| Electrospinning has been regarded as a prevailing method to fabricate nanofibers.The benefits of high surface to volume ratio and high porosity contribute to apromising application in the field of tissue engineering. The core of tissue engineeringis to prepare biomaterial scaffolds to mimic natural extracelluar matrix(ECM). Greatefforts have been made to encapsulate model drugs into electrospun nanofiberscaffolds. However, many drugs such as protein are easily inactivated when exposedto chemical environment.So it should be covered before electrospinning. However, fordrugs in such particulate form, it remains a challenge to well encapsulate them intothe ultrafine fibers completely, not to mention a sustainable drug release.To ensure a proper encapsulation of particle drugs by electrospun nanofibers,proposals have been put forward to use beaded nanofibers as drug carriers.The beadsin fibers own diameters up to several microns and therefore have sufficient capacityfor particle drugs. However, the process of preparing beaded nanofibers is unsteadyand the beads-on-string stucture is the premise of drug encapsulation. However, fewattentions have been paid to this stucture to discover the conditions for formingbeaded nanofibers and controlling the size of beaded nanofibers. Based on this goal,contents of the study and the corresponding conclusions are as follow:(1) Fabrication of electrospun beaded nanofibers. The concentration was selectedas the key factor to control the formation of beaded nanofibers. PEO was selected toprepare the spinning solutions in consideration of good spinnability. The morphologyof nanofibers was observed under an optical microscope and a scanning electronmicroscope.(2) Adjustment and charaterization of the size for beaded nanofibers. On thepremise of the stable preparation for beaded nanofibers, further studies about theeffects of concentration,voltage, spinning distance and velocity on the variationtendency of fiber diameter, bead diameter and bead number were conducted.4 different PEO concentrations were selected to study the influence of concentration onthe size. The6.0wt%PEO aqueous solution was used to study the influence ofspinning parameters on the size. SPSS and MATLAB softwares were used to analyzethe effects of main factors above on the size of beaded nanofibers.(3) The encapsulation of drug particles by beaded nanofibers. The paclitaxel wasselected as the model drug particles. Suitable spinning parameters were selected tofabricate beaded fibers and smooth fibers respectively.The first contrast experimentwas conducted to observe the variation of beaded nanofibers with and without drugs.Through analyzing whether drugs can cause a change in the size to acess the impactof drug particles on beaded nanofibers. The second contrast expriment was to observewhether particles on the surface of fibers to assess the encapsulation efficiency ofbeaded nanofibers and smooth fibers.The results showed that beaded nanofibers were stably prepared when PEOconcentration was kept in the range of2.5wt%to7.0wt%. when increasing theconcentration and the velocity, lowering the voltage appropriately, fiber diameter andbead diameter both increased. Meantime, when reducing the concentration andvoltage, increasing the flow velocity and the spinning distance appropriately, thenumber of beads increased. At all spinning conditions, the average fiber diameterbetween beads was controlled within50~500nm effectively, and the bead diameterwas up to1~2μm, a small part of beads diameter even could be up to3~4μm. Addingdrug particles during electrospinning, the surface of beaded nanofiber was found nobare particles, while fibers between the beads became thinner. However, a lot of largeparticles distributed on the surface of smooth fibers. As a result, only the fiber itselfhas a beads-on-string structure can effectively embed drug particles. In addition, thebeads size and number are not affected by particle drugs. |
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