Temperature-Responsive Self-Assemblies of ‘Kinked' Amphiphiles

2013 ◽  
Vol 66 (8) ◽  
pp. 899 ◽  
Author(s):  
Jennifer S. Squire ◽  
Grégory Durand ◽  
Lynne Waddington ◽  
Alessandra Sutti ◽  
Luke C. Henderson
Keyword(s):  
Temperature Response ◽  
Thermal Response ◽  
Carbon Chain ◽  
Critical Aggregation Concentration ◽  
Head Group ◽  
Hydrodynamic Diameter ◽  
Polar Head Group ◽  
Hydrophobic Region ◽  
Thermal Window ◽  
Starting Point

The synthesis of novel norbornane-based amphiphiles and the thermal response of their corresponding colloids is presented. It was found that the hydrodynamic diameter (DH) expansion or contraction of 1–4 in response to increasing temperature was governed by the length of the hydrophobic region possessed by the amphiphile (a 12 or 16 carbon chain). These data were used as a starting point to extend into an active tumour targeting system whereby two amphiphiles were modified to incorporate the oestrogen receptor antagonist Tamoxifen at the polar head group. This was achieved by a triazole moiety while both the C12 (18) or C16 (19) hydrophobic chains were incorporated as the hydrophobic region in an attempt to retain the response to thermal stimuli observed in our preliminary findings. These functionalised novel amphiphiles possessed critical aggregation concentration values of 510 and 19 µM, while aqueous self-assemblies of 56 and 106 nm for 18 and 19 were observed. Imaging by cryogenic transmission electron microscopy showed 18 to possess liposomal morphology, while 19, bearing a C16 hydrophobic portion, formed non-defined amorphous aggregates. Finally, the response to temperature of these assemblies was investigated with only the C12 variant 18 displaying a temperature response in the 5–55°C thermal window investigated.

scholarly journals Esterification of Alginate with Alkyl Bromides of Different Carbon Chain Lengths via the Bimolecular Nucleophilic Substitution Reaction: Synthesis, Characterization, and Controlled Release Performance

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3351
Author(s):  
Xiuqiong Chen ◽  
Qingmei Zhu ◽  
Chang Liu ◽  
Dongze Li ◽  
Huiqiong Yan ◽  
...  
Keyword(s):  
Sustained Release ◽  
Nucleophilic Substitution ◽  
Drug Loading ◽  
Carbon Chain ◽  
Critical Aggregation Concentration ◽  
Carbon Chain Length ◽  
Hydrodynamic Diameter ◽  
Ester Derivative ◽  
Sn2 Reaction ◽  
Alkyl Bromides

To extend the alginate applicability for the sustained release of hydrophobic medicine in drug delivery systems, the alkyl alginate ester derivative (AAD), including hexyl alginate ester derivative (HAD), octyl alginate ester derivative (OAD), decyl alginate ester derivative (DAD), and lauryl alginate ester derivative (LAD), were synthesized using the alkyl bromides with different lengths of carbon chain as the hydrophobic modifiers under homogeneous conditions via the bimolecular nucleophilic substitution (SN2) reaction. Experimental results revealed that the successful grafting of the hydrophobic alkyl groups onto the alginate molecular backbone via the SN2 reaction had weakened and destroyed the intramolecular hydrogen bonds, thus enhancing the molecular flexibility of the alginate, which endowed the AAD with a good amphiphilic property and a critical aggregation concentration (CAC) of 0.48~0.0068 g/L. Therefore, the resultant AAD could form stable spherical self-aggregated micelles with the average hydrodynamic diameter of 285.3~180.5 nm and zeta potential at approximately −44.8~−34.4 mV due to the intra or intermolecular hydrophobic associations. With the increase of the carbon chain length of the hydrophobic side groups, the AAD was more prone to self-aggregation, and therefore was able to achieve the loading and sustained release of hydrophobic ibuprofen. Additionally, the swelling and degradation of AAD microcapsules and the diffusion of the loaded drug jointly controlled the release rate of ibuprofen. Meanwhile, the AAD also displayed low cytotoxicity to the murine macrophage RAW264.7 cells. Thanks to the good amphiphilic property, colloidal interface activity, hydrophobic drug-loading performance, and cytocompatibility, the synthesized AAD exhibited a great potential for the development of hydrophobic pharmaceutical formulations.

