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Objective: Ova and parasite (O&P) examination is recommended for the laboratory diagnosis of agents causing parasitic infections; however, this exam requires scientific and technological improvements to enhance its diagnostic validity. Dissolved air flotation (DAF) is an efficient technical principle separating suspended solids in a liquid medium. We aimed to develop and validate a new procedure for intestinal parasite detection with DAF. Methods: In this study, we collected samples from 500 volunteers, screened them by direct examination, and transferred the material to tubes using the Three Faecal Test (TF‐Test) for triplicate DAF tests. We evaluated physical–chemical parameters and DAF prototype components through quantifying parasites recovered from floated and non‐floated regions of the flotation column. The DAF operation protocol was validated with the gold standard results. Results: The 10% saturated volume proportion and cationic surfactant showed regularity and high parasite recovery (80%). Modifications of the needle device did not influence parasite recovery (p > 0.05). Sensitivity, specificity, accuracy and kappa agreement obtained with the DAF protocol were 91%, 100%, 93% and substantial (k = 0.64), respectively. Conclusion: The DAF principle could be used to process faecal samples in routine laboratory exams, enabling intestinal parasite detection. [ABSTRACT FROM AUTHOR]

Slow-motionimaging of the rupture of soap bubbles generally showsthe edges of liquid films retracting at a constant speed (known asthe Taylor–Culick velocity). Here we investigate soap bubblesformed from simple solutions of a cationic surfactant (cetyltrimethylammonium bromide - CTAB)and sodium salicylate. The interaction of salicylate ions with CTABleads to the formation of wormlike micelles (WLM), which yield a viscoelasticbehavior to the liquid film of the bubble. We demonstrate that theseelastic bubbles collapse at a velocity up to 30 times higher thanthe Taylor–Culick limit, which has never been surpassed. Thisis because during the bubble inflation, the entangled WLM chains stretch,storing elastic energy. This extra energy is then released duringthe rupture of the bubble, yielding an additional driving force forfilm retraction (besides surface tension). This new mechanism forthe bursting of elastic bubbles may have important implications tothe breakup of viscoelastic sprays in industrial applications. [ABSTRACT FROM AUTHOR]

Hexadecylpyridinium chloride (CTPy), hexadecyltrimethylammonium chloride (CTAC), and thymol, typically found in mouthwash, exhibit inherent antimicrobial properties. When combined, these cationic surfactants and thymol can synergistically enhance these properties. Moreover, these molecules possess the necessary structure to form wormlike micelles (WLM) when thymol interacts with the cationic surfactants. This occurs because the aromatic rings spontaneously interpose themselves between the heads of the cationic surfactants, maintaining the hydroxyl group at the micelle interface. This arrangement minimizes repulsion between the surfactant heads, reducing aggregate curvature and leading to the formation of elongated aggregates. This preferential insertion of aromatic molecules into the micellar environment markedly increases thymol's solubility in aqueous solutions. Depending on the concentration of the components, WLM chains entangle, resulting in highly viscous systems. Consequently, these supramolecular gel-like structures enable prolonged disinfection of inclined or even vertical surfaces due to their slow sliding properties. The rheological properties of WLM, characterized using Cryo-TEM, and the phase diagram depicting thymol interactions with the two cationic surfactants, have been investigated. Additionally, the antimicrobial efficacy of a WLM formulation has been tested against various microbes. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The unexpected formation of a lamellar structure with concomitant gelation in solutions containing high urea concentration (40 wt%) and relatively low amount of cationic surfactant (3 wt%), indicates that a hierarchically structured complex is formed by both molecules. Gels formed by combination of aqueous solutions of urea and C 12 TAB, C 14 TAB or C 16 TAB were prepared in different proportions and their structures at microscopic and mesoscopic levels were investigated using XRD and SAXS, respectively. The elastic and viscous moduli and yield stress of the samples were determined and correlated with the composition and structuration of the gels. The lamellar structure is reversibly thermically destroyed and this process was investigated using DSC. XRD revealed that, at microscopic scale, the gels are formed through crystallization of adducts containing surfactant molecules loaded into the cavities of honeycomb-like urea assemblies. Such crystalline phase arranges itself in lamellae with interplanar distance around ∼20–30 nm, which were observed by SAXS. This hierarchical structure is independent of the chain length of the cationic surfactants. The blocks of lamellae dispersed in the continuous phase form a three-dimensional rigid particulate network structure, giving the characteristic rheological behavior of a hydrogel. DSC revealed a reversible thermal transition at around 20–25 °C, beyond which the adducts and the lamellar phase are destroyed and micelles are formed. The characteristic transition temperature is independent of the chain length of the surfactant, and thus, it is not associated with their Krafft temperatures. The structures of the gels indicate that they resemble alpha-gels formed by fatty-alcohols and surfactants, although they self-assemble by different driving forces. [ABSTRACT FROM AUTHOR]

Propofol, a phenol derivative, is commonly employed as an intravenous anesthetic during clinical procedures, formulated as an oil/water emulsion due to its poor solubility in water. The stability limitations associated with emulsions have prompted research efforts towards developing aqueous formulations of propofol. In this work, we investigate the solubility enhancement of propofol in anionic and cationic surfactants. Our findings reveal that the solubility of propofol can increase significantly, up to 100-fold, depending on the nature of the micellar aggregate, as observed for alkylammonium halogenates CnTAB (for n = 12, 14 and 16), contrasting with the lower solubility with SDS. Interestingly, C 14 TAB and C 16 TAB demonstrate significantly higher solubility than C 12 TAB. This was attributed to the formation of wormlike micelles, in which the propofol molecules are positioned between the cationic heads of the surfactant molecules, changing the micellar curvature and the morphology of the aggregate. Therefore, the aromatic molecules in the micellar environment can be partitioned into the micellar cores and their palisades. Regarding C 12 TAB, the alkyl chain is too short to form wormlike micelles, thus, concentrating propofol molecules mainly into the micellar core, and consequently, leading to their aggregation. Solubility diagrams of propofol were constructed in conjunction with different surfactants. The systems exhibiting viscoelastic behavior, indicative of wormlike micelle formation, were further investigated using rheology. Additionally, the fluorescent properties of propofol enabled the examination of the anesthetic molecule within diverse micellar environments. [Display omitted] • The anesthetic Propofol forms wormlike micelles with cationic surfactants. • Propofol is distinctly partitioned within different micellar morphologies. • WLM formation relates to higher solubilization of the anesthetic. • WLM are thermodynamically stable, allowing a new proposal for aqueous formulations of Propofol. [ABSTRACT FROM AUTHOR]

