Vitamine B9 | EPFL Graph Search

La vitamine B, autre nom de l'acide folique (folate, folacine ou vitamine M, acide pteroyl-L-glutamique, pteroyl-L-glutamate et acide pteroylmonoglutamique), est une vitamine hydrosoluble. L'acide folique est le précurseur métabolique d'une coenzyme, le tétrahydrofolate ( ou THF), impliquée notamment dans la synthèse des bases nucléiques, purines et pyrimidines, constituant les acides nucléiques (ADN et ARN) du matériel génétique. Le THF intervient également dans la synthèse d'acides aminés tels que la méthionine, l'histidine et la sérine. Histoire En 1929-1931, Lucy Wills décrit une anémie sévère touchant des femmes enceintes de Bombay en Inde. Il s'agissait de femmes vivant dans les conditions du Purdah, avec ségrégation physique et régime alimentaire monotone, dépourvu de fruits et légumes verts. Elle décrit ainsi une anémie mégaloblastique curable par extraits de levure. Cette anémie se retrouve dans d'autres populations ayant un régime analogue. Des travaux ultérieu

Iron oxide nanoparticles for diagnosis and therapy of lymph node metastases

Débora Bonvin

This thesis presents the synthesis, coating and characterization of iron oxide nanoparticles (IONPs) with properties especially designed for the ultimate simultaneous MRI detection and hyperthermia treatment of lymph node metastases, a combination called theranostics. This demanding aim requires to fulfill two different challenges at the same time: (i) synthesis of IONPs with exceptional properties for MRI and hyperthermia obtained with a synthesis method transferable to manufacturing facilities, and (ii) coating of IONPs with molecules, which simultaneously allow their dispersion and ideally have higher affinity to lymph node metastases than to other tissues. We therefore developed a novel simple aqueous method to synthesize IONPs by combining the standard co-precipitation method with a hydrothermal treatment. We studied the influence of the synthesis parameters, especially the hydrothermal treatment duration, on the IONPs' size, morphology, structure, crystallinity, as well as their magnetic, relaxometric and heating properties. As a result, we were able to control simultaneously the studied properties and to obtain IONPs with optimal properties for both MRI and hyperthermia. Subsequently, IONPs were coated in aqueous conditions with nine different molecules considered as biocompatible and non-toxic. In order to preserve the high relaxometric and heating properties of IONPs, we used small molecules to reduce the coating to a minimum. In that case, dispersion of IONPs with the chosen molecules were obtained by electrostatic stabilization. One of the major constraints was to obtain coated IONPs with hydrodynamic diameters smaller than 100 nm and with negative surface charges, both needed to access and be retained in the lymphatic system that is required for the targeting of lymph node metastases. In order to avoid to further enlarge the coating, we also used the available active groups of the coating molecules to target lymph node metastatic cells. In order to confirm the possibility to target such cells, we investigated the uptake of coated IONPs in four tumor cell lines from different cancer stages. Finally, the platform with optimal properties necessary for the targeting, detection and treatment of lymph node metastases was found to be IONPs coated with folic acid or adenosine triphosphate, which are targeting the prostate specific membrane antigen receptors or the highly metabolic nature of tumor cells, respectively. In the last part of this thesis, the interaction of IONPs with blood and lymph, especially the formation of the protein corona around IONPs, was investigated. Our study took into account the complex environment, which IONPs are subjected to in vivo. So far unconsidered in vitro conditions were examined, such as the dynamic variations of the flow or the transition of IONPs from one body fluid to the other.

