Kinetics of Release of a Bifunctional 2,2,5,5-Tetramethyl-4-Phenyl-3-Imidazoline-1-Oxyl-3-Oxide Probe from Poly-D,L-Lactide Films Formed Using Supercritical Carbon Dioxide

Optical spectroscopy and ESR spectroscopy were used for the first time to quantitatively describe the release of a nitroxyl probe from poly-D,L-lactide (PDLLA) films into phosphate buffer. The bifunctional probe, 2,2,5,5-tetramethyl-4-phenyl-3-imidazoline-1-oxyl-3-oxide (IMNO), contains a paramagnetic nitroxyl group and has a high extinction coefficient in the UV spectrum. Polymer films were obtained from porous PDLLA-based matrices formed and doped with IMNO in supercritical CO2 (SC-CO2). The combined use of the above-mentioned methods was shown to be promising to gain a more detailed information on the release of probes from PDLLA films, the duration of which did not exceed three weeks.