Title: New advanced anti-tumor therapies based on hybrid mesoporous nanodevices

Autor: Elena Lucena Sánchez

Abstract: The present PhD thesis entitled “New advanced anti-tumor therapies based on hybrid mesoporous nanodevices” focuses on the design, synthesis, characterization, and evaluation of new hybrid organic-inorganic nanodevices. We have developed mesoporous silica nanoparticles (MSNs) and Janus platinum-MSN and gold-MSN nanoparticles for tumor treatment.
The first chapter is a general introduction that includes an overview of the context related to the research developed in this thesis. In particular, the concept of nanotechnology and nanomedicine are presented, as well as basic information about mesoporous silica nanoparticles, janus nanoparticles, and their interactions with biological systems. Finally, cancer disease characteristics, actual treatments, and the application of nanomaterials as therapy are described.
Next, in the second chapter, the general objectives of this Ph.D. thesis and the specific objectives addressed in the following experimental chapters are presented.
The third and fourth chapters describe two nanotechnology-based therapeutic strategies based on the development of nanomotors to improve cancer therapy. Specifically, the first experimental chapter presents a self-moving nanodevice for controlled drug release in response to intracellular glutathione (GSH). It is based on Janus gold-mesoporous silica nanoparticles functionalized with the enzyme catalase in the gold face, loaded with doxorubicin and capped with disulfide-linked oligo(ethylene glycol) (S-S-PEG) chains on the silica face. Once synthesized and characterized, the nanosystem motion capability through hydrogen peroxide (fuel) conversion into oxygen by catalase was confirmed. The proper gating mechanism of the nanodevice was tested in the presence of GSH, thus corroborating that cargo release only occurs in the presence of the tripeptide. The cellular uptake and doxorubicin release capacity have been demonstrated in the human cervix cell line Hela, being increased in the presence of fuel.
Encouraged by the above results, chapter four describes a similar nanomotor design for antitumor therapy. In this case, the nanoparticle developed is composed of a Janus platinum-mesoporous silica nanoparticle, loaded with doxorubicin, and capped with S-S-PEG. As well as in the previous work, the catalytic decomposition of low concentrations of hydrogen peroxide, in this case by platinum, induced self-propulsion of the nanoparticles. The stimuli-responsive
cargo release kinetic profile was obtained and its application was confirmed in a monolayer THP-1 cell culture and in a microchip device mimicking capillary vessels.
Chapters five and six focus on a new therapeutic strategy, empowering the immune system action on tumors to reach tumor cell death. In the first of these experimental chapters, JQ-1 and transforming growth factor-beta (TGF-β) siRNA-loaded nanoparticles were used as efficient tumor immunotherapy. This nanodevice is based on MSNs loaded with JQ-1 drug, functionalized with polyethyleneimine (PEI) and a siRNA targeting TGF-β was binding through electrostatic interaction. The endosomal escape and efficient cytosolic delivery of siRNA by PEI was accomplished by using these nanoparticles, along with the programmed death-ligand 1 (PD-L1) downregulation and TGF-β silencing. Lastly, its application was confirmed by triggering a specific immunogenic removal of tumor cells in melanoma A375 cells pre-treated with nanoparticles.
In chapter six, the development of a new communication-based immunotherapeutic approach is reported. In this case, we employ Janus gold-MSN functionalized with a peptide called pHLIP onto silica face and anti-PD-1 antibody bound to gold face (J-pHLIP-PD1). Tumor cell membrane is decorated by this nanodevice through pHLIP self-insertion, leaving exposed on the surface PD-1 antibody. This antibody catches circulating T lymphocytes, which express PD-1, and facilitates cytotoxic synapse and communication with cancer cells, provoking immune system-induced-tumor leveling. Moreover, J-pHLIP-PD1 treatment-associated reduction of metastatic burden was also proven in a B16-F10-Luc metastatic model.
Finally, in the seventh and eighth chapter, the general discussion and conclusions derived from the presented experimental studies of this Ph.D. thesis are exposed. In conclusion, the preparation of mesoporous silica nanoparticles and their combination with metal particles and/or organic groups such as molecular gates, enzymatic effectors, environment modifiers, communication mediators, and drugs are presented in this thesis as a potential strategy to overcome tumor treatments limitations. We hope that the results obtained will open up new research opportunities and inspire the development of new advanced strategies with smart materials applied not only in the field of tumor therapy, but also in other biomedical areas to solve patient’s needs.