scholarly journals Molecular dynamics simulations and experimental studies reveal differential permeability of withaferin-A and withanone across the model cell membrane

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Renu Wadhwa ◽  
Neetu Singh Yadav ◽  
Shashank P. Katiyar ◽  
Tomoko Yaguchi ◽  
Chohee Lee ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Cell Membrane ◽  
Molecular Dynamics Simulations ◽  
Experimental Studies ◽  
Bilayer Membrane ◽  
Withaferin A ◽  
Head Group ◽  
Polar Head Group ◽  
Natural Drugs ◽  
Dynamics Simulations

AbstractPoor bioavailability due to the inability to cross the cell membrane is one of the major reasons for the failure of a drug in clinical trials. We have used molecular dynamics simulations to predict the membrane permeability of natural drugs—withanolides (withaferin-A and withanone) that have similar structures but remarkably differ in their cytotoxicity. We found that whereas withaferin-A, could proficiently transverse through the model membrane, withanone showed weak permeability. The free energy profiles for the interaction of withanolides with the model bilayer membrane revealed that whereas the polar head group of the membrane caused high resistance for the passage of withanone, the interior of the membrane behaves similarly for both withanolides. The solvation analysis further revealed that the high solvation of terminal O5 oxygen of withaferin-A was the major driving force for its high permeability; it interacted with the phosphate group of the membrane that led to its smooth passage across the bilayer. The computational predictions were tested by raising and recruiting unique antibodies that react to withaferin-A and withanone. The time-lapsed analyses of control and treated cells demonstrated higher permeation of withaferin-A as compared to withanone. The concurrence between the computation and experimental results thus re-emphasised the use of computational methods for predicting permeability and hence bioavailability of natural drug compounds in the drug development process.

Transient Thermal Response of the Media by Free Space Laser Heating in Heat Assisted Magnetic Recording

2016 ◽  
Author(s):  
Shaomin Xiong ◽  
Robert Smith ◽  
Na Wang ◽  
Dongbo Li ◽  
Erhard Schreck ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Heat Conduction Problem ◽  
Temperature Response ◽  
Thermal Response ◽  
Areal Density ◽  
Heat Assisted Magnetic Recording ◽  
Lumped Model ◽  
The Media ◽  
Transient Thermal ◽  
Transient Thermal Response

Heat assisted magnetic recording (HAMR) promises to deliver higher storage areal density than the current perpendicular magnetic recording (PMR) product. A laser is introduced to the HAMR system to heat the high coercively magnetic media above the Curie temperature (Tc) which is as high as 750 K in order to enable magnetic writing. The thermal response of the media becomes very critical for the success of the data writing process. In this paper, a new method is proposed to understand the transient thermal behavior of the HAMR media. The temperature response of the media is measured based on thermal erasure of the magnetically written signal. A lumped model is built to simplify the heat conduction problem to understand the transient thermal response. Finite element modeling (FEM) is implemented to simulate the transient thermal response of the media due to the laser pulse heating. The experimental and simulation results show fairly good agreement.

scholarly journals Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors

2019 ◽  
Vol 10 ◽  
pp. 565-577 ◽  
Author(s):  
Juan Casanova-Cháfer ◽  
Carla Bittencourt ◽  
Eduard Llobet
Keyword(s):  
Carbon Nanotubes ◽  
Nitrogen Dioxide ◽  
Photoelectron Spectroscopy ◽  
Gas Sensing ◽  
Carbon Chain ◽  
Head Group ◽  
Carbon Chain Length ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
Self Assembled