EPFL2017

Engineering of chitosan-based derivatives for non-viral gene delivery

Laura Camille Louise Nicolle

Gene therapy offers the possibility to treat or even cure diseases originating from genetic defects by introducing a therapeutic gene in target cells or correcting the initial defective gene. Amongst different options, non-viral vectors rely on the delivery of such genes using vehicles composed of lipids, inorganic nanoparticles or polymers. These systems are designed to protect the genetic material, while efficiently delivering it to the cells of interest. The initial backbone can be complemented with various components to help it overcome the many physiological barriers it may encounter during its journey. Amongst polymers, chitosan is a polysaccharide presenting many advantages for such purpose. Besides its biocompatibility and biodegradability, its potential for functionalization, thanks to numerous primary amines and hydroxyl groups, make it a backbone of choice for the preparation of a polymeric delivery vehicle. This work describes the covalent functionalization of chitosan with other polymers, peptides, and small molecules to later form polymeric nanoparticles condensing therapeutic DNA. Each component brings additional features to the initial system, thus finely tuning it for biological applications. The final system aims at treating liver inherited diseases such as ornithine transcarbamylase deficiency and phenylketonuria.This manuscript first exposes the preparation of a chitosan-based cationic system able to properly condense anionic DNA through electrostatic interactions. Due to its excellent DNA condensation properties, polyethylenimine was grafted to chitosan via a succinyl linker. The first in vitro investigations confirmed the potential of the resulting core system, but in vivo experiments highlighted toxicity coming from the remaining cationic charge on the nanoparticles. In order to better shield this cationic charge, bifunctional polyethylene glycol chains terminated by carboxylic acid moieties were grafted to chitosan amines. The resulting polymer was used to coat the first polymeric system through electrostatic interactions between the carboxylate groups and the remaining free amines of the chitosan-polyethylenimine derivative. The newly formed core-shell complex showed sustained cell viability in vitro and induced higher transfection efficiency of the gene as compared to the core system alone. However, its in vivo evaluation via retrograde intrabiliary infusion did not confirm such results: although transfection efficiency was retained, the core-shell complex did not significantly decrease the toxicity previously reported.The last part of this work includes the decoration of the core-shell system with targeting ligands making possible to perform in vivo assays via intravenous injection, for which the developed polymeric systems did not induce toxicity in preliminary experiments. So far, only a proof-of-concept with folic acid, an anti-cancer targeting ligand, was achieved. To do so, the shell polymer was further functionalized with folic acid-derived polyethylene glycol chains through strain-promoted azide-alkyne cycloaddition. The same strategy shall be applied in the near future with a liver-specific targeting ligand. Lastly, the improvement of the system's cell-penetration features was tackled by the grafting asparagusic acid-derived polyethylene glycol chains following the same strategy than for folic acid.

EPFL2022

Strategies in non-viral gene delivery: "to overcome serum effect"

Yun Suk Jo

Throughout these last years, many synthetic polymers have been developed for non-viral gene delivery systems in attempt to overcome potential shortcomings of viral vectors. However, it is still difficult to achieve highly efficient transfection under physiological condition due to severe interaction between cationic polyplexes and abundant proteins in serum. In this project, we aim to suggest different strategies to enhance transfection efficiency of non-viral polymeric vector, which was already developed in our research group, i.e. poly(N-acryloylpiperazine) (PAZ). As a first strategy, cancer-targeting delivery was attempted with a folic acid (FA)-conjugated poly(N-acryloylpiperazine) (PAZ-FA), because folic acid receptors (FRs) are over-expressed on many types of cancer cells. We hypothesized that folic acid moieties on PAZ-FA would facilitate the attachment and the internalization of polyplexes to cancer cells. As a second strategy, block copolymerization was attempted. In this approach, a diblock copolymer, i.e. poly[(N-acryloylmorpholine)-bl-(N-acryloylpiperazine)] (PAM-PAZ) was synthesized. We hypothesized that a neutral and hydrophilic poly(N-acryloylmorpholine) (PAM) block would reduce electrostatic interaction with proteins in serum which deteriorates transfection efficiency. Synthesized polymers were thoroughly characterized and details are described herein. The physical properties of polyplexes were examined such as size, surface charge by zetapotential and gel retardation assay, protection capability from enzyme, etc. To carry out transfection experiments, two types of cells, i.e. human embryonic kidney (293T) cells and human cervical epitheloid carcinoma (HeLa) cells were employed with green fluorescent protein (GFP)-expressing plasmid DNA. Transfection results were analyzed by fluorescence-activated cell sorting (FACS). As a positive control, linear poly(ethylene imine) (LPEI) was employed in the experiments. In serum-free condition, there was no substantial difference in size and/or zeta potential among PAZ-polyplexes, PAZ-FA polyplexes, PAM-PAZ polyplexes, and LPEI-polyplexes. This reveals that all PAZ derivatives are similarly capable to condense DNA into nano-sized particulate polyplexes as LPEI. PAZ and PAZ-FA showed comparable or even better transfection efficiency than LPEI, whereas PAM-PAZ showed lower transfection efficiency than the other two PAZ derivatives and LPEI. In the presence of 10% of fetal bovine serum (FBS), we observed that, the size of polyplexes of PAZ-derivatives spontaneously increased up to a few microns in an hour or two. This size increment was more severe compared to LPEI-polyplexes, although the surface charge of all polyplexes remained the same. As for transfection, with 10% of FBS in cell media, all PAZ-derivatives showed lower transfection efficiency than LPEI. To get a better insight of serum effect, we prepared a fluorescent-labeled PAZ and examined how serum affects the internalization of polyplexes. In result, we observed that serum prevents large extent of attachment on the extracellular membranes, but there was no difference in the actual amount of internalized polyplexes either with or without serum. Thus, we believe that serum does not influence on the internalization of polyplexes, but other critical pathway may involve an intracellular compartment.

2008