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The effect of the adsorption of tetraethylammonium (TEA) cations, which present both ionic and organic characteristics, on the reduction of Cd(II) ions have been studied from dc and ac measurements at the dropping mercury electrode. The resistance to the charge transfer (Rct) and Warburg coefficient (σ) parameters have been determined through impedance measurements. Thus, the global velocity constant has been obtained. The reduction process of Cd(II) in perchloric media is reversible and is affected by the adsorption of TEA cations, especially at high TEA concentrations. Values of E1/2, half wave potential, and DO, diffusion coefficient, obtained from both dc and ac measurements agree. The velocity constants show a decrease as TEA concentration increases, with values ranging from 0.6 to 0.01 cm·s−1. The inhibitory effect of TEA adsorption on the electrode process and the relationship between electrode coverage, θ, and velocity constants, K, using several isotherm equations, have been discussed. The best fit was obtained with the equation K = 0K(1 − θ)a with an a value close to three, indicating a blocking effect and electrostatic repulsion due to TEA.
Juan Torrent-Burgués. Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process. Electrochem 2021, 2, 415 -426.
AMA StyleJuan Torrent-Burgués. Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process. Electrochem. 2021; 2 (3):415-426.
Chicago/Turabian StyleJuan Torrent-Burgués. 2021. "Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process." Electrochem 2, no. 3: 415-426.
We studied the behaviour of three lipid tear products, commercialised by the same brand, as Langmuir films at the air/liquid interface to simulate the ocular environment. No significant differences were observed in the surface behaviour of two of them disclosing the same composition, but commercialised for different applications. The interaction of several subphases, namely sodium chloride, glucose, albumin and lysozyme present in the natural tear, with the lipid films was assessed at room temperature and the temperature of human tear using surface pressure-area isotherms and elastic modulus plots. There is a notable influence of sodium chloride and the proteins albumin and lysozyme on the surface pressure-area isotherm of the lipid Langmuir films. Albumin shifted this isotherm to lower areas while an opposite shift was caused by lysozyme. These studies could be useful for the formulation of new lipid-containing artificial tears, and for increasing the confidence of the customers in commercial eye care formulations.
Juan Torrent-Burgués; Javier Hoyo; Tzanko Tzanov. Lipid artificial tears at a mimetic ocular interface. Chemistry and Physics of Lipids 2021, 238, 105087 .
AMA StyleJuan Torrent-Burgués, Javier Hoyo, Tzanko Tzanov. Lipid artificial tears at a mimetic ocular interface. Chemistry and Physics of Lipids. 2021; 238 ():105087.
Chicago/Turabian StyleJuan Torrent-Burgués; Javier Hoyo; Tzanko Tzanov. 2021. "Lipid artificial tears at a mimetic ocular interface." Chemistry and Physics of Lipids 238, no. : 105087.
The influence of four common cryoprotectants (dimethyl sulfoxide, glycerol, ethylene glycol and dimethylformamide) on monolayers of four common phospholipids (DPPC, DOPC, POPC and POPE) have been studied using Langmuir isotherms and monolayer insertion experiments. The cryoprotectant concentrations were chosen to be directly relevant to cryoprotection. We show that DMSO causes an expansion of the DPPC area per lipid (in contrast to previous work at higher concentrations). However, it caused compression for POPC, and had little effect for POPE or DOPC. As most previous studies have involved only DPPC, this highlights the importance of studying different lipid types as these may have a significant effect on the interactions. We show that both ethylene glycol and glycerol cause a small expansion of the monolayer at fixed pressure, implying that they insert into the headgroup regions, regardless of lipid species, and consistent with their ability to penetrate membranes. By contrast, dimethylformamide causes monolayer compression for all lipid species, implying it dehydrates the lipid head groups. Membrane insertion experiments at physiological values of lateral pressure highlight that DPPC is the most difficult lipid to penetrate, implying that the penetrating action of cryoprotectants may only occur for unsaturated phospholipids. Thus, extrapolations of results based solely on the DPPC need to be made with care.
Rekha Raju; Juan Torrent-Burgués; Gary Bryant. Interactions of cryoprotective agents with phospholipid membranes - A Langmuir monolayer study. Chemistry and Physics of Lipids 2020, 231, 104949 .
