Proton NMR Based Investigation of the Effects of Temperature and NaCl on Micellar Properties of CHAPS

Effect of selected monovalent salts on surfactant stabilized foams

Surfactant-stabilized foams have been at the centre of scientific research for over a century due to their ubiquitous applications in different industries. Many of these applications involve inorganic salts either due to their natural presence (e.g. use of seawater in froth floatation) or their addition (e.g. in cosmetics) to manipulate foam characteristics for the best outcomes. This paper provides a clear understanding of the effect of salts on surfactant-stabilized foams through a critical literature survey of this topic. Available literature shows a double effect of salts (LiCl, NaCl and KCl) on foam characteristics in the presence of surfactants. To elucidate the underlying mechanisms of the stabilizing effect of salts on foams, the effect of salts on surfactant-free thin liquid films is first discussed, followed by a discussion on the effect of salts on surfactant-stabilized foams with the focus on anionic surfactants. We discuss two distinctive salt concentrations, salt transition concentration in surfactant-free solutions and salt critical concentration in surfactant-laden systems to explain their effects. Using the available data in literature supported by dedicated experiments, we demonstrate the destabilizing effect of salts on foams at and above their critical concentrations in the presence of anionic surfactants. This effect is attributed to retarding the adsorption of the surfactant molecules at the interface due to the formation of nano and micro-scale aggregates.

Detergent-Based Decellularization of Bovine Carotid Arteries for Vascular Tissue Engineering

Vascular diseases are an increasing health issue, and common alloplastic, allogenic or autologous vascular grafts show frequent complications. The aim of this study is to develop an acellular, xenogenic bypass-graft from a bovine carotid artery (BAC) using detergent-based protocols. We compared decellularization with sodium desoxycholate (DOA), 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps), sodium dodecyl sulfate (SDS), and Triton X100 and improved suitable methods by variation of concentration, buffer system, incubation time, temperature, rinsing, and flow rate. All processes were evaluated systematically based on cellular residues, biocompatibility, structural and mechanical integrity. Decellularization with SDS and Triton X100 was not sufficient for the removal of cellular components. We optimized protocols using 1% DOA and Chaps by a buffered system at 37 °C with extended decellularization and rinsing. Decellularization with DOA depleted DNA to 0.5 ± 0.1% and soluble proteins to 0.6 ± 0.2%. Using Chaps, DNA was reduced to 0.2 ± 0.2% and proteins to 0.6 ± 0.3%. The improved protocols eliminated RNA completely from the matrix, and no cytotoxic effects were detected. Mechanical and structural integrity of decellularized tissues was comparable to non-decellularized controls. Our method effectively removed cellular components from the extracellular matrix while preserving the structural and mechanical integrity of the tissue. Decellularized BACs could be a promising alternative for vascular replacement therapy.

Aggregation behavior and total miscibility of fluorinated ionic liquids in water

In this work, novel and nontoxic fluorinated ionic liquids (FILs) that are totally miscible in water and could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements, and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry, and surface tension measurements in order to study various thermodynamic and surface properties that demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures.

Drugging a stem cell compartment using Wnt3a protein as a therapeutic

The therapeutic potential of Wnt proteins has long been recognized but challenges associated with in vivo stability and delivery have hindered their development as drug candidates. By exploiting the hydrophobic nature of the protein we provide evidence that exogenous Wnt3a can be delivered in vivo if it is associated with a lipid vesicle. Recombinant Wnt3a associates with the external surface of the lipid membrane; this association stabilizes the protein and leads to prolonged activation of the Wnt pathway in primary cells. We demonstrate the consequences of Wnt pathway activation in vivo using a bone marrow engraftment assay. These data provide validation for the development of WNT3A as a therapeutic protein.

Thermodynamic characterization of 3-[(3-cholamidopropyl)-dimethylammonium]-1-propanesulfonate (CHAPS) micellization using isothermal titration calorimetry: temperature, salt, and pH dependence

A systematic investigation of the micellization process of a biocompatible zwitterionic surfactant 3-[(3-cholamidopropyl)-dimethylammonium]-1-propanesulfonate (CHAPS) has been carried out by isothermal titration calorimetry (ITC) at temperatures between 278.15 K and 328.15 K in water, aqueous NaCl (0.1, 0.5, and 1 M), and buffer solutions (pH = 3.0, 6.8, and 7.8). The effect of different cations and anions on the micellization of CHAPS surfactant has been also examined in LiCl, CsCl, NaBr, and NaI solutions at 308.15 K. It turned out that the critical micelle concentration, cmc, is only slightly shifted toward lower values in salt solutions, whereas in buffer media it remains similar to its value in water. From the results obtained, it could be assumed that CHAPS behaves as a weakly charged cationic surfactant in salt solutions and as a nonionic surfactant in water and buffer medium. Conventional surfactants alike, CHAPS micellization is endothermic at low and exothermic at high temperatures, but the estimated enthalpy of micellization, ΔHM0, is considerably lower in comparison with that obtained for ionic surfactants in water and NaCl solutions. The standard Gibbs free energy, ΔGM0, and entropy, ΔSM0, of micellization were estimated by fitting the model equation based on the mass action model to the experimental data. The aggregation numbers of CHAPS surfactant around cmc, obtained by the fitting procedure also, are considerably low (nagg ≈ 5 ± 1). Furthermore, some predictions about the hydration of the micelle interior based on the correlation between heat capacity change, Δcp,M0, and changes in solvent-accessible surface upon micelle formation were made. CHAPS molecules are believed to stay in contact with water upon aggregation, which is somehow similar to the micellization process of short alkyl chain cationic surfactants.