Margarita Valero

University of Salamanca · Department of Physical Chemistry

Background Human African trypanosomiasis (HAT or sleeping sickness) is caused by the parasite Trypanosoma brucei sspp. The disease has two stages, a haemolymphatic stage after the bite of an infected tsetse fly, followed by a central nervous system stage where the parasite penetrates the brain, causing death if untreated. Treatment is stage-specifi...

The present work examines the behavior of salicylic acid (SAL)-loaded F127 micelles as drug nanocarriers for controlled release by means of interaction with 2,6-dimethyl-β-cyclodextrin (DIMEB) in the intestine at basic pH = 7–8, both important excipients, of pharmaceutical formulations. The results show that acidic pH (pH = 1) strongly increases th...

The photochemistry and other properties of the anti-inflammatory drug (NSAID) naproxen (NP) in sodium dodecyl sulfate, SDS, micellar aqueous solutions at pH = 7 (NP is in anionic form) were studied. The large value of the partition coefficient (P) was obtained, logP = 2.7, showing that the most part of NP is localized in the micellar phase. The sol...

Hypotheses. Bile salts (BS) are biosurfactants released into the small intestine, which play key and contrasting roles in lipid digestion: they adsorb at interfaces and promote the adsorption of digestive enzymes onto fat droplets, while they also remove lipolysis products from that interface, solubilising them into mixed micelles. Small architectu...

The photochemistry, solubility and distribution between two phases of nabumetone (NB) in aqueous solution of sodium dodecyl sulfate (SDS) micelles were studied. The solubility (SNB) of NB was monitored using steady-state UV–Vis absorption spectroscopy. The linear relationship of SNB to SDS concentration ([SDS]) gave the large value of partition coe...

Gram-negative bacteria possess numerous defenses against antibiotics, due to the intrinsic permeability barrier of their outer membrane, explaining the recalcitrance of some common and life-threatening infections. We report the formulation of a new drug, PPA148, which shows promising activity against all Gram-negative bacteria included in the ESKAP...

Human African trypanosomiasis (HAT or sleeping sickness) is caused by the parasite Trypanosoma brucei sspp. The disease has two stages, a haemolymphatic stage after the bite of an infected tsetse fly, followed by a central nervous system stage where the parasite penetrates the brain, causing death if untreated. Treatment is stage-specific, due to t...

Polymeric micelles, in particular PEO-PPO-based Pluronic, have emerged as promising drug carriers, while cyclodextrins, cyclic oligosaccharides with an apolar cavity, have long been used for their capacity to form inclusion complexes with drugs. Dimethylated β-cyclodextrin (CD) has the capacity to fully break-up F127 Pluronic micelles, while this e...

Micelles of the triblock copolymer Pluronic F127 can encapsulate drugs with various chemical structures and their architecture has been studied by small-angle neutron scattering (SANS). Interaction with a derivative of β-cyclodextrin, namely, heptakis(2,6-di-O- methyl)-β-cyclodextrin (DIMEB), induces a complete break-up of the micelles, providing a...

We report the effect of native cyclodextrins (α-, β-, and γ-) and selected derivatives in modulating the self-assembly of the non-ionic surfactant polyoxyethylene cholesteryl ether (ChEO10), and its mixtures with triethylene glycol monododecyl ether (C12EO3), which form wormlike micelles. Cyclodextrins (CDs) generally induce micellar break-up throu...

We report the influence of five beta-cyclodextrin (beta-CD) derivatives, namely: randomly methylated-beta-cyclodextrin (MBCD), heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DIMEB), heptakis (2,3,6-tri-O-methyl)-beta-cyclodextrin (TRIMEB), 2-hydroxyethyl-beta-cyclodextrin (HEBCD) and 2-hydroxypropyl-beta-cyclodextrin (HPBCD), on the self-assembly of...

Spectroscopic measurements (uv/vis absorbance and fluorescence) and time-resolved small-angle neutron scattering experiments (TR-SANS) were used to follow the breakdown of Pluronic micelles by heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) over time in order to elucidate the mechanism of micellar rupture, generally attributed to polypseudotorotax...