AMA StyleRekha Raju, Juan Torrent-Burgués, Gary Bryant. Interactions of cryoprotective agents with phospholipid membranes - A Langmuir monolayer study. Chemistry and Physics of Lipids. 2020; 231 ():104949.
Chicago/Turabian StyleRekha Raju; Juan Torrent-Burgués; Gary Bryant. 2020. "Interactions of cryoprotective agents with phospholipid membranes - A Langmuir monolayer study." Chemistry and Physics of Lipids 231, no. : 104949.
Novel antimicrobial agents are focused to interact with the bacterial membrane whose lipid composition (number and position of unsaturations and lipid headgroup) is adapted according to environmental signals. The anticipation of the adapted membrane properties is of high relevance to increase the targetability of such drugs. Herein, natural lipids extracted from Escherichia coli -phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL)- are used to form biomimetic membranes constituted by several PE:lipid ratios using the Langmuir and Langmuir-Blodgett techniques. The use of these techniques and the natural myriad of each lipid structures that constitute the biological E.coli membrane establishes a simple and reproducible model to evaluate the lipid-lipid interactions. PE and PG present similar shape and size, thus establish ideal and fluid -liquid expanded (LE) state - mixtures, whereas the differences between PE and CL motivate the formation of non-ideal and fluid (LE state) mixtures. The same physical state and the minor differences in elasticity (differences in the inverse of the compressibility modulus < 15 mN·m) between both systems regardless the PE content in the (PE:lipid) mixture suggest that the changes in the lipid composition influence the membrane proteins function rather than affecting the rigidity of the bacterial membrane.
Javier Hoyo; Juan Torrent-Burgués; Tzanko Tzanov. Physical states and thermodynamic properties of model gram-negative bacterial inner membranes. Chemistry and Physics of Lipids 2019, 218, 57 -64.
AMA StyleJavier Hoyo, Juan Torrent-Burgués, Tzanko Tzanov. Physical states and thermodynamic properties of model gram-negative bacterial inner membranes. Chemistry and Physics of Lipids. 2019; 218 ():57-64.
Chicago/Turabian StyleJavier Hoyo; Juan Torrent-Burgués; Tzanko Tzanov. 2019. "Physical states and thermodynamic properties of model gram-negative bacterial inner membranes." Chemistry and Physics of Lipids 218, no. : 57-64.
Mixed fatty acids or mixed phospholipids systems with saturated-unsaturated hydrocarbon chains are of biological interest. In this work, the monolayers of oleic acid-stearic acid (OA-SA) and palmitoyloleoylphosphatidylcholine-dipalmitoylphosphatidylcholine (POPC-DPPC) have been studied. From the surface pressure-area isotherms, elastic modulus values and virial equation coefficients can be obtained. Thermodynamic treatment also yields excess (GE) and mixing (ΔGmix) free energies. Results indicate positive GE values, that is, molecular interactions in the mixed films are less favourable, due to the presence of unsaturation; however, the mixture is slightly favourable due to the entropic factor that affords positive ΔGmix values. For the OA-SA system, a high SA content and surface pressure facilitate the phase separation, even though a certain miscibility between both components still remains. For the POPC-DPPC system, the most favourable mixing conditions occur for XPOPC ≈ 0.4. For these mixed systems, the values of the elastic modulus are more similar to those of more fluid components (OA or POPC); analysis of the virial coefficients shows that the b1 virial coefficient values lie between those of the individual components and are higher than values suitable for an ideal mixing.
Juan Torrent-Burgués. Thermodynamic Behaviour of Mixed Films of an Unsaturated and a Saturated Polar Lipid. (Oleic Acid-Stearic Acid and POPC-DPPC). Colloids and Interfaces 2018, 2, 17 .
AMA StyleJuan Torrent-Burgués. Thermodynamic Behaviour of Mixed Films of an Unsaturated and a Saturated Polar Lipid. (Oleic Acid-Stearic Acid and POPC-DPPC). Colloids and Interfaces. 2018; 2 (2):17.
Chicago/Turabian StyleJuan Torrent-Burgués. 2018. "Thermodynamic Behaviour of Mixed Films of an Unsaturated and a Saturated Polar Lipid. (Oleic Acid-Stearic Acid and POPC-DPPC)." Colloids and Interfaces 2, no. 2: 17.
