Cationic Bilayer Research Articles

Biomimetic Lipid Polymer Nanoparticles for Drug Delivery.

Biomimetic nanoparticles are hybrid nanostructures in which the uppermost layer is similar to a cell membrane. In these nanoparticles, lipids and biopolymers can be organized to improve drug incorporation and delivery. This report provides instructions for the preparation and physical characterization of four different biomimetic nanoparticles: (1) polystyrene sulphate (PSS) nanoparticles covered with one cationic dioctadecyl dimethylammoniumbromide bilayer (DODAB), which incorporates dimeric channels of the antimicrobial peptide Gramicidin D; (2) silica nanoparticles covered with one single bilayer of the antimicrobial cationic lipid DODAB; (3) hybrid lipid/polymer indomethacin (IND) nanoparticles from injection of IND/DODAB ethanolic solution in a water solution of carboxymethyl cellulose (CMC); (4) bactericidal and fungicidal nanoparticles from DODAB bilayer fragments (BF) covered consecutively by a CMC and a poly(diallyl dimethyl ammonium chloride) (PDDA) layer. These examples provide the basis for the preparation and characterization of novel biomimetic nanoparticles with lipids and/or biopolymers in their composition. The polymers and lipids in the hybrid nanoparticle composition may impart stability and/or bioactivity and/or provide adequate microenvironments for carrying bioactive drugs and biomolecules.

Enveloped artificial viral capsids self-assembled from anionic β-annulus peptide and cationic lipid bilayer.

Anionic artificial viral capsids were self-assembled from β-annulus-EE peptide, then complexed with lipid-bilayer-containing cationic lipids via electrostatic interaction to form enveloped artificial viral capsids. The critical aggregation concentration of the enveloped artificial viral capsid was significantly lower than that of the uncomplexed artificial viral capsid, indicating that the lipid bilayer stabilised the capsid structure.

Aqueous Photon Upconversion by Anionic Acceptors Self-Assembled on Cationic Bilayer Membranes with a Long Triplet Lifetime

Anionic 9,10-diphenylanthracene chromophores electrostatically bound to cationic, chiral bilayer membranes show ordered self-assembly in water. The integrity of the chromophore-accumulated aqueous bilayer membranes is ensured by multiple hydrogen-bond networks introduced in the bilayer, which allowed adaptive accommodation of the guest chromophores at the inner surface of the bilayer while maintaining their cohesive interactions. The regular chromophore alignment in the aqueous assembly is confirmed by differential scanning calorimetry, circular dichroism, and circularly polarized luminescence spectra. Excitonic migration of triplet energy occurs among the chromophores densely organized at the inner surface of the bilayer, which lead to triplet–triplet annihilation-based photon upconversion (TTA-UC). This acceptor-bilayer self-assemblies show a notably long triplet lifetime of 8.0 ms, which allows TTA-UC at sufficiently low excitation light intensity. These results demonstrate the usefulness of the simple electrostatic accumulation approach for TTA-UC chromophores where the suitable molecular design of the TTA-UC chromophore-integrated bilayer membranes plays a key role.

Improving in vitro biocompatibility of gold nanorods with thiol-terminated triblock copolymer

Gold nanorods (AuNRs) are usually synthesized using cetyltrimethylammonium bromide (CTAB) surfactant as a structure-directing agent. CTAB is reported to form a tightly bound cationic bilayer on AuNR surface with the cationic trimethylammonium head group exposed to the aqueous media. However, CTAB is also known to be highly toxic in both in vitro and in vivo experiments. In this work, we investigated the cytotoxicity, colloidal stability and optical properties of AuNRs before and after substitution with thiol-terminated triblock copolymer of ethylene oxide-propylene oxide (PEO-PPO-PEO), or Pluronic F127® (PF127). For that, PF127 was first chemically functionalized with 3-mercaptopropionic acid (MPA) and further used as stabilizer for the AuNRs by replacing CTAB molecules. Unmodified PF127 was also tested and used as a control for biological experiments. Morphology of coated AuNRs was characterized by visible spectroscopy, transmission electron microscopy, zeta potential, and dynamic light scattering. We found that coating with PF127-SH guarantees both stability and biocompatibility of AuNRs for at least 45 days, besides improving cell viability when compared to the PF127-coated AuNRs, even after 72 h treatment. In addition, this new polymer coating can also provide hydrophobic domains assembled into the PPO blocks, which could be further loaded with organic active ingredients. The obtained results show the potential of this nanostructured system for future developments in multifunctional nanoplataforms for clinical applications such as drug delivery, hyperthermia, photodynamic therapy, and diagnostic imaging of cells and tissues.

