Carbon dioxide impregnation of electrospun polycaprolactone fibers

The electrospinning of polymers has become a potentially important process for the production of tissue engineering scaffolds. CO₂ impregnation of these scaffolds may provide a method for tailoring the chemistry of these relatively high surface area scaffolds without altering their biomimetic architecture. In pursuing this we found that electrospun polycaprolactone (PCL) fibers melt when exposed to supercritical CO₂ even at room temperature. However, CO₂ exposures ranging from 10 to 25 °C and 1.0 to 3.44 MPa provided chemical impregnation without apparent changes in physical structure. A test compound, carboxytetramethylrhodamine, was embedded into electrospun PCL using CO₂ at 3.44 MPa and 25 °C for 10 h. The subsequent release of carboxytetramethylrhodamine into phosphate buffered saline at 37 °C was then monitored. Release was observed for 30 days after which the fibers were shown to retain 8.54 μg of carboxytetramethylrhodamine/mg of PCL. Control samples not exposed to CO₂ showed no detectable release after 5 days.