Atmospheric Pressure Plasma Deposition of Hydrophilic/Phobic Patterns and Thin Film Laminates on Any Surface.

Patterned and layered hydrophilic/phobic coatings were deposited on multiple surfaces using nonfluorinated precursors (AA, acrylic acid; PMA, propargyl methacrylate) with an atmospheric pressure dielectric barrier discharge operating in open air. Water contact angles of the resulting films could be tuned from <5° (superhydrophilic) to >135° (very hydrophobic) by adjusting the AA/PMA feed ratio and/or via postdeposition exposure of films to an Ar/O2 plasma treatment. Coatings could be applied to any surface and were seen to be water stable, due in large part to cross-linking induced from the reactivity of the PMA pendant groups. Hybrid hydrophilic/phobic patterns at submillimeter length scales, and philic/phobic/philic laminates were produced using a shadow mask and sequential deposition, respectively. Chemical heterogeneity of films was assessed using XPS, SIMS, and micro-IR imaging and suggest that localization of COOH and OH groups are primarily responsible for hydrophilicity. Overall, this work demonstrates that atmospheric pressure plasma polymerization is a simple and scalable method for robust and tunable control of wettability of surfaces of all kinds.

Intracellular investigation on the differential effects of 4 polyphenols on MCF-7 breast cancer cells by Raman imaging.

The past decades have seen significant interest in the study of polyphenolic compounds as potential therapeutic agents in medicine because they display a vast array of cellular effects beneficial to treat or manage a plethora of chronic diseases including inflammatory diseases, cardiovascular abnormalities and several types of cancer. These compounds act at different stages of carcinogenesis but deciphering their mode of action is a complex task. Live MCF-7 breast cancer cells were investigated using Raman imaging to evaluate the perturbations induced after incubating cells with four different polyphenols: EGCG, gallic acid, resveratrol and tannic acid. First, clear spectral changes could be observed between the spectra of the cytoplasm and the nucleus of live MCF-7 cancer cells demonstrating a difference in their respective global chemical composition. The treatments induced significant modifications in the cells but no clear common pattern of modifications from the 4 drugs could be observed in the cell spectra in the 1800-600 cm-1 region. The high spatial resolution of Raman confocal microscopy enabled both the nucleus and cytoplasm to be independently targeted to study the impact of the polyphenols on the cell line. Positive spectral variations at 2851 cm-1 and 2920 cm-1 as well as in the 1460-1420 cm-1 and 1660-1650 cm-1 spectral regions inside cell cytoplasm reflected an increase of the lipid content after exposure to polyphenols. Lipid accumulation appears to be an early biomarker of drug-induced cell stress and subsequent apoptosis. Interestingly an increase of cytochrome c into the cytosol was also induced by EGCG. These multiple events are possibly associated with cell apoptosis. In conclusion, Raman micro-spectroscopy provides a complementary spectroscopic method to realize biological investigations on live cancer cells and to evaluate the effects of polyphenols at the subcellular level.

HTS-FTIR spectroscopy allows the classification of polyphenols according to their differential effects on the MDA-MB-231 breast cancer cell line.

Breast cancer is a major public health issue among women in the world. Meanwhile new anticancer treatments struggle more and more to be accepted in the pharmaceutical market and research costs still increase. There is therefore a need to find new treatments and new screening methods to test them more quickly and efficiently. Among natural compounds, an increasing interest has been given to polyphenols as they can take action at the different stages of carcinogenesis, from tumour initiation to metastasis formation, by disturbing multiple cellular signalling pathways. They constitute one of the largest groups of plant metabolites and more than 8000 compounds have already been identified based on their chemical structure. Traditionally in pharmacology, new anticancer drugs are first evaluated for their potential to inhibit the proliferation of cancer cell lines. Numerous potential drugs are discarded at this stage even though they could show interesting modes of action. In turn, there is an increasing demand for more systemic approaches in order to obtain a global and accurate insight into the biochemical processes mediated by drugs. Recently, FTIR spectroscopy was demonstrated to be an innovative tool to obtain a unique fingerprint of the effects of anticancer drugs on cells in culture. While this spectral technique appears to have a definite potential to sort drugs according to their spectral fingerprints, characteristic of the metabolic modifications induced, the present challenge remains to evaluate the drug-induced spectral changes in cancer cells on a larger scale. This article presents the results obtained for a 24 h-exposure of the breast cancer cell line MDA-MB-231 to 15 compounds belonging to different classes of polyphenols using FTIR spectroscopy connected to a high throughput screening extension. Through unsupervised and supervised statistical analyses (PCA, MANOVA, Student's t-tests and HCA), a distinction between polyphenol treatments and controls could be well established.

