scholarly journals Photoresponsive Photoacid-Macroion Nano-Assemblies

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1746
Author(s):  
Alexander Zika ◽  
Sarah Bernhardt ◽  
Franziska Gröhn
Keyword(s):  
Self Assembly ◽  
Electrostatic Interactions ◽  
Building Blocks ◽  
Charge Ratio ◽  
Hydroxyl Group ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Stability ◽  
Nanoscale Aggregates ◽  
State Dissociation

In this study, light-responsive nano-assemblies with light-switchable size based on photoacids are presented. Anionic disulfonated napthol derivates and cationic dendrimer macroions are used as building blocks for electrostatic self-assembly. Nanoparticles are already formed under the exclusion of light as a result of electrostatic interactions. Upon photoexcitation, an excited-state dissociation of the photoacidic hydroxyl group takes place, which leads to a more highly charged linker molecule and, subsequently, to a change in size and structure of the nano-assemblies. The effects of the charge ratio and the concentration on the stability have been examined with absorption spectroscopy and ζ-potential measurements. The influence of the chemical structure of three isomeric photoacids on the size and shape of the nanoscale aggregates has been studied by dynamic light scattering and atomic force microscopy, revealing a direct correlation of the strength of the photoacid with the changes of the assemblies upon irradiation.

scholarly journals Nanohydrogels Based on Self-Assembly of Cationic Pullulan and Anionic Dextran Derivatives for Efficient Delivery of Piroxicam

Pharmaceutics ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 622 ◽  
Author(s):  
Dorota Lachowicz ◽  
Przemyslaw Mielczarek ◽  
Roma Wirecka ◽  
Katarzyna Berent ◽  
Anna Karewicz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Dextran Sulfate ◽  
Force Microscopy ◽  
Grafting Reaction ◽  
Atomic Force ◽  
Transmission Electron ◽  
Efficient Delivery ◽  
Model Drug

A cationic derivative of pullulan was obtained by grafting reaction and used together with dextran sulfate to form polysaccharide-based nanohydrogel cross-linked via electrostatic interactions between polyions. Due to the polycation-polyanion interactions nanohydrogel particles were formed instantly and spontaneously in water. The nanoparticles were colloidally stable and their size and surface charge could be controlled by the polycation/polyanion ratio. The morphology of the obtained particles was visualized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The resulting structures were spherical, with hydrodynamic diameters in the range of 100–150 nm. The binding constant (Ka) of a model drug, piroxicam, to the cationic pullulan (C-PUL) was determined by spectrophotometric measurements. The value of Ka was calculated according to the Benesi—Hildebrand equation to be (3.6 ± 0.2) × 103 M−1. After binding to cationic pullulan, piroxicam was effectively entrapped inside the nanohydrogel particles and released in a controlled way. The obtained system was efficiently taken up by cells and was shown to be biocompatible.

Characterization of Hydrophobic Forces for in Liquid Self-Assembly of Micron-Sized Functional Building Blocks

2011 ◽  
Vol 1299 ◽  
Author(s):  
M. R. Gullo ◽  
L. Jacot-Descombes ◽  
L. Aeschimann ◽  
J. Brugger
Keyword(s):  
Atomic Force Microscopy ◽  
Self Assembly ◽  
Hydrophobic Interactions ◽  
Numerical Study ◽  
Building Blocks ◽  
Dynamic Simulations ◽  
Hydrophobic Force ◽  
Force Microscopy ◽  
Molecular Arrangement ◽  
Atomic Force

ABSTRACTThis paper presents the experimental and numerical study of hydrophobic interaction forces at nanometer scale in the scope of engineering micron-sized building blocks for self-assembly in liquid. The hydrophobic force distance relation of carbon, Teflon and dodeca-thiols immersed in degassed and deionized water has been measured by atomic force microscopy. Carbon and dodeca-thiols showed comparable attractive and binding forces in the rage of pN/nm2. Teflon showed the weakest binding and no attractive force. Molecular dynamic simulations were performed to correlate the molecular arrangement of water molecules and the hydrophobic interactions measured by atomic force microscopy. The simulations showed a depletion zone of 2Å followed by a layered region of 8Å in the axis perpendicular to the hydrophobic surface.

Nanowire Fabrication by DNA Metallization and Positioning

2012 ◽  
Vol 523-524 ◽  
pp. 604-609
Author(s):  
Hong Wei Guan ◽  
Si Chen Liu ◽  
Yasuko Yanagida ◽  
Takeshi Hatsuzawa
Keyword(s):  
Self Assembly ◽  
Dna Hybridization ◽  
Deoxyribonucleic Acid ◽  
Electronic Devices ◽  
Building Blocks ◽  
Dna Molecules ◽  
Complementary Sequence ◽  
Force Microscopy ◽  
Atomic Force ◽  
Sticky End