Here we describe the development of chemoresistive sensors employing oxygen-plasma-treated, Au-decorated multiwall carbon nanotubes (MWCNTs) functionalized with self-assembled monolayers (SAMs) of thiols. For the first time, the effects of the length of the carbon chain and its hydrophilicity on the gas sensing properties of SAMs formed on carbon nanotubes are studied, and additionally, the gas sensing mechanisms are discussed. Four thiols differing in the length of the carbon chain and in the hydrophobic or hydrophilic nature of the head functional group are studied. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to analyze the resulting gas-sensitive hybrid films. Among the different nanomaterials tested, short-chain thiols having a hydrophilic head group, self-assembled onto Au-decorated carbon nanotubes were most responsive to nitrogen dioxide and ethanol vapors, even in the presence of ambient humidity. In particular, this nanomaterial was about eight times more sensitive to nitrogen dioxide than bare Au-decorated carbon nanotubes when operated at room temperature. This response enhancement is attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor response and selectivity. This would make the detection of polar and nonpolar gas species employing low-power gas sensors easier, even under fluctuating ambient moisture conditions.

Thermal Response of a Magneto-Resistive Head When it Flies Over an Asperity

1999 ◽  
Vol 121 (4) ◽  
pp. 975-979 ◽  
Author(s):  
Shuyu Zhang ◽  
David B. Bogy
Keyword(s):  
Small Area ◽  
Temperature Response ◽  
Thermal Response ◽  
Air Bearing ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model ◽  
Current Value ◽  
Head Temperature ◽  
Bearing System

A two-dimensional model is developed for the heat transfer in a magneto-resistive (MR) head-air bearing system. Using this model, the MR head temperature response is studied for various cases. It is found that the temperature in the head depends on the current through it and the change is only significant within a small area around the MR transducer at the trailing edge. With a typical current value (say 13 mA), the MR head temperature is about 25°C higher than the ambient temperature. When the slider flies over an asperity without contact, the MR temperature fluctuation follows that of the air bearing spacing, which is caused by the cooling effect of the air bearing.

The effect of polar head group of dodecyl surfactants on the growth of wheat and cucumber

Chemosphere ◽  
2020 ◽  
Vol 254 ◽  
pp. 126918
Author(s):  
Aleksandar Tot ◽  
Ivana Maksimović ◽  
Marina Putnik-Delić ◽  
Milena Daničić ◽  
Slobodan Gadžurić ◽  
...  
Keyword(s):  
Head Group ◽  
Polar Head Group ◽  
Polar Head

Hemolytic Activity of Aminoethyl-dodecanoates

1998 ◽  
Vol 53 (1-2) ◽  
pp. 101-106 ◽  
Author(s):  
H. Kleszczyńska ◽  
J. Łuczyński ◽  
S. Witek ◽  
S. Przestalski
Keyword(s):  
Plasma Membrane ◽  
Membrane Fluidity ◽  
Erythrocyte Membrane ◽  
Hemolytic Activity ◽  
Protonated Form ◽  
Maximum Activity ◽  
Head Group ◽  
Dodecanoic Acid ◽  
Polar Head Group ◽  
Erythrocyte Membrane Fluidity

Abstract The effect of new lysosomotropic compounds on red blood cell hemolysis and erythrocyte membrane fluidity has been investigated. In earlier studies it was shown that the compounds inhibit the growth of yeast and plasma membrane H+-ATPase activity. The study was per­ formed with eight aminoethyl esters of lauric acid variously substituted at nitrogen atom. Esters of dodecanoic acid were chosen for study because at that chain length dimethylaminoethyl esters showed maximum activity. The hemolytic activity of the substances studied exhib­its diversified activity in their interaction with the erythrocyte membrane: they differ in hemolytic activity and affect membrane fluidity differently. Erythrocyte membrane fluidity changes under the effect of those compounds which possess highest hemolytic activity. The hemolytic activity of the aminoesters investigated was found to follow a sequence that de­pended on basicity (i.e. ability of the protonated form formation) of the compound and its polar head group size. The most active are the compounds that possess not more than four carbon atoms substituted at nitrogen and highest pKa value.

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