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1.
Sci Total Environ ; 916: 170215, 2024 Mar 15.
Article in English | MEDLINE | ID: mdl-38262536

ABSTRACT

Biosolids are considered a potentially major input of microplastics (MPs) to agricultural soils. Our study aims to identify the polymeric origin of MPs extracted from biosolid samples by comparing their Attenuated Total Reflection (ATR) - Fourier-transform infrared (FTIR) spectra with the corresponding near-infrared (NIR) spectra. The reflectance spectra were preprocessed by Savitzky-Golay (SG), first derivative (FD) and compared with analogous spectra acquired on a set of fifty-two selected commercial plastic (SCP) materials collected from readily available products. According to the results portrayed in radar chart and built from both ATR-FTIR and NIR spectral datasets, the MPs showed high correlations with polymers such as polyethylene (LDPE, HDPE), polyethylene terephthalate (PET), polystyrene (PS), polypropylene (PP) and polyamide (PA), determined in SCP samples. Each unknown MP sample had on average three or more links to several types of SCP, according to the correlation coefficients for each polymer ranging from 0.7 up to 1. The comparison analysis classified the majority of MPs as composed mainly by LDPE/HDPE, according to the top correlation coefficients (r > 0.90). PP and PET were better identified with NIR than ATR-FTIR. In contrast to ATR-FTIR analysis, NIR was unable to identify PS. Based on these results, the primary sources of MPs in the biosolids could be identified as discarded consumer packaging (containers, bags, bottles) and fibers from laundry, disposable glove, and cleaning cloth. SYNOPSIS: Microplastics (MPs) are considered contaminants of emerging concern. This study compares two simple and fast spectroscopy techniques to identify microplastics in the biosolid matrix.


Subject(s)
Microplastics , Water Pollutants, Chemical , Plastics/analysis , Biosolids , Polyethylene/analysis , Spectroscopy, Near-Infrared , Spectroscopy, Fourier Transform Infrared/methods , Polymers , Polystyrenes/analysis , Polypropylenes/analysis , Water Pollutants, Chemical/analysis , Environmental Monitoring/methods
2.
Molecules ; 29(2)2024 Jan 06.
Article in English | MEDLINE | ID: mdl-38257213

ABSTRACT

Enhanced oil recovery (EOR) processes are technologies used in the oil and gas industry to maximize the extraction of residual oil from reservoirs after primary and secondary recovery methods have been carried out. The injection into the reservoir of surface-active substances capable of reducing the surface tension between oil and the rock surface should favor its extraction with significant economic repercussions. However, the most commonly used surfactants in EOR are derived from petroleum, and their use can have negative environmental impacts, such as toxicity and persistence in the environment. Biosurfactants on the other hand, are derived from renewable resources and are biodegradable, making them potentially more sustainable and environmentally friendly. The present review intends to offer an updated overview of the most significant results available in scientific literature on the potential application of biosurfactants in the context of EOR processes. Aspects such as production strategies, techniques for characterizing the mechanisms of action and the pros and cons of the application of biosurfactants as a principal method for EOR will be illustrated and discussed in detail. Optimized concepts such as the HLD in biosurfactant choice and design for EOR are also discussed. The scientific findings that are illustrated and reviewed in this paper show why general emphasis needs to be placed on the development and adoption of biosurfactants in EOR as a substantial contribution to a more sustainable and environmentally friendly oil and gas industry.


Subject(s)
Anthracenes , Petroleum , Industry , Surface Tension
3.
Chemphyschem ; 24(24): e202300217, 2023 Dec 14.
Article in English | MEDLINE | ID: mdl-37691003