Photoreaction of 9,10-Anthraquinone-2,6-disulfonic Acid and Ascorbic Acid Complexed at the Cationic Bilayer Interface and Consecutive Radical Dynamics

The antioxidant ability of substances such as vitamin C has attracted wide attention, and many antioxidant effects on our body are considered to act in the biomembrane interface region. However, the detailed dynamics of the radicals at the interface have not been deeply clarified. Here, we studied the reaction of photoexcited 9,10-anthraquinone-2,6-disulfonic acid dianion (AQDS2–) and ascorbic acid in the cationic vesicle solution of didodecyldimethyl ammonium bromide using time-resolved electron paramagnetic resonance (TR-EPR) and UV–vis absorption methods. The results were compared with those of micellar and aqueous systems. Analysis of UV–vis spectra revealed the formation of an intermolecular charge-transfer complex of ascorbic acid monoanion (AscH–) and AQDS2– at the cationic bilayer interface. The TR-EPR spectra revealed a hydrogen atom abstraction reaction by the excited triplet state of AQDS2– from AscH– to form an ascorbic acid monoanion radical (Asc•–) and an anthrasemiquinone dianion radical (A...

A closer look into laurdan as a probe to monitor cationic DODAB bilayers

Laurdan is a fluorescent molecule largely used to probe the lipid packing and hydration of membranes. In phospholipid bilayers that undergo the gel-fluid thermal transition, Laurdan fluorescent band displays a significant red shift upon the transition. However, Laurdan in DODAB bilayers does not show this characteristic shift of the emission band. Hence, the analysis of the membrane fluidity through the so-called Generalized Polarization (GP) cannot be used with DODAB. Nevertheless, both static and time resolved fluorescence attest that the Laurdan fluorescence in DODAB, like in phospholipids, is composed of two emission bands. The emission bands are associated with excited states with different lifetimes, and the relative intensity of the bands is sensitive to the bilayer thermal phase. Analyses were performed by decomposing the emission spectrum into two Gaussian bands and by computing the Decay Associated Spectra (DAS), the latter with time resolved fluorescence. We conclude that Laurdan in DODAB bilayers is in a shallower position as compared with the probe in phospholipids, possibly due to the small DODAB head group. Hence, Laurdan could be a useful probe to monitor interactions at the surface of DODAB bilayers, for instance with genetic material, quite often associated with cationic vesicles in lipoplexes, with broad medical applications.

DNA Delivery Systems Based on Peptide-Mimicking Cationic Lipids-The Effect of the Co-Lipid on the Structure and DNA Binding Capacity.

In continuation of previous work, we present a new promising DNA carrier, OO4, a highly effective peptide-mimicking lysine-based cationic lipid. The structural characteristics of the polynucleotide carrier system OO4 mixed with the commonly used co-lipid DOPE and the saturated phospholipid DPPE have been studied in two-dimensional and three-dimensional model systems to understand their influence on the physical–chemical properties. The phase behavior of pure OO4 and its mixtures with DOPE and DPPE was studied at the air–water interface using a Langmuir film balance combined with infrared reflection-absorption spectroscopy. In bulk, the self-assembling structures in the presence and absence of DNA were determined by small-angle and wide-angle X-ray scattering. The amount of adsorbed DNA to cationic lipid bilayers was measured using a quartz crystal microbalance. The choice of the co-lipid has an enormous influence on the structure and capability of binding DNA. DOPE promotes the formation of nonlamellar lipoplexes (cubic and hexagonal structures), whereas DPPE promotes the formation of lamellar lipoplexes. The correlation of the observed structures with the transfection efficiency and serum stability indicates that OO4/DOPE 1:3 lipoplexes with a DNA-containing cubic phase encapsulated in multilamellar structures seem to be most promising.

Unraveling the Role of Monoolein in Fluidity and Dynamical Response of a Mixed Cationic Lipid Bilayer.