Infrared spectra of primary melanomas can predict response to chemotherapy: The example of dacarbazine.

Metastatic melanomas are highly aggressive and median survival is 6-9months for stage IV patients in the absence of treatment with anti-tumor activity. Dacarbazine is an alkylating agent that has been widely used in the treatment of metastatic melanomas and that could be still used in combination with targeted or immune therapies. Indeed, therapeutic benefits of these treatments in monotherapy are poor and one option to improve them is to combine drugs and/or to better anticipate the individual response to a defined treatment. To our best knowledge and to date, there is no test available to predict the response of a patient to dacarbazine. We show here that examination of melanoma histological sections by infrared micro-spectroscopy reveals the sensitivity of the cancer to dacarbazine. Unsupervised analysis of the FTIR spectra evidences spontaneous and significant clustering of infrared spectra into two groups that match the clinical responsiveness of the patients to dacarbazine used as a first-line treatment. A supervised model resulted in 83% of the patient status (responder/non-responder) being correctly identified. The spectra revealed a key modification in the nature and quantity of lipids in the cells of both groups.

Identification of melanoma cells and lymphocyte subpopulations in lymph node metastases by FTIR imaging histopathology.

While early stages of melanoma are usually cured by surgery, metastatic melanomas are difficult to treat because the widely available options have low response rates. Careful and precise diagnosis and staging are essential to determine patient's risk and to select appropriate treatments. Fortunately, the recent progress in immunotherapy is very encouraging. In this context, it is important to characterize the intratumoral infiltration of immune cells in each patient, which is however not done routinely due to the lack of standardized methods. In this study, we used Fourier transform infrared (FTIR) imaging combined with multivariate statistical analyses to investigate non-metastatic and metastatic lymph nodes from melanoma patients. Our results show that the different cell types have different infrared spectral features allowing automated identification of these cell types. High recognition rates were obtained using a supervised partial least square discriminant analysis (PLS-DA) model. Melanoma cells were recognized with 87.1% sensitivity and 85.7% specificity, showing that FTIR spectroscopy has similar detection power as immunohistochemistry. Besides, FTIR imaging could also distinguish lymphocyte subpopulations (B and T cells). Finally, we investigated the changes in lymphocytes due to the presence of metastases. Interestingly, specific features of spectra of lymphocytes present in metastatic or tumor-free lymph nodes could be evidenced by PCA. A PLS-DA model was capable of predicting whether lymphocytes originated from invaded or non-invaded lymph nodes. These data demonstrate that FTIR imaging is capable to distinguish known and also novel biological features in human tissues, with potential practical relevance for histopathological diagnosis and biomarker assessment.

Characterization of human breast cancer tissues by infrared imaging.