As a new proposal, natural tears collected from the Schirmer strips were studied using surface pressure-area, π-A, isotherms obtained with the Langmuir technique. Parameters such as limit surface pressure, πlimit, elastic modulus at the maximum, CS−1max, and surface pressure at the maximum, πmax, were correlated with clinical tests, such as the Schirmer (SCH) and the tear film breakup-time (TFBUT) tests. The analysis from the chi-square test indicates dependence between the SCH test and the type of isotherms with a value of P < 0.05. A moderate Pearson correlation coefficient with statistical significance (P < 0.05) between the values of the SCH test and the πlimit was obtained. On the other hand, a low Pearson correlation coefficient with no statistical significance (P > 0.05) between the values of the TFBUT test and the πlimit was obtained. Additionally, considering only the isotherms classified as good, moderate Pearson correlation coefficients with statistical significance (P < 0.05) between the values of the TFBUT test and πlimit or πmax can be obtained. This study shows that the isotherms obtained with the Langmuir technique correlate well with the tear secretion, and when the later is moderate or good, the isotherm parameters afford information about the tear film stability and the behaviour of the tear lipids.
E. Guaus; J. Torrent-Burgués. The Langmuir Technique Applied to the Study of Natural Tears. BioNanoScience 2018, 8, 559 -565.
AMA StyleE. Guaus, J. Torrent-Burgués. The Langmuir Technique Applied to the Study of Natural Tears. BioNanoScience. 2018; 8 (2):559-565.
Chicago/Turabian StyleE. Guaus; J. Torrent-Burgués. 2018. "The Langmuir Technique Applied to the Study of Natural Tears." BioNanoScience 8, no. 2: 559-565.
Ester Guaus; J. Torrent-Burgués; J. Hoyo. Thylakoid Membrane Bioenergetics. Encyclopedia of Interfacial Chemistry 2018, 529 -536.
AMA StyleEster Guaus, J. Torrent-Burgués, J. Hoyo. Thylakoid Membrane Bioenergetics. Encyclopedia of Interfacial Chemistry. 2018; ():529-536.
Chicago/Turabian StyleEster Guaus; J. Torrent-Burgués; J. Hoyo. 2018. "Thylakoid Membrane Bioenergetics." Encyclopedia of Interfacial Chemistry , no. : 529-536.
In this work biomimetic monolayers of a MGDG, monogalactosyldiacylglycerol, and DGDG, digalactosyldiacylglycerol mixture (MD), in a ratio close to that of the thylakoid membranes of oxygenic photosynthetic organisms, have been prepared. The lipid mixture incorporates plastoquinone-9 (PQ), that is the electron and proton shuttle of the photosynthetic reaction centres. The MD:PQ mixtures have been firstly studied using surface pressure-area isotherms. Langmuir-Blodgett (LB) films of those mixtures have been transferred onto a substrate forming a monolayer that mimics one of the bilayer side of the thylakoid membranes. These monolayers have been characterized topographically and electrochemically. The results show the influence of PQ in the MD matrix and its partial expulsion when increasing the surface pressure, obtaining two main PQ positions in the MD matrix. The calculated apparent electron transfer rate constants indicate a different kinetic control for the reduction and the oxidation of the PQ/PQH2 couple, being kRapp(I)= 0.7·10-6 s-1, kRapp(II)= 2.2·10-9 s-1, kOapp(I)= 7.4·10-4 s-1 and kOapp(II)= 5.2·10-5 s-1, respectively. The comparison of the different galactolipid:PQ systems that our group have studied is also presented, concluding that the PQ position in the galactolipid matrix can be tuned according to several controlled variables.
Javier Hoyo; Ester Guaus; Juan Torrent-Burgués. Influence of membrane galactolipids and surface pressure on plastoquinone behaviour. Bioelectrochemistry 2016, 111, 123 -130.
AMA StyleJavier Hoyo, Ester Guaus, Juan Torrent-Burgués. Influence of membrane galactolipids and surface pressure on plastoquinone behaviour. Bioelectrochemistry. 2016; 111 ():123-130.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Juan Torrent-Burgués. 2016. "Influence of membrane galactolipids and surface pressure on plastoquinone behaviour." Bioelectrochemistry 111, no. : 123-130.