Deoxyribonucleic acid (DNA) has the appropriate molecular recognition property that makes it a suitable building block for the construction of nanoscale electronic devices. In particular, DNA employed as conducting wires is expected to be an alternative to optical lithography, which has resolution limits and requires high cost steppers. Nano-oxidation experiments were conducted on a silicon substrate by atomic force microscopy (AFM) to produce nanosized dots as anchors for DNA fixing. Short strand DNA molecules were then fixed on the anchors, which can recognize a specific complementary sequence. After the substrate was treated with a solution containing specific DNAs, which can hybridize with the short strand DNAs at the DNA sticky end, the anchors were connected to the DNAs by a self-assembly processes of DNA hybridization. Finally, silver was plated along the DNA molecules by a chemical treatment to introduce electrical conductivity. This method is expected to have potential for the integration of nanosized building blocks applicable to nanodevice construction.

scholarly journals Membrane binding controls ordered self-assembly of animal septins

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Agata Szuba ◽  
Fouzia Bano ◽  
Gerard Castro Linares ◽  
Francois Iv ◽  
Manos Mavrakis ◽  
...  
Keyword(s):  
Self Assembly ◽  
Lipid Membranes ◽  
Electrostatic Interactions ◽  
Membrane Binding ◽  
Cytoskeletal Proteins ◽  
Double Layers ◽  
Cell Cortex ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

Septins are conserved cytoskeletal proteins that regulate cell cortex mechanics. The mechanisms of their interactions with the plasma membrane remain poorly understood. Here we show by cell-free reconstitution that binding to flat lipid membranes requires electrostatic interactions of septins with anionic lipids and promotes the ordered self-assembly of fly septins into filamentous meshworks. Transmission electron microscopy reveals that both fly and mammalian septin hexamers form arrays of single and paired filaments. Atomic force microscopy and quartz crystal microbalance demonstrate that the fly filaments form mechanically rigid, 12 to 18 nm thick, double layers of septins. By contrast, C-terminally truncated septin mutants form 4 nm thin monolayers, indicating that stacking requires the C-terminal coiled coils on DSep2 and Pnut subunits. Our work shows that membrane binding is required for fly septins to form ordered arrays of single and paired filaments and provides new insights into the mechanisms by which septins may regulate cell surface mechanics.

Self-Assembly of Nano-Sized Spherical Polyelectrolyte Brushes on Different Substrates as Observed by AFM

2011 ◽  
Vol 110-116 ◽  
pp. 3762-3769
Author(s):  
Shi Bin Huang ◽  
Xu Hong Guo ◽  
Li Li ◽  
Hong Ru Xu ◽  
Ya Ming Dong
Keyword(s):  
Self Assembly ◽  
Electrostatic Interactions ◽  
Substrate Surface ◽  
Core Shell ◽  
Surface Polarity ◽  
Force Microscopy ◽  
Polyelectrolyte Brushes ◽  
Atomic Force ◽  
Core Shell Structure ◽  
Spherical Polyelectrolyte Brushes

Nano-sized spherical poly (acrylic acid) (PAA) brushes (SPB) were prepared on the surface of colloidal polystyrene (PS) particles by photo-emulsion polymerization. Atomic force microscopy (AFM) was employed to observe the assembly of SPB on substrates of silicon, gold and mica with various surface properties and to determine the morphological information including particle size, shape and core-shell structure of SPB. We found that the surface polarity, electrostatic interactions between SPB and substrate surface and among SPB and capillary forces during sample drying affect the SPB assembly on substrate surface and their morphology.

scholarly journals Membrane binding controls ordered self-assembly of animal septins

2020 ◽  
Author(s):  
Agata Szuba ◽  
Fouzia Bano ◽  
François Iv ◽  
Manos Mavrakis ◽  
Ralf P. Richter ◽  
...  
Keyword(s):  
Self Assembly ◽  
Electrostatic Interactions ◽  
Membrane Binding ◽  
Coiled Coils ◽  
Cytoskeletal Proteins ◽  
Double Layers ◽  
Cell Cortex ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

AbstractSeptins are conserved cytoskeletal proteins that regulate cell cortex mechanics. The mechanisms of their interactions with the plasma membrane remain poorly understood. Here we show by cell-free reconstitution that membrane binding requires electrostatic interactions of septins with anionic lipids and promotes the ordered self-assembly of fly septins into filamentous meshworks. Transmission electron microscopy reveals that both fly and mammalian septins form arrays of single and paired filaments. Atomic force microscopy and quartz crystal microbalance demonstrate that the fly filaments form mechanically rigid, 12 to 18 nm thick, double layers of septins. By contrast, C-terminally truncated septin mutants form 4 nm thin monolayers, indicating that stacking requires the C-terminal coiled coils on DSep2 and Pnut subunits. Our work shows that membrane binding is required for fly septins to form ordered arrays of single and paired filaments and provides new insights into the mechanisms by which septins may regulate cell surface mechanics.

