Investigating Escape of Low MW Siloxanes from PDMS

Knowledge of the oxygen levels in a tumor is a current goal of cancer research due to the importance of hypoxia on tumor growth and treatment. Previous work by the Cima group at MIT has shown that an oxygen sensor made from low molecular weight siloxanes (LMWS) in a PDMS matrix can be implanted during a biopsy and effectively measure oxygen levels in rat tumors with MRI. The Cima group also found that the sensors experienced signal loss over time when stored in air. The purpose of this investigation was to explore the loss of signal over time of the sensor when stored in aqueous solution. The signal reduction over time in environments similar to the body could be approximated by measuring the spin-lattice relaxation times of the sensor in various aqueous solutions. It was hypothesized that diffusion of the LMWS from the sensor to the surrounding environment was the potential cause of the signal loss over time, so the amount of LMWS that escaped into aqueous solution was investigated. Thesis Supervisor: Michael Cima Title: Professor of Materials Science and Engineering