ABSTRACT

In this investigation the dynamics of two types of bitumens with different penetration grade were tested by using dynamic shear rheometry (DSR) and Nuclear Magnetic Resonance (NMR) at unaged conditions, and upon both short- and long-term artificial aging. The gel-sol transition temperature T g e l → s o l * ${{T}_{gel\to sol}^{^{\ast}}}$ was found to increase with increasing the time of aging treatment. Arrhenius parameters of the viscosity were found, unexpectedly, to be correlated with those of simple liquids, suggesting that the two kinds of systems, although chemically and physically quite different, share the same basic process at the molecular level. The molecular dynamics has been then investigated by NMR Pulsed Field Gradient Stimulated-Echo (PFGSE) and relaxometry (Carr-Purcell-Meiboom-Gill, CPMG, spin-echo pulse sequence) to capture the effect of aging upon dynamics variables such as self-diffusion coefficients D and transverse relaxation times T2 . The translational diffusion at T> T g e l → s o l * ${{T}_{gel\to sol}^{^{\ast}}}$ of the light molecular components of both types of bitumens was characterized by broad distributions of D which were found independent of the experimental time scale up to 0.2 s. Similarly, T2 data could be described as a continuous unimodal distributions of relaxation times determined both at T< T g e l → s o l * ${{T}_{gel\to sol}^{^{\ast}}}$ and T> T g e l → s o l * ${{T}_{gel\to sol}^{^{\ast}}}$ .

4.
Int J Mol Sci ; 24(11)2023 Jun 04.
Article in English | MEDLINE | ID: mdl-37298687

ABSTRACT

Alzheimer's disease (AD), a neurodegenerative disorder, is the most common cause of dementia in the elderly population. Since its original description, there has been intense debate regarding the factors that trigger its pathology. It is becoming apparent that AD is more than a brain disease and harms the whole-body metabolism. We analyzed 630 polar and apolar metabolites in the blood of 20 patients with AD and 20 healthy individuals, to determine whether the composition of plasma metabolites could offer additional indicators to evaluate any alterations in the metabolic pathways related to the illness. Multivariate statistical analysis showed that there were at least 25 significantly dysregulated metabolites in patients with AD compared with the controls. Two membrane lipid components, glycerophospholipids and ceramide, were upregulated, whereas glutamic acid, other phospholipids, and sphingolipids were downregulated. The data were analyzed using metabolite set enrichment analysis and pathway analysis using the KEGG library. The results showed that at least five pathways involved in the metabolism of polar compounds were dysregulated in patients with AD. Conversely, the lipid pathways did not show significant alterations. These results support the possibility of using metabolome analysis to understand alterations in the metabolic pathways related to AD pathophysiology.


Subject(s)
Alzheimer Disease , Humans , Aged , Alzheimer Disease/metabolism , Metabolomics/methods , Metabolome/physiology , Mass Spectrometry , Metabolic Networks and Pathways
5.
Nanomaterials (Basel) ; 12(21)2022 Oct 24.
Article in English | MEDLINE | ID: mdl-36364510

ABSTRACT

Microemulsions are known as thermodynamically stable nanodispersions driven by spontaneous emulsification and are commonly prepared as transparent mixtures composed of oil, water, a surfactant, and a cosurfactant [...].

6.
Chemosphere ; 303(Pt 2): 135172, 2022 Sep.
Article in English | MEDLINE | ID: mdl-35649442

ABSTRACT

Goethite, hematite, ferrihydrite, and other iron oxides bind through various sorption reactions with humic substances (HS) in soils creating nano-, micro-, and macro-aggregates with a specific nature and stability. Long residence times of soil organic matter (SOM) have been attributed to iron-humic substance (Fe-HS) complexes due to physical protection and chemical stabilization at the organic-mineral interface. Humic acids (HA) and fulvic acids (FA) contain many acidic functional groups that interact with Fe oxides through different mechanisms. Due to the numerous interactions between mineral Fe and natural SOM, much research has led into a better identification and definition of HS. In this review, we first focus on the surface colloidal properties of Fe oxides and their reactivity toward HS. These minerals can be efficiently identified by usual techniques, such as XRD, FTIR spectroscopy, XAS, Mössbauer, diffuse reflectance spectroscopies (DRS), HRTEM, ATM, NanoSIMS. Second, we present the recent state of art regarding the adsorption/precipitation of HS onto iron mineral surfaces and their effects on binding metalloid and trace elements. Finally, we consider future research directions based on recent scientific literature, with particular focus on the ability of Fe nano-particles to increase Fe bioavailability, improve carbon sequestration, reduce greenhouse gas emissions, and decrease the impact of persistent organic and inorganic pollutants. The methodology in this field has rapidly developed over the last decade. However, new procedures to estimate the nature of Fe-HA bonds will be important contributions in clarifying the role of natural iron oxides in soil for carbon stabilization.