Fourier Transform InfraRed (FTIR) spectroscopy coupled to microscopy (IR imaging) has shown unique advantages in detecting morphological and molecular pathologic alterations in biological tissues. The aim of this study was to evaluate the potential of IR imaging as a diagnostic tool to identify characteristics of breast epithelial cells and the stroma. In this study a total of 19 breast tissue samples were obtained from 13 patients. For 6 of the patients, we also obtained Non-Adjacent Non-Tumor tissue samples. Infrared images were recorded on the main cell/tissue types identified in all breast tissue samples. Unsupervised Principal Component Analyses and supervised Partial Least Square Discriminant Analyses (PLS-DA) were used to discriminate spectra. Leave-one-out cross-validation was used to evaluate the performance of PLS-DA models. Our results show that IR imaging coupled with PLS-DA can efficiently identify the main cell types present in FFPE breast tissue sections, i.e. epithelial cells, lymphocytes, connective tissue, vascular tissue and erythrocytes. A second PLS-DA model could distinguish normal and tumor breast epithelial cells in the breast tissue sections. A patient-specific model reached particularly high sensitivity, specificity and MCC rates. Finally, we showed that the stroma located close or at distance from the tumor exhibits distinct spectral characteristics. In conclusion FTIR imaging combined with computational algorithms could be an accurate, rapid and objective tool to identify/quantify breast epithelial cells and differentiate tumor from normal breast tissue as well as normal from tumor-associated stroma, paving the way to the establishment of a potential complementary tool to ensure safe tumor margins.

An infrared spectral signature of human lymphocyte subpopulations from peripheral blood.

Metastatic melanomas are frequently refractory to most adjuvant therapies such as chemotherapies and radiotherapies. Recently, immunotherapies have shown good results in the treatment of some metastatic melanomas. Immune cell infiltration in the tumor has been associated with successful immunotherapy. More generally, tumor infiltrating lymphocytes (TILs) in the primary tumor and in metastases of melanoma patients have been demonstrated to correlate positively with favorable clinical outcomes. Altogether, these findings suggest the importance of being able to identify, quantify and characterize immune infiltration at the tumor site for a better diagnostic and treatment choice. In this paper, we used Fourier Transform Infrared (FTIR) imaging to identify and quantify different subpopulations of T cells: the cytotoxic T cells (CD8+), the helper T cells (CD4+) and the regulatory T cells (T reg). As a proof of concept, we investigated pure populations isolated from human peripheral blood from 6 healthy donors. These subpopulations were isolated from blood samples by magnetic labeling and purities were assessed by Fluorescence Activated Cell Sorting (FACS). The results presented here show that Fourier Transform Infrared (FTIR) imaging followed by supervised Partial Least Square Discriminant Analysis (PLS-DA) allows an accurate identification of CD4+ T cells and CD8+ T cells (>86%). We then developed a PLS regression allowing the quantification of T reg in a different mix of immune cells (e.g. Peripheral Blood Mononuclear Cells (PBMCs)). Altogether, these results demonstrate the sensitivity of infrared imaging to detect the low biological variability observed in T cell subpopulations.

Infrared imaging of primary melanomas reveals hints of regional and distant metastases.

Melanoma is the deadliest form of skin cancer. Metastatic melanomas are resistant to almost all existing adjuvant therapies such as chemotherapy and radiotherapy, so detection of metastases remains a challenge, and no biomarkers are currently available to detect primary tumors with the highest risk of metastasis. Results presented in this paper show that Fourier Transform Infrared (FTIR) imaging of histological sections followed by supervised partial least squares discriminant analysis (PLS-DA) can accurately (>90%) identify the main cell types commonly found in melanoma tumors. Here we define six cell types: melanoma cells, erythrocytes, connective tissue (includes blood vessel walls, dermis and collagen regions), keratinocytes, lymphocytes and necrotic cells. Interestingly, more than 98% of the melanoma cells are correctly identified. The spectra of the cells identified as melanomas were then further analyzed. First, we compared melanoma cells in primary tumors (from 26 patients) with melanoma cells from metastases (from 25 patients). Neither supervised nor unsupervised analyses revealed any significant difference. Similarly, we found no significant correlation between the infrared spectra of melanoma cells and the number of proliferative cells assessed by Ki67 immunostaining. Finally, we compared the infrared spectra of primary tumors from patients diagnosed at different stages of the disease. Infrared spectroscopy was capable of pointing out differences between primary tumors of patients at stage I or II and patients at stage III or IV, even by unsupervised analysis. We then developed a supervised PLS-DA model capable of predicting whether tumor cells belonged to one of the two aggregated disease stage groups. The model predicted a high rate of true positives (sensitivity of 88.9%) and a good rate of true negatives (specificity of 70.6%) in external validation. These results demonstrate that infrared spectroscopy can be used to help identify melanoma characteristics related to the cells' invasive capability.

