Formation of Viscoelastic Protein Droplets on a Chemically Functionalized Surface

Belegrinou, Serena; Mannelli, Ilaria; Sirghi, Lucel; Bretagnol, F.; Valsesia, Andrea; Rauscher, Hubert; Rossi, François

doi:10.1021/jp073297x

Cited by 3 publications

(5 citation statements)

References 21 publications

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“…This model provides a good fit and gives a kinetic constant of 4.0 × 10 −2 s −1 , which underlines the strong attractive electrostatic forces. In fact, this is consistent with the previous observation that under these conditions lactoferrin forms aggregates (“droplets”) on the surface rather than a closed film, which indicates that for Lf on PAA the attractive forces between the protein molecules are even stronger than between the molecules and the surface …”

Section: Resultssupporting

confidence: 92%

“…In general, pronounced changes in dissipation can be associated for instance with strong structural changes , or phase transitions (e.g., spreading effects, rearrangements). , In the case of lactoferrin on PAA, however, this peculiar behavior was shown to result from the formation of protein aggregates, or droplets, on the surface . These aggregates initially have a high nucleation density on the surface and coagulate later to form larger droplets.…”

Section: Resultsmentioning

confidence: 99%

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pH-Dependent Immobilization of Proteins on Surfaces Functionalized by Plasma-Enhanced Chemical Vapor Deposition of Poly(acrylic acid)- and Poly(ethylene oxide)-like Films

et al. 2008

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The interaction of the proteins bovine serum albumin (BSA), lysozyme (Lys), lactoferrin (Lf), and fibronectin (Fn) with surfaces of protein-resistant poly(ethylene oxide) (PEO) and protein-adsorbing poly(acrylic acid) (PAA) fabricated by plasma-enhanced chemical vapor deposition has been studied with quartz crystal microbalance with dissipation monitoring (QCM-D). We focus on several parameters which are crucial for protein adsorption, i.e., the isoelectric point (pI) of the proteins, the pH of the solution, and the charge density of the sorbent surfaces, with the zeta-potential as a measure for the latter. The measurements reveal adsorption stages characterized by different segments in the plots of the dissipation vs frequency change. PEO remains protein-repellent for BSA, Lys, and Lf at pH 4-8.5, while weak adsorption of Fn was observed. On PAA, different stages of protein adsorption processes could be distinguished under most experimental conditions. BSA, Lys, Lf, and Fn generally exhibit a rapid initial adsorption phase on PAA, often followed by slower processes. The evaluation of the adsorption kinetics also reveals different adsorption stages, whereas the number of these stages does not always correspond to the structurally different phases as revealed by the D- f plots. The results presented here, together with information obtained in previous studies by other groups on the properties of these proteins and their interaction with surfaces, allow us to develop an adsorption scenario for each of these proteins, which takes into account electrostatic protein-surface and protein-protein interaction, but also the pH-dependent properties of the proteins, such as shape and exposure of specific domains.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

pH-Dependent Immobilization of Proteins on Surfaces Functionalized by Plasma-Enhanced Chemical Vapor Deposition of Poly(acrylic acid)- and Poly(ethylene oxide)-like Films

et al. 2008

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“…Supported 2D-arrays of clusters of protein molecules or protein solution droplets, protein chips, , hold promise as high-throughput platforms for biosensors, for profiling disease-related proteins, and for other applications. − Such arrays have been built using photolithography, , self-assembly of monolayers , and protein-coated colloids, soft lithography, microcontact printing, , microfluidic networks, , “dip-pen” nanolithography, , and other methods on substrates such as silicon, glass, and gold. ,,, These methods rely either on elaborate manipulation of single protein molecules or on deposition of protein solution droplets. In that latter case, the smallest droplets have been of nanoliter volumes, that is, of >100 μm size, with limitations due to solution viscosity and protein denaturation at high extruding pressures …”

Section: Introductionmentioning

confidence: 99%

Localized Generation of Attoliter Protein Solution Droplets by Electrofocused Liquid−Liquid Separation

Shah

Vekilov

2009

J. Phys. Chem. B

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We develop a simple technique for the generation of droplets of a high-concentration protein solution of attoliter volume and a diameter of >or=500 nm, containing several thousand protein molecules, and their accurate deposition on micron-size electrodes, standalone or in an array. The technique is based on liquid-liquid phase separation in the homogeneous region of the phase diagram, induced by a nonuniform weak electric field, which also accurately directs the generated droplets toward the electrode. We show that the protein molecules are not chemically modified and retain their integrity, conformation, and activity post deposition. The technique is applicable to the manufacture of various types of protein/microelectrode arrays and is tunable, scalable, and applicable to a broad range of proteins.

