Conception et caractérisation de nanoparticules polymères théragnostiques destinées au traitement des tumeurs cérébrales
The interest in developing new applications of nanotechnology in the pharmaceutical health care increases year after year. The role of nanosystems became clearer, especially after some of them contributed to revolutionary solutions in serious diseases. In our project, we sought to synthesize ‘intelligent’  nanoparticles  (NPs)  capable  of  selectively  delivering  anticancer  agents.  NPs  were synthesized to target brain cells affected by glioblastoma multiforme (GBM), a brain cancer with a poor prognosis and a very low rate of median survival. To this end, we planned to synthesize and analyze these nanoparticles and also to study the proof-of-concept of their efficiency. First,  we  carefully  selected  the  formulation  process  and  the  polymers  prior  to  optimize physicochemical characteristics of the nanogels (NGs) formulated with chitosan. After optimization of the NGs size, PDI and surface potential, we synthesized NGs loaded with active  substances.  Two  therapeutic  molecules  were  selected.  First  we  chose  doxorubicin  HCl (DOX) which is too hydrophilic to cross the BBB, whereas demonstrating in vitro efficacy against GBM. The second drug was temozolomide (TMZ), already used in the treatment of GBM as an adjuvant to radiotherapy after surgery. Analytical methods were then developed to determine the encapsulation efficiency (EE %) and drug loading efficiency (DLE %) of both drugs. For the preparation of theranostic nanogels, we followed the same procedures after the addition of the USPIO contrast agent during the NGs synthesis. Next, we needed to ensure the quality of our NGs during long-term storage. To achieve this goal, we developed a freeze-drying process using different kind of sugar cryoprotectants at varying concentrations, in order to protect NGs against mechanical and physical stresses at play during freeze-drying.  Most  promising  sugars  used  with  unloaded  NGs  were  subsequently  used  to cryoprotect DOX-loaded NGs. Finally, we studied the release of DOX from DOX-loaded NGs before and after freeze-drying. This study in particular had two objectives. The first was to compare the effect of the freeze-drying process on the behavior of the DOX-loaded NGs, observing the impact of this procedure on the release kinetics. The second purpose of the release study was to test the ability of NGs to release their contents at three different pH: 5.8 (intracellular pH of tumor cells), 6.8 (interstitial space of the tumor) and 7.4 (blood plasma).
GBM Nanogels Doxorubicin Nanoparticles Chitosan Freeze-drying Cryoprotectants