The transformation of penicillin G into nano/micro-sized spheres (nanopenicillin) using sonochemical technology was explored as a novel tool for the eradication of Gram-negative bacteria and their biofilms. Known by its effectiveness only against Gram-positive microorganisms, the penicillin G spherization boosted the inhibition of the Gram-negative Pseudomonas aeruginosa 10-fold (from 0.3 to 3.0 log-reduction) and additionally induced 1.2 log-reduction of Escherichia coli growth. The efficient penetration of the spheres within a Langmuir monolayer sustained the theory that nanopenicillin is able to cross the membrane and reach the periplasmic space in Gram-negative bacteria where they inhibit the β-lactam targets: the transferases that build the bacteria cell wall. Moreover, it considerably suppressed the growth of both bacterial biofilms on a medically relevant polystyrene surface, leaving majority of the adhered cells dead compared to the treatment with the non-processed penicillin G. Importantly, nanopenicillin was found innocuous towards human fibroblasts at the antibacterial-effective concentrations.
Margarida Fernandes; Kristina Ivanova; Antonio Francesko; Diana Rivera; Juan Torrent-Burgués; Aharon Gedanken; Ernest Mendonza; Tzanko Tzanov. Escherichia coli and Pseudomonas aeruginosa eradication by nano-penicillin G. Nanomedicine: Nanotechnology, Biology and Medicine 2016, 12, 2061 -2069.
AMA StyleMargarida Fernandes, Kristina Ivanova, Antonio Francesko, Diana Rivera, Juan Torrent-Burgués, Aharon Gedanken, Ernest Mendonza, Tzanko Tzanov. Escherichia coli and Pseudomonas aeruginosa eradication by nano-penicillin G. Nanomedicine: Nanotechnology, Biology and Medicine. 2016; 12 (7):2061-2069.
Chicago/Turabian StyleMargarida Fernandes; Kristina Ivanova; Antonio Francesko; Diana Rivera; Juan Torrent-Burgués; Aharon Gedanken; Ernest Mendonza; Tzanko Tzanov. 2016. "Escherichia coli and Pseudomonas aeruginosa eradication by nano-penicillin G." Nanomedicine: Nanotechnology, Biology and Medicine 12, no. 7: 2061-2069.
Lipid-containing artificial tears are a type of artificial tears that use lipid components in order to restore the lipid layer of the tear film. One of these components is lecithin which can be applied in spray solutions containing lecithin liposomes. In this work the behavior of three of these commercial tears based on lecithin, Innoxa, Opticalm and Optrex, are studied using the Langmuir technique. The obtained isotherms are presented, discussed and compared. This technique seems useful in order to see the film behavior of the lipid components of these tears and determine some important parameters such as fluidity and extension at the air-water interface, and allows us to discern differences between these commercial tears. Innoxa and Optrex tears are more similar to each other than to Opticalm tears. Opticalm presents more fluidity, probably due to the presence of more insaturations in the fatty acid chains of the phospholipids of the lecithin used in fabrication.
Juan Torrent-Burgués. Langmuir films study on lipid-containing artificial tears. Colloids and Surfaces B: Biointerfaces 2016, 140, 185 -188.
AMA StyleJuan Torrent-Burgués. Langmuir films study on lipid-containing artificial tears. Colloids and Surfaces B: Biointerfaces. 2016; 140 ():185-188.
Chicago/Turabian StyleJuan Torrent-Burgués. 2016. "Langmuir films study on lipid-containing artificial tears." Colloids and Surfaces B: Biointerfaces 140, no. : 185-188.
The relevance of biomimetic membranes using galactolipids has not been expressed in any extensive experimental study of these lipids. Thus, on the one hand, we present an in-depth article about the presence and role of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) in thylakoid membranes, their physical states and their applications. On the other hand, we use the Langmuir and Langmuir-Blodgett (LB) techniques to prepare biomimetic monolayers of saturated galactolipids MGDG, DGDG and MGDG:DGDG 2:1 mixture (MD)--biological ratio--. These monolayers are studied using surface pressure-area isotherms and their data are processed to enlighten their physical states and mixing behaviour. These monolayers, once transferred to a solid substrate at several surface pressures are topographically studied on mica using atomic force microscopy (AFM) and using cyclic voltammetry for studying the electrochemical behaviour of the monolayers once transferred to indium-tin oxide (ITO), which has good optical and electrical properties. Moreover, MD presents other differences in comparison with its pure components that are explained by the presence of different kinds of galactosyl headgroups that restrict the optimal orientation of the MGDG headgroups.
