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Based on compelling preclinical evidence concerning the progress of our novel ruthenium-based metallotherapeutics, we are focusing research efforts on challenging indications for the treatment of invasive neoplasms such as the triple-negative breast cancer (TNBC). This malignancy mainly afflicts younger women, who are black, or who have a BRCA1 mutation. Because of faster growing and spreading, TNBC differs from other invasive breast cancers having fewer treatment options and worse prognosis, where existing therapies are mostly ineffective, resulting in a large unmet biomedical need. In this context, we benefited from an experimental model of TNBC both in vitro and in vivo to explore the effects of a biocompatible cationic liposomal nanoformulation, named HoThyRu/DOTAP, able to effectively deliver the antiproliferative ruthenium(III) complex AziRu, thus resulting in a prospective candidate drug. As part of the multitargeting mechanisms featuring metal-based therapeutics other than platinum-containing agents, we herein validate the potential of HoThyRu/DOTAP liposomes to act as a multimodal anticancer agent through inhibition of TNBC cell growth and proliferation, as well as migration and invasion. The here-obtained preclinical findings suggest a potential targeting of the complex pathways network controlling invasive and migratory cancer phenotypes. Overall, in the field of alternative chemotherapy to platinum-based drugs, these outcomes suggest prospective brand-new settings for the nanostructured AziRu complex to get promising goals for the treatment of metastatic TNBC.

Ruthenium(III) complexes are very promising candidates as metal-based anticancer drugs, and several studies have supported the likely role of human serum proteins in the transport and selective delivery of Ru(III)-based compounds to tumor cells. Herein, the anticancer nanosystem composed of an amphiphilic nucleolipid incorporating a Ru(III) complex, which we named DoHuRu, embedded into the biocompatible cationic lipid DOTAP, was investigated as to its interaction with two human serum proteins thought to be involved in the mechanism of action of Ru(III)-based anticancer drugs, i.e., human serum albumin (HSA) and human transferrin (hTf). This nanosystem was studied in comparison with the simple Ru(III) complex named AziRu, a low molecular weight metal complex previously designed as an analogue of NAMI-A, decorated with the same ruthenium ligands as DoHuRu but devoid of the nucleolipid scaffold and not inserted in liposomal formulations. For this study, different spectroscopic techniques, i.e., Fluorescence Spectroscopy and Circular Dichroism (CD), were exploited, showing that DoHuRu/DOTAP liposomes can interact with both serum proteins without affecting their secondary structures.

The integration of nuclear imaging analysis with nanomedicine has tremendously grown and represents a valid and powerful tool for the development and clinical translation of drug delivery systems. Among the various types of nanostructures used as drug carriers, nanovesicles represent intriguing platforms due to their capability to entrap both lipophilic and hydrophilic agents, and their well-known biocompatibility and biodegradability. In this respect, here we present the development of a labelling procedure of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine)-based liposomes incorporating an ad hoc designed lipophilic NOTA (1,4,7-triazacyclononane-1,4,7-triacetic acid) analogue, derivatized with an oleic acid residue, able to bind the positron emitter gallium-68(III). Based on POPC features, the optimal conditions for liposome labelling were studied with the aim of optimizing the Ga(III) incorporation and obtaining a significant radiochemical yield. The data presented in this work demonstrate the feasibility of the labelling procedure on POPC liposomes co-formulated with the ad hoc designed NOTA analogue. We thus provided a critical insight into the practical aspects of the development of vesicles for theranostic approaches, which in principle can be extended to other nanosystems exploiting a variety of bioconjugation protocols.

pH-sensitive surfactants find applications in many fields, including responsive drug delivery and smart material design. The rational design of the surfactant molecular structure leads to species presenting strong variations of the micellization parameter (e.g., critical micelle concentration, cmc, and aggregate dimension) in a controlled pH range. In the present work, the micellization of the branched amine oxide surfactant N,N-dimethyl-2-propylheptan-1-amine oxide (C10DAO-branched) is studied as a function of pH in dilute aqueous mixtures. Its behavior is compared with that of the linear isomer N,N-dimethyldecan-1-amine oxide (C10DAO-linear). The samples are investigated by potentiometric titrations, fluorescence spectroscopy, and Dynamic Light Scattering (DLS). With increasing pH, micellized C10DAO-branched presents a higher tendency to remain in the protonated/cationic form with respect to the linear isomer. As a consequence, the minimum cmc value, observed when the protonated and the deprotonated/zwitterionic forms of the surfactant coexist in the micelles, is shifted to higher pH values. The volume of these C10DAO-branched “mixed micelles” is more than one order of magnitude higher than that of completely protonated or deprotonated aggregates. This is a singularity of the branched surfactant, not observed for the linear isomer. Overall, the results highlight that the branched molecular architecture of the surfactant tail, favoring the formation of low-curvature aggregates, enhances H-bonding between the protonated and deprotonated headgroups, which synergistically stabilizes the flatter surface of bulkier aggregates. Taking into account the good biodegradability of surfactants with a limited number of short side chains, purposely designed branched surfactants appear as a suitable option to accurately tune supramolecular aggregation in pH-responsive formulations.