Subject(s)
Humic Substances , Minerals , Adsorption , Humic Substances/analysis , Iron/chemistry , Magnetic Iron Oxide Nanoparticles , Minerals/chemistry , Oxides , Soil/chemistry
7.
Materials (Basel) ; 15(3)2022 Jan 25.
Article in English | MEDLINE | ID: mdl-35160850

ABSTRACT

Bitumen, one of the by-products of petroleum industry processes, is the most common binder used in road pavements and in the construction industry in general. It is a complex organic mixture of a broad range of hydrocarbons classified into four chemical families, collectively known with the acronym SARA fractions, which include saturates, aromatics, resins and asphaltenes. Since the 1940s, researchers working on bitumen and the science behind its existence, nature and application have investigated the spatial organization and arrangement of several molecular species present in the binder. Therefore, several models have been proposed in the literature, and they are more or less corroborated by experimental studies, although most of them are model-dependent; for example, the structural investigations based on scattering techniques. One of the most popular models that has met with a wide consensus (both experimentally and of the modeling/computational type) is the one aiming at the colloidal description of bitumen's microstructure. Other types of models have appeared in the literature that propose alternative views to the colloidal scheme, equally valid and capable of providing results that comply with experimental and theoretical evidence. Spurred by the constant advancement of research in the field of bitumen science, this literature review is aimed at providing a thorough, continuous and adept state of knowledge on the modeling efforts herein elaborated, in order to more precisely describe the intricacy of the bituminous microstructure. In this body of work, experimental evidence, along with details of bitumen's microstructure (depicting the colloidal state of bitumen), is particularly emphasized. We will also try to shed light on the evolution of the experimental and theoretical results that have focused on the aspect of the association and aggregation properties of asphaltenes in various models and real systems.

8.
Adv Colloid Interface Sci ; 285: 102283, 2020 Nov.
Article in English | MEDLINE | ID: mdl-33099178

ABSTRACT

Asphalt concretes are biphasic systems, with a predominant phase (c.a. 93-96% w/w) made by the macro-meter sized inorganic aggregates hold together by small amounts of a viscoelastic binding bitumen (c.a. 5%). Even if the bitumen is in minor amount, it plays an important role dictating all the desired properties: rheological performances, resistance to aging etc. What happens if nanoparticles are used as additive in such materials? They usually confer enhanced resistance under mechanical stress and give sometimes interesting added-values properties so, despite the high costs of their production, nanoparticles are interesting materials which are being monitored for large scales applications. This work introduces the reader to the properties of nanoparticles in an easy to review their use in bitumen and asphalt preparation. Silica, ceramic, clay, other oxides and inorganic nanoparticles are presented and critically discussed in the framework of their use in bitumen and asphalt preparation for various scopes. Organic and functionalized nanoparticles are likewise discussed. Perspectives and cost analysis are also given for a more complete view of the problematic, hoping this could help researchers in their piloted design of material for road pavements with ever-increasing performances.

9.
Nanomaterials (Basel) ; 10(9)2020 Aug 24.
Article in English | MEDLINE | ID: mdl-32846957

ABSTRACT

Microemulsions are thermodynamically stable, transparent, isotropic single-phase mixtures of two immiscible liquids stabilized by surfactants (and possibly other compounds). The assortment of very different microstructures behind such a univocal macroscopic definition is presented together with the experimental approaches to their determination. This tutorial review includes a necessary overview of the microemulsion phase behavior including the effect of temperature and salinity and of the features of living polymerlike micelles and living networks. Once these key learning points have been acquired, the different theoretical models proposed to rationalize the microemulsion microstructures are reviewed. The focus is on the use of these models as a rationale for the formulation of microemulsions with suitable features. Finally, current achievements and challenges of the use of microemulsions are reviewed.

