Interplay between aggregation number, micelle charge and hydration of catanionic surfactants

Medoš, Žiga; Friesen, Sergej; Buchner, Richard; Bešter‐Rogač, Marija

doi:10.1039/d0cp00877j

Cited by 12 publications

(24 citation statements)

References 56 publications

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“…[9][10][11]17 Their fraction in solution is relatively small and condition-dependent, which makes the total description of the COSAN aggregation a challenging task. 15 The isothermal titration calorimetry (ITC) is a powerful tool for the investigation of binding and aggregation processes such as micellization of surfactants 34,35,48 as well as the COSAN aggregation. 11,14,15 It provides not only the thermodynamic properties (Gibbs free energy, Δ agg G θ , enthalpy, Δ agg H θ , and entropy, Δ agg S θ , of the aggregation) and the value of CAC, but also the aggregation number, n, and degree of counterion binding, β.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Counterion-Induced Aggregation of Metallacarboranes

et al. 2022

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The model of counterion-induced metallacarborane aggregation in water was verified on sodium bis(1,2-dicarbollide), one of the most studied examples of metallacarboranes. This case study introduces a novel approach in anionic boron cluster self-assembly that resembles the behavior of polyoxometalate nanoions. The key prerequisite of the counterion binding to the aggregates is the strongly uneven charge distribution of cobalt bis(dicarbollide) clusters. Simultaneously, the size of the counterion should fit into the void between the metallacarborane clusters within the aggregate. In consequence, compact pentamers with two bound sodium cations via Coulombic-driven assembly are formed. This behavior cannot be explained solely by the hydrophobic effectthe paradigm of metallacarborane aggregation in the current literature. The pentamers can merge into bigger nanostructures via the second aggregation mechanism that sheds light on the complex behavior of metallacarboranes in water. The proof-ofconcept of counterion-induced metallacarborane aggregation and the proposed total description of the self-assembly via the two-process model are results of calorimetry modeling, quantum chemistry calculations, and molecular dynamics simulations. Article pubs.acs.org/JPCC

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Section: ■ Results and Discussionmentioning

confidence: 99%

Counterion-Induced Aggregation of Metallacarboranes

et al. 2022

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“…In contrast to several previous approaches, ,− we have included two independent dilution contributions for both the free monomers and the micelles, which makes the description of the molar heat profile more realistic. An alternative model that also considers the dilution enthalpy of free monomers and micelles in a completely different way has been recently proposed. − Our choice to model these contributions is based on the linear interpolation between the minimum dilution enthalpy, which by definition should correspond to the point where the concentrations of the mixed liquids are identical, and the maximum, expected when the concentration difference between the cell and syringe is maximum. In this way, a single parameter is required to model each dilution contribution and the results are easy to interpretate.…”

Section: Resultsmentioning

confidence: 99%

“…However, using a more elaborate protocol, by combining multitemperature experiments with a global fitting, it is possible to reduce the number of degrees of freedom during the minimization process. This has already been done by several authors to explicitly include the effect of counterions. − Although this method is definitely interesting, it cannot be applied to single demicellization isotherms, which is the aim of the present work, due to the large number of fitting parameters required.…”

Section: Discussionmentioning

confidence: 99%

“…Mass action-type models explicitly contemplate the equilibrium between monomers and micelles, and they are considered to be more rigorous than pseudo-phase separation models. The direct information obtained from the analysis of demicellization ITC isotherms is typically the value of the cmc and the enthalpy of the micelle formation process, but more thermodynamic information including the free energy of micellization, solute dilution enthalpy, and even an estimation of the aggregation number can be obtained. − Several approaches have been proposed to optimize the analysis of these experiments, including the simultaneous use of different calorimetric techniques, global multitemperature fittings, or manipulations in the equations to decouple the fitting parameters, thus facilitating the application of the model.…”

