-assembled nanostructures as drug nano-carriers.
    Polymer 09/2012; 53(21):4569–4578. DOI:10.1016/j.polymer.2012.08.016 · 3.56 Impact Factor
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    ABSTRACT: In this work, we describe a new methodology for the preparation of monodisperse and thermosensitive microgels with magnetic core. In order to produce such a material, hydrophobic magnetic Fe(3)O(4) nanoparticles were prepared by two methods: thermal decomposition and coprecipitation. The surface of these nanoparticles was modified by addition of 3-butenoic acid, and after that these nanoparticles were dispersed in water and submitted to free radical polymerization at 70 °C in the presence of N-isopropylacrylamide (NIPAM) and bisacrylamide. The result of this reaction was monodisperse microgels with a magnetic core. By varying the amount of 3-butenoic acid, it was possible to obtain hybrid microgels with different magnetic core sizes and different architectures.
    Langmuir 08/2011; 27(17):10484-91. DOI:10.1021/la201723a · 4.46 Impact Factor
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    ABSTRACT: We report the fluorescence decrease of the water-soluble π-π-conjugated polymer poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene, MPS-PPV) by the catalytic activity of horseradish peroxidase in the presence of H(2)O(2). MPS-PPV acts as a donor substrate in the catalytic cycle of horseradish peroxidase where the electron-deficient enzymatic intermediates compounds I and II can subtract electrons from the polymer leading to its fluorescence decrease. The addition of phenolic drug acetaminophen to the former solution favors the decrease of the polymer fluorescence, which indicates the peroxidase-catalyzed co-oxidation of MPS-PPV and acetaminophen. The encapsulation of horseradish peroxidase within polyacrylamide microgels allows the isolation of intermediates compound I and compound II from the polymer, leading to a fluorescence decrease that is only due to the product of biocatalytic acetaminophen oxidation. This system could be used to develop a new device for phenolic compounds detection.
    Biomacromolecules 02/2011; 12(4):1332-8. DOI:10.1021/bm200091m · 5.75 Impact Factor
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    ABSTRACT: In this work, we present a facile and reproducible method to obtain thermally responsive, monodisperse, fluorescent microgels with diameters smaller than 700 nm based on poly(N-isopropyl acrylamide) (PNIPAM) interpenetrated with poly(thiophene-ethyl buthyl sulfonate) (PTEBS). Changing the temperature and inducing the microgel volume phase transition, it is possible to modify the photoluminescence (PL) properties of the microgels. Thus, when the temperature was below the low critical solution temperature (LCST) of PNIPAM, the PL intensity was higher than that above the LCST. Time-resolved fluorescence measurements indicate that, in the swollen state, the increment of cross-linking increases the fluorescence decay time of PTEBS. By contrast, in the collapsed state, variations in the decay time were attributed to higher rigidity of the PNIPAM-PTEBS system, which was confirmed by neutron scattering measurements. Moreover, the shift in the wavelength of the fluorescence emission peak observed above the LCST indicates that the collapsed PNIPAM matrix was able to interact with the PTEBS chains hindering the formation of pi-pi interactions. This property is envisaged for developing a picric acid microsensor based on the formation of pi-pi interactions with the pi-conjugated polymer, thus quenching its PL emission. Above the LCST of PNIPAM-PTEBS microgels, the interactions would be broken and the initial PL emission would be recovered. This property could render reusable microsensors for detection of nitro aromatic compounds.
    Langmuir 06/2009; 25(16):9579-84. DOI:10.1021/la900864a · 4.46 Impact Factor
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    ABSTRACT: In this work, we report the influence of surfactant chain length and surfactant concentration on the photoluminescence (PL) of water-soluble pi-conjugated poly(thienyl ethylene oxide butyl sulfonate) (PTE-BS). We have used alkylammomium surfactants with 8, 9, 10, and 12 carbon atoms per hydrocarbon chain. The surfactant concentration was varied from 0.125 the critical micelle concentration (CMC) up to 2 times the CMC. The results show that at premicellar concentrations all the surfactants promote the polymer aggregation inducing an increase in the interchain charge transfer by pi-pi interactions, which competes with PL emission processes. However, in the premicellar range, the polymer PL emission is sharply affected by the surfactant chain length. Thus, the PL is quenched by the surfactants with the shortest tails, whereas the surfactants with the longest ones provoke an enhancement of the PL emission. This behavior has been associated with the capacity of the surfactants with the longest hydrocarbon chains to accommodate their tails inside the polymer, obstructing the appearance of pi-pi interchain interactions during aggregation and reducing intrachain defects. By contrast, at the CMC, the surfactant chain length does not modify the PL emission, since the excess of surfactant inhibits polymer aggregation, thus enhancing the efficiency of light emissive processes.
    Langmuir 12/2008; 24(23):13321-7. DOI:10.1021/la802246g · 4.46 Impact Factor

Publication Stats

74 Citations
50.91 Total Impact Points


  • 2014
    • McGill University
      • Faculty of Dentistry
      Montréal, Quebec, Canada
  • 2008-2013
    • Complutense University of Madrid
      • • Department of Physical Chemistry II (Physic-Chemistry Pharmaceutic)
      • • Department of Physical Chemistry I
      Madrid, Madrid, Spain