An alternative radiolytic route for synthesizing conducting polymers in an organic solvent

A new and simple promising method for synthesizing conducting polymers in organic solvents was successfully achieved for the first time thanks to the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers dissolved in dichloromethane by means of gamma-radiolysis. The EDOT polymerization was controlled and optimized thanks to the study of the dose effect under an inert atmosphere. UV-Vis absorption spectroscopy was used to follow the polymerization process and to estimate both the radiolytic yield of EDOT oxidation and the required irradiation dose for quantitative poly(3,4-ethylenedioxythiophene) (PEDOT) preparation. Size exclusion chromatography (SEC) was used to determine the molar mass of the PEDOT polymers and thus their degree of polymerization. Polymers containing up to 20 EDOT units were detected. After deposition, ATR-FTIR spectroscopy and Energy-Dispersive X-ray (EDX) analysis highlighted the in situ doping of PEDOT polymers with chloride ions generated during dichloromethane radiolysis, while XRD analysis demonstrated the amorphous structure of the polymers. The morphology of the radiosynthesized PEDOT polymers was characterized in solution by Cryo-TEM microscopy and after deposition by SEM microscopy as well as by high-resolution AFM-IR microscopy coupled with infrared nanospectroscopy. In all cases, aggregated and packed spheroidal PEDOT particles with diameters comprising between 100 nm and 1.5 μm were observed. Besides, cyclic voltammetry (CV), four-point probe measurements and thermogravimetric analysis (TGA) showed that the PEDOT polymers radiosynthesized in dichloromethane are characterized by interesting electrical properties and good thermal stability. The present study bears witness to the tremendous potential of our radiation-based methodology and gives us a glimpse of future promising syntheses of different kinds of conducting polymers in organic solvents and even in complex matrices

Optimal strategy based on radiation chemistry for facile and direct synthesis of poly(3-thiophene acetic acid) polymers in water and dichloromethane

In this work, synthesis of nanostructured conducting poly(3-thiophene acetic acid) (PTAA) polymers was developed by means of γ-induced oxidative polymerization of TAA monomers dissolved either in water or in dichloromethane. This synthesis was shown to be facile and directly feasible without any prior esterification of TAA and in the absence of oxidizing agents. Radiolytic yields of TAA oxidation as well as irradiation doses required for quantitative PTAA preparation were determined for each solvent. UV-Vis and ATR-FTIR spectroscopies demonstrated the successful formation of two PTAA polymers, so-called "PTAAH2O"and "PTAACH2Cl2". Size exclusion chromatography (SEC) highlighted convergent molecular weight values corresponding to approximately 13 monomer units. A similar behavior for both radio-synthesized PTAAs was monitored by thermogravimetric analysis (TGA). The morphological structures of PTAAH2O and PTAACH2Cl2 were analyzed in solution by Cryo-TEM and after deposition by SEM and AFM. Microscopic observations revealed the presence of two distinguishable nanostructures: nano-spherules of several hundreds of nanometers made of PTAAH2O and nano-granules of several tens of nanometers made of PTAACH2Cl2. Cyclic voltammetry analysis and the Tauc plot method were employed to calculate the electrical and optical band gaps. Both polymers possess similar electrical band gaps. However, PTAACH2Cl2 affords a lower optical band gap than PTAAH2O. Four-point probe measurements showed that the radio-synthesized PTAA polymers are characterized by interesting electrical properties: a higher electrical conductivity was nevertheless recorded for PTAACH2Cl2. This study highlights the powerful ability of the radiation chemistry-based methodology to lead, as a simple, versatile and reliable method, to nanostructured PTAA conducting polymers either in aqueous or organic solutions

Multiscale approach to provide a better physicochemical description of women breast microcalcifications

Despite the incidence of breast cancer among women, mammography and anatomopathology investigations are still the gold standard method for preventive screening and diagnosis. Several criteria are used to diagnose precisely the severity of the pathology like the distribution and shape of breast microcalcifications (BMCs). However, the link between the different chemical phases of BMCs and the cancer stage remains unclear. As BMCs physicochemical speciation has the potential to help clinicians during their diagnosis, this study aims to propose a methodology using advanced spectroscopical analysis techniques to finely characterize BMCs and uncover the relationship between mineralization processes and breast cancer. A state of the art in the domain is first proposed to highlight the role of BMCs and the importance of extensive analytical analysis using electron microscopy and vibrational techniques. Secondly, a detailed methodology for BMCs multiscale analysis is proposed and the relevance of each technique illustrated through the study of a biopsy from a patient suffering of an infiltrating low-grade ductal carcinoma: scanning electron microscopy analysis was used for the morphological description of BMCs, infrared micro and nanospectroscopy techniques for their chemical speciation at the micrometric and sub-micrometric scales

Multiscale approach to provide a better physicochemical description of women breast microcalcifications