Gold nanoparticles (AuNPs) are considered suitable systems for drug delivery and diagnostics with several applications in biomedicine. Size, shape and surface functionalization of these nanoparticles are important parameters influencing their behavior in a biological environment. This study describes the preparation and the characterization of lysophosphocholine coated AuNPs by means of Small Angle Neutron Scattering (SANS), Electron Paramagnetic Resonance (EPR) and Fluorescence Spectroscopy. In particular the structure of the functionalized AuNP suspension, as well as the physical properties, of the nanoparticle organic coating are discussed. The experimental results indicated that functionalized lysophosphocholine-AuNPs form aggregates, which are composed by nanoparticles with core-shell structure. Nevertheless, the nanoparticle suspension resulted to be stable, without significant structural rearrangements even when the temperature was increased to 50 °C. At the same time, experimental evidences also suggested that the 18LPC layer around AuNPs presented a reduced chain packing compared to pure 18LPC aggregates.

Formulations for industrial applications are often mixtures of different surfactants and additives, including salts; thus, it is crucial to understand the reciprocal effects of the different components on the properties of the system such as cmc and morphology of the aggregates in solution. In this respect, we have studied the effects of anions occupying different positions within the so-called Hofmeister series, namely Cl−, Br−, SCN−, on the aggregation properties of mixtures containing a cationic and a non-ionic surfactant largely employed in formulation chemistry: dodecyltrimethyl ammonium bromide (DTAB) and pentaethylenglycol mono octyl ether (C8E5). We determined the cmc of the mixtures with different relative content of the two surfactants, as well as of pure DTAB and C8E5 systems, in water and in the presence of salts. Dynamic light scattering measurements were used to evaluate the hydrodynamic size of the aggregates, while small-angle neutron scattering to determine their morphology, as a function of increasing DTAB content, at constant salt concentration. We found no significant effect of salts on the cmc or aggregate dimensions of C8E5. On the other hand, increasing DTAB content, the salt effect is clearly detectable and ion-dependent: salt addition decreases the cmc in the order SCN− ≫ Br− > Cl−; moreover, halides seem to affect structural properties of mixed C8E5-DTAB systems very slightly whereas SCN− leads to a morphological change from a spherical to a cylindrical aggregate shape. Thus, this study well demonstrates how formulation properties can be fine-tuned by salt addition through a proper choice of ions species.

The safe application of nanotechnology devices in biomedicine requires fundamental understanding on how they interact with and affect the different components of biological systems. In this respect, the cellular membrane, the cell envelope, certainly represents an important target or barrier for nanosystems. Here we report on the interaction between functionalized SuperParamagnetic Iron Oxide Nanoparticles (SPIONs), promising contrast agents for Magnetic Resonance Imaging (MRI), and lipid bilayers that mimic the plasma membrane. Neutron Reflectometry, supported by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) experiments, was used to characterize this interaction by varying both SPION coating and lipid bilayer composition. In particular, the interaction of two different SPIONs, functionalized with a cationic surfactant and a zwitterionic phospholipid, and lipid bilayers, containing different amount of cholesterol, were compared. The obtained results were further validated by Dynamic Light Scattering (DLS) measurements and Cryogenic Transmission Electron Microscopy (Cryo-TEM) images. None of the investigated functionalized SPIONs were found to disrupt the lipid membrane. However, in all case we observed the attachment of the functionalized SPIONs onto the surface of the bilayers, which was affected by the bilayer rigidity, i.e. the cholesterol concentration.

Ruthenium complexes are attracting increasing attention as second-generation metal-based anticancer agents, with NAMI-A and KP1019 as the major representatives of this class having undergone clinical trials. Our recent interest has been focused on the synthesis and characterization of new amphiphilic derivatives of nucleosides (nucleolipids). These compounds have been selected as core scaffolds linked to RuIII complexes and capable of self-assembly into stable nanostructures in aq. solutions so to transport the metal ions efficiently into the cell. Through the use of ribo- and deoxyribonucleosides as starting building blocks, a mini-library of nucleolipidic RuIII complexes decorated with diverse hydrophilic and lipophilic chains and incorporating the NAMI-A analogue AziRu has been prepared. When co-aggregated with biocompatible lipids, these RuIII-containing nucleolipids proved to be stable for months under physiological conditions. Detailed microstructural characterization, carried out by a combined approach including different physico-chemical techniques, allowed their stability, size and shape to be determined. Tested on a panel of human and non-human cells, all of the studied RuIII complexes showed potent in vitro anticancer activity, significantly higher than that of NAMI-A-like analogues, and minimal toxicity. Here we summarize the design and synthetic procedures developed to prepare these new Ru-containing candidate drugs, discussing the beneficial effects achievable through exploiting nucleolipid appendages in the delivery of metal-based drugs.

The RuIII-based prodrug AziRu efficiently binds to proteins, but the mechanism of its release is still disputed. Herein, in order to test the hypothesis of a reduction-mediated Ru release from proteins, a Raman-assisted crystallographic study on AziRu binding to a model protein (hen egg white lysozyme), in two different oxidation states, RuII and RuIII, was carried out. Our results indicate Ru reduction, but the Ru release upon reduction is dependent on the reducing agent. To better understand this process, a pH-dependent, spectroelectrochemical surface-enhanced Raman scattering (SERS) study was performed also on AziRu-functionalized Au electrodes as a surrogate and simplest model system of RuII- and RuIII-based drugs. This SERS study provided a p Ka of 6.0 ± 0.4 for aquated AziRu in the RuIII state, which falls in the watershed range of pH values separating most cancer environments from their physiological counterparts. These experiments also indicate a dramatic shift of the redox potential E0 by >600 mV of aquated AziRu toward more positive potentials upon acidification, suggesting a selective AziRu reduction in cancer lumen but not in healthy ones. It is expected that the nature of the ligands (e.g., pyridine vs imidazole, present in well-known RuIII complex NAMI-A) will modulate the p Ka and E0, without affecting the underlying reaction mechanism.

