13 research outputs found
Adsorption and binding dynamics of graphene-supported phospholipid membranes using the QCM-D technique
We report on the adsorption dynamics of phospholipid membranes on
graphene-coated substrates using the quartz crystal microbalance with
dissipation monitoring (QCM-D) technique. We compare the lipid vescle
interaction and membranne formation on gold and silicon dioxide QCM crystal
surfaces with their graphene oxide (GO) and reduced (r)GO coated counterparts,
and report on the different lipid structures obtained. We establish graphene
derivative coatings as support surfaces with tuneable hydrophobicity for the
formation of controllable lipid structures. One structure of interest formed
are lipid monolayer membrannes which were formed on rGO, which are otherwise
challenging to produce. We also demonstrate and monitor biotin-avidin binding
on such a membranne, which will then serve as a platform for a wide range of
biosensing applications. The QCM-D technique could be extended to both
fundamental studies and applications of other covalent and non-covalent
interactions in 2-dimensional materials
Elastic flow instabilities and macroscopic textures in graphene oxide lyotropic liquid crystals
Graphene oxide (GO) forms a well-aligned lyotropic liquid crystal (LC) phase in aqueous dispersions at relatively low concentrations. Under a remarkably wide range of shear rates, we report hitherto unobserved shear-induced polarized light image patterns, a Maltese cross combined with shear banding, recorded in real time and in situ during rheological measurements. This is shown to be a result of elastic flow instabilities that manifest as a helical flow in alternating bands of left- and right-handed helices, arising from a combination of shear flow and Taylor-type vortex flow. The instability is observed for LCs formed from large aspect ratio GO particles owing to their unique viscoelastic properties, but not for smaller aspect ratio particles. This phenomenon coincides with rheopecty and anomalous small-angle X-ray scattering patterns under shear flow, which confirm the instabilities. The results presented here could lead to advanced control over macroscopic periodic alignment in technologically relevant dispersions of two-dimensional material particles
Designing Peptide/Graphene Hybrid Hydrogels through Fine-Tuning of Molecular Interactions
A recent strategy that has emerged for the design of increasingly functional hydrogels is the incorporation of nanofillers in order to exploit their specific properties to either modify the performance of the hydrogel or add functionality. The emergence of carbon nanomaterials in particular has provided great opportunity for the use of graphene derivatives (GDs) in biomedical applications. The key challenge when designing hybrid materials is the understanding of the molecular interactions between the matrix (peptide nanofibers) and the nanofiller (here GDs) and how these affect the final properties of the bulk material. For the purpose of this work, three gelling β-sheet-forming, self-assembling peptides with varying physiochemical properties and five GDs with varying surface chemistries were chosen to formulate novel hybrid hydrogels. First the peptide hydrogels and the GDs were characterized; subsequently, the molecular interaction between peptides nanofibers and GDs were probed before formulating and mechanically characterizing the hybrid hydrogels. We show how the interplay between electrostatic interactions, which can be attractive or repulsive, and hydrophobic (and π–π in the case of peptide containing phenylalanine) interactions, which are always attractive, play a key role on the final properties of the hybrid hydrogels. The shear modulus of the hydrid hydrogels is shown to be related to the strength of fiber adhesion to the flakes, the overall hydrophobicity of the peptides, as well as the type of fibrillar network formed. Finally, the cytotoxicity of the hybrid hydrogel formed at pH 6 was also investigated by encapsulating and culturing human mesemchymal stem cells (hMSC) over 14 days. This work clearly shows how interactions between peptides and GDs can be used to tailor the mechanical properties of the resulting hydrogels, allowing the incorporation of GD nanofillers in a controlled way and opening the possibility to exploit their intrinsic properties to design novel hybrid peptide hydrogels for biomedical applications
Biomimetic phospholipid membrane organization on graphene and graphene oxide surfaces: A molecular dynamics simulation study
Supported phospholipid membrane patches stabilized on graphene surfaces have shown potential in sensor device functionalization, including biosensors and biocatalysis. Lipid dip-pen nanolithography (L-DPN) is a method useful in generating supported membrane structures that maintain lipid functionality, such as exhibiting specific interactions with protein molecules. Here, we have integrated L-DPN, atomic force microscopy, and coarse-grained molecular dynamics simulation methods to characterize the molecular properties of supported lipid membranes (SLMs) on graphene and graphene oxide supports. We observed substantial differences in the topologies of the stabilized lipid structures depending on the nature of the surface (polar graphene oxide vs nonpolar graphene). Furthermore, the addition of water to SLM systems resulted in large-scale reorganization of the lipid structures, with measurable effects on lipid lateral mobility within the supported membranes. We also observed reduced lipid ordering within the supported structures relative to free-standing lipid bilayers, attributed to the strong hydrophobic interactions between the lipids and support. Together, our results provide insight into the molecular effects of graphene and graphene oxide surfaces on lipid bilayer membranes. This will be important in design of these surfaces for applications as biosensor devices
Le Conservateur : Journal politique de l'arrondissement de Marennes...
17 juillet 18871887/07/17 (A10,N527)
Biomimetic Phospholipid Membrane Organization on Graphene and Graphene Oxide Surfaces:A Molecular Dynamics Simulation Study
Supported
phospholipid membrane patches stabilized on graphene
surfaces have shown potential in sensor device functionalization,
including biosensors and biocatalysis. Lipid dip-pen nanolithography
(L-DPN) is a method useful in generating supported membrane structures
that maintain lipid functionality, such as exhibiting specific interactions
with protein molecules. Here, we have integrated L-DPN, atomic force
microscopy, and coarse-grained molecular dynamics simulation methods
to characterize the molecular properties of supported lipid membranes
(SLMs) on graphene and graphene oxide supports. We observed substantial
differences in the topologies of the stabilized lipid structures depending
on the nature of the surface (polar graphene oxide <i>vs</i> nonpolar graphene). Furthermore, the addition of water to SLM systems
resulted in large-scale reorganization of the lipid structures, with
measurable effects on lipid lateral mobility within the supported
membranes. We also observed reduced lipid ordering within the supported
structures relative to free-standing lipid bilayers, attributed to
the strong hydrophobic interactions between the lipids and support.
Together, our results provide insight into the molecular effects of
graphene and graphene oxide surfaces on lipid bilayer membranes. This
will be important in the design of these surfaces for applications
such as biosensor devices