Fabrication And Sustained-release Performance Of Emulsion Electrospun Poly (ε-caprolactone) Nanofibers Loaded With Tetracycline Hydrochloride

Electrospinning is a novel method in fabricating continuous polymer nanofibers. Theelectrospinning technology has made a lot of progress in the theoretical research and experimentalparameters study in recent years. The electrospun nanofibers have smaller diameter than cells andcan simulate the structure and biological function of the extracellular matrix. The electrospunnanofibers have also high specific surface area and porosity, which has many potentialapplications in filtering, nanocomposites, wound dressing, and biological medicine. Especially inthe field of biomedicine, electrospinning nanofibers can be widely used as tissue engineeringscaffolds, drug delivery and the carrier of controlled release, etc.However, the conventional electrospinning method has several limitations to a successfuldrug delivery. For instance, most of the electrospinning methods fabricate drug-loaded nanofibersby blending drugs and spinning solutions, resulting in non-uniform drug solution due to mismatchof solvent polarities leading to uncontrolled drug release.In order to alleviate the burst in vitro release of drugs, fabrication of emulsion electrospunnanofibers with core-sheath structures was considered. The core-sheath structure was expected toencapsulate model drugs tetracycline hydrochloride（Tet）. Towards this objective, contents of thepresent study are as following.(1) Influence of emulsion electrospinning parameters on fiber morphologyBy changing, respectively, the spinning parameters, such as PCL concentration of thespinning liquid, drug concentration, volume ratios of water phase to oily phase, spinning voltage,the spinning flow rate, spinning distance and etc, emulsion electrospun nanofiber samples werefabricated. After the analysis of fiber diameter distribution and morphology, some followingobservations can be made. Within the changing range of the experiment parameters, a greaterconcentration of PCL leads to a higher solution viscosity, directly leads to the increase of theviscous stress and reduction in tensile stress, the average fiber diameter increased gradually. Withthe increase of drug concentration in the aqueous phase, fiber uniformity can be improved. As thevolume ratios of water phase to oily phase increases, fiber morphology is more uniform and theaverage diameters are about350nm. The surfaces are smooth and no drug crystals are detected. Obviously, the Tet is located inside the PCL fiber. When the voltage increases, fiber diameter isdecreased first and then increased. As the flow rate increases, fiber diameter is increased. Whenthe spinning distance is21cm, the fiber diameter and scaffold morphology is better.(2) Drug entrapment efficiency and loading efficiencyThe nanofibrous scaffolds for tissue engineering can be obtained by changing the twoimportant parameters, i.e. drug concentration and volume ratios of water phase to oily phase.Experiment results show that, as the volume ratios of water phase to oily phase increases, the drugloading efficiency increases and the drug encapsulation efficiency decreases. With the increasingof drug concentration, the drug loading efficiency increases and drug encapsulation efficiencydecreases. The reason why the actual loading performance was less than the theoretical valuemight be that Tet was the hydrophilic drug, and the viscosity of polymer solution decreased whenthe water phase of Tet were added dropwise into the oil phase. In addition, Tet solution had thesubsidence phenomenon. All of these decrease the spinning performance and lead to the loss ofemulsions in the electrospinning process.(3) In vitro evaluation of the sustained-release performance the nanofibersThe result of fibers encapsulating Tet in vitro release test demonstrated that the core-sheathstructure can alleviate the burst release phenomenon and obtain a better release effect. In vitrorelease tests showed that a higher volume ratio of water phase to oily phase or drug concentrationled to a lower release rate resulted from the thicker sheath of electrospun fibers.In summary, this research studied the effect on the formation of the core-sheath structure ofemulsion electrospinning process parameters, analyzed the encapsulation of the drug by thecore-sheath structure by means of the scanning electron microscopy, confocal laser scanningmicroscopy and transmission electron microscopy, and proved through in vitro release test.Experimental results show that the emulsion electrospun fibers with core-sheath structure have abetter release performance in capsulation of drugs and have broad application prospects in thefield of tissue engineering.