The maintenance of cell membrane fluidity is of critical importance for various cellular functions. At lower temperatures when membrane fluidity decreases, plants and cyanobacteria react by introducing unsaturation in the lipids, so that the membranes return to a more fluidic state. To probe how introduction of unsaturation leads to reduced membrane fluidity, a model cationic lipid dioctadecyldimethylammonium bromide (DODAB) has been chosen, and the effects of an unsaturated lipid monoolein (MO) on the structural dynamics and phase behavior of DODAB have been monitored by quasielastic neutron scattering and time-resolved fluorescence measurements. In the coagel phase, fluidity of the lipid bilayer increases significantly in the presence of MO relative to pure DODAB vesicles and becomes manifest in significantly enhanced dynamics of the constituent lipids along with faster hydration and orientational relaxation dynamics of a fluorophore. On the contrary, MO restricts both lateral and internal motions of the lipid molecules in the fluid phase (>330 K), which is consistent with relatively slow hydration and orientational relaxation dynamics of the fluorophore embedded in the mixed lipid bilayer. The present study illustrates how incorporation of an unsaturated lipid at lower temperatures (below the phase transition) assists the model lipid (DODAB) in regulating fluidity via enhancement of dynamics of the constituent lipids.

Structural characterization of cationic DODAB bilayers containing C24:1 β-glucosylceramide

The effect of 5 mol%, 9 mol%, and 16 mol% of C24:1 β-glucosylceramide (βGlcCer) on the structure of cationic DODAB bilayers was investigated by means of differential scanning calorimetry (DSC), electron spin resonance (ESR) spectroscopy and fluorescence microscopy. βGlcCer is completely miscible with DODAB at all fractions tested, since no domains were observed in fluorescence microscopy or ESR spectra. The latter showed that βGlcCer destabilized the gel phase of DODAB bilayers by decreasing the gel phase packing. As a consequence, βGlcCer induced a decrease in the phase transition temperature and cooperativity of DODAB bilayers, as seen in DSC thermograms. ESR spectra also showed that βGlcCer induced an increase in DODAB fluid phase order and/or rigidity. Despite their different structures, a similar effect of loosening the gel phase packing and turning the fluid phase more rigid/organized has also been observed when low molar fractions of cholesterol were incorporated in DODAB bilayers. The structural characterization of mixed membranes made of cationic lipids and glucosylceramides may be important for developing novel immunotherapeutic tools such as vaccine adjuvants.

Lipid bilayer disruption induced by amphiphilic Janus nanoparticles: the non-monotonic effect of charged lipids.

In this study, we report the complex effects of charged lipids on the interaction between amphiphilic Janus nanoparticles and lipid bilayers. Janus nanoparticles are cationic on one hemisphere and hydrophobic on the other. We show that the nanoparticles, beyond threshold concentrations, induce holes in both cationic and anionic lipid bilayers mainly driven by hydrophobic interactions. However, the formation of these defects is non-monotonically dependent on ionic lipid composition. The electrostatic attraction between the particles and anionic lipid bilayers enhances particle adsorption and lowers the particle concentration threshold for defect initiation, but leads to more localized membrane disruption. Electrostatic repulsion leads to reduced particle adsorption on cationic bilayers and extensive defect formation that peaks at intermediate contents of cationic lipids. This study elucidates the significant role lipid composition plays in influencing how amphiphilic Janus nanoparticles interact with and perturb lipid membranes.

The electric double layer structure modulates poly-dT25 conformation and adsorption kinetics at the cationic lipid bilayer interface.

The conformation and adsorption kinetics of oligonucleotides at lipid membrane interfaces are crucial to their biological functions, but are yet not clearly understood. Poly-dT oligonucleotide molecules have been widely used as primers for reverse translation of RNA molecules, as well as a surface recognition agent for mRNA purification and extraction. In this research, the adsorption processes of poly-dT25 on lipid membranes in different ionic solutions were investigated by sum frequency generation vibrational spectroscopy (SFG-VS) together with a single molecule tracking technique in situ and in real time. These systematic studies provide us with molecular insight into the chemical and physical nature of oligonucleotide-membrane interactions, and show us how the electric double layer (EDL) structure changes the conformation and adsorption kinetics of oligonucleotides. The SFG-VS results indicate that an increase of ionic concentration not only decreases the adsorption density of oligonucleotides but also changes the conformation of oligonucleotides from an elongated conformation to a coiled conformation, causing stronger thermodynamic interactions with membranes, as demonstrated by single molecule tracking techniques. It is also shown that the ionic solution can tune the balance between the surface diffusion rate and solution diffusion rate of oligonucleotides significantly. These results demonstrated that the spectra and kinetics collected by in situ label-free SFG-VS detection and the single molecular tracking technique can provide new molecular insights into the mechanisms of oligonucleotide-membrane interactions. These new understandings may help researchers to control the assembly of oligonucleotide-liposome complexes and to improve the efficiency of transportation and delivery of oligonucleotide molecules.

