Dendrimer assisted dispersion of carbon nanotubes: a molecular dynamics study

Pramanik, Debabrata; Maiti, Prabal K.

doi:10.1039/c6sm02015a

Cited by 22 publications

(25 citation statements)

References 65 publications

(99 reference statements)

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“…We understand more about this nonmontonicity in the upcoming sections. A point to note is that the order of the PMF values ( ) is in agreement with the previous MD studies of the adsorption of PAMAM dendrimer on mica, carbon nanotube. , …”

Section: Resultssupporting

confidence: 88%

Understanding the Thermodynamics of the Binding of PAMAM Dendrimers to Graphene: A Combined Analytical and Simulation Study

Gosika

Sen²,

Kundagrami³

et al. 2019

Langmuir

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We investigate the thermodynamics of the binding of a poly(amidoamine) dendrimer to an uncharged graphene sheet as a function of the pH level using umbrella sampling simulations and a mean-field theory for generations three and four. We find that the dendrimer strongly binds to the graphene sheet ( (100) kcal/mol) from our potential of mean force (PMF) calculations. In specific, we find that the dendrimer binds the most at neutral pH (∼7) and the least at low pH (∼4). We explain this nonmonotonic nature of the dendrimer's adsorption by studying the interactions contributing to the PMF, i.e., the dendrimer−graphene, dendrimer−water, and dendrimer−ion interactions. We also corroborate our PMF calculations with molecular mechanics generalized Born surface area analysis and free energies obtained from a mean-field theory of Flory−Huggins−Debye−Huckel type [Muthukumar, M., et al. J. Chem. Phys. 2010, 132, 084901], including electrostatic interactions. We find that the van der Waals interactions between the dendrimer and the graphene alone cannot capture the accurate trends in the binding free energies (BEs) as a function of pH. The solvent and the counterions present in the system are also found to have a major influence on these trends. We demonstrate that the dendrimer−graphene and dendrimer−water interactions become favorable, whereas the dendrimer−ion interaction becomes unfavorable, as the dendrimer binds to graphene. These opposing effects lead to the observed nonmonotonicity in the BE trends. Our theoretical model also reproduces these trends in the subinteractions contributing to the PMF. To the best of our knowledge, this is a novel attempt where an equivalence between theory and simulations is made in the context of the dendrimer's adsorption.

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Section: Resultssupporting

confidence: 88%

Understanding the Thermodynamics of the Binding of PAMAM Dendrimers to Graphene: A Combined Analytical and Simulation Study

Gosika

Sen²,

Kundagrami³

et al. 2019

Langmuir

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“…PSPC has an experimental main phase transition value of around 49 °C at atmospheric pressure 46 , which acts as a reference to validate our findings. We first considered two fundamental structural properties of lipid bilayers-area per lipid (APL) and bilayer thickness, at different temperatures.…”

Section: Pure Pspc Bilayersupporting

confidence: 79%

“…Thus, from brute force MD simulations, we elucidated various structural quantities for the pure PSPC and PEGylated PSPC systems at different temperatures. Further, to understand the interaction behavior between the PTX drug with the rest of the lipid systems from a quantitative perspective, we performed umbrella sampling (US)-based enhanced sampling simulations. − In the US simulations, we choose center-of-mass (COM) distance between the heavy atoms of the ligand and bilayer plane as the reaction coordinate to bias the system. The distance was chosen in the plane perpendicular to the bilayer plane.…”

Section: Model and Simulation Detailsmentioning

confidence: 99%

Phase Behavior of Pure PSPC and PEGylated Multicomponent Lipid and Their Interaction with Paclitaxel: An All-Atom MD Study

2021

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The study of the structural behaviour of pure and multi-component lipids at various temperatures and the interaction of these multi-component lipids with pharmaceutically important drugs carry huge importance. Here, we investigated the phase behaviour of the pure PSPC (1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine), and multicomponent PSPC and DSPE-PEG2000(1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N[amino(polyethylene glycol)-2000]) membranes at seven different temperatures ranging from 280 K to 360 K, and calculated their structural properties. We observe a transition from the gel phase to the liquid crystalline phase between 320 K and 330 K in agreement with experimental reports for pure PSPC. PSPC remained in the tilted gel phase Lβ' at 320 K and 310 K, entered the "mixed ordered" domain with a partially interdigitated region at 300 K, and finally formed the sub gel phase at 280 K. We studied the self-assembly for the multicomponent PSPC and DSPE-PEG2000 membranes and found the coexistence of ordered and disordered phases at 320 K. In comparison to the pure PSPC, for multicomponent system, this transition was gradual, and a complete liquid crystalline to gel phase transformation occurred between 320 K and 310 K.We further studied the interaction of Paclitaxel with pure PSPC and PEGylated multicomponent lipid bilayers using umbrella sampling technique and observed PEG promotes the interaction of Paclitaxel with the later one in comparison to the former. Above the bilayer transition temperature, Paclitaxel interacts more with the bilayer and enters inside the bilayer easily for both systems. Understanding of structural and interaction behaviour of the PEGylated multicomponent lipid bilayers with Paclitaxel will help explore Paclitaxel based drug applications in the future.

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“…The details of the all simulated systems and the US windows are given in Table . Similar methodology was followed in our earlier studies to obtain PMF profiles. ,− …”

Section: Materials and Methodsmentioning

confidence: 92%

Modulating Interdendrimer Interactions through Surface Adsorption

2020

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Physical confinement of polymers not only affects their structure but also modifies their effective interaction profiles. In this article, we investigate the nature of graphene-adsorbed poly(amidoamine) (PAMAM) dendrimers' interactions using fully atomistic molecular dynamics simulations. Using the umbrella sampling technique, we calculate the potential of mean force (PMF) profiles for the interaction between two graphene-adsorbed PAMAM dendrimers of generations 3 and 4 as a function of their protonation levels. We find that the attractive PMF profile observed for the interaction between two nonprotonated (high pH) PAMAM dendrimers in bulk becomes repulsive upon adsorption. Also, the repulsive interdendrimer interactions known in bulk for the protonated dendrimers become enhanced for the adsorbed case. We further explain these weakened interactions by explicitly showing that the dendrimer−graphene interaction is an order of magnitude larger than the dendrimer−dendrimer bulk interaction. Using the force integration method, we obtain the contributions from various subinteractions present in the system, that is, dendrimer−water, dendrimer−ions, dendrimer−graphene, and dendrimer−dendrimer to the total PMF. From these contributions, we conclude that the reduced dendrimer−dendrimer interactions in the adsorbed case, as compared to those in bulk, lead to the enhanced repulsive effective interdendrimer interactions. Our PMF profiles fit well with the sum of exponential and Gaussian functions, proposed in the bulk interdendrimer interaction study. We hope the current results provide the microscopic origin of how adsorption weakens the interpolymer interactions in general.

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Dendrimer assisted dispersion of carbon nanotubes: a molecular dynamics study

Cited by 22 publications

References 65 publications

Understanding the Thermodynamics of the Binding of PAMAM Dendrimers to Graphene: A Combined Analytical and Simulation Study

Understanding the Thermodynamics of the Binding of PAMAM Dendrimers to Graphene: A Combined Analytical and Simulation Study

Phase Behavior of Pure PSPC and PEGylated Multicomponent Lipid and Their Interaction with Paclitaxel: An All-Atom MD Study

Modulating Interdendrimer Interactions through Surface Adsorption

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