PhD Thesis

PRESENTED

Synthesis and characterization of plasma-treated liquid and hydrogels for bone cancer therapy

During the last decade, the anticancer capacity of cold plasmas has been illustrated in different cancer cell lines such as breast, skin, lung, pancreas, cervix or brain and has shown ability to kill cancer cells without damaging the surrounding tissues.This PhD Thesis is focused on investigating potential novel vehicles of plasma-treated liquids for bone cancer with the aim to provide an alternative to the current treatments (i.e. surgery, chemotherapy, radiation therapy and cryosurgery) that are not completely effective.Cold plasma sources can be used to treat liquid media, thereby generating plasma-treated liquids, which can be applied to the cancer cells afterwards. Reactive oxygen and nitrogen species are generated from cold plasmas, which have been related to the biological effects of plasmas and plasma-treated liquids. Despite the exact mechanisms are not completely described yet, the reactive species generated are thought to be the main responsible of the biological effects of plasmas. Many of the radicals generated during the discharge can contribute to complex reactions in liquids: formation of other short and long-lived species in the solution. As plasma-treated liquids will probably be washed in the body through the blood flow when injected, another option for the reactive species transport should be employed.Given the high capacity of hydrogels to store liquids, and their proven capacity as drug delivery agents, the use of biocompatible hydrogels will be studied as novel vehicles for plasma-generated reactive species for bone cancer treatment. This may allow avoiding invasive surgery to the patient, as hydrogels can be used to target tumours by injection. Within this context, the effect of the atmospheric pressure plasma jet will be investigated in liquids and hydrogels to develop novel vehicles for plasma-based therapies.In the first place, a literature review on plasma-treated polymers for biomedical applications will be presented, with special emphasis on the future evolution and new possibilities arising in the treatment of polymer solutions or hydrogels by cold plasmas for biomedical applications. In a first experimental step, the efficiency of direct plasma treatment will be compared to plasma treated or conditioned media with regard to their effects on healthy and cancer bone cells. The concentration of reactive species generated in cell culture media in different plasma treatment conditions will be related to the biological effects observed.Then, the effect of plasma treatment will be carefully studied on the chemistry and physico-chemical properties of different hydrogel-forming polymers: natural (alginate), semi-synthetic (methacrylated gelatin) and synthetic (poly(oxide)ethylene based triblock copolymer) polymers. The generation, stability and release of reactive species generated in solution from plasma will be discussed regarding the different kinds of polymers with different hydrogel-forming ability employed. The potential of polymer solutions and hydrogels as reservoirs and vehicles of reactive species from cold plasmas will be examined here.

PRESENTED

Evaluation of biological effects of atmospheric plasmas in bone cancer

President: MORA GRAUPERA, JAUME

Secretary: MAS MORUNO, CARLES 

Vocal: PRIVAT MALDONADO, ÁNGELA

Osteosarcoma is the most common primary bone tumor and approximately 35% of patients fail the first line of treatment, with a 5-year survival rate in children and teenagers of 70% if diagnosed before it has metastasized or 20% if spread at the time of diagnosis, stressing the need for novel therapies. Recently, Cold Atmospheric Plasmas, consisting in ionized gases composed by UV-visible radiation, electromagnetic fields and a great variety of reactive species, and Plasma-Treated Liquids have shown potential to eliminate cancer cells selectively in different type of cancers, through the generation of reactive oxygen and nitrogen species which induce oxidative damage. The aim of this thesis is to obtain mechanistic insights on the selective anti-cancer effect of Plasma-Treated Liquids in osteosarcoma. Moreover, this thesis has the objective of evaluating the impact of Plasma-Treated Liquids in critical challenges for the development of osteosarcoma therapies, like bone microenvironment, tumor heterogeneity and specific oncogenes and cellular pathways associated with osteosarcoma progression.

PRESENTED

Effects of cold atmospheric plasmas on biomaterials: hydrogels and composites with calcium phosphates

Cold atmospheric plasmas and plasma conditioned liquids (PCL) are gaining increasing attention in the oncological field, as they have shown to selectively induce apoptotic cancer cell death. In this context, PCLs constitute very interesting alternatives to plasmas because they may allow treatment of malignant tumors located in inner organs of the body by intratumoral injection, thus avoiding surgeries and allowing multiple administrations. However, injection of a liquid in the body results in fast diffusion due to extracellular fluids and blood flow. Therefore, the development of efficient vehicles which allow local confinement and delivery of RONS to the diseased site is a fundamental requirement. Our group has recently reported that RONS can be generated into hydrogels, enabling future localized therapies and demonstrating that hydrogels have the potential to be used as drug delivery vehicles of RONS. Nonetheless, hydrogels lack mechanical stability and do not have cues to stimulate bone formation, necessary after bone tumor resection. For this reason, the combination of a hydrogel with another material with osteogenic properties such as Calcium Phosphates (CaPs) is a common strategy followed in the development of biomaterials as bone substitutes. The aim of my thesis is to develop novel composite materials made of hydrogel/CaP in order to obtain a synergistic effect between the CaP phase, namely bioactivity; and the hydrogel phase, namely controlled delivery of plasma-generated RONS.

ON GOING

Cold-atmospheric plasma-treated hydrogels for cancer (immuno)therapy

Cold atmospheric plasma (CAP) is an adjustable source of reactive oxygen and nitrogen species (RONS), which is exploited in selective cancer therapy, where damage to healthy cells is absent/minimal. It has been shown recently that CAP can also promote anti-tumor immunity to achieve systemic and robust tumor clearance. This makes CAP attractive for combination with immunotherapies, a promising emerging possibility. There are two ways in which immune cells can be stimulated using CAP: (1) by inducing immunogenic cell death in cancer cells, leading to release of immunostimulatory molecules, or (2) by treating immune cells (e.g., macrophages) to increase their pro-inflammatory phenotype, migration, and similar.

Our laboratory has pioneered a form of indirect CAP treatment: CAP-treated hydrogels, which serve as vehicles to deliver RONS to cells. Hydrogels offer the advantage over traditionally used CAP-treated liquids since they are not washed away and can enable sustained and localized delivery of RONS and potentially other reagents/drugs. Additionally, hydrogels can be designed to be injectable and to mimic extracellular matrix. As this approach is new, development and optimization of suitable hydrogel formulations for CAP-based therapies is required, as formulation impacts quality, quantity, and stability of generated RONS, delivery route, biocompatibility etc. Furthermore, it is important to investigate the biological activity of CAP-treated hydrogels in the context of cancer therapy and anti-tumor immunity, which will be in focus of this thesis.