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 degrees 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 degrees C for 10 It. The subsequent release of carboxytetramethylrhodamine into phosphate buffered saline at 37 degrees C was then monitored. Release was observed for 30 days after which the fibers were shown to retain 8.54 mu g of carboxytetramethylrhodamine/mg of PCL. Control samples not exposed to CO2 showed no detectable release after 5 days. (c) 2006 Elsevier B.V. All rights reserved.