Kinetics of drug release from electrospun poly([epsilon]-caprolactone)

Electrospinning is a procedure used to produce submicron, fibrous polymeric mats. Interest in electrospinning for many biomedical applications, such as tissue engineering and drug delivery, is growing due to the ability to control fiber diameter and morphology with simple equipment. The objective of this paper was to study the kinetics of drug release from porous electrospun poly(-caprolactone) (PCL) and compare it to the release from dense cast films. Fibers and cast films were produced from 13 wt% PCL in tetrahydrofuran (THF). Prior to electrospinning or casting, appropriate amounts of alizarin red or acetaminophen were incorporated into the polymer solution. The release of these two compounds was studied to determine the correlation between the effective diffusion coefficient and the size of the molecule. The morphology of the electrospun samples was characterized by scanning electron microscopy. The in vitro release of alizarin red or acetaminophen from the drug delivery systems were measured by UV-VIS spectroscopy. An increased loading of alizarin red or acetaminophen led to greater average fiber diameters. Diffusion was determined to be the dominant mode of mass transfer because the release of both alizarin red and acetaminophen was linear when plotted against the square root of time. Based on Fick\u27s Second Law of Diffusion and the appropriate boundary conditions from our experimental set up, a mathematical model was used to calculate the effective diffusion coefficients. Effective diffusion coefficients of alizarin red through PCL films and electrospun samples were calculated to be 2.3 x 10-14 m2/s and 2.4 x 10-12 m2/s, respectively. Diffusion coefficients for acetaminophen through PCL films and electrospun samples were calculated to be 5.8 x 10-14 m2/s and 1.6 x 10-11 m2/s, respectively. These diffusion coefficients are in agreement with those reported in the 2 literature under similar conditions. Release of alizarin red from electrospun samples was over 100 times faster than from dense films while release of acetaminophen was over 270 times faster out of electrospun samples than the dense films. Release out of the electrospun samples was dominated by diffusion through the pores. The release from electrospun mats can be controlled by altering the fiber diameter and pore size. Electrospun drug delivery systems could have applications where rapid, controlled release is desired