Javier Hoyo; Ester Guaus; Juan Torrent-Burgués. Monogalactosyldiacylglycerol and digalactosyldiacylglycerol role, physical states, applications and biomimetic monolayer films. The European Physical Journal E 2016, 39, 1 .
AMA StyleJavier Hoyo, Ester Guaus, Juan Torrent-Burgués. Monogalactosyldiacylglycerol and digalactosyldiacylglycerol role, physical states, applications and biomimetic monolayer films. The European Physical Journal E. 2016; 39 (3):1.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Juan Torrent-Burgués. 2016. "Monogalactosyldiacylglycerol and digalactosyldiacylglycerol role, physical states, applications and biomimetic monolayer films." The European Physical Journal E 39, no. 3: 1.
The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being k(Rapp)(I) = 2.2 · 10(-5) s(-1), k(Rapp)(II) = 5.1 · 10(-14) k(Oapp)(I) = 3.3 · 10(-3) s(-1) and k(Oapp)(II) = 6.1 · 10(-6) s(-1), respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.
Javier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. Electrochemistry of LB films of mixed MGDG:UQ on ITO. Bioelectrochemistry 2015, 104, 26 -34.
AMA StyleJavier Hoyo, Ester Guaus, Juan Torrent-Burgués, Fausto Sanz. Electrochemistry of LB films of mixed MGDG:UQ on ITO. Bioelectrochemistry. 2015; 104 ():26-34.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. 2015. "Electrochemistry of LB films of mixed MGDG:UQ on ITO." Bioelectrochemistry 104, no. : 26-34.
The photosynthesis is the process used by plants and bacteria cells to convert inorganic matter in organic thanks to the light energy. This process consist on several steps, being one of them the electronic transport from the photosystem II to the cytochrome thanks to plastoquinone-9 (PQ). Here we prepare membranes that mimic the characteristics and composition of natural photosynthetic cell membranes and we characterize them in order to obtain the PQ molecules position in the membrane and their electrochemical behaviour. The selected galactolipid is digalactosyldiacylglycerol (DGDG) that represents the 30% of the thylakoid membrane lipid content. The results obtained are worthful for several science fields due to the relevance of galactolipids as anti-algal, anti-viral, anti-tumor and anti-inflammatory agents and the antioxidant and free radical scavenger properties of prenylquinones. Both pure components (DGDG and PQ) and the DGDG:PQ mixtures have been studied using surface pressure-area isotherms. These isotherms give information about the film stability and indicate the thermodynamic behaviour of the mixture and their physical state. The Langmuir-Blodgett (LB) film has been transferred forming a monolayer that mimics the bottom layer of the biological membranes. This monolayer on mica has been topographically characterized using AFM and both the height and the physical state that they present have been obtained. Moreover, these monolayers have been transferred onto ITO that is a hydrophilic substrate with good optical and electrical features, so that, it is suitable for studying the electrochemical behaviour of these systems and it is a good candidate for energy producing devices.
Javier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone. Biochimica et Biophysica Acta (BBA) - Biomembranes 2015, 1848, 1341 -1351.
AMA StyleJavier Hoyo, Ester Guaus, Juan Torrent-Burgués, Fausto Sanz. Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone. Biochimica et Biophysica Acta (BBA) - Biomembranes. 2015; 1848 (6):1341-1351.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. 2015. "Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone." Biochimica et Biophysica Acta (BBA) - Biomembranes 1848, no. 6: 1341-1351.
Photosynthetic organisms use light to convert the inorganic matter in organic one. Photosynthetic process consists on several steps, and one of them involves plastoquinone (PQ) that acts as electron and proton shuttle between photosystem II and cytochrome. We prepared membranes that mimic the characteristics and composition of natural photosynthetic membranes and we characterized them using several techniques in order to obtain both the PQ molecules disposition in the membrane and their electrochemical behavior. The selected lipid was monogalactosyldiacylglycerol (MGDG) that represents the 50% of the lipid content of the thylakoid membrane. Both MGDG and PQ, and the MGDG:PQ mixtures have been studied using surface pressure–area isotherms and the presence of PQ alters the physical state and compactness of the MGDG matrix. Langmuir–Blodgett (LB) films have been obtained by transferring a monolayer that mimics half of the bilayer of a biological membrane. The AFM topographical characterization of the monolayers on mica indicates the presence of differentiated domains, corresponding to different physical states linked to the influence of the PQ content. Moreover, the electrochemical behavior of the monolayers has been studied when transferred on ITO, observing one main electrochemical process that is due to the diving position of PQ molecules in the lipid matrix.
