13 research outputs found
Mechanofluorescent Polymer Brush Surfaces that Spatially Resolve Surface Solvation
Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophoresâ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the airâwaterâsolid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution
Integrated FRET Polymers Spatially Reveal Microâ to Nanostructure and Irregularities in Electrospun Microfibers
Abstract A spatial view of macroscopic polymer material properties, in terms of nanostructure and irregularities, can help to better understand engineering processes such as when materials may fail. However, bridging the gap between the molecularâscale arrangement of polymer chains and the spatially resolved macroscopic properties of a material poses numerous difficulties. Herein, an integrated messenger material that can report on the material microâ to nanostructure and its processes is introduced. It is based on polymer chains labeled with fluorescent dyes that feature Förster resonance energy transfer (FRET) dependent on chain conformation and concentration within a host polymer material. These FRET materials are integrated within electrospun polystyrene microfibers, and the FRET is analyzed by confocal laser scanning microscopy (CLSM). Importantly, the use of CLSM allows a spatial view of material nanostructure and irregularities within the microfibers, where changes in FRET are significant when differences in fiber geometries and regularities exist. Furthermore, changes in FRET observed in damaged regions of the fibers indicate changes in polymer conformation and/or concentration as the material changes during compression. The system promises high utility for applications where nanoâtoâmacro communication is needed for a better understanding of material processes
Lactosylated Glycogen Nanoparticles for Targeting Prostate Cancer Cells
Glyconanoparticles
that exhibit multivalent binding to lectins are desirable for molecular
recognition and therapeutic applications. Herein we explore the use
of glycogen nanoparticles as a biosourced glycoscaffold for engineering
multivalent glyconanoparticles. Glycogen nanoparticles, a naturally
occurring highly branched polymer of glucose, was functionalized with
lactose, achieved through copperÂ(I)-catalyzed alkyneâazide
cycloaddition chemistry, for targeted interaction with lectins ex
situ and on prostate cancer cells. The lactosylated glycogen, which
contains terminal ÎČ-galactoside moieties, is termed galacto-glycogen
(GG), and is found to interact strongly with peanut agglutinin (PNA),
a ÎČ-galactoside-specific lectin, as observed by optical waveguide
lightmode spectroscopy, dynamic light scattering, and quartz crystal
microbalance measurements. The GG nanoparticles exhibit multivalent
binding to PNA with an affinity constant of 3.4 Ă 10<sup>5</sup> M<sup>â1</sup>, and the GGâPNA complex cannot be displaced
by lactose, demonstrating the competitive binding of GG to the lectin.
These GG nanoparticles were tested for association with prostate cancer
cell membranes in vitro, where the particles exhibited a high affinity
for the membrane, as observed from flow cytometry and confocal microscopy.
This is inferred to result from specific extracellular galectin-1
targeting. Furthermore, the GG nanoparticles induce aggregation between
prostate cancer cells. Our results highlight a strategy for engineering
a biosourced polysaccharide with surface moieties that exhibit strong
multivalent interactions with lectins, and targeted interaction with
prostate cancer cells
Mechanofluorescent Polymer Brush Surfaces that Spatially Resolve Surface Solvation
Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophoresâ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the airâwaterâsolid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution
Mechanofluorescent Polymer Brush Surfaces that Spatially Resolve Surface Solvation
Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophoresâ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the airâwaterâsolid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution
Mapping the ThreeâDimensional Nanostructure of the Ionic LiquidâSolid Interface Using Atomic Force Microscopy and Molecular Dynamics Simulations
Abstract Ionic liquids (ILs) are a widely investigated class of solvents for scientific and industrial applications due to their desirable and âtunableâ properties. The ILâsolid interface is a complex entity, and despite intensive investigation, its true nature remains elusive. The understanding of the ILâsolid interface has evolved over the last decade from a simple 1D double layer, to a 2D ordered interface, and finally a liquidâspecific, complex 3D ordered liquid interface. However, most studies depend solely on one technique, which often only examine one aspect of the interfacial nanostructure. Here, a holistic study of the protic ILâsolid interface is presented, which provides a more detailed picture of IL interfacial solvation. The 3D nanostructure of the ethylammonium nitrate (EAN)âmica interface is investigated using a combination of 1D, 2D, and 3D amplitude modulatedâatomic force microscopy and molecular dynamics simulations. Importantly, it is found that the EANâmica interface is more complex than previously reported, possessing surfaceâadsorbed, nearâsurface, surfaceânormal, and lateral heterogeneity, which propagates at relatively large distances from the solid substrate. The work presented in this study meaningfully enhances the understanding of the ILâsolid interface
Molecular Transport within Polymer Brushes: A FRET View at Aqueous Interfaces
Molecular permeability through polymer brush chains is implicated in surface lubrication, wettability, and solute capture and release. Probing molecular transport through polymer brushes can reveal information on the polymer nanostructure, with a permeability that is dependent on chain conformation and grafting density. Herein, we introduce a brush system to study the molecular transport of fluorophores from an aqueous droplet into the external âdryâ polymer brush with the vapour phase above. The brushes consist of a random copolymer of N-isopropylacrylamide and a Förster resonance energy transfer (FRET) donor-labelled monomer, forming ultrathin brush architectures of about 35 nm in solvated height. Aqueous droplets containing a separate FRET acceptor are placed onto the surfaces, with FRET monitored spatially around the 3-phase contact line. FRET is used to monitor the transport from the droplet to the outside brush, and the changing internal distributions with time as the droplets prepare to recede. This reveals information on the dynamics and distances involved in the molecular transport of the FRET acceptor towards and away from the droplet contact line, which are strongly dependent on the relative humidity of the system. We anticipate our system to be extremely useful for studying lubrication dynamics and surface droplet wettability processes
Mechanofluorescent Polymer Brush Surfaces that Spatially Resolve Surface Solvation
Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophoresâ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the airâwaterâsolid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution