Eva Bernal - Academia.edu (original) (raw)

Papers by Eva Bernal

Electrochemistry Communications, 2016

Potentiometric measurements based on the use of ion-selective electrodes have been used to study ... more Potentiometric measurements based on the use of ion-selective electrodes have been used to study the interaction (adsorption) of anionic and cationic surfactants with functionalized single-walled carbon nanotubes (SWCNT-COOH). According to results, the interaction is driven by hydrophobic forces between the hydrocarbon tails of the surfactants and the nanotube walls. Electrostatic interactions practically exert no influence on the interaction. Driving forces in the dispersion processes are different.

Pharmaceutics

The research on flavonoids has exponentially grown since their first therapeutic evidence, in 193... more The research on flavonoids has exponentially grown since their first therapeutic evidence, in 1937. They are effective in vitro in a wide range of human diseases, particularly those mediated by free radicals, such as cancer, atherosclerosis, AIDS, or neuronal diseases. However, their applications have been reduced due to their low solubility, poor absorption, and rapid metabolism. Flavonoid encapsulation in nanocarriers significantly improves their oral absorption, protects the drug against degradation, decreases the first-pass hepatic effect, and makes absorption through the lymphatic system easier. In this work, carbon nanotubes were used as nanocarriers of 7-hydroxyflavone, 7-HF. The encapsulation of 7-HF into pristine single- and multi-walled carbon nanotubes, and into -COOH functionalized single-walled carbon nanotubes has been investigated. The equilibrium association constants were estimated. The structural backbone of 7-HF, two benzene rings linked through three carbon atoms...

Chemosensors

Gene therapy is a technique that is currently under expansion and development. Recent advances in... more Gene therapy is a technique that is currently under expansion and development. Recent advances in genetic medicine have paved the way for a broader range of therapies and laid the groundwork for next-generation technologies. A terminally substituted difluorene-diester Schiff Base calix[4]arene has been studied in this work as possible nanovector to be used in gene therapy. Changes to luminescent behavior of the calixarene macrocycle are reported in the presence of ct-DNA. The calixarene macrocycle interacts with calf thymus DNA (ct-DNA), generating changes in its conformation. Partial double-strand denaturation is induced at low concentrations of the calixarene, resulting in compaction of the ct-DNA. However, interaction between calixarene molecules themselves takes place at high calixarene concentrations, favoring the decompaction of the polynucleotide. Based on cytotoxicity studies, the calixarene macrocycle investigated has the potential to be used as a nanovehicle and improve th...

International Journal of Molecular Sciences, 2021

The interaction (adsorption process) of commercial ionic surfactants with non-functionalized and ... more The interaction (adsorption process) of commercial ionic surfactants with non-functionalized and functionalized carbon nanotubes (CNTs) has been studied by potentiometric measurements based on the use of ion-selective electrodes. The goal of this work was to investigate the role of the CNTs’ charge and structure in the CNT/surfactant interactions. Non-functionalized single- (SWCNT) and multi-walled carbon nanotubes (MWCNT), and amine functionalized SWCNT were used. The influence of the surfactant architecture on the CNT/surfactant interactions was also studied. Surfactants with different charge and hydrophobic tail length (sodium dodecyl sulfate (SDS), octyltrimethyl ammonium bromide (OTAB), dodecyltrimethyl ammonium bromide (DoTAB) and hexadecyltrimethyl ammonium bromide (CTAB)) were studied. According to the results, the adsorption process shows a cooperative character, with the hydrophobic interaction contribution playing a key role. This is made evident by the correlation betwee...

Colloids and surfaces. B, Biointerfaces, Jan 14, 2016

Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammoniu... more Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammonium salts (m-s-m) have been the most common type of dimeric surfactants investigated and it is generally admitted that those that posses a short spacer (s≤3) show better efficiency to bind or compact DNA. However, experimental results in this work show that 12-s-12 surfactants with long spacers make the surfactant/ctDNA complexation more favorable than those with short spacers. A larger contribution of the hydrophobic interactions, which control the binding Gibbs energy, as well as a higher average charge of the surfactant molecules bound to the nucleic acid, which favors the electrostatic attractions, could explain the experimental observations. Dimeric surfactants with intermediate spacer length seem to be the less efficient for DNA binding.

RSC Advances, 2014

Two cyclodextrins producing a decrease of KSV once they form a mixture can produce an increase.