Javier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. Biomimetic Monolayer Films of Monogalactosyldiacylglycerol Incorporating Plastoquinone. The Journal of Physical Chemistry B 2015, 119, 6170 -6178.
AMA StyleJavier Hoyo, Ester Guaus, Juan Torrent-Burgués, Fausto Sanz. Biomimetic Monolayer Films of Monogalactosyldiacylglycerol Incorporating Plastoquinone. The Journal of Physical Chemistry B. 2015; 119 (20):6170-6178.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Juan Torrent-Burgués; Fausto Sanz. 2015. "Biomimetic Monolayer Films of Monogalactosyldiacylglycerol Incorporating Plastoquinone." The Journal of Physical Chemistry B 119, no. 20: 6170-6178.
The objective of this work is to apply Atomic Force Microscopy in Peak Force mode to obtain topographic characteristics (mean roughness, root-mean-square roughness, skewness and kurtosis) and mechanical characteristics (adhesion, elastic modulus) of Siloxane-Hydrogel Soft Contact Lenses (CLs) of two different materials, Lotrafilcon B of Air Optix (AO) and Asmofilcon A of PremiO (P), after use (worn CLs). Thus, the results obtained with both materials will be compared, as well as the changes produced by the wear at a nanoscopic level. The results show significant changes in the topographic and mechanical characteristics of the CLs, at a nanoscopic level, due to wear. The AO CL show values of the topographic parameters lower than those of the P CL after wear, which correlates with a better comfort qualification given to the former by the wearers. A significant correlation has also been obtained between the adhesion values found after the use of the CLs with tear quality tests, both break-up-time and Schirmer.
Clara Abadías; Carme Serés; Juan Torrent-Burgués. AFM in peak force mode applied to worn siloxane-hydrogel contact lenses. Colloids and Surfaces B: Biointerfaces 2015, 128, 61 -66.
AMA StyleClara Abadías, Carme Serés, Juan Torrent-Burgués. AFM in peak force mode applied to worn siloxane-hydrogel contact lenses. Colloids and Surfaces B: Biointerfaces. 2015; 128 ():61-66.
Chicago/Turabian StyleClara Abadías; Carme Serés; Juan Torrent-Burgués. 2015. "AFM in peak force mode applied to worn siloxane-hydrogel contact lenses." Colloids and Surfaces B: Biointerfaces 128, no. : 61-66.
Contact lenses (CLs) are of common use and the biocompatibility, topography and mechanical properties of the used materials are of major importance. The objective of this contribution is to apply the AFM in mode Peak Force to obtain surface topography and mechanical characteristics of un-worn CLs of different materials. One material of hydrogel, two of siloxane-hydrogel and one of rigid gas-permeable were used in the study. The results obtained with different materials have been compared, at a nanoscopic level, and the conclusions are diverse. There is no significant influence of the two environments used to measure the characteristics of the CLs, either water or saline solution. The pHEMA hydrogel CL (Polymacon of Soflens) shows the highest values of roughness, adhesion and elastic modulus. The siloxane-hydrogel CL named Asmofilcon A of PremiO presents the lowest values of mean roughness (Ra), root-mean-square roughness (RMS or Rq), adhesion (Adh) and elastic modulus (Ym), meanwhile the siloxane-hydrogel CL named Lotrafilcon B of Air Optix presents the lowest value of skewness (Rsk) and the rigid gas-permeable CL, named RXD, presents the lowest values of kurtosis (Rku) and maximum roughness (Rmax).
Juan Torrent-Burgués; F. Sanz. AFM in mode Peak Force applied to the study of un-worn contact lenses. Colloids and Surfaces B: Biointerfaces 2014, 121, 388 -394.
AMA StyleJuan Torrent-Burgués, F. Sanz. AFM in mode Peak Force applied to the study of un-worn contact lenses. Colloids and Surfaces B: Biointerfaces. 2014; 121 ():388-394.
