M. Masson

Orientation of anthracyclines in lipid monolayers and planar asymmetrical bilayers: a surface-enhanced resonance Raman scattering study.

The interaction of anthracyclines (daunorubicin and idarubicin) with monolayers of zwitterionic palmitoyloleoylphosphatidylcholine (POPC) and anionic dipalmitoylphosphatidic acid (POPC-DPPA 80-20 mol%) was studied by surface pressure measurements and compared with previous results obtained with other anthracyclines (pirarubicin and adriamycin). These anthracycline/phospholipid monolayers were next transferred by a Langmuir-Blodgett technique onto planar supports and studied by surface-enhanced resonance Raman scattering (SERRS), which gave information about the orientation of anthracycline in the monolayers. On the whole, the adsorption of anthracyclines in zwitterionic monolayers increases with the anthracycline hydrophobic/hydrophilic balance, which underlines the role of the hydrophobic component of the interaction. On the contrary, the anthracyclines remain adsorbed on the polar headgroups of the phospholipids in the presence of DPPA and form a screen that limits a deeper penetration of other anthracycline molecules. To study by SERRS measurements the crossing of pirarubicin through a phospholipid bilayer used as a membrane model, asymmetrical POPC-DPPA/POPC or POPC/POPC-DPPA bilayers were transferred by the Langmuir-Schäfer method, thanks to a laboratory-built set-up, and put in contact with a pirarubicin aqueous solution. It has been shown that the presence of anionic DPPA in the first monolayer in contact with pirarubicin would limit its crossing. This limiting effet is not observed if the first monolayer is zwitterionic.

Surface-enhanced Raman scattering studies of lipid planar bilayers in water

Abstract A set-up enabling the recording of surface-enhanced Raman scattering (SERS) of phospholipid bilayers in contact with water is reported. Monolayers or bilayers of dimyristoyl-phosphatidylcholine (DMPC), palmitoyl-oleoyl-phosphatidylcholine (POPC) or palmitoyl-oleoyl-phosphatidylethanolamine (POPE) and cholesterol were transferred by the Langmuir-Blodgett technique onto a high index rutile prism on which a silver coating (15 nm thick) had been deposited. The bilayers were enclosed in a water-tight box. The prism is illuminated with a laser beam under an angle greater than the limiting reflection angle. SERS spectra of monolayer or bilayer films were compared with the Raman spectrum of anhydrous molecules. An enhancement in the relative intensity of bands corresponding to the vibrations of the polar head group was observed. In the 2750–3050 cm −1 region the monolayer spectra of POPC and DMPC were different from those of the bilayers; this difference was assigned to the mobility of the choline CH 3 groups, near the silver coating. No differences appear between SERS spectra of POPC-cholesterol bilayers and those of pure POPC bilayers.

Polarized Raman spectra of thin films. III. Conformational analysis of Langmuir–Blodgett multilayers (1 to 49) of barium stearate

Polarized Raman spectra of Langmuir–Blodgett multilayers of barium stearate have been studied in the 2800–3000 cm−1 region (C–H stretching vibrations). The samples have been excited by evanescent waves produced by the plasmon illumination method. Only TM excitation can be used for very thin films. Therefore the polarized Raman spectra are complex, but, due to the smallness of some nondiagonal terms of the Raman tensor, these spectra are similar to the pure polarized spectra given by the TE excitation. When the film thickness decreases from 122.5 to 22.5 nm, the spectra are only slightly modified. The study of the ν(C–C) lines in the 1000–1200 cm−1 region have shown that the chains are still all‐trans plane. With ultrathin films (<20 nm) changes are observed in the shape and in the polarization of the 2800–3000 cm−1 band. The first modification (appearance and disappearance of shoulders or peaks) is attributed to conformational change of the acyl chains. The second modification (unpolarization) is related ...