Journal of Photochemistry and Photobiology A: Chemistry, 2014

Chemical reactivity under restricted geometry conditions can be described through the equations o... more Chemical reactivity under restricted geometry conditions can be described through the equations of the Pseudophase Model (a two state model). This model is based on the assumption of an equilibrium between these two states (free and bound) which is not perturbed by the reactive event. This implies that the reaction in which these states participate must be slow, in relation to the exchange processes between the two states. This condition holds in the case of chemical reactions, but does not hold for very rapid photochemical reactions. However, the Pseudophase Model seems to be applicable, apparently, in the case of excited state reactions. According to this a similar formal behavior is observed in chemical and photochemical reactions. However, a closer inspection of the data reveals important differences between the two types of reactions, in particular in the meaning of the parameters appearing in the equations of the Pseudophase Model. These similarities, and differences, are considered in this work using, as representative examples, the reactions between [Fe(CN) 5 (4-CNpy)] 3− and [Co(NH 3) 4 (pzCO 2)] 2+ (chemical) and the quenching of pyrene by the iodide ion (photochemical), under restricted geometry conditions. These conditions are due to the presence of receptors (CTACl micelles and DNA, respectively) in the reaction media. An explanation for these facts is given.

Chemical Physics Letters, 2011

The classical Pseudophase Model (a two state model) describes well the reactivity in the presence... more The classical Pseudophase Model (a two state model) describes well the reactivity in the presence of receptors. This model assumes that the exchange between free and bound reactants is at equilibrium in spite of the reaction, a condition that usually cannot be maintained if the reactants are excited. However, the equation of the Pseudophase Model holds, at least formally, in this case. The formalism developed to clarify this question indicates that the parameters acquire a somewhat different meaning in the case of photochemical reactions. The experiments carried out in the presence of DNA and b-cyclodextrin support the formalism developed.

Pharmaceutics

The formation of calixarene-based liposomes was investigated, and the characterization of these n... more The formation of calixarene-based liposomes was investigated, and the characterization of these nanostructures was carried out using several techniques. Four amphiphilic calixarenes were used. The length of the hydrophobic chains attached to the lower rim as well as the nature of the polar group present in the upper rim of the calixarenes were varied. The lipid bilayer was formed with one calixarene and with the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, DOPE. The cytotoxicity of the liposomes for various cell lines was also studied. From the results obtained, the liposomes formed with the least cytotoxic calixarene, (TEAC12)4, were used as nanocarriers of both nucleic acids and the antineoplastic drug doxorubicin, DOX. Results showed that (TEAC12)4/DOPE/p-EGFP-C1 lipoplexes, of a given composition, can transfect the genetic material, although the transfection efficiency substantially increases in the presence of an additional amount of DOPE as coadjuvant. On the ot...

Molecules, 2010

The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturab... more The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturable receptors (cyclodextrins and calixarenes) and more complex systems (mixing some of the above mentioned catalysts) have been reviewed. In these microheterogeneous systems the observed changes in the rate constants have been rationalized using the Pseudophase Model. This model produces equations that can be derived from the Brönsted equation, which is the basis for a more general formulation of catalytic effects, including electrocatalysis. When, in the catalyzed reaction one of the reactants is in the excited state, the applicability (at least formally) of the Pseudophase Model occurs only in two limiting situations: the lifetime of the fluorophore and the distributions of the quencher and the probe are the main properties that define the different situations.

RSC Adv., 2015

Applicability of the pseudophase model to photochemical reactions in the presence of receptors (m... more Applicability of the pseudophase model to photochemical reactions in the presence of receptors (micelles) in spite of the fact that the equilibrium condition between free and bound reactants does not hold.

Citation: Ostos, F.J.; Lebrón, J.A.; Moyá, M.L.; Bernal, E.; Flores, A.; Lépori, C.; Maestre, Á.;... more Citation: Ostos, F.J.; Lebrón, J.A.; Moyá, M.L.; Bernal, E.; Flores, A.; Lépori, C.; Maestre, Á.; Sánchez, F.; López-Cornejo, P.; López-López, M.

The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturab... more The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturable receptors (cyclodextrins and calixarenes) and more complex systems (mixing some of the above mentioned catalysts) have been reviewed. In these microheterogeneous systems the observed changes in the rate constants have been rationalized using the Pseudophase Model. This model produces equations that can be derived from the Brönsted equation, which is the basis for a more general formulation of catalytic effects, including electrocatalysis. When, in the catalyzed reaction one of the reactants is in the excited state, the applicability (at least formally) of the Pseudophase Model occurs only in two limiting situations: the lifetime of the fluorophore and the distributions of the quencher and the probe are the main properties that define the different situations.