[Display omitted] • Depending on the pH, wormlike micelles are formed by combination of CTAB and phthalic acid. • Increase or decrease in viscosity of the system can be triggered by pH variations. • The charge of phthalic acid defines the partition of the aromatic molecule between micellar and bulk phases. • Fat alcohols highly affects the rheological behavior of the wormlike micelles. Responsive wormlike micelles are intriguing systems capable of transitioning their viscosity from that of water to a gel-like state in response to external stimuli such as pH changes. Referred to as "smart wormlike micelles", these structures offer the unique ability to adapt their viscosity for specific applications. In this study, we explored the rheological behavior of smart wormlike micelles formed by combining a cationic surfactant, Cetyltrimethylammonium bromide (C 16 TAB) with phthalic acid. The aromatic nature of phthalic acid, featuring two pKas at 2.9 and 4.5, provides control over the system's pH, enabling adjustments in the fraction of neutral, anionic, or dianionic species and thereby modulating the micellar rheology. The partitioning of phthalic acid between the micelle palisade and bulk solution plays a crucial role in inducing the formation of wormlike micelles by influencing curvature changes of the aggregate. This partitioning behavior is intricately governed by the balance between charge and hydrophobicity of the aromatic molecule. The investigation spanned a wide pH range, encompassing various concentrations of C 16 TAB and phthalic acid. Cryo-TEM imaging allowed direct characterization of distinct aggregate types formed at different pH levels. Additionally, to minimize electrostatic repulsion between cationic micellar heads in wormlike micelles, long alkyl alcohols were introduced as cosurfactants, enabling the exploration of synergistic effects at the micelle interface. [ABSTRACT FROM AUTHOR]

The combination of cationic surfactants with some aromatic anions can result in the formation of long aggregates, named as wormlike micelles. Like polymers, they can be used as viscosity controllers. The stabilization of the aromatic anions inserted into the micelles and their position at the surface is central to change the curvature of the aggregates and its consequent growth. Therefore, the affinity between these two components defines the potential to wormlike micelle formation and the understand of the molecular aspects that driven the process is central. In this sense, in this work it was investigated the effect of the presence of F, Cl Br or I at the position 4 of the aromatic ring of halogenbenzoates on the incorporation of the anions into the micelles of C 14 TAB. By using the isothermal titration calorimetry, the spontaneity of the process was determined by measuring the magnitude of the energy released and the critical concentration for wormlike micelle formation. Wormlike micelles are only formed for Cl, Br and I, and the formation is more pronounced for halogen atom more voluminous. It can be expected that the fitting into the water structure of the anion with a more voluminous halogen is more difficult. Therefore, the hydrophobic effect is an important driven force to the partitioning of the aromatic anion from water to the micellar pseudo-phase. The processes of formation, growth and shortening of the wormlike micelle chains were determined by measuring the hydrodynamic radius of the aggregates and correlated with the enthalpimetric curves. In high concentration regime, the micelles are entangled and the characteristics of the supramolecular gel-like formed were investigated by using linear and non-linear rheology. Unlabelled Image • In low concentration, benzoate and 4-fluorbenzoate form spherical micelles. • 4-Chloro, 4-bromo and 4-iodobenzoate form wormlike micelles. • ΔH and the critical concentration for aggregate formation were determined. • Wormlike micelle formation, growing and shortening were investigated. • Rheology of wormlike micelles was investigated. [ABSTRACT FROM AUTHOR]

When tetradecyltrimethylammonium bromide, TTAB, is added to aqueous solution of sodium salicylate, NaSal, the threading of the aromatic anion into the micellar palisade leads to the formation of wormlike micelles. Based on the calorimetric titration of NaSal with TTAB, and on the lifetime of fluorescence of salicylate, we propose that the aggregation of the two components directly leads to the formation of wormlike micelles, without any pre-aggregation. By using an isothermal titration calorimeter, aliquots of TTAB were added to a dilute solution of NaSal. The energy involved in each addition was then integrated and the variation of enthalpy was determined. In the same range of concentrations and molar ratios, the surface tensiometry and time-resolved emission spectroscopy experiments were performed. A very characteristic calorimetric signal associated with wormlike micelle formation was obtained, being the enthalpy variation of this process, Δ W L M H 298 0 < 0. When 1.2 mmol L−1 of NaSal is titrated with 11.0 mmol L−1 of TTAB at 298.15 K, Δ f H 298 0 = −10.31 kJ per mol of injectant. By adding TTAB to NaSal solution, two fluorescence lifetimes of salicylate were observed solely after wormlike micelle being formed. The correspondent lifetime values of 4.0 ns and 7.2 ns are respectively associated with the free and associated species of salicylate. The new results demonstrated that wormlike micelles are the first aggregate formed when TTAB is added to salicylate. This aspect is relevant for understanding the mechanism of wormlike micelles formation. [ABSTRACT FROM AUTHOR]