Chicago/Turabian StyleJuan Torrent-Burgués; F. Sanz. 2014. "AFM in mode Peak Force applied to the study of un-worn contact lenses." Colloids and Surfaces B: Biointerfaces 121, no. : 388-394.
In this work we report the fabrication of Langmuir and Langmuir-Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl) phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (pi-A) and surface potential (Delta V-A) isotherms as well as UV-vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air-water interface together with UV-vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The pi-A and Delta V-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9mN/m and a multilayer formation at surface pressures around 19-20 mN/ m; at a surface pressure around 27 mN/ m a disordered collapse of the film occurs. In addition, AFM images of LB films at p= 10mN/ mand p= 20 mN/ m show a monomolecular and a multilayered film, respectively. The comparison of the UV-vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV-vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the randomdistribution in solution. The UV-vis Reflection spectra are also consistentwith multilayer formation at surface pressures around 19-20 mN/ m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB filmwhich is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular organizations. (C) 2014 Elsevier B. V. All rights reserved.Postprint (published version
J. Torrent-Burgués; P. Cea; I. Giner; E. Guaus. Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine. Thin Solid Films 2014, 556, 485 -494.
AMA StyleJ. Torrent-Burgués, P. Cea, I. Giner, E. Guaus. Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine. Thin Solid Films. 2014; 556 ():485-494.
Chicago/Turabian StyleJ. Torrent-Burgués; P. Cea; I. Giner; E. Guaus. 2014. "Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine." Thin Solid Films 556, no. : 485-494.
Bacterial-mediated diseases are a major healthcare concern worldwide due to the rapid spread of antibiotic-resistant bacteria. One strategy to manage the bacterial infections while avoiding the emergence of resistant strains implies specific targeting and disruption of bacteria membranes. This work evaluates the potential of nanostructured biopolymer derivatives, nanocapsules (NCs), to disrupt the bacteria cell walls and effectively kill planktonic microorganisms. Two biopolymers, chitosan and cellulose, were chemically modified to synthesize derivatives with improved cationic character (thiolated chitosan and aminocellulose) prior to their processing into nanocapsules via a one-step sonochemical process. The interactions of NCs, displaying an average size of around 250 nm, with bacteria membrane were evaluated using two membrane models: Langmuir monolayers and liposome bilayers composed of a l-α-phosphatidylglycerol phospholipid extracted from Escherichia coli. NCs possessed improved membrane disturbing capacity in comparison to the nonprocessed biopolymer derivatives, by drastically increasing the monolayer fluidity and inducing more than 50% leakage of a dye inserted in the bilayered liposomes. In addition, membrane disturbance was directly proportional to the NCs cationic charge. Whereas evidence showed that thiolated chitosan and aminocellulose interacted with the bacteria membrane through a “carpet model”, the NCs were found to induce larger surface defects and high local perturbance through a “detergent model”. Importantly, the degree of disruption caused by the biopolymer derivatives and NCs correlated well with the antimicrobial capacity against Escherichia coli, selectively killing bacteria cells without imparting toxicity to human fibroblasts.
Margarida M. Fernandes; Antonio Francesko; Juan Torrent-Burgués; F. Javier Carrión-Fité; Thomas Heinze; Tzanko Tzanov. Sonochemically Processed Cationic Nanocapsules: Efficient Antimicrobials with Membrane Disturbing Capacity. Biomacromolecules 2014, 15, 1365 -1374.
AMA StyleMargarida M. Fernandes, Antonio Francesko, Juan Torrent-Burgués, F. Javier Carrión-Fité, Thomas Heinze, Tzanko Tzanov. Sonochemically Processed Cationic Nanocapsules: Efficient Antimicrobials with Membrane Disturbing Capacity. Biomacromolecules. 2014; 15 (4):1365-1374.
Chicago/Turabian StyleMargarida M. Fernandes; Antonio Francesko; Juan Torrent-Burgués; F. Javier Carrión-Fité; Thomas Heinze; Tzanko Tzanov. 2014. "Sonochemically Processed Cationic Nanocapsules: Efficient Antimicrobials with Membrane Disturbing Capacity." Biomacromolecules 15, no. 4: 1365-1374.