10.
Nanomaterials (Basel) ; 10(6)2020 Jun 19.
Article in English | MEDLINE | ID: mdl-32575602

ABSTRACT

The asphalt industry's incentive to reduce greenhouse gas emissions has increased since the 1990s due to growing concerns on environmental issues such as global warming and carbon footprint. This has stimulated the introduction of Warm Mix Asphalt (WMA) and its technologies which serve the purpose of reducing greenhouse gas emissions by reducing the mixing and compaction temperatures of asphalt mix. WMA gained popularity due to the environmental benefit it offers without compromising the properties, performance and quality of the asphalt mix. WMA is produced at significantly lower temperatures (slightly above 100 °C) and thus results in less energy consumption, fewer emissions, reduced ageing, lower mixing and compaction temperatures, cool weather paving and better workability of the mix. The latter of these benefits is attributed to the incorporation of additives into WMA. These additives can also confer even better performance of WMA in comparison to conventional Hot Mix Asphalt (HMA) methods. Even though there are recommended dosages of several WMA additives, there is no general standardized mixture design procedure and this makes it challenging to characterize the mechanism(s) of action of these additives in the warm mix. The effects of the addition of additives into WMA are known to a reasonable extent but not so much is known about the underlying interactions and phenomena which bring about the mechanism(s) by which these additives confer beneficial features into the warm mix. Additives in a certain way are being used to bridge the gap and minimize or even nullify the effect of the mixing temperature deficit involved in WMA processes while improving the general properties of the mix. This review presents WMA technologies such as wax, chemical additives and foaming processes and the mechanisms by which they function to confer desired characteristics and improve the durability of the mix. Hybrid techniques are also briefly mentioned in this paper in addition to a detailed description of the specific modes of action of popular WMA technologies such as Sasobit, Evotherm and Advera. This paper highlights the environmental and technical advantages of WMA over the conventional HMA methods and also comprehensively analyzes the mechanism(s) of action of additives in conferring desirable characteristics on WMA, which ultimately improves its durability.

11.
Molecules ; 24(11)2019 Jun 07.
Article in English | MEDLINE | ID: mdl-31181687

ABSTRACT

Silymarin, a mixture of flavonolignan and flavonoid polyphenolic compounds extractable from milk thistle (Silybum marianum) seeds, has anti-oxidant, anti-inflammatory, anti-cancer and anti-viral activities potentially useful in the treatment of several liver disorders, such as chronic liver diseases, cirrhosis and hepatocellular carcinoma. Equally promising are the effects of silymarin in protecting the brain from the inflammatory and oxidative stress effects by which metabolic syndrome contributes to neurodegenerative diseases. However, although clinical trials have proved that silymarin is safe at high doses (>1500 mg/day) in humans, it suffers limiting factors such as low solubility in water (<50 µg/mL), low bioavailability and poor intestinal absorption. To improve its bioavailability and provide a prolonged silymarin release at the site of absorption, the use of nanotechnological strategies appears to be a promising method to potentiate the therapeutic action and promote sustained release of the active herbal extract. The purpose of this study is to review the different nanostructured systems available in literature as delivery strategies to improve the absorption and bioavailability of silymarin.


Subject(s)
Metabolic Syndrome/drug therapy , Silybum marianum/chemistry , Silymarin/pharmacokinetics , Biological Availability , Clinical Trials as Topic , Delayed-Action Preparations , Humans , Intestinal Absorption , Seeds/chemistry , Silymarin/chemistry , Silymarin/therapeutic use
12.
J Biomed Nanotechnol ; 12(4): 770-80, 2016 Apr.
Article in English | MEDLINE | ID: mdl-27301203

