Quantitative ToF-SIMS studies of protein drug release from biodegradable polymer drug delivery membranes

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used in the same capacity to identify the molecular ion peak of the surfactant and polymer and use this to determine surface concentration. In the polymer matrix, the surfactant molecular ion peak was observed in the positive and negative mode at m/z 467 and 421, respectively. These peaks were determined to be [AOT + Na+] and [AOT − Na+]. These methods are used to identify the surfactant and protein from the polymer matrix and are used to measure the rate of surface accumulation. The second step was to compare this accumulation rate with the release rate of the protein into an aqueous solution during the degradation of the biodegradable film. This rate is compared to that from fluorescence spectroscopy measurements using the protein autofluorescence from that released into aqueous solution [C.M. Mahoney, J. Yu, A. Fahey, J.A.J. Gardella, SIMS depth profiling of polymer blends with protein based drugs, Appl. Surf. Sci. 252 (2006), 6609-6614.].