Ph.D Thesis


Ph.D StudentLimor Baruch
SubjectDevelopment and Characterization of Polymeric Systems
Entrapping Genetic Engineered Cells for
Antiangiogenic Cancer Therapy
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Full Professors Machluf Marcelle
Full Thesis textFull thesis text - English Version


Abstract

Microencapsulation of living cells is an emerging approach for the local and continuous delivery of therapeutic agents. Cell microencapsulation technology is based on the entrapment of cells within a polymeric matrix surrounded by a non-degradable semi-permeable membrane, which isolates the cells.

Our research focused on the release of anti-angiogenic proteins from encapsulated cells along with the development of novel encapsulation systems of increased biocompatibility. Engineered cells secreting anti-angiogenic factors were encapsulated and their therapeutic efficacy was studied in vitro and in vivo. Anti-angiogenic factors secreted from encapsulated cells have retained their biological activity in vitro. In the in vivo studies, anti-angiogenic factors secreted from encapsulated cells have inhibited tumor growth by up to 94% in comparison to the control, when transplanted to tumor bearing mice. The considerable reduction in tumors size demonstrates the biological efficacy of the cell microencapsulation delivery system, placing it as a powerful tool in cancer therapy.

We have also focused on the development of new microencapsulation systems with increased biocompatibility. The two systems developed were studied in vitro and in vivo. Alginate-chitosan cell microencapsulation system was developed by the application of a new polymer, chitosan, to the microcapsules. Optimization and characterization in vitro studies were performed in order to achieve optimal cell viability along with improved physical properties of the microcapsules. The biocompatibility of the alginate-chitosan system was evaluated in vivo. When transplanted in mice, alginate-chitosan system resulted with improved biocompatibility in comparison to commonly used encapsulation systems. These findings take the development of alginate-chitosan encapsulation system a huge and significant step towards clinical application.

A novel combined microencapsulation system was also developed by co-encapsulating small polymeric microspheres along with the cells. The small microspheres were loaded with anti-inflammatory drug, which is released to the immediate vicinity of the microcapsules, aiming to reduce the immune response towards them. The system was built and its feasibility was proven in vitro. In vivo study was performed in order to evaluate the combined system biocompatibility. When transplanted in mice, a reduced immune response was seen in the first week after transplantation. However, a week later, the immune response reached the level of the control. In conclusion, the combined encapsulation system has improved short term but not long term system performance. In order to provide long term efficacy, a prolonged release profile of ibuprofen should be implemented as well as a combination of anti-inflammatory drugs.