High throughput absorbance spectra of cancerous cells: a microscopic investigation of spectral artifacts.

FTIR spectroscopy was recently demonstrated to be a useful tool to obtain a unique fingerprint of the effects of several anticancer drugs on cells in culture. While FTIR spectroscopy appears to have a definite potential to sort anticancer drugs on the basis of the metabolic modifications they induced, the present challenge is to evaluate the drug-induced spectral changes in cancer cells on a larger scale. The coupling of FTIR spectroscopy with a high throughput screening extension could become a useful method to generate drug classifications based on their "modes of action". Practically, the robustness of this approach is jeopardized by the variability that can appear from one cell smear to the next. When a few cells are scattered on the support, strong scattering effects are observed and locally dense cell aggregates could result in non-linearity of the signal. A microscopic study using infrared imaging demonstrates that the mean HTS (96-well High Throughput Spectroscopy) spectra recorded on 96 well ZnSe plates are the averages of contributions characterized by a wide absorbance distribution and by Mie scattering effects which significantly vary from point to point. Spectrum quality is at its best at the highest cell concentrations, i.e. from 300 000 to 400 000 cells per well, which present the best S/N and a relatively smaller Mie scattering effect. When the breast cancer cell line MDA-MB-231 was treated with four different polyphenols, spectra showed quite similar variations with respect to control spectra, with more intense variations for the quercetin and EGCG compared to resveratrol and capsaicin. Correction of the spectra with the RMieS algorithm improved their clustering according to the polyphenolic treatment.

Label-free phenotyping of peripheral blood lymphocytes by infrared imaging.

It is now widely accepted that the immune microenvironment of tumors and more precisely Tumor Infiltrating Lymphocytes (TIL) play an important role in cancer development and outcome. TILs are considered to be important prognostic and predictive factors based on a growing body of clinical evidence; however, their presence at the tumor site is not currently assessed routinely. FTIR (Fourier transform infrared) imaging has proven it has value in studying a range of tumors, particularly for characterizing tumor cells. Currently, very little is known about the potential for FTIR imaging to characterize TIL. The present proof of concept study investigates the ability of FTIR imaging to identify the principal lymphocyte subpopulations present in human peripheral blood (PB). A negative cell isolation method was employed to select pure, label-free, helper T cells (CD4(+)), cytotoxic T cells (CD8(+)) and B cells (CD19(+)) from six healthy donors PB by Fluorescence Activated Cell Sorting (FACS). Cells were centrifuged onto Barium Fluoride windows and ten infrared images were recorded for each lymphocyte subpopulation from all six donors. After spectral pre-treatment, statistical analyses were performed. Unsupervised Principal Component Analyses (PCA) revealed that in the absence of donor variability, CD4(+) T cells, CD8(+) T cells and B cells each display distinct IR spectral features. Supervised Partial Least Square Discriminant Analyses (PLS-DA) demonstrated that the differences between the three lymphocyte subpopulations are reflected in their IR spectra, permitting their individual identification even when significant donor variability is present. Our results also show that a distinct spectral signature is associated with antibody binding. To our knowledge this is the first study reporting that FTIR imaging can effectively identify T and B lymphocytes and differentiate helper T cells from cytotoxic T cells. This proof of concept study demonstrates that FTIR imaging is a reliable tool for the identification of lymphocyte subpopulations and has the potential for use in characterizing TIL.

A new dimension for cell identification by FTIR spectroscopy: depth profiling in attenuated total reflection.

