Review on bibliography related to antimicrobials

In this report, a bibliographic research has been done in the field of antimicrobials.In this report, a bibliographic research has been done in the field of antimicrobials. Not all antimicrobials have been included, but those that are being subject of matter in the group GBMI in Terrassa, and others of interest. It includes chitosan and other biopolymers. The effect of nanoparticles is of great interest, and in this sense, the effect of Ag nanoparticles and antibiotic nanoparticles (nanobiotics) has been revised. The report focuses on new publications and the antimicrobial effect of peptides has been considered. In particular, the influence of antimicrobials on membranes has deserved much attention and its study using the Langmuir technique, which is of great utility on biomimetic studies. The building up of antimicrobials systems with new techniques (bottom-up approach), as the Layer-by-Layer technique, can also be found in between the bibliography. It has also been considered the antibiofilm effect, and the new ideas on quorem sensing and quorum quenching.Preprin

Langmuir and Langmuir-Blodgett films revisited

A review on Langmuir and Langmuir-Blodgett filmsThe Langmuir and Langmuir-Blodgett (LB) technique has been applied for a long time. It exist several books and reviews on the subject. Also, a big number of works and papers have been made. This work only intends to afford a revision of the subject under the point of view of the author, and centered mostly in new references.Preprin

Thermodynamic behaviour of mixed films of an unsaturated and a saturated polar lipid : (Oleic Acid-Stearic Acid and POPC-DPPC)

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 (DGmix) 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 DGmix 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.Peer ReviewedPostprint (published version

Oleamide and oleamide-lipid mixed monolayers

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Tear film constituents and medicines for eyes investigated as Langmuir films

The tear flm has an important role on the quality of the vision process and is of importance in the felds of ophthalmology and optometry. The lipid layer, the outermost part of the tear flm, can be investigated with the Langmuir technique, as well as the interaction of components of the aqueous part of the tear flm with those of the lipid layer. Dysfunctions in the stability and composition of the tear flm are the causes of eye diseases, as the dry eye syndrome. For the treatment of this disease, the artifcial tears are used, and one type of them are the lipid tears, which can be investigated with the Langmuir technique. This technique can also be used to investigate the infuence on the lipid layer of other artifcial tear components or medicines instilled in the eye. This review presents investigations where the Langmuir technique has been used in relation with the tear flm. In particular, the surface properties of natural tears and of four commercial lipid-containing artifcial tears have been reported and discussed in connection with their composition.Peer ReviewedPostprint (published version

Lysozyme influence on monolayers of individual and mixed lipids

Fatty acids, cholesterol, and phospholipids are amphiphilic compounds of biological interest, which form ordered monolayers mimicking biomembranes, and can be studied with the Langmuir technique using surface pressure-area isotherms and compressibility plots. Proteins are also components of biomembranes or are present in body fluids. In this study, the influence of lysozyme on different films of a fatty acid (stearic acid or oleic acid), cholesterol, a phospholipid (dipalmitoylphosphatidylcholine, DPPC, or palmitoyloleoylphosphatidylcholine, POPC), and mixtures of them is presented using a 0.9% saline solution as subphase. Results show that the presence of lysozyme alters the lipid monolayer formation in an important way at the beginning (low surface pressures) and the middle (intermediate surface pressures) parts of the isotherm. At high surface pressures, the phospholipids DPPC and POPC and the saturated fatty acid, stearic acid, expel lysozyme from the surface, while oleic acid and cholesterol permit the presence of lysozyme on it. The mixtures of oleic acid-DPPC also expel lysozyme from the surface at high surface pressures, while mixtures of oleic acid-POPC and cholesterol-POPC permit the presence of lysozyme on it. The compressibility of the monolayer is affected in all cases, with an important reduction in the elastic modulus values and an increase in the fluidity, especially at low and intermediate surface pressuresPeer ReviewedPostprint (published version

Effect of lysozyme subphase and insertion on several lipid films

The influence of proteins on lipid monolayers is a subject of biological interest. In this work the influence of lysozyme on lipid films of stearic acid, oleic acid, cholesterol, DPPC and POPC has been studied. The Langmuir monolayer technique, using surface pressure-area isotherms and elastic modulus plots, as well as protein insertion experiments in lipid monolayers, have been used. Results indicate that lysozyme affects the lipid monolayer formation, the elastic modulus and, sometimes, the physical state of the monolayer. This influence is more important till moderate surface pressures. At high surface pressures and near the physiological value of lateral pressure of 33 mN/m, there is expulsion of lysozyme out of the monolayer. This expulsion is more important for stearic acid, DPPC and POPC. The lower value of maximum insertion pressure is for stearic acid and the higher one is for oleic acid. The relation between the initial and the increased surface pressure in insertion experiments has been analysedPeer ReviewedPostprint (published version

Tuning ubiquinone position in biomimetic monolayer membranes

Artificial lipid bilayers have been extensively studied as models that mimic natural membranes (biomimetic membranes). Several attempts of biomimetic membranes inserting ubiquinone (UQ) have been performed to enlighten which the position of UQ in the lipid layer is, although obtaining contradictory results. In this work, pure components (DPPC and UQ) and DPPC:UQ mixtures have been studied using surface pressure-area isotherms and Langmuir-Blodgett (LB) films of the same compounds have been transferred onto solid substrates being topographically characterized on mica using atomic force microscopy and electrochemically on indium tin oxide slides. DPPC:UQ mixtures present less solid-like physical state than pure DPPC indicating a higher-order degree for the latter. UQ influences considerably DPPC during the fluid state, but it is mainly expelled after the phase transition at ˜˜ 26 mN·m^-1 for the 5:1 ratio and at ˜˜ 21 mN·m^-1 for lower UQ content. The thermodynamic studies confirm the stability of the DPPC:UQ mixtures before that event, although presenting a non-ideal behaviour. The results indicate that UQ position can be tuned by means of the surface pressure applied to obtain LB films and the UQ initial content. The UQ positions in the biomimetic membrane are distinguished by their formal potential: UQ located in “diving” position with the UQ placed in the DPPC matrix in direct contact with the electrode surface ( -0.04±0.02 V), inserted between lipid chains without contact to the substrate ( 0.00±0.01 V) and parallel to the substrate, above the lipid chains ( 0.09±0.02 V).Peer ReviewedPostprint (author's final draft

Studies on lipid artificial tears

Report-review sobre llàgrima artificial, llàgrima lipídica.The use of artificial tears is related with dry eye problems or ocular irritations. It exist different types of artificial tears. One type of them is the lipid artificial tears which tray to repair or improve the lipid layer present in the outermostpart of the tear film. Several lipid artificial tears are present in the market and commercialised by several companies. In the composition of some of these lipid tears occurs as a principal item a phospholipid component that is lecithin of soya, which is composed mainly by phospholipids as phosphocholine or also named phosphatidylcholine (PC). The film formation on the water/air interface (Langmuir film technique) has been applied to study the behaviour of Meibomian lipids. The Langmuir technique has been applied previously by the author to study the behaviour of lipid and phospholipid films. In this work Langmuir films have been performed from lipid artificial tears and the corresponding surface pressure-area isotherms registered. Three commercial lipid artificial tears, and presented in dispensers for spray applications, have been used, INNOXA, OPTICALM and OPTREX.Preprin

Detección de películas nanométricas por microscopia de ángulo de Brewster

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