Despite the incidence of breast cancer among women, mammography and anatomopathology investigations are still the gold standard method for preventive screening and diagnosis. Several criteria are used to diagnose precisely the severity of the pathology like the distribution and shape of breast microcalcifications (BMCs). However, the link between the different chemical phases of BMCs and the cancer stage remains unclear. As BMCs physicochemical speciation has the potential to help clinicians during their diagnosis, this study aims to propose a methodology using advanced spectroscopical analysis techniques to finely characterize BMCs and uncover the relationship between mineralization processes and breast cancer. A state of the art in the domain is first proposed to highlight the role of BMCs and the importance of extensive analytical analysis using electron microscopy and vibrational techniques. Secondly, a detailed methodology for BMCs multiscale analysis is proposed and the relevance of each technique illustrated through the study of a biopsy from a patient suffering of an infiltrating low-grade ductal carcinoma: scanning electron microscopy analysis was used for the morphological description of BMCs, infrared micro and nanospectroscopy techniques for their chemical speciation at the micrometric and sub-micrometric scales

Imagerie 3D résolue en temps pour l'aide au diagnostic médical : développement d'un système de microscopie de fluorescence multipoints sous excitation à deux photons.

Confocal and two-photon microscopies are key methods for biomedical research and cells or tissue imaging. However, one of the main drawbacks of the conventional two-photon microscope is the imaging speed. Consequently, the first aim of this work was to speed up acquisition in order to preserve samples from too long experiments. In this context, we have developed an original set-up called multifocal multiphoton microscope composed of an optical system creating an 8×8 beam array. The second aspect of this work was to develop new methods of medical diagnosis. An early diagnosis of malignant tumors is essential to increase the therapy success and the patient's survival. But, the current standard to diagnose the presence of tumoral cells is of limited value because of its low sensitivity especially to atypical cells. Thus, the enhancement of early cancer diagnosis and treatment has involved the development of new methods to identify cancer signatures. For that purpose, we have an interest in fluorescence imaging methods for ex vivo diagnosis of cervix cancers. We then applied the same approach to detect possible resistance to drugs currently used in bladder chemotherapy. At the present time, patients attacked by a bladder cancer can be efficiently treated with combined chemotherapy such as M-VAC, but drug resistance may appear. In order to detect possible resistance to M-VAC, we have developed an ex vivo method from urinary samples, based upon the visible excitation of the drug fluorescence. Such pre-treatment step which does not exist at the present time will constitute a reliable, non constraining and inexpensive test enabling us to assess chemotherapy effectiveness.L'utilisation de la microscopie confocale et biphotonique de fluorescence est de plus en plus répandue dans le domaine biomédical. En effet, l'imagerie d'intensité, de spectre et de durée de vie de fluorescence permettent de détecter, quantifier et imager les composants fluorescents intrinsèques d'un milieu biologique ainsi que les sondes extrinsèques. Dans le cadre du dépistage précoce de cancer, les modes de détection non-invasifs actuellement mis en place manquent de sensibilité pour permettre d'établir de manière fiable un diagnostic. Les médecins ont alors recours à des examens complémentaires, invasifs, comme la biopsie. Dans le cas de notre étude, différentes techniques de microscopie ont été exploitées pour mettre en place une méthode de diagnostic précoce non-invasive de cancer. Nous avons ainsi utilisé conjointement la microscopie confocale résolue spectralement et la microscopie biphotonique pour les images de durée de vie de fluorescence (FLIM). Cette dernière technique a d'ailleurs été récemment optimisée avec la mise en place d'un système d'excitation biphotonique multipoint qui permet d'accélérer significativement la vitesse d'acquisition des images. Il s'agit d'un système optique générant une matrice de 64 faisceaux excitateurs ce qui réduit considérablement le temps d'exposition des échantillons biologiques, les préservant ainsi des photodégradations. Ces techniques, largement complémentaires, ont permis de différencier, sur différents types de cytologies, les cellules présentant une faible malignité des cellules saines en utilisant comme facteur de contraste la fluorescence des entités intracellulaires. Grâce à cette méthode, les cellules de bas grades de malignité ont pu ainsi être identifiées sur des cytologies du col de l'utérus. En s'appuyant sur une démarche expérimentale similaire, un nouveau test a également été élaboré permettant de déceler avant traitement chez un patient une résitance à des polychimiothérapies usuellement utilisées dans le traitement des cancers urothéliaux tel que M-VAC. A l'issu de ce travail, une signature spectroscopique permettant de discriminer les cellules résistantes des cellules sensibles à la polychimiothérapie a pu être identifiée

Imagerie 3D résolue en temps pour l'aide au diagnostic médical : développement d'un système de microscopie de fluorescence multipoints sous excitation à deux photons.