The multiresistant phenotype is an important problem in cancer chemotherapy. It is characterized by cell resistance to multiple and structurally unrelated drugs. We have shown previously that K562 multiresistant leukemia cells could be differentiated from their sensitive counterparts (wild-type K562 cells) on the basis of their infrared spectrum. In ATR FTIR mode, the penetration depth is controlled by both the wavelength and the incident angle, allowing depth profiling of samples. In this paper we took advantage of the ATR capability to modulate the penetration depth of the infrared wave into the cell, by modulating the incident angle, to investigate the differences between K562 multiresistant cells and their sensitive counterparts (wild-type K562 cells) as a function of this penetration depth. It is shown that focusing the IR beam on the most discriminant depth allows improvement of the discrimination between multiresistant and sensitive K562 cells. It is suggested that the depth profile of the difference spectra could allow a more precise localization of the biochemical modifications arising within the multidrug resistance phenotype.

Breast cancer and melanoma cell line identification by FTIR imaging after formalin-fixation and paraffin-embedding.

Over the past few decades, Fourier transform infrared (FTIR) spectroscopy coupled to microscopy has been recognized as an emerging and potentially powerful tool in cancer research and diagnosis. For this purpose, histological analyses performed by pathologists are mostly carried out on biopsied tissue that undergoes the formalin-fixation and paraffin-embedding (FFPE) procedure. This processing method ensures an optimal and permanent preservation of the samples, making FFPE-archived tissue an extremely valuable source for retrospective studies. Nevertheless, as highlighted by previous studies, this fixation procedure significantly changes the principal constituents of cells, resulting in important effects on their infrared (IR) spectrum. Despite the chemical and spectral influence of FFPE processing, some studies demonstrate that FTIR imaging allows precise identification of the different cell types present in biopsied tissue, indicating that the FFPE process preserves spectral differences between distinct cell types. In this study, we investigated whether this is also the case for closely related cell lines. We analyzed spectra from 8 cancerous epithelial cell lines: 4 breast cancer cell lines and 4 melanoma cell lines. For each cell line, we harvested cells at subconfluence and divided them into two sets. We first tested the "original" capability of FTIR imaging to identify these closely related cell lines on cells just dried on BaF2 slides. We then repeated the test after submitting the cells to the FFPE procedure. Our results show that the IR spectra of FFPE processed cancerous cell lines undergo small but significant changes due to the treatment. The spectral modifications were interpreted as a potential decrease in the phospholipid content and protein denaturation, in line with the scientific literature on the topic. Nevertheless, unsupervised analyses showed that spectral proximities and distances between closely related cell lines were mostly, but not entirely, conserved after FFPE processing. Finally, PLS-DA statistical analyses highlighted that closely related cell lines are still successfully identified and efficiently distinguished by FTIR spectroscopy after FFPE treatment. This last result paves the way towards identification and characterization of cellular subtypes on FFPE tissue sections by FTIR imaging, indicating that this analysis technique could become a potential useful tool in cancer research.

Change in the microenvironment of breast cancer studied by FTIR imaging.

Fourier transform infrared (FTIR) imaging was applied on histopathological specimens of breast cancer of different tumor histological grades. Focus was given to the extracellular matrix. FTIR spectral changes were observed when examining the extracellular matrix close to and far from carcinoma. Major changes were observed, in particular in the relative intensities of the collagen bands at 1640 and 1630 cm(-1). PCA analysis and global fitting indicate a continuous progression in collagen spectral features when moving away from the tumor. These preliminary results suggest FTIR spectral features present in the 1700-1600 cm(-1) spectral range could be used as spectral markers to identify cancer-induced modifications in collagen. This chemical imaging approach to analyze the breast cancer microenvironment could be used in the future for improving diagnostics of breast cancer.

Amphipols from A to Z.