Amine-oxide surfactants have emerged as highly stable, nontoxic, and cost-effective constituents of detergent formulations, specifically as wetting agents and foam boosters. With the aim of enhancing their functional behavior, a new member of this family, N,N-dimethyl-2-propylheptan-1-amine oxide, bearing a branched alkyl tail (C 10 DAO-branched) was synthesized and purified using a simple and easily scalable strategy starting from 2-propylheptan-1-ol. 2D-nuclear magnetic resonance (NMR) and mass spectrometry confirm the obtainment of the desired product in high yield and purity. The protonation behavior of the branched surfactant is not affected by alkyl tail branching, as shown by potentiometric titrations. In contrast, surface activity and aggregation behavior of C 10 DAO-branched is dramatically different from that of the linear analog N,N-dimethyldecyl-1-amine oxide (C 10 DAO-linear), in that it occupies a higher area at the solution interface and aggregates at much higher concentration, forming larger aggregates, as detected using tensiometry and dynamic light scattering (DLS), respectively. Aggregation behavior of C 10 DAO-branched is less sensitive to pH variations. Foaming tests show that C 10 DAO-branched is a more effective foam booster than its linear analog, in both acidic and basic solutions. The experimental results indicate that the branched surfactant can be used in applications that require enhanced and pH-independent surface activity and foamability.

NU172&mdash, a 26-mer oligonucleotide able to bind exosite I of human thrombin and inhibit its activity&mdash, was the first aptamer to reach Phase II clinical studies as an anticoagulant in heart disease treatments. With the aim of favoring its functional duplex-quadruplex conformation and thus improving its enzymatic stability, as well as its thrombin inhibitory activity, herein a focused set of cyclic NU172 analogues&mdash, obtained by connecting its 5&prime, and 3&prime, extremities with flexible linkers&mdash, was synthesized. Two different chemical approaches were exploited in the cyclization procedure, one based on the oxime ligation method and the other on Cu(I)-assisted azide-alkyne cycloaddition (CuAAC), affording NU172 analogues including circularizing linkers with different length and chemical nature. The resulting cyclic NU172 derivatives were characterized using several biophysical techniques (ultraviolet (UV) and circular dichroism (CD) spectroscopies, gel electrophoresis) and then investigated for their serum resistance and anticoagulant activity in vitro. All the cyclic NU172 analogues showed higher thermal stability and nuclease resistance compared to unmodified NU172. These favorable properties were, however, associated with reduced&mdash, even though still significant&mdash, anticoagulant activity, suggesting that the conformational constraints introduced upon cyclization were somehow detrimental for protein recognition. These results provide useful information for the design of improved analogues of NU172 and related duplex-quadruplex structures.

SuperParamagnetic Iron Oxide Nanoparticles (SPIONs) represent a suitable system for several applications especially in nanomedicine. Great efforts have been made to design stable and biocompatible functionalized SPIONs suitable for diagnostics and drug delivery. In particular, zwitterionic-surfactant functionalized SPIONs, obtained through a coating strategy based on hydrophobic interaction, are promising systems for biomedical applications. The size of functionalized SPIONs has emerged as a crucial parameter determining their fate in living organisms. However, not all the proposed functionalization strategies lead to monodispersed systems and SPION clustering often occurs. In this study, we report a systematic investigation on different surfactant-functionalized SPIONs in order to explore the possibility of tuning the particle size by choosing an appropriate amphiphilic molecule. By combining Small-Angle Neutron Scattering (SANS) and Dynamic Light Scattering (DLS) analysis, we have provided a detailed description of the functionalized SPION structure. Furthermore, we have also related the surfactant aggregation properties, i.e. the Critical Micelle Concentration (CMC), to their efficiency in coating the SPION surface. A lack in the formation of a compact shell leads to a clusters formation. On this basis, the present study contributes to furnishing decisive information to define synthetic strategies able to tune functionalized-SPION design.

The mutual diffusion coefficients, Dij, of the ternary system sodium cholate (NaC, component 1) + sodium deoxycholate (NadC, component 2) + water have been determined at five average compositions (c1, c2) keeping c1 constant and varying c2. The possibility to obtain expressions for the four diffusion coefficients in term of the micellization parameters and of the diffusivity of the species in solution is discussed. Data have been qualitatively interpreted. Results for the main term diffusion coefficients have been used in the much more difficult analysis of the cross term diffusion coefficients.

We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D(11), decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells.