Measurement of Forces between Supported Cationic Bilayers by Colloid Probe Atomic Force Microscopy: Electrolyte Concentration and Composition.

The interactions between supported cationic surfactant bilayers were measured by colloidal probe atomic force spectroscopy, and the effect of different halide salts was investigated. Di(alkylisopropylester)dimethylammonium methylsulfate (DIPEDMAMS) bilayers were fabricated by the vesicle fusion technique on muscovite mica. The interactions between the bilayers were measured in increasing concentrations of NaCl, NaBr, NaI, and CaCl2. In NaCl, the bilayer interactions were repulsive at all concentrations investigated, and the Debye length and surface potential were observed to decrease with increasing concentration. The interactions were found to follow the electrical double layer (EDL) component of DLVO theory well. However, van der Waals forces were not detected; instead, a strong hydration repulsion was observed at short separations. CaCl2 had a similar effect on the interactions as NaCl. NaBr and NaI were observed to be more efficient at decreasing surface potential than the chloride salts, with the efficacy increasing with the ionic radius.

Diverse stacked and entangled topologies in cadmium tricarballylate coordination polymers with nitrobenzene detection capability

Hydrothermal reaction of cadmium salts, tricarballylic acid (H3tca) and dipyridyl ligands resulted in generation of four coordination polymers that were characterized by single-crystal X-ray diffraction. The nature of the ancillary dipyridyl ligand plays a primary role in enforcing differing structural topologies across the series of new phases. [Cd2(tcaH)2(dpe)2]n (1, dpe = 1,2-di(4-pyridyl)ethane) displays a 2-fold interpenetrated 3D 41263pcu net based on 6-connected {Cd2(O)(OCO)} cluster nodes. [Cd(tcaH)(dpp)(H2O)]n (2, dpp = 1,2-di(4-pyridyl)propane) manifests a 1D + 1D → 3D interlocked system of loop-containing perpendicular ribbon motifs. {[Cd4(tca)2(Htca)(bpmp)5(H2O)2]·27H2O}n (3, bpmp = bis(4-pyridylmethyl)piperazine) has intersecting [Cd4(tca)2(Htca)(H2O)2]n layer, [Cd(bpmp)(H2O)]n chain, and [Cd2(bpmp)3]n ladder submotifs and forms a complicated 3,4,5-connected trinodal 3D self-penetrated network with (6.92)(42638)(42638.9310) topology. {[Cd(tcaH)(Hbpmp)](ClO4)·5.5H2O}n (4) exhibits stacked cationic bilayer (4,4) grid slabs. All compounds showed potential as potential detectors for nitrobenzene in ethanol suspension via luminescence quenching, with 1 showing the highest uptake of analyte.

Stern-Layer Adsorption of Oligonucleotides on Lamellar Cationic Lipid Bilayer Investigated by Polarization-Resolved SFG-VS.

The molecular interaction between the oligonucleotides and lipid membranes is the key to the functions of virus, aptamer, and various oligonucleotide-based materials. In this study, the conformational changes of oligonucleotides (dT25) on lamellar cationic 1,2-dimyristoyl-3-trimethylammonium-propane (DMTAP) bilayer were investigated by polarization-resolved sum frequency generation vibrational spectroscopy (SFG-VS) in situ. The SFG-VS spectra within different wavenumber ranges were analyzed to give conformation details of thymine groups, phosphate groups, and OD/OH groups and to provide a comprehensive and fundamental understanding of the oligonucleotide adsorption on a model bilayer. It is shown that the adsorption of dT25 on DMTAP bilayer reaches maximum at CdT ≈ 500 nM. And the conformation of dT25 molecules change significantly when surface charge of DMTAP bilayer reaches the point of zero charge (PZC) at CdT ≈ 100 nM. Combined spectroscopic evidences also indicate that the formation of electric double layer at the DMTAP/dT25 surface follows the Gouy–Chapman–Stern model. The analysis results also show that the symmetric PO2– stretching mode of oligonucleotide molecules can serve as a sensitive vibration molecular probe for quantifying the oligonucleotide/lipid charge ratio and determine the point of zero charge (PZC) of lipid bilayer surface, which may help researchers to control the layer-by-layer assembly of oligonucleotide–lipid complexes and to improve the efficiency genetic therapy against cancer and viral infections.