ABSTRACT

Liposomes are nanocarriers able to solubilize and deliver a wide range of hydrophobic pharmaceuticals and to increase drug bioavailability. They show a natural tendency to hepatic accumulation, and thus represent an optimal drug delivery system for the treatment of liver diseases, including chronic virus hepatitis C. Silibinin, the main and more active component of the seed extract from Silybum Marianum, is a hydrophobic flavolignan emerging as an alternative medication for the treatment of hepatitis C virus infection, as it has been shown to inhibit hepatitis C virus entry and replication. In this study we compared cellular delivery and antiviral activity of silibinin encapsulated into phytoliposomes or not, used at the aim to overcome its poor water-solubility and bioavailability. First, it was confirmed the inhibitory activity manifested by lipid-free silibinin in preventing hepatitis C virus entry into the cells. Our data clearly demonstrated that phytoliposome-encapsulated silibinin was absorbed by the cells 2.4 fold more efficiently than the free molecule and showed a three hundreds fold more potent pharmacological activity. Moreover, we surprisingly observed that phytoliposomes themselves inhibited virus entry by reducing the infectivity of viral particles. Based on these observations, phytoliposomes used in this study might be proposed as a delivery system actively contributing to the antiviral efficacy of the encapsulated drug.


Subject(s)
Hepacivirus/drug effects , Hepacivirus/physiology , Hepatitis C/prevention & control , Liposomes/chemistry , Nanocapsules/chemistry , Silymarin/administration & dosage , Animals , Antioxidants/administration & dosage , Antiviral Agents/administration & dosage , Antiviral Agents/chemistry , Cell Survival/drug effects , Cell Survival/physiology , Diffusion , Hepatitis C/virology , Humans , Nanocapsules/ultrastructure , Plant Extracts/administration & dosage , Plant Extracts/chemistry , Silybin , Silymarin/chemistry
13.
Chemosphere ; 138: 821-8, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26295541

ABSTRACT

Atomic force microscopy in contact (AFM-C) mode was used to investigate the molecular dynamics of leonardite humic acid (HA) aggregate formed at different pH values. HA nanoparticles dispersed at pH values ranging from 2 to 12 were observed on a mica surface under dry conditions. The most clearly resolved and well-resulted AFM images of single particle were obtained at pH 5, where HA appeared as supramolecular particles with a conic shape and a hole in the centre. Those observations suggested that HA formed under these conditions exhibited a pseudo-amphiphilic nature, with secluded hydrophobic domains and polar subunits in direct contact with hydrophilic mica surface. Based on molecular simulation methods, a lignin-carbohydrate complex (LCC) model was proposed to explain the HA ring-like morphology. The LCC model optimized the parameters of ß-O-4 linkages between 14 units of 1-4 phenyl propanoid, and resulted in an optimized structure comprising 45-50 linear helical molecules looped spirally around a central cavity. Those results added new insights on the adsorption mechanism of HA on polar surfaces as a function of pH, which was relevant from the point of view of natural aggregation in soil environment.


Subject(s)
Humic Substances/analysis , Microscopy, Atomic Force , Minerals/analysis , Nanoparticles/chemistry , Adsorption , Aluminum Silicates/chemistry , Hydrogen-Ion Concentration , Hydrophobic and Hydrophilic Interactions , Minerals/chemistry , Molecular Dynamics Simulation , Soil/chemistry
14.
Int J Pharm ; 471(1-2): 173-81, 2014 Aug 25.
Article in English | MEDLINE | ID: mdl-24858381