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“…We postulate that due to the positive charge of polylysine, the increase in adsorption of this species was due to an increase in negative charge-bearing moieties on the surface of plasma-oxidized film. As with many materials, even a brief exposure to oxygen plasma, hydroxyl groups will be added to the surface, transiently increasing the density of negatively charge, which can promote more adsorption of polylysine. − Indeed, the XPS analysis of our PEO-like material showed a marked increase in carboxyl and ester groups on the plasma oxidized surfaces, which was accompanied by a change in surface energy as seen in the change in the decrease in water contact angles. Previous studies have in fact shown that surface charge and wettability do have a significant influence the adsorption of molecules to surfaces…”

Section: Resultsmentioning

confidence: 87%

“…As with many materials, even a brief exposure to oxygen plasma, hydroxyl groups will be added to the surface, transiently increasing the density of negatively charge, which can promote more adsorption of polylysine. [31][32][33][34][35] Indeed, the XPS analysis of our PEO-like material showed a marked increase in carboxyl and ester groups on the plasma oxidized surfaces, Figure 3. AFM imaging of the surface topography of the native film's surface.…”

Section: Protein Adsorptionmentioning

confidence: 97%

Novel High-Resolution Micropatterning for Neuron Culture Using Polylysine Adsorption on a Cell Repellant, Plasma-Polymerized Background

Chang

Sretavan

2008

Langmuir

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The ability to organize individual neurons and their processes in culture provides important benefits to both basic neuroscience research applications and the development of biomedical microdevices. While numerous methods have been used to produce such micropatterning of neurons and cells in general, there has yet been no method to simultaneously provide high-resolution patterns with high compliance of cells to desired patterns and good manufacturability. To develop such a process, this work used a plasma polymerized, nonfouling poly ethylene oxide (PEO)-like film to provide a cell repellant substrate on which cell adhesive micropatterns can be selectively laid down. While the use of plasma polymerized, organic films have been used for cell micropatterning, this process exploits the often-overlooked tendency for the surface of this PEO-like material to adsorb polylysine from aqueous solution while remaining nonfouling with respect to other species, such as bovine serum albumin (BSA) and immunoglobulin G (IgG). When the adsorption of polylysine was enhanced by brief plasma oxidation, which slightly alters the surface chemistry of the material, simple photolithographic liftoff could be used to micropattern stable, cell adhesive areas on an otherwise cell repellant background. We showed that the application of photolithography itself on the PEOlike material did not alter its chemical properties, nor did it result in the erosion of the micropatterned polylysine on its surface. Hippocampal neurons from embryonic mice flourished on these micropatterned substrates and exhibited viability comparable to neurons cultured on polylysine coated glass. Furthermore, the compliance of cell bodies and outgrowing neurites to the micropatterns was nearly perfect. In addition to providing cell adhesive regions, the micropatterned polylysine coating also served as a template mediating the immobilization of other bioactive species such as IgG and laminin. Using this "piggybacking" of laminin on polylysine, we were also able to culture and micropattern retinal ganglion cells (RGC).

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Formation of Viscoelastic Protein Droplets on a Chemically Functionalized Surface

Cited by 3 publications

References 21 publications

pH-Dependent Immobilization of Proteins on Surfaces Functionalized by Plasma-Enhanced Chemical Vapor Deposition of Poly(acrylic acid)- and Poly(ethylene oxide)-like Films

pH-Dependent Immobilization of Proteins on Surfaces Functionalized by Plasma-Enhanced Chemical Vapor Deposition of Poly(acrylic acid)- and Poly(ethylene oxide)-like Films

Localized Generation of Attoliter Protein Solution Droplets by Electrofocused Liquid−Liquid Separation

Novel High-Resolution Micropatterning for Neuron Culture Using Polylysine Adsorption on a Cell Repellant, Plasma-Polymerized Background

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