Cationic Biomimetic Particles of Polystyrene/Cationic Bilayer/Gramicidin for Optimal Bactericidal Activity.

Nanostructured particles of polystyrene sulfate (PSS) covered by a cationic lipid bilayer of dioctadecyldimethylammonium bromide (DODAB) incorporated gramicidin D (Gr) yielding optimal and broadened bactericidal activity against both Escherichia coli and Staphylococcus aureus. The adsorption of DODAB/Gr bilayer onto PSS nanoparticles (NPs) increased the zeta-average diameter by 8–10 nm, changed the zeta-potential of the NPs from negative to positive, and yielded a narrow size distributions for the PSS/DODAB/Gr NPs, which displayed broad and maximal microbicidal activity at very small concentrations of the antimicrobials, namely, 0.057 and 0.0057 mM DODAB and Gr, respectively. The results emphasized the advantages of highly-organized, nanostructured, and cationic particles to achieve hybrid combinations of antimicrobials with broad spectrum activity at considerably reduced DODAB and Gr concentrations.

Biomimetic Cationic Nanoparticles Based on Silica: Optimizing Bilayer Deposition from Lipid Films.

The optimization of bilayer coverage on particles is important for a variety of biomedical applications, such as drug, vaccine, and genetic material delivery. This work aims at optimizing the deposition of cationic bilayers on silica over a range of experimental conditions for the intervening medium and two different assemblies for the cationic lipid, namely, lipid films or pre-formed lipid bilayer fragments. The lipid adsorption on silica in situ over a range of added lipid concentrations was determined from elemental analysis of carbon, hydrogen, and nitrogen and related to the colloidal stability, sizing, zeta potential, and polydispersity of the silica/lipid nanoparticles. Superior bilayer deposition took place from lipid films, whereas adsorption from pre-formed bilayer fragments yielded limiting adsorption below the levels expected for bilayer adsorption.

Structural insights on biologically relevant cationic membranes by ESR spectroscopy.

Cationic bilayers have been used as models to study membrane fusion, templates for polymerization and deposition of materials, carriers of nucleic acids and hydrophobic drugs, microbicidal agents and vaccine adjuvants. The versatility of these membranes depends on their structure. Electron spin resonance (ESR) spectroscopy is a powerful technique that employs hydrophobic spin labels to probe membrane structure and packing. The focus of this review is the extensive structural characterization of cationic membranes prepared with dioctadecyldimethylammonium bromide or diC14-amidine to illustrate how ESR spectroscopy can provide important structural information on bilayer thermotropic behavior, gel and fluid phases, phase coexistence, presence of bilayer interdigitation, membrane fusion and interactions with other biologically relevant molecules.

Multifunctional Dextran Sulfate-Coated Reconstituted High Density Lipoproteins Target Macrophages and Promote Beneficial Antiatherosclerotic Mechanisms.

An atorvastatin calcium (AT)-loaded dextran sulfate (DXS)-coated core-shell reconstituted high density lipoprotein (rHDL), termed AT-DXS-LP-rHDL, was developed for targeted drug delivery to macrophages and suppression of inflammation via the high affinity of DXS with scavenge receptor class AI (SR-AI) as well as depletion of intracellular cholesterol by apolipoprotein A-I (apoA-I)-mediated cholesterol efflux. These core-shell nanoparticles comprising an AT-loaded negatively charged poly(lactide-co-glycolide) (PLGA) core and a cationic lipid bilayer shell were prepared by nanoprecipitation method followed by thin film hydration and extrusion. The nanoparticles were further functionalized with apoA-I and DXS via sodium cholate mediation and electrostatic interaction, respectively. The core-shell structure and the surface coating of apoA-I and DXS were verified by the increased particle size, inverted zeta potential, and reduced in vitro drug release rate. The TEM image further confirmed the entrapment of the PLGA nanoparticles in the aqueous interior of the liposomes. In vitro cell viability assay showed the biocompatibility of the AT-loaded nanocarriers. The cellular uptake study illustrated that the targeting efficacy to macrophages increased in the following order: PLGA nanoparticles (P-NP), core-shell nanoparticles (LP-NP), core-shell rHDL (LP-rHDL), and DXS-LP-rHDL. Moreover, cellular drug efficacy of AT-loaded nanoparticles in preventing macrophage-derived foam cell formation and inflammation such as intracellular lipid deposition, cholesterol esters content, DiI-oxLDL uptake, cholesterol efflux, and secretion of TNF-α, IL-6, and IL-10 was much better than that of the drug-free nanoparticles, consistent with the results of cellular uptake study. Collectively, AT-DXS-LP-rHDL, as multifunctional carriers, could not only deliver more drug to macrophages, but also present antiatherogenic actions of the biofunctional nanocarriers through damping oxidized low density lipoproteins (oxLDL) uptake and promoting cholesterol efflux.

