Deposition of anionic conjugated poly(phenylenevinylene) onto silica nanoparticles via electrostatic interactions — Assembly and single-particle spectroscopy

Ngo, An Thien; Lau, Kai Lin; Quesnel, Jeffrey S.; Aboukhalil, Robert AboukhalilR.; Cosa, Gonzalo

doi:10.1139/v10-141

Cited by 8 publications

(10 citation statements)

References 37 publications

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“…We first explored at the ensemble level the interaction of MPS-PPV-coated NPs with 100-nm-diameter DOTAP liposomes by adding a suspension of NPs to a 100-fold excess of 100-nm-diameter liposomes (final concentrations of 0.1 and 13 nM, respectively). To prepare the MPS-PPV-coated NPs, we adapted a previously reported method to functionalize 100 nm SiO 2 nanoparticles with an aminosilane group, thus rendering the particles positively charged at neutral to low pH and facilitating the adsorption of the polyanion via electrostatic interactions. , The full characterization of the functionalization of SiO 2 to SiO 2 NH 3 + and of the adsorption of MPS-PPV onto these particles by transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV–vis and fluorescence spectroscopy is described in the Supporting Information section (Figures S1–S4). A 23-fold emission enhancement and a new shoulder at 585 nm were observed in the emission spectrum of MPS-PPV adsorbed on the NPs immediately after mixing with the DOTAP liposomes (Figure A, see also normalized emission spectra, Figure S5).…”

Section: Resultsmentioning

confidence: 99%

“…Conjugated polyanion poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene (MPS-PPV) was adsorbed onto the surface of amino-functionalized 100-nm-diameter silica nanoparticles (NPs), and the NPs were in turn immobilized onto a coverslip for single-molecule imaging. , Using total internal reflection fluorescence microscopy (TIRFM) with a two-color detection scheme, we were able to monitor in real time the encounter and subsequent deformation of incoming liposomes prepared from cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) on the surface of the NPs. Deaggregation of MPS-PPV upon interaction with excess liposomes led to dramatic (average 23-fold) MPS-PPV emission intensity enhancements.…”

Section: Introductionmentioning

confidence: 99%

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Exploiting Conjugated Polyelectrolyte Photophysics toward Monitoring Real-Time Lipid Membrane-Surface Interaction Dynamics at the Single-Particle Level

2015

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Herein we report the real-time observation of the interaction dynamics between cationic liposomes flowing in solution and a surface-immobilized charged scaffolding formed by the deposition of conjugated polyanion poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene (MPS-PPV) onto 100-nm-diameter SiO2 nanoparticles (NPs). Contact of the freely floating liposomes with the polymer-coated surfaces led to the formation of supported lipid bilayers (SLBs). The interaction of the incoming liposomes with MPS-PPV adsorbed on individual SiO2 nanoparticles promoted the deaggregation of the polymer conformation and led to large emission intensity enhancements. Single-particle total internal reflection fluorescence microscopy studies exploited this phenomenon as a way to monitor the deformation dynamics of liposomes on surface-immobilized NPs. The MPS-PPV emission enhancement (up to 25-fold) reflected on the extent of membrane contact with the surface of the NP and was correlated with the size of the incoming liposome. The time required for the MPS-PPV emission to reach a maximum (ranging from 400 to 1000 ms) revealed the dynamics of membrane deformation and was also correlated with the liposome size. Cryo-TEM experiments complemented these results by yielding a structural view of the process. Immediately following the mixing of liposomes and NPs the majority of NPs had one or more adsorbed liposomes, yet the presence of a fully formed SLB was rare. Prolonged incubation of liposomes and NPs showed completely formed SLBs on all of the NPs, confirming that the liposomes eventually ruptured to form SLBs. We foresee that the single-particle studies we report herein may be readily extended to study membrane dynamics of other lipids including cellular membranes in live cell studies and to monitor the formation of polymer-cushioned SLBs.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exploiting Conjugated Polyelectrolyte Photophysics toward Monitoring Real-Time Lipid Membrane-Surface Interaction Dynamics at the Single-Particle Level

2015

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“…Our work with CPEs was sparked by an interest in generating a technology capable of addressing (via fluorescence) individual surface-tethered liposomes in order to conduct high-throughput membrane binding assays [37][38][39][40] on liposome arrays [41]. We have been working on an innovative solution relying on the encapsulation of water-soluble CPEs within liposomes to generate a liposome beacon platform.…”

Section: Conjugated Polyelectrolyte-lipid Interactionsmentioning

confidence: 99%

Conjugated polyelectrolyte–lipid interactions: Opportunities in biosensing

Ngo

Karam

Cosa

2010

Pure and Applied Chemistry

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Fluorescent conjugated polyelectrolytes (CPEs) have attracted considerable interest over the past decade as novel materials for developing biosensing schemes and sensing devices for biomolecules. This interest stems from the exquisite polymer sensitivity to the presence of fluorescence quenchers, enabling amplified sensing of molecules of interest. Efficient energy transport along the polymer backbone is critical to their sensing capabilities. Considerable research efforts have thus gone into understanding and controlling energy transport along the polymer backbone. In particular, it has been shown that interactions between CPEs with either surfactants or lipid molecules may significantly reduce energy transport along the polymer backbone that in turn may provide for unique biosensing opportunities. In the first half of this review, we give a historical overview on energy transport in conjugated polymers and polyelectrolytes. In the second half, we summarize the most recent work on the interaction of CPEs with surfactants with an emphasis on our own work elucidating electronic energy transport in CPEs encapsulated into lipid vesicles or embedded within the membrane of lipid vesicles.