Amphipols (APols) are short amphipathic polymers that can substitute for detergents to keep integral membrane proteins (MPs) water soluble. In this review, we discuss their structure and solution behavior; the way they associate with MPs; and the structure, dynamics, and solution properties of the resulting complexes. All MPs tested to date form water-soluble complexes with APols, and their biochemical stability is in general greatly improved compared with MPs in detergent solutions. The functionality and ligand-binding properties of APol-trapped MPs are reviewed, and the mechanisms by which APols stabilize MPs are discussed. Applications of APols include MP folding and cell-free synthesis, structural studies by NMR, electron microscopy and X-ray diffraction, APol-mediated immobilization of MPs onto solid supports, proteomics, delivery of MPs to preexisting membranes, and vaccine formulation.

Cholesterol modulates the exposure and orientation of pulmonary surfactant protein SP-C in model surfactant membranes.

Cholesterol is the major neutral lipid in lung surfactant, accounting for up to 8-10% of surfactant mass, while surfactant protein SP-C ( approximately 4.2 kDa) accounts for no more than 1-1.5% of total surfactant weight but plays critical roles in formation and stabilization of pulmonary surfactant films. It has been reported that surfactant protein SP-C interacts with cholesterol in lipid/protein interfacial films and this interaction could have a potential role on modulating surfactant function. In the present study, we have analyzed the effect of cholesterol on the structure, orientation and dynamic properties of SP-C embedded in physiologically relevant model membranes. The presence of cholesterol does not induce substantial changes in the secondary structure of SP-C, as analyzed by Attenuated Reflection Fourier Transformed Infrared spectroscopy (ATR-FTIR). However, the presence of cholesterol modifies the orientation of the transmembrane helix and the dynamic properties of the protein, as demonstrated by hydrogen/deuterium exchange kinetics. The effect of cholesterol on SP-C reconstituted in zwitterionic, entirely fluid, membranes made of POPC (palmitoyloleoylphospatidylcholine) or in anionic membranes with coexistence of ordered and disordered phases, such as those made of dipalmitoylphosphatidylcholine (DPPC):POPC:Palmitoyloleoylphosphatidylglycerol (POPG) (50:25:15) is dual. Cholesterol decreases the exposure of the protein to the aqueous environment and the tilt of its transmembrane helical segment up to a ratio Cholesterol:SP-C of 4.8 and 2.4 (mol/mol) in the two lipid systems tested, respectively, and it increases the exposure and tilt at higher cholesterol proportions. The results presented here suggest the existence of an interaction between SP-C and cholesterol-enriched phases, with consequences on the behavior of the protein, which could be of relevance for cholesterol-dependent structure-function relationships in pulmonary surfactant membranes and films.

Ligand-receptor interactions in complex media: a new type of biosensors for the detection of coagulation factor VIII.

Detection of receptor-ligand interaction in complex media remains a challenging issue. We report experimental results demonstrating the specific detection of the coagulation factor VIII in the presence of a large excess of other proteins using the new BIA-ATR technology based on attenuated total reflection Fourier transform infrared spectroscopy. The principle of the detection is related to the ability of factor VIII molecules to bind to lipid membranes containing at least 8% phosphatidylserine. Several therapeutic concentrates of factor VIII were analyzed and the binding of the coagulation factor was monitored as a function of time. We show that a non-specific adsorption of stabilizing agents (typically, von Willebrand factor and human serum albumin) may be avoided by controlling the geometry of the ATR element. A linear response of the sensors as a function of the factor VIII concentration is described for different lipid membrane compositions.

Biochemical interaction analysis on ATR devices: a wet chemistry approach for surface functionalization.

A new generic device suitable for the investigation of ligand-receptor interactions is presented. In particular, the research focused on optical waveguides constituted by an attenuated total internal reflection (ATR) element, transparent in the infrared and whose surfaces were activated in view of covalently binding a receptor. Silicon and germanium ATR elements were considered. The original method is based on the grafting of bifunctional spacer molecules directly at the surface of the germanium crystal, avoiding the deposition of an intermediate metal layer. The grafting of these binding molecules (under their N-hydroxysuccinimidyl ester forms) was performed either by wet chemistry or by photochemistry. The functionalized surfaces, which allow the binding of molecules bearing peripherical NH2 groups, were successfully used, e.g., for the detection of proteins (streptavidin) or of small molecules (biotin). In the latter case, the biotin was readily detected for concentrations as low as 10(-12) M.