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

The structural and relaxometric characterization of a novel class of supramolecular aggregates, as potential tumor-specific contrast agents in magnetic resonance imaging (MRI), is reported. The aggregates are based on a new monomer with an upsilon shape (MonY) that contains, in the same molecule, all three fundamental tasks that are required: 1) a hydrophobic moiety that allows the formation of supramolecular aggregates; 2) the bioactive CCK8 peptide for target recognition; and 3) a chelating agent able to give stable gadolinium complexes. As indicated by dynamic light scattering and small-angle neutron scattering (SANS) measurements, MonY and its gadolinium complex MonY(Gd) aggregate in aqueous solution to give ellipsoidal micelles with a ratio between the micellar axes of approximately 1.7 and an aggregation number N(agg) of approximately 30. There are no differences in the aggregation behavior of MonY and MonY(Gd), which indicates that the presence of metal ions, and therefore the reduction of the net charge, does not influence the aggregation behavior. When MonY or MonY(Gd) are blended with dioleoyl phosphatidylcholine (DOPC), the aggregation behavior is dictated by the tendency of DOPC to give liposomes. Only when the amount of MonY or MonY(Gd) is higher than 20 % is the coexistence of liposomes and micelles observed. The thickness d of the bilayer is estimated by SANS to be approximately 35-40 A, whereas cryogenic transmission electron microscopy images show that the diameter of the liposomes ranges from approximately 50 to 150 nm. Self-assembling micelles of MonY(Gd) present high relaxivity values (r(1p)=15.03 mM(-1) s(-1)) for each gadolinium complex in the aggregate. Liposomes containing MonY(Gd) inserted in the DOPC bilayer at a molar ratio of 20:80 present slightly lower relaxivity values (r(1p)=12.7 mM(-1) s(-1)), independently of their internal or external position in the liposome.

The diffusion coefficients, D ij , for the ternary system water + chloroform + acetic acid are reported at five compositions. This system presents a large solubility gap due to the almost complete insolubility between water and chloroform. The analyzed compositions have a fixed mole ratio of water and chloroform and a decreasing amount of acetic acid when approaching the binodal curve. The difficulty of interpreting the D ij is stressed, and the use of different choices of which component is the solvent and a different reference frame for the diffusive transport is suggested to extract all the possible information from the diffusion coefficients.

We use accurate thermodynamic derivatives extracted from high-precision measurements of the four volume-fixed diffusion coefficients in ternary solutions of lysozyme chloride in aqueous NaCl, NH4Cl, and KCl at pH 4.5 and 25 degrees C to (a) assess the relative contributions of the common-ion and nonideality effects to the protein chemical potential as a function of salt concentration, (b) compare the behavior of the protein chemical potential for the three salts, which we found to be consistent with the Hofmeister series, and (c) discuss our thermodynamic data in relation to the dependence of the protein solubility on salt concentration. The four diffusion coefficients are reported at 0.6 mM lysozyme chloride and 0.25, 0.5, 0.9, 1.2, and 1.5 M KCl and extend into the protein-supersaturated region. The chemical potential cross-derivatives are extracted from diffusion data using the Onsager reciprocal relation and the equality of molal cross-derivatives of solute chemical potentials. They are compared to those calculated previously from diffusion data for lysozyme in aqueous NaCl and NH4Cl. We estimate the effective charge on the diffusing lysozyme cation at the experimental concentrations. Our diffusion measurements on the three salts allowed us to analyze and interpret the four diffusion coefficients for charged proteins in the presence of 1:1 electrolytes. Our results may provide guidance to the understanding of protein crystallization.

Small angle neutron scattering (SANS) has been used to study the interaction of sodium decyl sulfate (C100S) and sodium decanesulfonate (C10S) with poly(vinylpyrrolidone) (PVP). The measurements were performed on aqueous solutions of C100S and C10S in the presence and absence of PVP. In all ternary systems the polymer concentration was kept constant at I wt%, and the surfactant molal concentration ranged from 0.002 to 0.150 mol kg(-1). The analysis of the collected SANS profiles confirms the absence of any appreciable interaction between PVP and C10S in contrast with what observed for the PVP-C100S-D2O system. In this latter system, in fact, a clear interaction peak in the scattering pattern appears well below the cmc of the surfactant, which suggests a complex formation between PVP and C100S. The preferential interaction of poly(vinylpyrrolidone) toward sodium decyl sulfate with respect to sodium decanesulfonate reflects the difference in the chemical structure of the two surfactants that produces meaningful differences in the values of their cmc and aggregation number, as shown by the results here presented.

Measurements of osmotic coefficients, mutual diffusion coefficients, and conductivity were performed on the binary system sodium n-octyl sulfonate (C8SO3Na)-water at 25degreesC both below and above the micellar composition range. The osmotic coefficient data were obtained through vapor-pressure osmometry, while the Taylor dispersion method was used to measure diffusion coefficients. The mass equilibrium model was applied to this self-aggregating system, taking into account the deviation of the activity coefficients from the Debye-Huckel limiting law by using the Guggenheim corrective terms for mixed electrolyte solutions. The expressions derived from the model fit the experimental osmotic and diffusion coefficient data well, when the same values of aggregation number, fraction of condensed counterions, and equilibrium constant are used. Osmotic coefficients were also used to determine the thermodynamic factor required to compute the solute mobility from diffusion data. Conductivity data were used to test two theoretical models, namely, the Onsager-Fuoss and the Mean Spherical Approximation theories. Both models have been found to yield unsatisfactory fits to our experimental data and some arbitrary terms had to be applied to the theoretical expressions to obtain good agreement between experiment and theory.