ABSTRACT

Among various phospholipid-mediated drug delivery systems (DDS) suitable for topic and oral administration, phytosome technology represents an advanced innovation, widely used to incorporate standardized bioactive polyphenolic phytoconstituents into phospholipid molecular complexes. In order to extend their potential therapeutic efficiency also to other routes of administration, we proposed a novel phytosome carrier-mediated vesicular system (phyto-liposome) as DDS for the flavonolignan silybin (SIL), a natural compound with multiple biological activities related to its hepatoprotective, anticancer and antioxidant (radical scavenging) effects. We screened the optimum fraction of its phytosome, available in the market as Siliphos™, into liposomes prepared by extrusion, such that vesicle sizes and charges, monitored through dynamic light scattering and laser doppler velocimetry, satisfied several quality requirements. Special emphasis was placed on the study of host-guest interaction by performing UV-vis absorption, spectrofluorimetry and NMR experiments both in aqueous and non-polar solvents to probe the effect of the presence of phospholipids on the electronic properties of SIL and its propensity to engage H bonding with the lipid headpolar groups. Finally, fluorescence microscopy observations confirmed the ability of phyto-liposomes to be internalized in human hepatoma cells, which was promising for their potential application in the treatment of acute or chronic liver diseases.


Subject(s)
Drug Carriers/chemistry , Nanostructures/chemistry , Phospholipids/chemistry , Silymarin/administration & dosage , Water/chemistry , Cell Line, Tumor , Cell Survival/drug effects , Drug Compounding , Humans , Liposomes , Molecular Structure , Particle Size , Silybin , Silymarin/chemistry , Silymarin/pharmacokinetics , Silymarin/pharmacology , Solubility , Surface Properties
15.
Chemosphere ; 99: 239-47, 2014 Mar.
Article in English | MEDLINE | ID: mdl-24315181

ABSTRACT

Humic acids (HA) have a colloidal character whose size and negative charge are strictly dependent on surface functional groups. They are able to complex large amount of poorly ordered iron (hydr)oxides in soil as a function of pH and other environmental conditions. Accordingly, with the present study we intend to assess the colloidal properties of Fe(II) coprecipitated with humic acids (HA) and their effect on Fe hydroxide crystallinity under abiotic oxidation and order of addition of both Fe(II) and HA. TEM, XRD and DRS experiments showed that Fe-HA consisted of Ferrihydrite with important structural variations. DLS data of Fe-HA at acidic pH showed a bimodal size distribution, while at very low pH a slow aggregation process was observed. Electrophoretic zeta-potential measurements revealed a negative surface charge for Fe-HA macromolecules, providing a strong electrostatic barrier against aggregation. Under alkaline conditions HA chains swelled, which resulted in an enhanced stabilization of the colloid particles. The increasing of zeta potential and size of the Fe-HA macromolecules, reflects a linear dependence of both with pH. The increase in the size and negative charge of the Fe-HA precipitate seems to be more affected by the ionization of the phenolic acid groups, than by the carboxylic acid groups. The main cause of negative charge generation of Fe/HA is due to increased dissociation of phenolic groups in more expanded structure. The increased net negative surface potential induced by coprecipitation with Ferrihydrite and the correspondent changes in configuration of the HA could trigger the inter-particle aggregation with the formation of new negative surface. The Fe-HA coprecipitation can reduce electrosteric repulsive forces, which in turn may inhibit the aggregation process at different pH. Therefore, coprecipitation of Ferrihydrite would be expected to play an important role in the carbon stabilization and persistence not only in organic soils, but also in waters containing dissolved organic matter.


Subject(s)
Chemical Precipitation , Colloids/chemistry , Ferric Compounds/chemistry , Humic Substances/analysis , Soil/chemistry , Iron/chemistry , Oxidation-Reduction , Particle Size , Static Electricity
16.
Biomacromolecules ; 14(8): 2549-60, 2013 Aug 12.
Article in English | MEDLINE | ID: mdl-23705931