Conformations and membrane-driven self-organization of rodlike fd virus particles on freestanding lipid membranes.

Membrane-mediated interactions and aggregation of colloidal particles adsorbed to responsive elastic membranes are challenging problems relevant for understanding the microscopic organization and dynamics of biological membranes. We experimentally study the behavior of rodlike semiflexible fd virus particles electrostatically adsorbed to freestanding cationic lipid membranes and find that their behavior can be controlled by tuning the membrane charge and ionic strength of the surrounding medium. Three distinct interaction regimes of rodlike virus particles with responsive elastic membranes can be observed. (i) A weakly charged freestanding cationic lipid bilayer in a low ionic strength medium represents a gentle quasi-2D substrate preserving the integrity, structure, and mechanical properties of the membrane-bound semiflexible fd virus, which under these conditions is characterized by a monomer length of 884 ± 4 nm and a persistence length of 2.5 ± 0.2 μm, in perfect agreement with its properties in bulk media. (ii) An increase in the membrane charge leads to the membrane-driven collapse of fd virus particles on freestanding lipid bilayers and lipid nanotubes into compact globules. (iii) When the membrane charge is low, and the mutual electrostatic repulsion of membrane-bound virus particles is screened to a considerable degree, membrane-driven self-organization of membrane-bound fd virus particles into long linear tip-to-tip aggregates showing dynamic self-assembly/disassembly and quasi-semiflexible behavior takes place. These observations are in perfect agreement with the results of recent theoretical and simulation studies predicting that membrane-mediated interactions can control the behavior of colloidal particles adsorbed on responsive elastic membranes.

Counterion effect of cationic surfactants on the oxidative degradation of Alizarin Red-S photocatalysed by TiO2 in aqueous dispersion

Abstract The TiO 2 photocatalyzed degradation of a hazardous texile dye, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid sodium salt (Alizarin Red-S, ARS), has been assisted by various cationic surfactants and examined in air-equilibrated aqueous medium under UV light irradiation. Absorption spectral analysis showed that ARS degrades slowly via a pH-dependent process in TiO 2 dispersions containing no surfactant. The photodegradation efficiency of the dye was significantly enhanced, especially in alkaline media, by the addition of surfactants such as cetyltrialkylammonium salts (CTRAX). Since both ARS and the TiO 2 surface are negatively charged in basic conditions, the addition of cationic surfactants has effectively allowed the mutual interaction among the dye, CTRAX and TiO 2 . The cooperation between the inorganic and organic components, which is very likely realized through the formation of cationic surfactant bilayers on the TiO 2 particles, permitted an improvement in the coadsorption of ARS onto the TiO 2 particles and thus rendering ARS more available to the action of the photo-yielded oxidative species formed on the semiconductor surface. The crucial influence of the surfactant adsorption was clearly pointed out by the investigation of the counterion effect on the degree of ARS photodecomposition as a function of the cetyltrimethylammonium salt (CTAX) concentration. Two particularly significant aspects have emerged from this investigation: the almost complete degradation of ARS was achieved, for all surfactants used, at a concentration close to 1 mM (value well above the cmc in the experimental conditions); also, by increasing the surfactant concentration, the photocatalytic reaction became less and less efficient and significantly dependent on the counterion nature. These results have allowed to gain insight and a better understanding of the surfactant-assisted photocatalytic degradation mechanism of the dye.