Cell discrimination by attenuated total reflection-Fourier transform infrared spectroscopy: the impact of preprocessing of spectra.

Fourier transform infrared (FT-IR) spectroscopy has become a powerful tool for biodiagnostics and cell line classification. Typical experimental perturbations included in spectra are baseline shift and scale variation between spectra. They have to be removed by data preprocessings to allow further data analysis and classification. In this work, we addressed baseline shift corrections and normalizations in attenuated total reflection (ATR) FT-IR spectra. We compared the efficiency of several preprocessing methods with series of spectra containing typical perturbations (baseline shift, scaling factor, and noise) and a priori known definite spectral difference. Several baseline-correction and normalization possibilities were evaluated. Our results were generally sensitive, selective, and robust with respect to baseline and scaling. Full-range scaling generated more false-positive results. Use of first- and second-derivative spectra was tested. Results obtained on model spectra were confirmed with series of spectra from sensitive and multidrug-resistant leukemia K562 cells. We showed that the use of derived spectra did not provide more efficiency and required additional preprocessing such as smoothing to obtain results similar to those obtained from non-derived ones. On the other hand, results obtained with derivatives were less sensitive to scaling, a useful feature when scaling is problematic.

Effect of the antibiotic azithromycin on thermotropic behavior of DOPC or DPPC bilayers.

Azithromycin is a macrolide antibiotic known to bind to lipids and to affect endocytosis probably by interacting with lipid membranes [Tyteca, D., Schanck, A., Dufrene, Y.F., Deleu, M., Courtoy, P.J., Tulkens, P.M., Mingeot-Leclercq, M.P., 2003. The macrolide antibiotic azithromycin interacts with lipids and affects membrane organization and fluidity: studies on Langmuir-Blodgett monolayers, liposomes and J774 macrophages. J. Membr. Biol. 192, 203-215]. In this work, we investigate the effect of azithromycin on lipid model membranes made of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Thermal transitions of both lipids in contact with azithromycin are studied by (31)P NMR and DSC on multilamellar vesicles. Concerning the DPPC, azithromycin induces a suppression of the pretransition whereas a phase separation between the DOPC and the antibiotic is observed. For both lipids, the enthalpy associated with the phase transition is strongly decreased with azithromycin. Such effects may be due to an increase of the available space between hydrophobic chains after insertion of azithromycin in lipids. The findings provide a molecular insight of the phase merging of DPPC gel in DOPC fluid matrix induced by azithromycin [Berquand, A., Mingeot-Leclercq, M.P., Dufrene, Y.F., 2004. Real-time imaging of drug-membrane interactions by atomic force microscopy. Biochim. Biophys. Acta 1664, 198-205] and could help to a better understanding of azithromycin-cell interaction.

The infrared spectrum of human glioma cells is related to their in vitro and in vivo behavior.

The present research investigates whether infrared spectra can be related to the biological characteristics of glioma cell lines. We used nine human glioma cell lines for which a series of in vitro and in vivo biological features had already been established [Glia 36 (2001) 375] and were able to show that their characteristic infrared spectra reflect their in vitro migration (i.e., motility and invasiveness) properties and their in vivo aggressiveness. More particularly, the infrared data evidenced correlations at the level of the lipid/protein ratio. These relationships were found to be tissue-dependent when controlled on seven pancreatic carcinoma cell lines. We also showed that oligodendroglial and astrocytic tumor cells, whose identification remains difficult, can easily be identified by their infrared spectra in the lipid acyl chain region as well as in the nucleic acid region. We concluded that infrared spectroscopy could usefully complement information provided by more conventional diagnostic and prognostic (e.g., morphological and molecular) approaches.