Release behavior under proteinase K and existing position of Domiphen® in its complexed poly-L-lactic acid micro-fibers electrospun from solution and W/O emulsion

To study the release behavior and the existing position of Domiphen (R) in its its complexed poly-L-lactic acid (PLLA) micro-fibers, two series of fibrous films were prepared by electrospinning solution and W/O emulsion, which was added to Domiphen (R) directly and emulsified by Domiphen (R), respectively, by complexing methods. The mass ratio of Domiphen (R) to PLLA was 0.25%, 0.5%, 0.75%, and 1% for both methods. According to the scanning electron microscopic observation, W/O emulsion and fibers of narrow-distributed diameters were obtained by W/O emulsion electrospinning. Fluorescence microscopic observation suggested that Domiphen (R) was incorporated within fibers by W/O emulsion electrospinning. X-ray diffraction and differential thermal analysis characterization suggested that Domiphen (R) complexed well with PLLA according to noncrystalline Domiphen (R) existing within and on PLLA fibers prepared by both methods. Domiphen (R) release curves were prepared and fitted after the amount of Domiphen (R) released from the PLLA fibers was determined by high-performance liquid chromatography. It was discovered that, with regard to the fibrous films prepared by homogeneous solution electrospinning, Domiphen (R) released from fibers in accordence with the Freundlich's equation suggesting that Domiphen (R) almost existed within the outermost border of the fiber cross section and its release behavior could be considered as the counter adsorption process, while with regard to the fibers prepared by W/O emulsion electrospinning, the release curves were S shape under the effect of proteinase K degradation and could be fitted to the corrosion-mechanism Peppas' equation of n value >0.5, which suggested that Domiphen (R) existed both on the surfaces in small proportion and the inner border of the core-sheath fibers in big proportion.