Effects of addition of polar organic solvents on micellization

Micellization of several surfactants in water-organic solvent mixtures has been investigated. Only solvents localized mainly in the bulk phase of the micellar solutions (they do not incorporate into the micelles) were studied, with either higher or lower permittivity than that of pure water. Results show that the influence of organic solvent addition on the aggregation process can be approximately accounted for by considering the changes in the bulk phase cohesive energy density, described by the Gordon parameter, G. To our knowledge, this is the first time that, for a given surfactant, the Gibbs energies of micellization, Delta G M degrees , obtained in several water-organic solvent mixtures have been fitted together. It is worth noting that data from different research groups have been considered. The Delta G M degrees versus G correlation will permit the estimation of the variations in the Gibbs energy of micellization upon addition of known quantities of a given polar organic solvent. Speaking in a general way, organic solvent addition results in the bulk phase becoming a better solvent for the surfactant molecules. This would make the hydrophobic tail transfer from the bulk phase into the micelles less favorable and, as a consequence, Delta G M degrees increases (becomes less negative), making the aggregation process less spontaneous.     

Role of the solvophobic effect on micellization

Experimental data of amphiphiles aggregation phenomena in water-organic solvent mixtures were considered with the idea of investigating the role of the solvophobic effect on micellization. Changes in the critical micelle concentration, in the micellar ionization degree (for ionic surfactants) and in the aggregation number accompanying variations in the composition of the bulk phase of the micellar solutions were examined with the scope of understanding which properties of the water-organic solvent mixtures are important in the micellization process. Results point out that the cohesive energy density, measured either through the Hildebrand-Hansen solubility parameter or the Gordon parameter, seems to play an important role in determining the contribution of the solvophobic effect on the Gibbs energy of micellization in water-organic solvents mixtures.     

New Oxaliplatin-Pyrophosphato Analogs with Improved In Vitro Cytotoxicity

Two new Pt(II)-pyrophosphato complexes containing the carrier ligands cis-1,3-diaminocyclohexane (cis-1,3-DACH) and trans-1,2-diamine-4-cyclohexene (1,2-DACHEX), variants of the 1R,2R-diaminocyclohexane ligand present in the clinically used Pt-drug oxaliplatin, have been synthesized with the aim of developing new potential antitumor drugs with high bone tropism. The complexes are more stable at physiological pH than in acid conditions, with Na₂[Pt(pyrophosphato)(cis-1,3-DACH)] (1) slightly more stable than [Pt(dihydrogenpyrophosphato)(1,2-DACHEX)] (2). The greater reactivity at acidic pH ensures a greater efficacy at the tumor site. Preliminary NMR studies indicate that 1 and 2 react slowly with 5’-GMP (used as a model of nucleic acids), releasing the pyrophosphate ligand and affording the bis 5’-GMP adduct. In vitro cytotoxicity assays performed against a panel of four human cancer cell lines have shown that both compounds are more active than oxaliplatin. Flow cytometry studies on HCT116 cells showed that the pyrophosphato compounds with the non-classical 1,3- and 1,4-diaminocyclohexane ligands (1 and 4) are the most capable to induce cells’ death by apoptosis and necrosis.     

Spirocyclic Amide Acetal Synthesis by [CpRu]-Catalyzed Condensations of α-Diazo-β-Ketoesters with γ-Lactams

The synthesis of spirocyclic amide acetals (33–93 %) has been achieved through Ru(II)-catalyzed condensations of N-carbamate protected pyrrolidinones with metal carbenes derived from α-diazo-β-ketoesters. Thanks to the mildness of the diazo decomposition conditions induced by a 1 : 1 combination of [CpRu(MeCN)₃][BAr_F] and 1,10-phenanthroline, the formation of the sensitive products is possible. Full characterization of this carbonyl-ylide mediated process is provided by DFT calculations.     

Towards improved gene delivery: Flip of cationic lipids in highly polarized liposomes

Hyperpolarization of cationic liposomes improves their stability in the presence of human serum albumin.     

Study of the reaction 2-(p-nitrophenyl)ethyl bromide + OH⁻ in dimeric micellar solutions

The dehydrobromination reaction 2-(p-nitrophenyl)ethyl bromide + OH? was investigated in several alkanediyl-α-ω-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br? (with s = 2, 3, 4, 5, 6, 8, 10, 12) micellar solutions, in the presence of NaOH 5 × 10?3 M. The kinetic data were quantitatively rationalized within the whole surfactant concentration range by using an equation based on the pseudophase ion-exchange model and taking the variations in the micellar ionization degree caused by the morphological transitions into account. The agreement between the theoretical and the experimental data was good in all the dimeric micellar media studied, except for the 12-2-12,2Br? micellar solutions. In this case, the strong tendency to micellar growth shown by the 12-2-12,2Br? micelles could be responsible for the lack of accordance. Results showed that the dimeric micelles accelerate the reaction more than two orders of magnitude as compared to water.     

Strain maps obtained by phase-shifting interferometry: An uncertainty analysis

We used Moiré interferometry to evaluate the strains induced on a specimen subjected to a steady tensile load. The strains were evaluated by differentiating the whole-field phase values obtained by a phase-shifting algorithm. Because the direct differentiation of even slightly noisy data may lead to unacceptable derivative errors, the strain evaluation procedure included the application of a low-pass filter, which allowed us to smooth out local fluctuations in the phase data. In addition to the noise, the strain values were also affected by systematic errors in the phase values rendered by the phase-shifting algorithm as well as uncertainties in the determination of both the interferometer sensitivity and the magnification of the imaging system. In this paper, the influence of these error sources was assessed by applying a Monte Carlo-based uncertainty propagation technique; the strain uncertainty evaluation was based on simulating a large number of times, both the phase-shifting procedure and the post-image processing (which included the filter application). We found that the strain uncertainty strongly depends on the low-pass filter used to counteract the noise effect. Although we obtained the phase data from a Moiré pattern, the procedure presented to evaluate the strain uncertainty is valid independently of the techniques used to generate the fringe pattern or the algorithm applied to exploit the phase-shifting procedure.     

Simultaneous measurement with one-capture of the two in-plane components of displacement by electronic speckle pattern interferometry

We present the simultaneous measurement of the two in-plane displacement components by electronic speckle pattern interferometry with three object beams and without an in-line reference beam. Three interference fringe patterns, corresponding to three different sensitivity vectors, are recorded in a single interferogram and separated by means of the Fourier transform method. Then, two interference fringe patterns are selected to obtain the in-plane displacement components.