Vesicles are widely used in technological applications including cosmetic products, in microencapsulation for drug delivery, as anticancer agents and in the technology of adhesives, paints and inks. The vesicle size and the surface charge are very important properties from a technological point of view. Thus, the challenge in formulation is to find...

The triblock-copolymer poly(ethylene oxide)-poly(propyleneoxide)-poly(ethylene oxide) (PEO-PPO-PEO), referred to as Pluronic, is widely studied for its unique aggregation properties and its applications in drug delivery and targeting. In previous studies [Dreiss, C. A.; et al. Soft Matter 2009, 5, 1888-1896], we showed that the interaction of hepta...

The associative structures between F127 Pluronic micelles and four drugs, namely, lidocaine (LD), pentobarbital sodium salt (PB), sodium naproxen (NP), and sodium salicylate (SAL), were studied by small-angle neutron scattering (SANS). Different outcomes for the micellar aggregates are observed, which are dependent on the chemical nature of the dru...

The quenching of the anti-inflammatory drug nabumetone by iodide was studied by means of steady-state and time-resolved fluorescence techniques. A downward curvature in the Stern–Volmer plot was observed. This behaviour has been interpreted based on the existence of two conformers of the drug that interact with the quencher with different ability,...

The state of water in AOT-n-decane-water microemulsions has been studied by using Fourier Transform Infrared spectroscopy (FT-IR). The existence of three kinds of water, which correspond to water populations with different degrees of organization, has been observed. Densities of these microemulsions have been measured. From these studies (FT-IR and...

Dynamic light scattering and Cryo-TEM measurements have allowed us to obtain the size and structure of spontaneous aggregates formed by mixtures of Aerosol OT, AOT, and ethylene glycol polymers of different molecular mass. The results presented in this work show that small unilamellar vesicles predominate in pure Aerosol OT solutions and in dilute...

The aim of the present study was to investigate the effect of the presence of the water-soluble polymer polyvinylpyrrolidone (PVP) MW=24,000 g/mol, on the complexing of the anti-inflammatory drug nabumetone, with β-cyclodextrin (β-CD). The data show that the polymer interacts with the free nabumetone and with the nabumetone:β-CD inclusion complex,...

The effect of the formation of the naproxen:cyclodextrin inclusion complex on the quenching of the drug by iodide has been studied. The results show that α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD) provide good protection for the drug against iodide quenching. The trend of protection is α-CD>HP-β-CD≈β-CD...

The effect of the polyvinylpyrrolidone and/or hydroxypropyl-beta-cyclodextrin on the photo-lability of aqueous solutions of the anti-inflammatory drug Naproxen was studied. Kinetic studies revealed that the presence of all of these additives reduced drug photodegradation. In all cases, the presence of the different additives elicited a change in th...

The properties of the interface of vesicles of pure sodium bis-(2-ethyl-hexyl) sulfosuccinate (AOT) and binary mixtures composed of AOT with poly(ethylene) glycol (PEG), poly(sodium 4-styrensulfonate) (PSS) and sodium chloride were investigated using absorption and steady-state fluorescence of nabumetone and electrophoretic mobility measurements. R...

The effect of the polyvinylpyrrolidone and/or hydroxypropyl-p-cyclodextrin on the photolability of aqueous solutions of the antiinflammatory drug Naproxen was studied. Kinetic studies revealed that the presence of all of these additives reduced drug photodegradation. In all cases, the presence of the different additives elicited a change in the pho...

The effect of the polyethylene glycol and/or beta-cyclodextrin on the photolability of aqueous solutions of the anti-inflammatory drug Naproxen was studied. In all systems studied, the photodegradation process followed zero-order kinetics, leading to the same photoproducts as in the absence of these additives. Kinetic studies revealed that the pres...

The effect of the polyethylene glycol and/or β-cyclodextrin on the photolability of aqueous solutions of the anti-inflammatory drug Naproxen was studied. In all systems studied, the photodegradation process followed zero-order kinetics, leading to the same photoproducts as in the absence of these additives. Kinetic studies revealed that the presenc...