Section: Introductionmentioning

confidence: 99%

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Simple ApproximaTion for Aggregation Number Determination by Isothermal Titration Calorimetry: STAND-ITC

et al. 2021

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A new proposal to obtain aggregation numbers from isothermal titration calorimetry dilution experiments is described and tested using dodecyl trimethyl ammonium bromide, dodecyl methylimidazolium chloride, dodecyl methylimidazolium sulfonate, and didecyl methylimidazolium chloride aqueous solutions at different temperatures. The results were compared to those obtained from fluorescence measurements and also with data from the literature. In addition to the aggregation number, the molar free energy to transfer a solute molecule from the aggregate to the bulk solution, the enthalpy corresponding to the formation of the self-assembled suprastructures, the molar heat corresponding to the dilution of monomers and aggregates, and an offset parameter to account for unpredictable external contributions are simultaneously obtained using the same method. The new equations are compared to those obtained from previous proposals, and they are also analyzed in detail to assess the impact of each fitting parameter in the profile of the calorimetric isotherm. This new approach has been implemented in a computational code that automatically determines the fitting parameters as well as the corresponding statistical uncertainties for the large variety of calorimetric profiles that have been tested. Given the high sensitivity of the dilution experiments to the aggregation number for relatively small assemblies, our approach is proposed also to quantify the oligomerization state of biomolecules such as proteins and peptides.

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“…The catanionic vesicles are fabricated by mixing oppositely charged surfactants in water (in appropriate molar ratios) due to strong electrostatic interactions between oppositely charged head groups of surfactants. These catanionic mixtures have many advantages over existing delivery system, in terms of lower critical aggregation concentration (CAC), controlled size, and surface charge variation ability, which can encapsulate both hydrophilic and hydrophobic drugs and cationic and anionic drugs. They exhibit structures such as rod-like, cubic, and hexagonal, and lamellar phases that could be prepared by controlling the interaction between the amphiphiles. − The main applications of the catanionic vesicles are in dye encapsulation, , drug delivery, , sensing, corrosion protection, etc.…”

Section: Introductionmentioning

confidence: 99%

Efficient Photodynamic Therapy against Gram-Positive and Gram-Negative Bacteria Using Rose Bengal Encapsulated in Metallocatanionic Vesicles in the Presence of Visible Light

Sharma

Thakur

Kaur

et al. 2020

ACS Appl. Bio Mater.

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Significant consumption of antibiotics has generated multidrug resistance in bacteria, which is a major menace to human beings. Antibacterial photodynamic therapy (aPDT) is a progressing technique for inhibition of bacterial infection with minimal side effects. Metals and delivering agents play a major role in aPDT efficiency. Herein, we report a formulation to enrich the antibacterial photodynamic therapy utilizing metallocatanionic vesicles (MCVs) against both Gram-positive and Gram-negative bacteria. These MCVs were synthesized by utilizing iron-based double-chain metallosurfactant [FeCPC(II)] as a cationic surfactant and AOT, a double-chain anionic surfactant. These synthesized MCV fractions were characterized by distinct techniques like DLS, zeta potential, FE-SEM, confocal microscopy, SAXS, and UV–Visible spectroscopy. Polyhedral-shaped MCVs with a size of 200 nm were formed, wherein the charge and size of the catanionic vesicle can be controlled by varying the mixing ratios. Both Gram-positive bacteria, i.e., methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria, i.e., Escherichia coli (E. coli), were used for aPDT using Rose Bengal (RB) as a photosensitizer (PS) encapsulated in MCVs in the presence of a 532 nm wavelength laser. The aPDT against bacterial cells was evaluated for both dark and light toxicities. Pure MCVs also exhibited good antibacterial properties; however, much enhancement was observed in the presence of RB encapsulated in MCVs under light, where eradication of bacteria (E. coli and MRSA) was achieved in 30 min. The observations demonstrated that it is the presence of metal that enhances the singlet oxygen quantum yield of RB and MCVs help in retarding self-quenching and enhanced solubilization of RB. The cationic surfactant-rich fraction shows strong adhesion toward bacteria via electrostatic interactions. The outcome of this research shows that these newly fabricated metal-based metallocatanionic vesicles were effective against both Gram-positive and Gram-negative bacteria using aPDT and must be exploited for clinical applications as well as an alternative for antibiotics in the future.

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Interplay between aggregation number, micelle charge and hydration of catanionic surfactants

Abstract: Alkyltrimethylammonium alkanecarboxylates, [CxMe3N]+[Cy]−, with medium to long alkyl chains on both cation and anion (x,y = 6–10), were investigated in aqueous solution by density and zeta potential measurements, ITC, and DRS.

Cited by 12 publications

References 56 publications

Counterion-Induced Aggregation of Metallacarboranes

Counterion-Induced Aggregation of Metallacarboranes

Simple ApproximaTion for Aggregation Number Determination by Isothermal Titration Calorimetry: STAND-ITC

Efficient Photodynamic Therapy against Gram-Positive and Gram-Negative Bacteria Using Rose Bengal Encapsulated in Metallocatanionic Vesicles in the Presence of Visible Light

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