Confocal and two-photon microscopies are key methods for biomedical research and cells or tissue imaging. However, one of the main drawbacks of the conventional two-photon microscope is the imaging speed. Consequently, the first aim of this work was to speed up acquisition in order to preserve samples from too long experiments. In this context, we have developed an original set-up called multifocal multiphoton microscope composed of an optical system creating an 8×8 beam array. The second aspect of this work was to develop new methods of medical diagnosis. An early diagnosis of malignant tumors is essential to increase the therapy success and the patient's survival. But, the current standard to diagnose the presence of tumoral cells is of limited value because of its low sensitivity especially to atypical cells. Thus, the enhancement of early cancer diagnosis and treatment has involved the development of new methods to identify cancer signatures. For that purpose, we have an interest in fluorescence imaging methods for ex vivo diagnosis of cervix cancers. We then applied the same approach to detect possible resistance to drugs currently used in bladder chemotherapy. At the present time, patients attacked by a bladder cancer can be efficiently treated with combined chemotherapy such as M-VAC, but drug resistance may appear. In order to detect possible resistance to M-VAC, we have developed an ex vivo method from urinary samples, based upon the visible excitation of the drug fluorescence. Such pre-treatment step which does not exist at the present time will constitute a reliable, non constraining and inexpensive test enabling us to assess chemotherapy effectiveness.L'utilisation de la microscopie confocale et biphotonique de fluorescence est de plus en plus répandue dans le domaine biomédical. En effet, l'imagerie d'intensité, de spectre et de durée de vie de fluorescence permettent de détecter, quantifier et imager les composants fluorescents intrinsèques d'un milieu biologique ainsi que les sondes extrinsèques. Dans le cadre du dépistage précoce de cancer, les modes de détection non-invasifs actuellement mis en place manquent de sensibilité pour permettre d'établir de manière fiable un diagnostic. Les médecins ont alors recours à des examens complémentaires, invasifs, comme la biopsie. Dans le cas de notre étude, différentes techniques de microscopie ont été exploitées pour mettre en place une méthode de diagnostic précoce non-invasive de cancer. Nous avons ainsi utilisé conjointement la microscopie confocale résolue spectralement et la microscopie biphotonique pour les images de durée de vie de fluorescence (FLIM). Cette dernière technique a d'ailleurs été récemment optimisée avec la mise en place d'un système d'excitation biphotonique multipoint qui permet d'accélérer significativement la vitesse d'acquisition des images. Il s'agit d'un système optique générant une matrice de 64 faisceaux excitateurs ce qui réduit considérablement le temps d'exposition des échantillons biologiques, les préservant ainsi des photodégradations. Ces techniques, largement complémentaires, ont permis de différencier, sur différents types de cytologies, les cellules présentant une faible malignité des cellules saines en utilisant comme facteur de contraste la fluorescence des entités intracellulaires. Grâce à cette méthode, les cellules de bas grades de malignité ont pu ainsi être identifiées sur des cytologies du col de l'utérus. En s'appuyant sur une démarche expérimentale similaire, un nouveau test a également été élaboré permettant de déceler avant traitement chez un patient une résitance à des polychimiothérapies usuellement utilisées dans le traitement des cancers urothéliaux tel que M-VAC. A l'issu de ce travail, une signature spectroscopique permettant de discriminer les cellules résistantes des cellules sensibles à la polychimiothérapie a pu être identifiée

Minimising contributions from scattering in infrared spectra by means of an integrating sphere

Mid-infrared spectra of biological matter such as tissues or microbial and eukaryotic cells measured in a transmission-type optical setup frequently show strongly distorted line shapes which arise from mixing of absorption and scattering contributions. Scattering-associated distorted line shapes may considerably complicate the analysis and interpretation of the infrared spectra and large efforts have been made to understand the mechanisms of scattering in biological matter and to compensate for spectral alterations caused by scattering. The goals of the present study were two-fold: firstly, to get a deeper understanding of the physics of scattering of biological systems and to explore how physical parameters of the scatterers such as shape, size and refractive index influence the line shape distortions observed. In this context, simulations based on the full Mie scattering formalism for spherical particles were found to be useful in explaining the characteristics of the Mie scatter-associated distortions and yielded a size criterion for the scattering particles similar to the well-known near field criterion. The second objective of the study was to investigate whether alternative optical setups allow minimisation of the effects of scattering. For this purpose, an optical system is proposed which is composed of an integrating sphere unit originally designed for diffuse reflection measurements, an off-axis DLaTGS detector to collect scattered and transmitted light components and a commercial Fourier transform infrared (FTIR) spectrometer. In the context of this study transmission type (tt-) FTIR spectra and spectra acquired by means of the integrating sphere setup (is-FTIR) were acquired from monodisperse poly(methyl) methacrylate (PMMA) microspheres of systematically varying sizes. The tt-FTIR spectral data of different PMMA particles confirmed earlier observations such as the presence of size-dependent oscillating spectral baselines, peak shifts, or derivative-like spectral line shapes. Such effects could be dramatically minimised when is-FTIR spectra were acquired by the integrating sphere unit. Utilisation of an integrating sphere is suggested as a convenient and easy-to use alternative to computer-based methods of scatter correction

Investigation of Single Amyloids Fibrils at the Nanoscale: Challenges and Prospects using IR Nanospectroscopy AFMIR

info:eu-repo/semantics/publishe