Electrochemistry Communications, 2016

Potentiometric measurements based on the use of ion-selective electrodes have been used to study ... more Potentiometric measurements based on the use of ion-selective electrodes have been used to study the interaction (adsorption) of anionic and cationic surfactants with functionalized single-walled carbon nanotubes (SWCNT-COOH). According to results, the interaction is driven by hydrophobic forces between the hydrocarbon tails of the surfactants and the nanotube walls. Electrostatic interactions practically exert no influence on the interaction. Driving forces in the dispersion processes are different.

Pharmaceutics

The research on flavonoids has exponentially grown since their first therapeutic evidence, in 193... more The research on flavonoids has exponentially grown since their first therapeutic evidence, in 1937. They are effective in vitro in a wide range of human diseases, particularly those mediated by free radicals, such as cancer, atherosclerosis, AIDS, or neuronal diseases. However, their applications have been reduced due to their low solubility, poor absorption, and rapid metabolism. Flavonoid encapsulation in nanocarriers significantly improves their oral absorption, protects the drug against degradation, decreases the first-pass hepatic effect, and makes absorption through the lymphatic system easier. In this work, carbon nanotubes were used as nanocarriers of 7-hydroxyflavone, 7-HF. The encapsulation of 7-HF into pristine single- and multi-walled carbon nanotubes, and into -COOH functionalized single-walled carbon nanotubes has been investigated. The equilibrium association constants were estimated. The structural backbone of 7-HF, two benzene rings linked through three carbon atoms...

Chemosensors

Gene therapy is a technique that is currently under expansion and development. Recent advances in... more Gene therapy is a technique that is currently under expansion and development. Recent advances in genetic medicine have paved the way for a broader range of therapies and laid the groundwork for next-generation technologies. A terminally substituted difluorene-diester Schiff Base calix[4]arene has been studied in this work as possible nanovector to be used in gene therapy. Changes to luminescent behavior of the calixarene macrocycle are reported in the presence of ct-DNA. The calixarene macrocycle interacts with calf thymus DNA (ct-DNA), generating changes in its conformation. Partial double-strand denaturation is induced at low concentrations of the calixarene, resulting in compaction of the ct-DNA. However, interaction between calixarene molecules themselves takes place at high calixarene concentrations, favoring the decompaction of the polynucleotide. Based on cytotoxicity studies, the calixarene macrocycle investigated has the potential to be used as a nanovehicle and improve th...

International Journal of Molecular Sciences, 2021

The interaction (adsorption process) of commercial ionic surfactants with non-functionalized and ... more The interaction (adsorption process) of commercial ionic surfactants with non-functionalized and functionalized carbon nanotubes (CNTs) has been studied by potentiometric measurements based on the use of ion-selective electrodes. The goal of this work was to investigate the role of the CNTs’ charge and structure in the CNT/surfactant interactions. Non-functionalized single- (SWCNT) and multi-walled carbon nanotubes (MWCNT), and amine functionalized SWCNT were used. The influence of the surfactant architecture on the CNT/surfactant interactions was also studied. Surfactants with different charge and hydrophobic tail length (sodium dodecyl sulfate (SDS), octyltrimethyl ammonium bromide (OTAB), dodecyltrimethyl ammonium bromide (DoTAB) and hexadecyltrimethyl ammonium bromide (CTAB)) were studied. According to the results, the adsorption process shows a cooperative character, with the hydrophobic interaction contribution playing a key role. This is made evident by the correlation betwee...

Colloids and surfaces. B, Biointerfaces, Jan 14, 2016

Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammoniu... more Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammonium salts (m-s-m) have been the most common type of dimeric surfactants investigated and it is generally admitted that those that posses a short spacer (s≤3) show better efficiency to bind or compact DNA. However, experimental results in this work show that 12-s-12 surfactants with long spacers make the surfactant/ctDNA complexation more favorable than those with short spacers. A larger contribution of the hydrophobic interactions, which control the binding Gibbs energy, as well as a higher average charge of the surfactant molecules bound to the nucleic acid, which favors the electrostatic attractions, could explain the experimental observations. Dimeric surfactants with intermediate spacer length seem to be the less efficient for DNA binding.

RSC Advances, 2014

Two cyclodextrins producing a decrease of KSV once they form a mixture can produce an increase.