Orientational analysis of pelargonic acid at liquid–solid interfaces, drops, and ultrathin liquid films, by polarized Raman spectroscopy

Polarized Raman spectra of pelargonic acid (PA), CH3–(CH2)7–CO2H, at liquid–solid interfaces were recorded, using the excitation of the surface plasmon of silver. In this device, the exciting electric field decreases exponentially (or quasi‐exponentially) into the sample. Therefore, the molecules in the vicinity of the solid surface are preferentially illuminated. This study was performed on two types of systems: 1°—One interface: a drop of PA is deposited on a solid surface [silver, silica, cetyltrimethylammonium bromide (CTAB), or Langmuir–Blodgett (LB) layers of barium stearate]; 2°—two interfaces: liquid ultrathin films of PA are placed between silica or barium stearate LB layers; the thickness of the film (250 to 5 nm) being measured by an interferential method. The shape of the 2800–3000 cm−1 band, which is very sensitive to the chain conformation, was studied. Since in the convenient polarization, the spectra of the drops were different from the spectrum of the isotropic liquid (classical cell), we...

Surface Enhanced Raman Scattering and Surface Pressure Studies of the Interaction of Pirarubicin With Phospholipids Planar Bilayers in Water

Anthracycline antibiotics are frequently used in chemotherapy. However a problem of drug resistance appears during treatment. One way to overcome the resistance is to increase the penetration of the antibiotic into the cell. Therefore it is necessary to understand the type of interaction between antibiotics and membranes [1]. Here we studied the interaction of pirarubicin (pira.), (fig 1), with supported Palmitoyl-Oleoyl-Phosphatidylcholine (POPC) monolayers and bilayers by a spectroscopic method: Surface Enhanced Raman Scattering (S.E.R.S.). A preliminary Surface Pressure study was done in various conditions to estimate the percentage of pira. incorporated in POPC monolayers. The resulting monolayers or bilayers were transferred by the Langmuir-Blodgett technique onto a high index prism on which a silver coating (15 nm thick) had been deposited (S.E.R.S. effect), [2].

The passive diffusion of anthracyclines through lipid Langmuir-Blodgett bilayers studied by Surface Enhanced Raman Spectroscopy (SERS)

Anthracyclines are antibiotics used in chemotherapy. After the crossing of the cellular membranes by passive diffusion, these molecules are able to interact with various cellular targets such as DNA [1]. One of the most important problems during the treatment is the appearance of cells which are resistant to the drug (multidrug resistance, MDR). This resistance is related to a membrane protein which expells the drug out of the cells, reducing its intracellular rate, and thus its efficiency [2]. A possible solution to overcome this problem is to find anthracyclines able to cross the membrane more quickly. This solution implies the understanding of the anthracycline-membrane interactions. We report here the results of a study concerning the interaction of four positively charged anthracyclines presenting an increasing hydrophobic/hydrophilic balance (adriamycin< pirarubicin<daunorubicin<idarubicin) with phospholipid planar monolayers and bilayers (used as simplified membrane models) by Surface Pressure measurements (Langmuir trough) and surface-enhanced resonant Raman spectroscopy (SERRS). The Surface Pressure measurements enabled us to estimate the percentages of anthracyclines kept at the interface after their adsorption into a phospholipid monolayer. SER(R)S gave us information about the orientation of the anthracyclines in lipid planar monolayers tranferred onto supports by a Langmuir-Blodgett technique [3–5]. These results enabled us in a second step to study by SERRS the passive diffusion of pirarubicin through symmetrical and asymmetrical phospholipid bilayers [5].

Sers and Fluorescence Studies of the Interaction of Exogenous Molecules with Phospholipid Planar Bilayers Used as a Simplified Membrane Model

Pirarubicin is an anthracycline used in chemotherapy. A major problem appearing during treatments is the resistance of the cells to the anthracycline toxicity owing to a membrane protein, which expels the drug out of the cell. A possible solution is to increase the amount and the speed of penetration of this kind of molecule into the cell, in order to maintain an intracellular rate sufficient to inhibit the cellular growth. It implies a better understanding of the antibiotic-membrane interaction [1].

Orientation of Anthracyclines Into Phospholipid Bilayers Depending on Their Hydrophilic-Hydrophobic Balance

Anthracyclines are antibiotics used in chemotherapy. However problems of resistance appear during treatment: a membrane protein, expelling the antibiotic out of the cell, limits the effects of the drug. A possible solution consists of finding new derivatives of anthracyclines able to cross more quickly the biological membrane in order to maintain a sufficient amount of anthracycline into the cell. This solution implies a better understanding of the anthracycline-membrane interaction.