The aim of the present study was to investigate the effect of the presence of thewater-soluble polymer polyvinylpyrrolidone (PVP) MW = 24000 g/mol, on thecomplexation of the phototoxic anti-inflammatory drug naproxen, in its sodiumsalt form, with hydroxypropil--cyclodextrin (HP--CD). The datashown that the polymer interacts with the free naproxen a...

The photolability of the anti-inflammatory drug Nabumetone was studied in n-butanol. The photoproducts were followed by UV-Vis absorption, fluorescence and FTIR spectroscopies as well as gas chromatography–mass spectrometry (GC/MS).The photodegradation process in this organic medium followed first-order kinetics. In contrast with what was expected...

The aim of this study was to investigate the effect of the presence of the water-soluble polymer polyethylene glycol (PEG)-MW=35000 g/mol-on the complexation of the phototoxic anti-inflammatory drug naproxen, in its sodium salt form, with beta-cyclodextrin (beta-CD). The data revealed that the polymer does not interact with the uncomplexed naproxen...

The photolability of the anti-inflammatory drug Nabumetone (4-(6-methoxy-2-naphthyl)-butan-2-one) was studied in water. The photoproducts were followed by UV-Vis absorption, fluorescence and FTIR spectroscopies as well as gas chromatography–mass spectrometry (GC–MS).The photodegradation process in water followed first-order kinetics, with an half-l...

The aim of this study was to investigate the effects of the presence of the water-soluble polymer polyvinylpyrrolidone K-25 (MW=24000g/mol) on the complexation of the AINE naproxen, in its sodium salt form, with the beta-cyclodextrin. The data revealed that the polyvinylpyrrolidone K-25 interacts with the drug as well as with the drug:beta-cyclodex...

The structure of CTAB micelles in the presence of -, - and hydroxypropyl--cyclodextrin has been investigated by means of conductivity and spectroscopic measurements – absorption and steady state fluorescence – using Naproxen, Nabumetone and pyrene as probes. In the presence of the three cyclodextrins, two types of micelles have been detected. The f...

By using electrical conductivity and static and dynamic light scattering measurements, the behavior of water-oil (w/o) microemulsions formed by Aerosol OT dissolved in toluene has been examined. To study the effect of the droplet volume fraction on the microemulsion behavior, the water and the surfactant concentrations were systematically modified...

Spectroscopic and photophysical properties of a non-steroidal anti-inflammatory drug, Nabumetone, were studied in dioxane/water mixtures, cyclodextrins (α-CD, β-CD and HP-β-CD) and besides that, for comparison, in a wide range of solvents with different polarities, viscosities and hydrogen bonding ability.The fluorescence quantum yields (φf) and li...

The inclusion of the anti-inflammatory drug, Nabumetone, in -, - and hydroxypropyl--cyclodextrin (CDs) is studied using UV-VIS absorption and steady-state fluorescence emission. Binding constants and thermodynamic parameters of complex formation are determined by spectrofluorimetry. The inclusion phenomena of Nabumetone with the three cyclodextrins...

In this lab experiment we describe an investigation of the thermodynamics of the formation of cyclodextrin inclusion complexes by using fluorescence spectroscopy. A naphthalene derivative, 4-(6-methoxy-2-naphthyl)-2 butanone (nabumetone), was used as a guest and two different cyclodextrins, β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin, (H...

UV-absorption spectroscopy technique enables the determination of the binding constants of some non-steroidal anti-inflammatory drugs to α-, β-, and γ-cyclodextrins. In all cases the stoichiometry of the complex is 1:1 and the drugs have a higher affinity for β-cyclodextrin than for α-cyclodextrin or γ-cyclodextrin. The dielectric constant of the c...

Photophysical properties of a non-steroidal anti-inflammatory drug, Naproxen (6-methoxy alpha-methyl-2-naphthalene acetic acid sodium salt), were investigated in solvents of different polarity, hydrogen donor ability and also in cyclodextrins. The results indicate that in all cases the emitting state is the 1L(b) singlet. In alcoholic solvents, an...

The characterization and study of the polarity of mixed micelles of sodium decyl and sodium dodecyl sulfate and sodium cholate by fluorescence probing have been carried out. Pyrene and Pyrene-1-carboxaldehyde were used. The obtained results allow the discussion of the changes of micelle structure with composition.