Journal of Photochemistry and Photobiology A: Chemistry, 2014

Chemical reactivity under restricted geometry conditions can be described through the equations o... more Chemical reactivity under restricted geometry conditions can be described through the equations of the Pseudophase Model (a two state model). This model is based on the assumption of an equilibrium between these two states (free and bound) which is not perturbed by the reactive event. This implies that the reaction in which these states participate must be slow, in relation to the exchange processes between the two states. This condition holds in the case of chemical reactions, but does not hold for very rapid photochemical reactions. However, the Pseudophase Model seems to be applicable, apparently, in the case of excited state reactions. According to this a similar formal behavior is observed in chemical and photochemical reactions. However, a closer inspection of the data reveals important differences between the two types of reactions, in particular in the meaning of the parameters appearing in the equations of the Pseudophase Model. These similarities, and differences, are considered in this work using, as representative examples, the reactions between [Fe(CN) 5 (4-CNpy)] 3− and [Co(NH 3) 4 (pzCO 2)] 2+ (chemical) and the quenching of pyrene by the iodide ion (photochemical), under restricted geometry conditions. These conditions are due to the presence of receptors (CTACl micelles and DNA, respectively) in the reaction media. An explanation for these facts is given.

Chemical Physics Letters, 2011

The classical Pseudophase Model (a two state model) describes well the reactivity in the presence... more The classical Pseudophase Model (a two state model) describes well the reactivity in the presence of receptors. This model assumes that the exchange between free and bound reactants is at equilibrium in spite of the reaction, a condition that usually cannot be maintained if the reactants are excited. However, the equation of the Pseudophase Model holds, at least formally, in this case. The formalism developed to clarify this question indicates that the parameters acquire a somewhat different meaning in the case of photochemical reactions. The experiments carried out in the presence of DNA and b-cyclodextrin support the formalism developed.

Pharmaceutics

The formation of calixarene-based liposomes was investigated, and the characterization of these n... more The formation of calixarene-based liposomes was investigated, and the characterization of these nanostructures was carried out using several techniques. Four amphiphilic calixarenes were used. The length of the hydrophobic chains attached to the lower rim as well as the nature of the polar group present in the upper rim of the calixarenes were varied. The lipid bilayer was formed with one calixarene and with the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine, DOPE. The cytotoxicity of the liposomes for various cell lines was also studied. From the results obtained, the liposomes formed with the least cytotoxic calixarene, (TEAC12)4, were used as nanocarriers of both nucleic acids and the antineoplastic drug doxorubicin, DOX. Results showed that (TEAC12)4/DOPE/p-EGFP-C1 lipoplexes, of a given composition, can transfect the genetic material, although the transfection efficiency substantially increases in the presence of an additional amount of DOPE as coadjuvant. On the ot...

Molecules, 2010

The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturab... more The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturable receptors (cyclodextrins and calixarenes) and more complex systems (mixing some of the above mentioned catalysts) have been reviewed. In these microheterogeneous systems the observed changes in the rate constants have been rationalized using the Pseudophase Model. This model produces equations that can be derived from the Brönsted equation, which is the basis for a more general formulation of catalytic effects, including electrocatalysis. When, in the catalyzed reaction one of the reactants is in the excited state, the applicability (at least formally) of the Pseudophase Model occurs only in two limiting situations: the lifetime of the fluorophore and the distributions of the quencher and the probe are the main properties that define the different situations.

RSC Adv., 2015

Applicability of the pseudophase model to photochemical reactions in the presence of receptors (m... more Applicability of the pseudophase model to photochemical reactions in the presence of receptors (micelles) in spite of the fact that the equilibrium condition between free and bound reactants does not hold.

Citation: Ostos, F.J.; Lebrón, J.A.; Moyá, M.L.; Bernal, E.; Flores, A.; Lépori, C.; Maestre, Á.;... more Citation: Ostos, F.J.; Lebrón, J.A.; Moyá, M.L.; Bernal, E.; Flores, A.; Lépori, C.; Maestre, Á.; Sánchez, F.; López-Cornejo, P.; López-López, M.

The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturab... more The catalytic effect of micelles, polymers (such as DNA, polypeptides) and nanoparticles, saturable receptors (cyclodextrins and calixarenes) and more complex systems (mixing some of the above mentioned catalysts) have been reviewed. In these microheterogeneous systems the observed changes in the rate constants have been rationalized using the Pseudophase Model. This model produces equations that can be derived from the Brönsted equation, which is the basis for a more general formulation of catalytic effects, including electrocatalysis. When, in the catalyzed reaction one of the reactants is in the excited state, the applicability (at least formally) of the Pseudophase Model occurs only in two limiting situations: the lifetime of the fluorophore and the distributions of the quencher and the probe are the main properties that define the different situations.