ABSTRACT

An efficient drug delivery strategy is presented for novel anticancer amphiphilic ruthenium anionic complexes, based on the formation of stable nanoparticles with the cationic lipid 1,2-dioleyl-3-trimethylammoniumpropane chloride (DOTAP). This strategy is aimed at ensuring high ruthenium content within the formulation, long half-life in physiological media, and enhanced cell uptake. An in-depth microstructural characterization of the aggregates obtained mixing the ruthenium complex and the phospholipid carrier at 50/50 molar ratio is realized by combining a variety of techniques, including dynamic light scattering (DLS), small angle neutron scattering (SANS), neutron reflectivity (NR), electron paramagnetic resonance (EPR), and zeta potential measurements. The in vitro bioactivity profile of the Ru-loaded nanoparticles is investigated on human and non-human cancer cell lines, showing IC(50) values in the low µM range against MCF-7 and WiDr cells, that is, proving to be 10-20-fold more active than AziRu, a previously synthesized NAMI-A analog, used for control. Fluorescence microscopy studies demonstrate that the amphiphilic Ru-complex/DOTAP formulations, added with rhodamine-B, are efficiently and rapidly incorporated in human MCF-7 breast adenocarcinoma cells. The intracellular fate of the amphiphilic Ru-complexes was investigated in the same in vitro model by means of an ad hoc designed fluorescently tagged analog, which exhibited a marked tendency to accumulate within or in proximity of the nuclei.


Subject(s)
Antineoplastic Agents/chemistry , Coordination Complexes/chemistry , Liposomes/chemistry , Ruthenium/chemistry , Allyl Compounds/chemistry , Animals , Antineoplastic Agents/metabolism , Antineoplastic Agents/pharmacology , Cell Survival/drug effects , Colloids , Coordination Complexes/metabolism , Coordination Complexes/pharmacology , Drug Screening Assays, Antitumor , Drug Stability , Electron Spin Resonance Spectroscopy , Half-Life , Humans , Inhibitory Concentration 50 , Lipids/chemistry , Liposomes/metabolism , Liposomes/pharmacology , MCF-7 Cells , Nanoparticles/chemistry , Neutron Diffraction , Particle Size , Ruthenium/metabolism , Ruthenium/pharmacology , Scattering, Small Angle , Surface-Active Agents/chemistry
17.
J Colloid Interface Sci ; 390(1): 129-36, 2013 Jan 15.
Article in English | MEDLINE | ID: mdl-23099249

ABSTRACT

Here, the phase behavior of the commercial non-ionic surfactant Solutol® HS15 in water was investigated. The focus was on the evolution of the system nanostructure at low water content. Particularly, it was demonstrated that spherical micelles found in dilute surfactant solutions coalesce at a surfactant volume fraction close to 0.5. As consequence, a heterogeneous pseudo-binary mixture occurs. No liquid crystalline phases were detected even at the highest HS15 concentrations in water. Alteration of the micellar morphology induced by the addition of Δ(9)-tetrahydrocannabinol to the surfactant/water binary system was also investigated. It was found that the cannabinoid molecules become entrapped within the surfactant hydrophobic tails, thus increasing the surfactant effective packing parameter and inducing a radical change of the micelle shape. At sufficiently low water content (18-35 wt.%), such alteration of the interfacial packing results in a lamellar organization of the surfactant molecules.


Subject(s)
Dronabinol/chemistry , Micelles , Nanostructures/chemistry , Polyethylene Glycols/chemistry , Stearic Acids/chemistry , Water/chemistry , Solubility
18.
Phys Chem Chem Phys ; 15(2): 586-95, 2013 Jan 14.
Article in English | MEDLINE | ID: mdl-23184218

ABSTRACT

The aim of the present study was to provide experimental evidence that base pairing, commonly occurring between nucleic bases in more complex supramolecular arrangements, may affect the reaction pathways associated with the alkylation of bases themselves. In pursuit of this aim, dilute aqueous solutions of Cytidine- (CMP) and Guanosine-Mono-Phosphate (GMP) as single reactants or in an equimolar mixture were treated with the electrophilic alkylating agent 1,2-Dodecyl-Epoxide (DE), which was preventively dispersed into micellar solutions prepared with the cationic surfactant hexadecyltrimethylammonium bromide (CTAB). In the early stage of the reaction, CTAB micelles acted as micro-heterogeneous nanoreactors, but as the reaction progressed the systems evolved toward the formation of polydisperse aggregates, whose size and surface-charge properties were monitored as a function of reaction time. From mass spectrometry analyses, it was found that the deamination of cytosine, a side reaction related to the alkylation of the amino group of CMP, was reduced when both the complementary ribonucleotides were present in the same reaction mixture. The involvement of specific sites able to establish C:G interactions (possibly via H-bonding or π-π stacking) could explain the reduced reactivity occurring at the level of some of the nucleophilic centers responsible for molecular recognition.