The transport properties of NaCl in poly(ethylene glycol)-water (PEG-water) mixtures are presented, with special regard to the dielectric and hydrodynamic effects. We report experimental data of mutual diffusion, viscosity, and conductivity for the aqueous ternary system containing PEG with an average molecular weight of 2000 a.m.u. (PEG2000, component 1) and sodium chloride (NaCl, component 2). Both PEG2000 and NaCl are used extensively as protein-crystallizing agents. The four diffusion coefficients ( D11, D12, D21, and D22) that are required to describe the diffusive properties of a ternary system correctly were determined by the precise Gouy interferometric method. We also report measurements of the dielectric constant for several aqueous binary systems containing PEG with three different molecular weights (200, 400, and 2000 a.m.u.), which significantly decreases the dielectric constant of aqueous solutions. The experimental values of the four diffusion coefficients are discussed in terms of obstruction, excluded volume, and dielectric effects. The dependence of the PEG main-term diffusion coefficient, D11, on the salt concentration is quantitatively described by the corresponding change of viscosity. The cross-term diffusion coefficients, D12 and D21, are described in terms of excluded volume effects and PEG-salt nonpreferential interactions. The dependence of the salt main term diffusion coefficient, D22, on PEG concentration is essentially due to obstruction effects. Moreover, a remarkable agreement between D22 and the salt equivalent conductivity has been determined. This correlation suggests that, even though the dielectric constant significantly changes in the presence of PEG, the electrostatic ion-ion interactions (the summation of the extent of ion-pairing and electrophoretic contributions) are not significantly modified by the polymer. This analysis of the diffusive and conductivity properties of electrolytes in the presence of PEG have allowed us to clarify important aspects of the electrostatic properties of aqueous PEG-salt systems and supplies valuable information for salt properties in “mixed solvents”. A useful classification of mixed solvents is proposed, distinguishing between “viscous” and “dielectric” mixed solvents.

We investigate the precision of Rayleigh interferometry in evaluating the nine mutual diffusion coefficients Dij defining a four-component system by investigating the system lysozyme−tetra(ethylene glycol)−NaCl−H2O. We believe our results to be the most successful experimental determination of diffusion coefficients in quaternary systems. This choice of system is motivated by its relevance to protein crystal growth. The comparison of the Dij coefficients of the quaternary system and the Dij coefficients from the corresponding ternary and binary systems enables us to extract some information about the hydrodynamics and thermodynamics in solutions where protein crystals grow.

The ternary system water–pentaethyleneglycol monooctyl ether (C8E5)–octyltrimethyl ammonium bromide (C8TAB) has been studied at 25 °C. Accurate c.m.c. values have been determined through spectrofluorimetric measurements, by using DL-tryptophan as a molecular probe. The surfactant intradiffusion coefficients have been measured through the PGSE-NMR technique. Experimental data show the formation of mixed micelles. The compositions of the aqueous and micellar pseudo-phase have been computed over the whole micellar composition range; they indicate that C8E5 has a larger tendency to form aggregates than C8TAB. The aggregation number and the Gibbs energy of mixed micelle formation are calculated and interpreted in terms of interactions among the surfactants in the micellar aggregates. The experimental results have been compared with those predicted by the regular solution model finding reasonable agreement.

Nanostructures are gaining interest in drug release applications. Amphiphilic molecules can give, in water solution, a variety of nanostructures as well as thermodynamically stable mesophases three-dimensional inverse cubic structures. These mesophases are attractive candidates for biomedical applications containing extensive water channel networks and could act as very efficient delivery systems of drugs or contrast agents. In order to discover, optimize, and develop these systems, we have performed a deep physicochemical characterization by dynamic light scattering and small-angle neutron scattering of nanoparticles of monoolein (MO) and Pluronic PF127, containing different amounts (1, 5, 10, and 20 %) of the synthetic amphiphilic gadolinium complex (C18)2DTPA(Gd). Nanoparticle size is found in the 70–400 nm range for all investigated systems; the morphology of the aggregates is driven by the main constituents MO/PF127 and is a mixture of multilayer vesicles and bicontinuous aggregates. Nanostructures are also able to encapsulate doxorubicin (drug-loading content between 70 and 90 % for the different systems) acting as a potential theranostic for simultaneous cancer therapy and MRI visualization.

The subject of this article is the combined interpretation of intradiffusion and mutual-diffusion data for polymer–solvent mixtures in terms of integrals over velocity self-correlation functions and velocity cross-correlation functions. The combination of mutual-diffusion, intradiffusion, and activity data allows the evaluation of velocity-correlation coefficients (VCCs) and distinct-diffusion coefficients in systems containing one monodisperse solute. This study is the first attempt to extend these approaches to polymers that are polydisperse solutes. Because of the polydispersity, this correlation analysis may become critical for polymers. Its application to polydisperse samples requires the reduction of intradiffusion and mutual-diffusion coefficients to the same average. After such a reduction, the VCCs and distinct-diffusion coefficients are evaluated for a homologous series of poly(ethylene glycol)s (PEGs). Attractive PEG–PEG interactions depend on the chain length and concentration of PEG. In this analysis, network formation in PEG–water systems appears to be a smooth process. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 43–51, 2002

Recent predictive equations for evaluating the value of diffusion coefficients, developed for two hard sphere-solvent systems, have been extended to n-hard-sphere-solvent systems. This model has been used to predict the diffusion behavior of nonionic polymer-solvent mixtures as a first-order function of volume fraction from the knowledge of the distribution function. Hence, the entire diffusion matrix for polydisperse systems, which include both main- and cross-term diffusion coefficients, has been built up for the first time. The main-terms diffusion coefficients D ii. are mostly affected by the variation in viscosity. The magnitude of the cross-term diffusion coefficients D ij is strictly related to the abundance and diffusivity of solute i and to the molecular volume corresponding to solute j. The predicted diffusion coefficients have been used to calculate the apparent, average diffusion coefficients, which are compared with the experimental values measured by the Gouy interferometry method in the case of the poly(ethylene glycol) homologous series. The agreement between the calculated and experimental Gouy parameters is good. The cross-term diffusion coefficients are found to be significant in the calculation of the apparent diffusion coefficient for a polydisperse solute. Some comments on the study of ternary systems containing a polydisperse solute are done.