The antibacterial activity of chitosan modified with the thiol-containing 2-iminothiolane HCl (TC-IMI) and N-acetyl-l-cysteine (TC-NAC) was studied by Langmuir film balance technique using a dipalmitoylphosphatidylglycerol (DPPG) monolayer bacterial membrane model. The interactions of the biopolymer with the membrane model were assessed by monitoring the differences in the shape of the compression isotherms recorded in the absence and presence of chitosan and thiolated conjugates in the subphase. A low molecular weight chitosan (15 kDa) shifted the compression isotherms of DPPG monolayers towards larger areas (A 0,CS = 145 Å2), confirming its membrane disturbance capacity. Further thiolation induced higher yield of expansion, more pronounced in the case of TC-IMI. The expansion of the monolayer increased significantly (A 0,TC-NAC = 150 Å2 vs A 0,TC-IMI = 175 Å2) and the elasticity at a surface pressure of 30 mN/m, typical for bio-membranes decreased to a greater extent Cs,30TC-NAC-1 = 120 mN/m vs Cs,30TC-IMI-1 = 87 mN/m) in presence of TC-IMI. Antibacterial tests against a Gram-negative Escherichia coli and a Gram-positive Staphylococcus aureus were in good agreement with these findings, suggesting that chitosan thiolated with 2-iminothiolane HCl acts as a bactericide disrupting the integrity of the bacterial cell membrane.
Margarida Fernandes; Antonio Francesko; Juan Torrent-Burgués; Tzanko Tzanov. Effect of thiol-functionalisation on chitosan antibacterial activity: Interaction with a bacterial membrane model. Reactive and Functional Polymers 2013, 73, 1384 -1390.
AMA StyleMargarida Fernandes, Antonio Francesko, Juan Torrent-Burgués, Tzanko Tzanov. Effect of thiol-functionalisation on chitosan antibacterial activity: Interaction with a bacterial membrane model. Reactive and Functional Polymers. 2013; 73 (10):1384-1390.
Chicago/Turabian StyleMargarida Fernandes; Antonio Francesko; Juan Torrent-Burgués; Tzanko Tzanov. 2013. "Effect of thiol-functionalisation on chitosan antibacterial activity: Interaction with a bacterial membrane model." Reactive and Functional Polymers 73, no. 10: 1384-1390.
Ubiquinone (UQ) is one of the main electron and proton shuttle molecules in biological systems, and dipalmitoylphosphatidylcholine (DPPC) is one of the most used model lipids. Supported planar bilayers (SPBs) are extensively accepted as biological model membranes. In this study, SPBs have been deposited on ITO, which is a semiconductor with good electrical and optical features. Specifically, topographic atomic force microscopy (AFM) images and force curves have been performed on SPBs with several DPPC:UQ ratios to study the location and the interaction of UQ in the SPB. Additionally, cyclic voltammetry has been used to understand the electrochemical behavior of DPPC:UQ SPBs. Obtained results show that, in our case, UQ is placed in two main different positions in SPBs. First, between the DPPC hydrophobic chains, fact that originates a decrease in the breakthrough force of the bilayer, and the second between the two leaflets that form the SPBs. This second position occurs when increasing the UQ content, fact that eventually forms UQ aggregates at high concentrations. The formation of aggregates produces an expansion of the SPB average height and a bimodal distribution of the breakthrough force. The voltammetric response of UQ depends on its position on the bilayer.
Javier Hoyo; Ester Guaus; Gerard Oncins; Juan Torrent-Burgués; Fausto Sanz. Incorporation of Ubiquinone in Supported Lipid Bilayers on ITO. The Journal of Physical Chemistry B 2013, 117, 7498 -7506.
AMA StyleJavier Hoyo, Ester Guaus, Gerard Oncins, Juan Torrent-Burgués, Fausto Sanz. Incorporation of Ubiquinone in Supported Lipid Bilayers on ITO. The Journal of Physical Chemistry B. 2013; 117 (25):7498-7506.
Chicago/Turabian StyleJavier Hoyo; Ester Guaus; Gerard Oncins; Juan Torrent-Burgués; Fausto Sanz. 2013. "Incorporation of Ubiquinone in Supported Lipid Bilayers on ITO." The Journal of Physical Chemistry B 117, no. 25: 7498-7506.