Subject(s)
Base Pairing , Ribonucleotides/chemistry , Alkylating Agents/chemistry , Alkylation , Cetrimonium , Cetrimonium Compounds/chemistry , Chromatography, High Pressure Liquid , Cytidine Monophosphate/chemistry , Guanosine Monophosphate/chemistry , Micelles , Spectrometry, Mass, Electrospray Ionization , Surface-Active Agents/chemistry
19.
J Colloid Interface Sci ; 374(1): 118-26, 2012 May 15.
Article in English | MEDLINE | ID: mdl-22381942

ABSTRACT

The aim of this work was to investigate the surface structure of aqueous hematite dispersions characterized by a large variability of morphology and particle size combining structural investigations obtained from Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) techniques with in vitro particle size distributions and zeta potential measurements from Dynamic Light Scattering (DLS) technique, and we achieved a self-consistent and detailed characterization of hematite particles whose sizes and morphologies could be correlated to the synthesis conditions (type of added anion, Al substitution and pH). Surface AFM characterization provided an accurate analysis of particle microstructure and also indicated that the growth of microcrystals followed different surface roughness. DLS, AFM, and TEM techniques furnished complementary information on the average particle dimensions, whose variation could be attributed to the morphological difference of hematites, ranging from platy to regular or irregular hexagonal or ellipsoidal shape. Finally, a correlation between the average particle dimensions and the measured zeta potential was also been found in aqueous dilute suspensions characterized by neither pH nor-ionic-strength-control, for which a drop of zeta potential from positive to negative values was detected for hematite particle dimensions larger than a threshold size of ~150 nm.

20.
Phys Chem Chem Phys ; 12(28): 7977-87, 2010 Jul 28.
Article in English | MEDLINE | ID: mdl-20517544

ABSTRACT

This article focuses on the physico-chemical investigation of the time evolution of self-assembled structures composed by oppositely charged surfactant monomers. The cationic components were represented by the well known cetyl-trimethyl-ammonium-bromide (CTAB) while the anionic monomers consisted of amphiphilic ribonucleotide derivatives, also called nucleo-lipids (NL). The latter were generated in situ by direct reaction between a hydrophobic precursor, dodecyl epoxide (DE), and a pair of complementary ribonucleotide mono-phosphates: adenosine mono-phosphate (AMP) and uridine mono-phosphate (UMP). Analysis of reaction mixtures by liquid chromatography-electrospray ionization-single, tandem and sequential mass spectrometry (LC-ESI-MS, MS/MS and MS(3)) confirmed that the generated NL corresponded to ribonucleotides linked to one, two and even three hydroxy-dodecyl tails on their molecular structures and whose amounts had peculiar time dependences. In the solutions incubated with an equimolar mixture of both types of ribonucleotides, a remarkable positive feedback effect on the reaction products was ascribed to the contemporary presence of AMP and UMP. The variation of aggregate sizes, due to the incorporation process of NL monomers into starting CTAB micelles, was monitored through time-resolved measurements of both dynamic light-scattering (DLS) and electrophoretic mobilities, together with calculated zeta-(zeta)-potential. Finally, a kinetic model based on auto-catalytic mechanisms was outlined to analyze the process of the catanionic vesicles growth observed during the whole reaction time-course. The model was also in good agreement with MS data. The proposed colloidal system may be considered a simplified model whereby to study the potential role of complementary nucleic bases in triggering primitive chemical selections.


Subject(s)
Nanostructures/chemistry , Ribonucleotides/chemistry , Adenosine Monophosphate/chemistry , Catalysis , Chromatography, High Pressure Liquid , Kinetics , Quaternary Ammonium Compounds/chemistry , Spectrometry, Mass, Electrospray Ionization , Uridine Monophosphate/chemistry
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