The diffusion of a model system describing a polydisperse sample has been investigated experimentally. Precise mutual diffusion coefficients were measured, with a Gouy interferometer, for the ternary system hexa(ethylene glycol)(6)–di(ethylene glycol)(2)–water at four values of the concentration ratio β6 = C6/(C6 + C2), and at a constant total concentration C6 + C2 = 0.3000 mol dm−3. The main-term diffusion coefficient, D22, shows a substantial decrease with β6, while D66 varies modestly. Both cross-term diffusion coefficients are positive, the largest, D26, reaches a value that is about 15% of the corresponding main-term. The experimental diffusion coefficients of this system have been interpreted through an extension of the common hard sphere hydrodynamic theory. Good agreement between the experimental diffusion coefficients and those predicted by a set of equations recently proposed by the authors for systems of non-ionic and slightly interacting solutes has been found. These equations, accounting only for the “ excluded volume” effect, succeed in the evaluation of the value of the diffusion coefficients in ternary systems with solute size mismatch. A comparative analysis, with analogous systems investigated previously confirms the efficiency of our predictive procedure.

Mutual diffusion in aqueous solution of polydisperse poly(ethyleneglycol) samples (PEG) was analysed through Gouy interferometry with special attention to the molecular weight and concentration effects. For PEG samples with molecular weight higher than 1000 g mol-1 the diffusive trend on concentration is justified in thermodynamic terms. The diffusion properties of polydisperse samples and pure oligomers are compared. We emphasise that the refractive index gradient at the diffusion boundary in polydisperse PEG significantly deviates from a Gaussian distribution expected where the PEG monodisperse. The combination of mutual diffusion with literature intradiffusion and activity data allows testing of the Darken equation for each PEG sample. Because of the polydispersity the analysis of the velocity cross correlation coefficients (VCCs) or the distinct diffusion coefficients becomes critical.

Mutual diffusion coefficients were measured with the Gouy technique for two ternary systems: (A) α-cyclodextrin - polyoxyethylene 5 hexylether -water, a non-ionic system, and (B) α-cyclodextrin - sodium 1 hexylsulfonate -water, a ionic system. For both systems the four measured diffusion coefficients allow us to estimate the diffusion coefficients of the actual species present in solution, assuming for the inclusion constant the values obtained from calorimetric data.

Mutual diffusion coefficients have been measured, at 25 °C, for binary systems of some ethylene glycol oligomers in aqueous solution over the whole mole fraction range. The results have been combined with activity and intradiffusion data to calculate the velocity cross-correlation coefficients (VCCs). An attempt has been made to explain the results in terms of molecular interactions.

Mutual diffusion coefficients have been measured for several average compositions of the system sodium cholate-sodium deoxycholate-water at 25 °C. The experiments have been grouped in different sets having constant concentration of one component and variable concentration of the other one. Following this approach, it has been found that the trends of the main- and cross-term diffusion coefficients can be interpreted on the basis of the diffusion and equilibrium results of similar experiments performed on the two binary systems sodium cholate-water and sodium deoxycholate-water. Implications of the presented results in the transport of lipids operated by bile salt aggregates are mentioned. The method proposed in this work, able to connect the diffusivities of an n-component system to those of the related n-1 subsystems, can be extended to obtain qualitative prediction on the diffusion coefficient trends for mixtures of other surfactants, of both industrial and biological interest.

Diffusion was systematically studied in the ternary system NaCl (0.5M)−KCl (0.5M)−H2O at 25°C. There were four purposes. First, current methods to extractD ij from Gouy and Rayleigh interferometry data depend on treating theD ij as effectively constant. If concentration differences ΔC i across the boundary are large, this may not be true. To explore this issue, four sets of experiments were performed. Each set had four experiments with approximately the same total number of fringesJ. Each set also had the same corresponding ΔC 1/ΔC 2 ratios as the other three, but the ΔC i were adjusted such that the four sets hadJ≈30, 60, 90, and 120, respectively. Noclear dependence of theD ij on ΔC i was found within their realistic errors. Second, the Gosting diffusiometer can yield both Rayleigh and Gouy fringe patterns during the same experiment. Therefore, theD ij from both methods were compared, and agree well. Third, a new method for analyzing Gouy fringe positions (Miller; program TNY) can be compared to the classical one (Fujita-Gosting; program RFG). TheD ij from both analyses agree well. Fourth, we compared results from the Gosting diffusiometer with those at the same composition from other diffusiometers: one data set by O[Donnell and Gosting from an older Gouy apparatus, and three Rayleigh sets at differentJ values from our older Model H diffusiometer. Results from older diffusiometers were more scattered, but correspondingD ij agree within realistic errors. As reported previously, realistic errors are approximately four times the statistical errors obtained by least squares. Recommended Rayleigh and GouyD ij are presented for this composition.