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“…The PMOH-functionalized surface-grafted polymers were imaged using a wide-field objective-based total internal reflection (TIRF) microscopy setup consisting of an inverted microscope (IX71, Olympus) equipped with a laser-based TIRF illumination module (IX2-RFAEVA-2, Olympus). , Laser excitation was provided by a 25 mW, 532 nm output, diode-pumped cw laser (CL532–025-S, CrystaLaser), attenuated with metallic ND filters and providing 2–7 μW output at the objective. The excitation beam was directed to the sample by reflection on a dichroic beamsplitter (z532rdc) and focused on the back focal plane of a high numerical aperture (N.A.…”

Section: Surface Characterizationmentioning

confidence: 99%

Monitoring in Real-Time the Degrafting of Covalently Attached Fluorescent Polymer Brushes Grafted to Silica Substrates—Effects of pH and Salt

et al. 2011

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Polymer-bearing surfaces are of particular interest because of their thermal and solvent response, 1,2 their prospective use as protein and cell adhesive platforms, 3À5 or as self-biolubricating substrates, among others. 6 Surface-tethered polymer chains provide the means to tailor the surface properties by undergoing externally stimulated conformational changes. This is particularly true for polyelectrolyte polymers such as poly(acrylic acid) (PAA) whose degree of ionization is highly influenced by pH, ionic strength, and the presence of multivalent species. 7,8 Various polymer conformations including pancake and brushes are possible with end-tethered polyelectrolytes by varying surface density and the media. 9 The control of conformational properties have allowed for advances in areas such as surface friction modulation, switchable wettability, autophobicity, 10À12 antifouling 13À16 and lubricity, 6,17À21 to name but a few.Surface-bound polymers of well-defined discrete degrees of polymerization and high surface homogeneity are desired for ensuring control of surface properties and reversible surface response with external stimuli such as temperature, pH and ionic strength. These polymers can be obtained by controlled polymerization with an ATRP initiator chemically linked to the substrate. For silica substrates, the substrateÀinitiator linkage (Si substrate ÀOÀSi initiator bond) is generally robust enough for both sustaining the reaction conditions required for ATRP and subsequent polymer brush formation and characterization. We recently showed that PAA brushes built on mica by anchoring polystyrene-poly(acrylic acid)(PS-b-PAA) diblock copolymers in a polystyrene monolayer covalently attached to OH-activated mica surfaces resist to cleavage at pH 5.5 with added salt for several days. 22 However, there is still uncertainty regarding the robustness of the substrateÀpolymer bond and whether it is resistant to the extreme pH and ionic strengths that are required for conformational analyses of polyelectrolyte brushes. It is unknown whether these extreme conditions hydrolyze the SiÀOÀSi bond and cleave the polymer from the substrate leading to undesired decrease in polymer grafting density, similar to what was reported for poly(methacrylic acid) brushes and PAA brushes grafted from silica-based substrates. 23À25 Knowing the conditions under which undesired polymer cleavage occurs is pivotal for accurate surface-property studies. They are also important for controlling reversible polymer conformational changes, while preventing polymer degrafting. Although we previously provided indirect evidence for polymer cleavage from mica at high pH and salt concentrations, 23 determining the exact conditions under which PAA cleavage occurred was not possible. Also, unequivocal evidence for polymer degrafting from silica substrates has not yet been demonstrated.ABSTRACT: Poly(acrylic acid) (PAA) covalently immobilized on glass substrates was made fluorescent by grafting a BODIPY derivative (PMOH) via an ester linkage. Although...

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Deposition of anionic conjugated poly(phenylenevinylene) onto silica nanoparticles via electrostatic interactions — Assembly and single-particle spectroscopy

Cited by 8 publications

References 37 publications

Exploiting Conjugated Polyelectrolyte Photophysics toward Monitoring Real-Time Lipid Membrane-Surface Interaction Dynamics at the Single-Particle Level

Exploiting Conjugated Polyelectrolyte Photophysics toward Monitoring Real-Time Lipid Membrane-Surface Interaction Dynamics at the Single-Particle Level

Conjugated polyelectrolyte–lipid interactions: Opportunities in biosensing

Monitoring in Real-Time the Degrafting of Covalently Attached Fluorescent Polymer Brushes Grafted to Silica Substrates—Effects of pH and Salt

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