Synthèse et caractérisations de matériaux photosensibles à partir de lignines - Vers une utilisation en Traitement Photodynamique Antimicrobien appliqué à l'agronomie

Abstract : The overexploitation of the planet's resources is nowadays a major problem and makes the replacement of non-renewable sources of energy and raw materials, one of the major challenges of the XXIe century. For this purpose, lignins, by their availability and their biocompatibility, appear as one of the alternatives to fossil resourcesIn this context, the PEIRENE Laboratory decided to carry out this PhD work on the development of new photosensitive materials based on modified lignins. For this purpose, three lignins from different origin were acetylated. Their study by EPR spectroscopy revealed that blocking their antioxidant functions considerably increases the quantity of reactive oxygen species they are able to generate under light irradiation. Thus it is possible to envisage the use of this modified biopolymer in many areas such as antimicrobial photodynamic therapy. In order to make them water-dispersible and thus to widen their field of applications, these materials with promising properties were put in the form of nanoparticles. Their photosensitive behavior has been also valuated by EPR spectroscopy. It has been demonstrated that once dispersed in water in the form of nanoparticles, the acetylated lignins were still capable of producing singlet oxygen under light irradiation. This activity, which has not yet been reported in the literature to our knowledge, however, remains quite limited and therefore needs to be improved. In order to widen the range of the solar spectrum allowing their activation, a photosensitizer has also been associated with these nano-objects by encapsulation and covalent grafting. The results of these studies make possible to envisage the development of systems based on acetylated lignins nanoparticles in in many field, in particular pharmaceutical and phytosanitary.
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Guillaume Marchand. Synthèse et caractérisations de matériaux photosensibles à partir de lignines - Vers une utilisation en Traitement Photodynamique Antimicrobien appliqué à l'agronomie. Chimie organique. Université de Limoges, 2018. Français. ⟨NNT : 2018LIMO0108⟩. ⟨tel-02049310⟩

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