Aqueous solutions of three surfactants: (1) Sodium 1- hexylsulfonate, (2) Polyoxyethylene - 5 - hexylether, and (3) 1- Hexaminium N,N,N triethyl bromide have been characterized through viscosity, density and calorimetry runs at 25°C. The interaction of these surfactants with α-Cyclodextrin was also studied calorimetrically. The enthalpy of inclusion and the inclusion constant were measured.

Viral fusion glycoproteins present a membrane-proximal external region (MPER) which is usually rich in aromatic residues and exhibits a marked tendency to stably reside at the membrane interfaces, leading, through unknown mechanisms, to a destabilization of the bilayer structure. This step has been proposed to be fundamental for the fusion process between target membrane and viral envelope. In the present work, we investigate the interaction between an octapeptide (C8) deriving from the MPER domain of gp36 of feline immunodeficiency virus and POPC bilayers by combining experimental results obtained by neutron reflectivity, electron spin resonance, circular dichroism, and fluorescence spectroscopy with molecular dynamics simulations. Our data indicate that C8 binds to the lipid bilayer adsorbing onto the membrane surface without deep penetration. As a consequence of this interaction, the bilayer thickness decreases. The association of the peptide with the lipid membrane is driven by hydrogen bonds as well as hydrophobic interactions that the Trp side chains form with the lipid headgroups. Upon peptide-bilayer interaction, C8 forms transient secondary structures ranging from 3(10) helices to turn conformations, while acyl chains of the peptide-exposed POPC molecules assume a more ordered packing. At the same time, lipid headgroups' hydration increases. The asymmetric lipid bilayer perturbation is proposed to play a fundamental role in favoring the membrane fusion process.

Thirteen isothermal ternary diffusion experiments have been performed for a single composition of the system raffinose-KCl-H[sub 2]O at 25[degree]C. Both Rayleigh and Gouy optical systems were used in all experiments for direct comparison of results from these two configurations. Various data analysis procedures are compared. Good agreement is found between the recommended results from the two optical methods, although diffusion coefficients D[sub if] obtained by the Rayleigh method are generally slightly lower than those obtained by the Gouy method. The sensitivity of the D[sub ij] to both experimental error and choices of subsets of the 13 experiments is discussed. Standard errors of coefficients are an inadequate measure of accuracy. This study has led to higher standards for acceptability of individual experiments. This system has the same mean solute concentrations as the four experiments reported by Dunlop, for which a test of the Onsager reciprocal relations (ORR) failed. 51 refs., 4 figs., 10 tabs.

Diffusion, density, and viscosity data are presented on the binary system monobuthylurea- water at 25°C as a function of concentration and on the ternary system (L)-phenylalanine - monobuthylurea - water at 25 °C at three main concentrations. The results are briefly discussed.

Sodium cholate (NaC) and sodium deoxycholate (NaDC) in binary and ternary aqueous mixtures were investigated by means of surface tension, electron paramagnetic resonance spectroscopy (EPR), small angle neutron scattering (SANS) and mutual diffusion coefficient analysis. Concerning the NaC-H(2)O and NaDC-H(2)O binary mixtures, the surface tension, EPR and diffusion measurements confirmed the formation of micelles above a well detectable critical concentration. The SANS data indicated for both systems, the formation of ellipsoidal micelles whose major axis increased with concentration and minor axis remained constant. The data were interpreted under the assumption that aggregate growth occurred via hydrogen bonding of small aggregates along one preferential direction. For the NaC-NaDC-H(2)O ternary mixtures, the surface tension and EPR results were in good agreement with the Clint model prediction for the ideal mixed micellization. Based on this model, the SANS data enabled a complete description of the mixed aggregates in terms of dimensions, composition and concentration. In turn, this strategy allowed for a satisfactory interpretation of the main and cross-term diffusion coefficient trends, which are quite complex.

The mutual diffusion coefficients for two aqueous ternary systems, both containing a protein, human serum albumin (HSA, component 1), were measured. The first system contained a neutral polymer, polyethylene glycol (PEG, component 2), and the second an "organic solvent", 2-methyl-2,4-pentanediol (MPD, component 3). Both PEG and MPD are used as co-precipitants in HSA crystallization protocols. Measurements were performed at constant protein concentration, with increasing precipitant content. The results obtained for the two systems were discussed and compared. In both cases, the two main diffusion coefficients, relative to the motion of the protein and of the precipitant under their own concentration gradient, can be interpreted in terms of non-specific volume interactions between the solutes. Particularly, it was showed that any possible direct HSA-MPD interaction may not have a significant effect on the values of these two diffusion coefficients. Differences arise between the cross precipitant's diffusion coefficients, relative to the motion of the precipitant under the protein concentration gradient, D(i1) with i = 2, 3. In the case of PEG, the D(21) trend vs. c(2) can be simply interpreted in terms of an "exclude volume" effect. In contrast, in the case of MPD, the D(31)vs. c(3) trend seems to indicate a more complex mechanism of transport. Because the cross precipitant's diffusion coefficient plays an important role in the crystallization process, the implication of the observed difference on the crystallization procedure was also discussed.

