Morphology of Ionic Micelles as Studied by Numerical Solution of the Poisson Equation

Зуева, О. С.; Rukhlov, V. S.; Zuev, Yu. F.

doi:10.1021/acsomega.1c06665

Cited by 10 publications

(7 citation statements)

References 64 publications

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“…Furthermore, the distances fall within a rather short range of 0.27 nm (from 1.49 to 1.76 nm), while the variation of Ψ reaches 127 mV (or 80 mV for corrected Ψ calc corr values). If it is the distance that causes the variation, then we may deduce the average potential decline rate of 30–50 mV per 0.1 nm, which is unrealistically sharp if compared with the theoretical estimations, giving at most 15 mV per 0.1 nm gradient at the very surface and less farther from it. − …”

Section: Resultsmentioning

confidence: 87%

Estimation of Nanoparticle’s Surface Electrostatic Potential in Solution Using Acid–Base Molecular Probes II: Insight from Atomistic Simulations of Micelles

et al. 2023

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Exploiting acid–base indicators as molecular probes is one of the most popular methods for determining the surface electrostatic potential Ψ in hydrophilic colloids like micellar surfactant solutions and related systems. Specifically, the indicator’s apparent acidity constant index is measured in the colloid solution of interest and, as a rule, in a nonionic surfactant solution; the difference between the two is proportional to Ψ. Despite the widespread use of this approach, a major problem remains unresolved, namely, the dissimilarity of Ψ values obtained with different indicators for the same system. The common point of view recognizes the effect of several factors (the choice of the nonionic surfactant, the probe’s localization, and the degree of hydration of micellar pseudophase) but does not allow to quantitatively assess their impact and decide which indicator reports the most correct Ψ value. Here, based on the ability to predict the reported Ψ values in silico, we examined the role of these factors using molecular dynamics simulations for five probes and two surfactants. The probe’s hydration in the Stern layer was found responsible for approximately half of the dissimilarity range. The probe’s localization is found important but hard to quantify because of the irregular structure of the Stern layer. The most accurate indicators among the examined set were identified. Supplementing experiments on measuring Ψ with molecular dynamics simulation is proposed as a way of improving the efficacy of the indicator method: the simulations can guide the choice of the most suitable probe and nonionic surfactant for the given nanoparticles.

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Section: Resultsmentioning

confidence: 87%

Estimation of Nanoparticle’s Surface Electrostatic Potential in Solution Using Acid–Base Molecular Probes II: Insight from Atomistic Simulations of Micelles

et al. 2023

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“…The SDS data show an emerging structure factor upon increasing concentration, as expected by an anionic surfactant; by contrast, DDAO is zwitterionic, , with zero overall charge, and no structure factor contribution is present, even at 50 mM, well above CMC ≃ 1.1 mM . The SDS scattering profiles show the expected micelle formation at 10 mM (above the CMC of SDS, 8.2 mM) ,,, with the presence of a form factor and further presence of a significant structure factor at 50 mM due to the dissociation of Na + in solution, generating negatively charged micelles and leading to an intermicelle electric double-layer interaction. − Details of physicochemical parameters are given and compared to mixtures in the following section.…”

Section: Resultsmentioning

confidence: 98%

Concentration Dependent Asymmetric Synergy in SDS–DDAO Mixed Surfactant Micelles

Torquato,

Tyagi,

Sharratt

et al. 2024

Langmuir

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We investigate the structure and interactions of a model anionic/amphoteric mixed surfactant micellar system, namely, sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine N-oxide (DDAO), employing SANS, FTIR, DLS, and pH measurements, in the range 0.1–100 mM total surfactant concentration and 0–100% DDAO. Increasing surfactant concentration is found to elongate the prolate ellipsoid micelles (R Polar ∼ 25–40 Å), accompanied by up to a 6-fold increase in micellar charge. The surfactant synergy, in terms of micellar charge and size, diffusion coefficient, solution pH, and headgroup interactions, was found to vary with concentration. At lower concentrations (≤50 mM), the SDS–DDAO ratio of maximum synergy is found to be asymmetric (at 65–85% DDAO), which is rationalized using regular solution theory, suggesting an equilibrium between Na+ dissociation, DDAO protonation, and counterion concentration. At higher concentrations, maximum synergy shifts toward the equimolar ratio. Overall, our study expands and unifies previous reports, providing a comprehensive understanding for this model, synergetic mixed micellar system.

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“…Counterions condensed onto this layer due to Coulombic electrostatic interaction comprise an electrical double layer, with counterions immediately surrounding COOH groups forming a Stern layer 36 . The Stern layer orients water molecules toward the electrical layer, 31,37 and their vibrational and rotational dynamics are notably different from those in bulk water. Therefore, water‐dye interactions are reduced inside micelles, and the overall fluorescence of IR‐1061 is protected.…”

Section: Discussionmentioning

confidence: 99%

Enhancing near‐infrared fluorescence intensity and stability of PLGA‐b‐PEG micelles by introducing Gd‐DOTA at the core boundary

Doan,

Umezawa,

Okubo

et al. 2023

J Biomed Mater Res

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Micelles have been extensively used in biomedicine as potential carriers of hydrophobic fluorescent dyes. Their small diameters can potentially enable them to evade recognition by the reticuloendothelial system, resulting in prolonged circulation. Nevertheless, their lack of stability in physiological environments limits the imaging utility of micelles. In particular, when a dye sensitive to water, such as IR‐1061, is encapsulated in the micelle core, the destabilized structure leads to interactions between water and dye, degrading the fluorescence. In this study, we investigated a method to improve micelle stability utilizing the electrical effect of gadolinium (Gd3+) and tetraazacyclododecane tetraacetic acid (DOTA), introduced into the micelles. Three micellar structures, one containing a poly(lactic‐co‐glycolic acid)‐block‐poly(ethylene glycol) (PLGA‐b‐PEG) block copolymer, and two other structures, including PLGA‐b‐PEG with DOTA or Gd‐DOTA introduced at the boundary of PLGA and PEG, were prepared with IR‐1061 in the core. Structures that contained DOTA at the border of the PLGA core and PEG shell exhibited much higher fluorescence intensity than probes without DOTA. With Gd3+ ions at the DOTA center, fluorescence stability was enhanced remarkably in physiological environments. Most interesting is the finding that fluorescence is enhanced with increased Gd‐DOTA concentrations. In conclusion, we found that overall fluorescence and stability are improved by introducing Gd‐DOTA at the boundary of the PLGA core and PEG shell. Improving micelle stability is crucial for further biomedical applications of micellar probes such as bimodal fluorescence and magnetic resonance imaging.

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Morphology of Ionic Micelles as Studied by Numerical Solution of the Poisson Equation

Cited by 10 publications

References 64 publications

Estimation of Nanoparticle’s Surface Electrostatic Potential in Solution Using Acid–Base Molecular Probes II: Insight from Atomistic Simulations of Micelles

Estimation of Nanoparticle’s Surface Electrostatic Potential in Solution Using Acid–Base Molecular Probes II: Insight from Atomistic Simulations of Micelles

Concentration Dependent Asymmetric Synergy in SDS–DDAO Mixed Surfactant Micelles

Enhancing near‐infrared fluorescence intensity and stability of PLGA‐b‐PEG micelles by introducing Gd‐DOTA at the core boundary

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