Biomedical subjects

Margarita Valero

Publications and source records attributed to Margarita Valero.

5 recordsLinked to original sources

PubMed2004

Effect of binary and ternary polyvinylpyrrolidone and/or hydroxypropyl-beta-cyclodextrin complexes on the photochemical and photosensitizing properties of Naproxen.

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 the photomixture composition, being the alcoholic derivative the major photoproduct formed. Nevertheless, the change in the efficiency of the process and the amount of the photoproducts formed in the different systems were not related with the biodamage produced by the drug. In this sense, the presence of free Naproxen clearly sensitized the photoperoxidation of linoleic acid. The photosensitizing effect decreased as the PVP concentration increased. Different protection provides the binary (Naproxen:HP-beta-CD) and ternary (Naproxen:HP-beta-CD:PVP) complexes. The binary complex formation had not effect on the prevention of photooxidation of linoleic acid sensitized by the drug, whereas the ternary complex formation suppresses the drug effect. The different behaviour observed with beta-CD and HP-beta-CD and the structural differences of both cyclodextrins seem to indicate that in the case of the HP-beta-CD the linoleic binds with the CD and takes contact with the drug. These results confirm that in these systems the prevention of biodamage would be due to a decrease in the contact between the short-lived species generated during Naproxen photodegradation and biological structures, rather than due to the nature or amount of the photoproducts. In addition, the ability of the complex to interact with the biological structure depends on the structure of both interacting species.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2004

Effect of the addition of water-soluble polymers on the interfacial properties of aerosol OT vesicles.

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. Results confirm those obtained in a previous work indicating that the addition of PEG, PSS, and NaCl stabilizes the AOT vesicles. The stabilization mechanism is the screening of the surface charge in the case of binary mixtures of AOT/PSS and AOT/NaCl and the polymer adsorption on the interface for vesicles of AOT/PEG.

Journal Article↗

PubMed2004

Effect of binary and ternary polyethyleneglycol and/or beta-cyclodextrin complexes on the photochemical and photosensitizing properties of Naproxen.

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 presence of polyethylene glycol (PEG) reduced drug photodegradation (phi=0.11 in water and phi=0.045 in the presence of 1% of PEG). By contrast, the binary inclusion complex, Naproxen:beta-CD, did not protect the drug from degradation, phi=0.11. However, the ternary complex, Naproxen:beta-CD:PEG, reduced the efficiency of the photodegradative process to a considerable extent, with phi=0.022 in this system. In all cases the presence of the different additives elicited a change in the photomixture composition, the alcoholic derivative being the major photoproduct formed. Nevertheless, the change in the efficiency of the process and the amount of the photoproducts formed in the different systems were not related with the biodamage produced by the drug. In this sense, the presence of free Naproxen clearly sensitized the photoperoxidation of linoleic acid. The photosensitizing effect decreased as the PEG concentration increased and was completely abolished by both the binary (Naproxen:beta-CD) and ternary (Naproxen:beta-CD:PEG) complexes. In light of these observations, it is possible to speculate that in these systems the prevention of biodamage would be due to a decrease in the contact between the short-lived species generated during Naproxen photodegradation and biological structures, rather than to the nature or amount of the photoproducts.

Kinetics↗

PubMed2003

Ternary naproxen: beta-cyclodextrin:polyethylene glycol complex formation.

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 whereas it does with the beta-CD. The presence of different proportions of PEG, in the 0-1% (w/w) range, systematically lowers K(app) of the formation of the naproxen:beta-CD inclusion complex. The reason for the decrease in the complexed drug is the presence of other competing equilibria, the first one is an interaction of the polymer with the beta-CD, which in turn reduces the amount of free CD available for including the naproxen, and the second is the formation of a naproxen:beta-CD:PEG ternary complex with lower affinity than the binary complex. The binding constant of these processes are K(2)=(4.5+/-1.0) x 10(5) M(-1) and K(3)=870+/-19 M(-1), respectively. In addition the presence of the PEG produces an important change in the driving force of the complex formation. In this case the process is enthalpically unfavoured and entropically favoured; these are typical characteristics of processes governed by hydrophobic interactions.

Cyclodextrins↗

PubMed2003

Effect of PVP K-25 on the formation of the naproxen:beta-ciclodextrin complex.

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-cyclodextrin inclusion complex. The polymer shows more affinity for the inclusion complex, K=(6.67+/-0.292) x 10(-5)M(-1) than for the free drug, (2.08+/-0.208) x 10(-5)M(-1). The presence of different proportions of polymer, in a range 0-1% (w/w) of polyvinylpyrrolidone, does not increase the ability of drug-cyclodextrin complexation but important changes in the driving force of complex formation were detected, depending on the percentage of polyvinylpyrrolidone K-25 present. At low polymer concentrations, the complexation process is driven entropically, while at higher PVP proportions it is enthalpically favored. In the ternary system, polyvinylpyrrolidone K-25 partially or totally coats the drug:beta-cyclodextrin inclusion complex interacting with the beta-cyclodextrin (through hydrogen bonds), and with the naproxen.

Anti-Inflammatory Agents, Non-Steroidal↗