The nine mutual diffusion coefficients D ij (i, j=1-3) of the quaternary system α-cyclodextrin (0.02 M)-L-phenylalanine (0.06 M)-monobutylurea (0.06 M)-H 2 O have been determined at 25 o C. Eight reliable experiments were performed at these mean concentrations by the free-diffusion method with a Gouy optical interferometer. A minimum of three experiments is required to obtain the nine diffusion coefficients

The four diffusion coefficients describing the isothermal interdiffusion transport in the three-component system BaCl2(1)-KCl(2)-H2O(3) at one concentration were measured. The conditions for the growth of convection inside the diffusion boundary (double diffusive convection) were computed according to the theory proposed by McDougall and compared with the experimental results. Good agreement was found between theory and experimental results. In this system, convection at the borders of the boundary grows even if the heavier components BaCl2 and KCl are more concentrated at the bottom of the diffusion boundary.

A rapid new procedure is described for getting the total number of fringes J from Gouy fringe pattern data. This PQ method is exact and the results excellent (within 0.01–0.03 fringe) for ideal systems (Ωj=0 for all j, Q0=0). Such systems include most binaries; for these, the diffusion coefficient is either constant or a polynomial function of concentration with small concentration differences. For multicomponent systems and some binaries, Q0 can be significantly different from 0. In these cases, the PQ method unambiguously gives the integer number of fringes. If in addition Q0/Q1 is larger than 2.0, then J obtained from a second extrapolation procedure is also good.

Large unilamellar liposomes formed by the Re LPS (from here below named LOS) from Salmonella enterica serotype minnesota strain 595 (Re mutant) have been prepared by the extrusion techniques. The physico-chemical investigation of these systems has been performed by a combined experimental strategy, which has allowed a characterization at different observation scales, from the morphological to the micro-structural level. Particularly, dynamic light scattering (DLS) measurements have revealed the formation of liposomes with a narrow dimension distribution; small-angle neutron scattering (SANS) measurements have led to an estimation of the thickness of the LOS bilayer, which is consistent with an extended conformation of the acyl chains; electron paramagnetic resonance (EPR) measurements have allowed to investigate the bilayer fluidity, as determined by LOS acyl chain conformation and packing; Pulsed-field-gradient stimulated echo nuclear magnetic resonance (PGSTE-NMR) measurements have shown that water permeability through the LOS bilayer is low. The effect of temperature has been considered. Liposome dimension does not change; however, centered at 30-35 degrees C, a progressive transition of the acyl chain self-organization from a gel to a liquid crystalline phase is detected. Above this temperature, the water permeability through the bilayer increases. The effect of introducing the zwitterionic phospholipid dilauroyl phosphatidylcholine (DLPC) in the liposome formulation have been also analysed. A comparative analysis of the results points out a clear relation between the microstructure of LOS molecules in the bilayer and liposome functional properties.

Two novel amphiphilic unimers containing an aliphatic hydrophobic chain (PDA) with two C≡C triple bonds and hydrophilic heads presenting the chelating agent DTPAGlu and the CCK8 bioactive peptide, respectively, have been prepared by solid phase synthesis. Aggregates obtained by mixing together PDA-DTPAGlu, or its Gd(III) complex, and PDA-L2-CCK8 in 70/30 molar ratio before and after a polymerization process carried out by UV irradiation have been structurally characterized by means of small angle neutron scattering. The relaxivity properties of aggregates containing Gadolinium complexes have also been investigated. Elongated mixed micelles have been observed, in which the relaxivity value r 1p for each Gadolinium complex, measured at 20 MHz and 298 K, is around 12 mM–1 s–1.

Diffusion coefficients, densities, and viscosities were measured on the systems (D,L)Norleucine-water and (L)Phenylalanine-water, at 25°C as a function of the amino-acid concentration. For the system (L)Phenylalanine-water enthalpies of dilution were also measured. The experimental results are discussed and compared with some literature data available for the amino-acid series.

Diffusion coefficients in the ternary system {alpha}-cyclodextrin (at one concentration)-L-phenylalanine (at four concentrations)-water have been measured by using the Gouy interferometric technique. The effect of the inclusion equilibrium on the cross-term diffusion coefficients was observed. The measured diffusion coefficients in the ternary systems were used to calculate values of the binding constants. These values are in good agreement with the value obtained from calorimetric studies.

Diffusion, density, and viscosity data are collected for the systems α-cyclodextrin and β-cyclodextrin in water. Frictional coefficients were computed with the help of literature activity data and a qualitative discussion of their concentration dependence was attempted.

The structure of chemically-crosslinked chitosan and chitosan-poly(vinylpyrrolidone) (PVP) hydrogels is investigated by means of the combined use of small-angle neutron scattering (SANS), electron paramagnetic resonance spectroscopy (EPR), intradiffusion, and swelling degree measurements. These hydrogels may be described in terms of an inhomogeneous structure composed by polymer-rich and polymer-poor regions. The polymer-rich regions, whose correlation distance zeta is ranged between approximately 600 and approximately 850 A, are, in turn, characterized by the presence of a network formed by the chemical crosslinks, with a mean correlation distance xi approximately 90 A. The structures of chitosan and chitosan-PVP hydrogels have also been analyzed in the presence of sodium decylsulfate micelles that could provide a multidomain system useful, in principle, for drug delivery applications. Both SANS and EPR measurements show that sodium decylsulfate micelles do not significantly interact with both the gels. Finally, intradiffusion and swelling degree measurements show an improved hydrophilicity of chitosan-PVP gels, even further magnified by the presence of C10OS surfactant.