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Production of mesoporous silica nanoparticles for the development of personalized anti-cancer nanovaccines: a proof of concept study

Book - Dissertation

With cancer being a leading cause of mortality, immunotherapy is emerging as an innovative procedure to control the disease. It is a fast evolving complex field aiming to stimulate components of the immune system against tumor cells. One of these approaches is active specific immunotherapy based on the injection of autologous mature dendritic cells loaded with autologous tumor lysate. Proof-of-principle studies have shown that these vaccines are safe, elicit an anti-tumor immune response and control tumor growth. Unfortunately, the small-scale production process of dendritic cell-based vaccines is expensive, with an estimated cost of more than 50 000 euro per patient. Our project was established in response to these challenges. We focused on a standardized methodology and technology. An "easy to apply" approach, resulted in efficient vaccine production and therefore provided a cost-effective alternative for dendritic cell immunotherapy. This was accomplished by using nanoparticles as a carrier of immunogenic autologous tumor lysate. Nanomaterials are increasingly valued players in drug delivery research as they offer enhanced stability, controlled release and more effective encapsulation of drugs. Mesoporous silica nanoparticles in particular, are promising delivery systems due to their high chemical and mechanical stability while remaining biodegradable. This doctoral dissertation provides proof of concept of mesoporous silica nanoparticlebased vaccines as a cost-effective replacement for dendritic cell vaccination. The results will be applicable for multiple immunogenic tumors, therefore providing improvements in clinical cancer therapy and the patients' comfort during treatment. In a first stage, we optimized the synthesis and surface functionalization of mesoporous silica nanoparticles for further protein conjugation. These consisted of a one-pot wet chemistry process which can easily be up-scaled to industrial production. Small manipulations during synthesis enabled modification of physicochemical properties and biodegradability. The quality of the particles was assessed by extensive characterization of their properties and biodegradability. The main characterization techniques in this work included transmission electron microscopy, dynamic light scattering, zeta potential measurements, Fourier transform infrared spectroscopy and thermogravimetric analysis. Molybdenum blue chemistry and spectrophotometric analysis were used to determine the degradation behavior of the produced particles in saline solution. We produced particles within the desired size range for passive targeting of dendritic cells. Fourier transform infrared spectroscopy, thermogravimetric analysis and zeta potential confirmed carboxylic surface functionalization required for subsequent protein conjugation. The developed nanoparticles were resistant against agglomeration at experimental and physiological pH. In addition, they were biodegradable over a time span of one week. The degradation behavior strongly depended on synthesis parameters, such as temperature, catalyst concentration and surface chemistry. In the second stage, the mesoporous silica nanoparticles were loaded with ovalbumin for the formation of a nanovaccine. This vaccine was tested in vitro on dendritic cell cultures to examine the toxicity, uptake, maturation effect and potential immunogenicity. The particles were sterilized using UV-radiation and their quality was reassessed. UVsterilization of the mesoporous silica nanoparticles did not induce any decrease in particle quality, nor did it induce toxic effects on dendritic cells in culture. Cell staining and confocal microscopy showed nanoparticle and nanovaccine uptake by dendritic cells, which was determined to be an active (ATP-dependent) process and not merely particles penetrating the cells. In addition, maturation of nanoparticle treated cells was observed in the form of increased expression levels of major histocompatibility complex and costimulatory molecules. In general, this implied a possible adjuvant effect of mesoporous silica nanoparticle-based vaccines on dendritic cells and perhaps the adaptive immune system. Finally, confocal microscopy and flow cytometry demonstrated the increased ability of dendritic cells to cross-present an ovalbumin peptide when delivered by the nanovaccine as compared to control conditions. This could suggest the ability of dendritic cells to stimulate cytotoxic T-cells against the protein. These results support the large potential of mesoporous silica nanoparticle-based vaccines as a replacement of the expensive dendritic cell vaccination for active specific immunotherapy, offering a more standardized production process and possibly higher efficacy.
Publication year:2020
Accessibility:Closed