scholarly journals Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

2021 ◽  
Vol 17 ◽  
pp. 166-185
Author(s):  
Alexander Zika ◽  
Franziska Gröhn
Keyword(s):  
Self Assembly ◽  
Supramolecular Assembly ◽  
Building Blocks ◽  
Titration Calorimetry ◽  
Ph Responsive ◽  
Interaction Forces ◽  
Vis Spectroscopy ◽  
The Stability ◽  
State Dissociation ◽  
Naphthol Derivatives

Light- and pH-responsive nano-assemblies with switchable size and structure are formed by the association of a photoacid, anthocyanidin, and a linear polyelectrolyte in aqueous solution. Specifically, anionic disulfonated naphthol derivatives, neutral hydroxyflavylium, and cationic poly(allylamine) are used as building blocks for the ternary electrostatic self-assembly, forming well-defined supramolecular assemblies with tunable sizes of 50 to 500 nm. Due to the network of possible chemical reactions for the anthocyanidin and the excited-state dissociation of the photoacid upon irradiation, different ways to alter the ternary system through external triggering are accessible. The structure and trigger effects can be controlled through the component ratios of the samples. Dynamic and static light scattering (DLS, SLS) and ζ-potential measurements were applied to study the size and the stability of the particles, and information on the molecular structure was gained by UV–vis spectroscopy. Isothermal titration calorimetry (ITC) provided information on the thermodynamics and interaction forces in the supramolecular assembly formation.

Clathrin-Inspired Coating and Stabilization of Liposomes by DNA Self-Assembly

2019 ◽  
Author(s):  
Kevin N. Baumann ◽  
Luca Piantanida ◽  
Javier García-Nafría ◽  
Diana Sobota ◽  
Kislon Voïtchovsky ◽  
...  
Keyword(s):  
Self Assembly ◽  
Mechanical Stability ◽  
Lipid Vesicles ◽  
The Self ◽  
Force Microscopy ◽  
Atomic Force ◽  
Cryo Electron Microscopy ◽  
Further Development ◽  
Liposome Surface ◽  
Dna Coating

The self-assembly of the protein clathrin on biological membranes facilitates essential processes of endocytosis in biological systems and has provided a source of inspiration for materials design by the highly ordered structural appearance. By mimicking the architecture of clathrin self-assemblies to coat liposomes with biomaterials, new classes of hybrid carriers can be derived. Here we present a method for fabricating DNA-coated liposomes by hydrophobically anchoring and subsequently growing a DNA network on the liposome surface which structurally mimics clathrin assemblies. Dynamic light scattering (DLS), ζ-potential and cryo-electron microscopy (cryo-EM) measurements independently demonstrate successful DNA coating. Nanomechanical measurements conducted with atomic force microscopy (AFM) show that the DNA coating enhances the mechanical stability of the liposomes relative to uncoated ones. Furthermore, we provide the possibility to reverse the coating process by triggering the disassembly of the DNA coating through a toehold-mediated displacement reaction. Our results describe a straightforward, versatile, and reversible approach for coating and stabilizing lipid vesicles by an interlaced DNA network. This method has potential for further development towards the ordered arrangement of tailored functionalities on the surfaces of liposomes and for applications as hybrid nanocarrier.

scholarly journals Morphometric characterization of fibrinogen's αC regions and their role in fibrin self-assembly and molecular organization

Nanoscale ◽  
2017 ◽  
Vol 9 (36) ◽  
pp. 13707-13716 ◽  
Author(s):  
Anna D. Protopopova ◽  
Rustem I. Litvinov ◽  
Dennis K. Galanakis ◽  
Chandrasekaran Nagaswami ◽  
Nikolay A. Barinov ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Self Assembly ◽  
Molecular Organization ◽  
Microscopy Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
Atomic Force Microscopy Imaging ◽  
Morphometric Characterization

High-resolution atomic force microscopy imaging reveals the role of fibrinogen αC regions in the early stages of fibrin self-assembly.

Self-assembly layer-by-layer fabrication using porphyrin dye anion and polycation

2009 ◽  
Vol 13 (07) ◽  
pp. 774-778 ◽  
Author(s):  
Byung-Soon Kim ◽  
Young-A Son
Keyword(s):  
Ultrathin Films ◽  
Self Assembly ◽  
Film Surface ◽  
Layer By Layer ◽  
Preparation Technique ◽  
Force Microscopy ◽  
Atomic Force ◽  
Diallyldimethylammonium Chloride ◽  
Afm Analysis ◽  
Progressive Growth

In this study, self-assembled alternating film using poly(diallyldimethylammonium chloride) (PDDAC) and meso-tetrakis(4-carboxyphenyl)porphyrin (MTCP) was prepared as a multilayer deposition on glass substrate. This preparation technique for dye deposition may provide new feasibilities to achieve the manufacture of ultrathin films for nanotechnology application. The deposition films were characterized by UV-vis spectrophotometer and Atomic Force Microscopy (AFM) analysis. The results of UV-vis spectra showed that the absorbance characteristic of the multilayer films linearly increased with an increased number of PDDAC and MTCP bilayers. AFM analysis showed the film surface was relatively uniform and the progressive growth of layers was determined.

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