## 4 Results and Discussion  
To prepare optimal electrospinninging solutions for a suitable carrier of Bup, the first PVP solution was prepared. The solution was subjected to electrospinninging process in the following condition: 20 kV voltage, 0.5 mL/h flow rate and 15 cm nozzle-to-collector distance. Then, the formation of nanofibers and morphology of the electrospun nanofibers were examined using a scanning electron microscope (SEM). Figure 1a shows the SEM images of electrospun PVP nanofiber mats. This image shows the formation of narrow, uniform and smooth surface morphology of polymeric nanofibers. The histogram of PVP nanofibers diameters size distribution is shown in Figure 1b, approving the narrow size distribution with an average diameter size of 49 nm. As shown in Figure 1c, the contact angle test was conducted to determine the contact angle of water droplet on the solid surface of the pure PVP nanofibers as a function to examine the wettability and impenetrability water in the sample surface. As can be seen, the contact angle of electrospun PVP nanofiber mats was 89\({}^{\circ}\), indicative of a typical hydrophobic feature of nanofibers. Figure 1: _Cont._  
To improve the hydrophilicity of the mat and to increase water penetration, the PVA polymer was added to PVP. PVA is a biocompatible, biodegradable, cheap and water-soluble polymer attractive to researchers in potential biomedical applications. However, the water solubility and fast swelling of the PVA limit its application in the aqueous medium. It seems that the preparation of PVP/PVA composite can improve polarity, wettability and swelling properties in contrast to PVP or PVA. Thus, in the next step, the composite PVP/PVA nanofibers were fabricated by the electrospinning of PVP/PVA (50/50 W/W) solution in the same electrospinning condition of PVP. The SEM analysis of PVP/PVA nanofibers (Figure 2a) indicated the formation of smooth, bead-less and uniform nanofibers mat. The morphology of electrospun PVP/PVA nanofibers showed a higher uniformity than electrospun PVP nanofibers. The higher hydrophilicity of PVA caused a reduced polarity and made more well-ordered nanofibers. Figure 1: (**a**) Scanning electron microscope (SEM) images, (**b**) fiber diameter distribution, (**c**) the contact angle of PVP nanofibers. Figure 2: _Cont._  
The analysis of the PVP/PVA nanofiber diameter distribution, as depicted in Figure 2b, estimated that the mean fiber diameter of electrospun PVP/PVA was 104 nm. It seems that the addition of 50% \(w\)/\(w\) PVA to PVP increased the diameter distribution two times (49 nm for PVP nanofibers in comparison to PVP/PVA nanofibers with 104 nm). As shown in Table 2, the addition of PVA increased the electrical conductivity of the PVP/PVA polymers solution. An increase in solution conductivity tended to speed up Taylor cone formation and the ejection of polymer jet. A rise in the conductivity of the solution and the electrical conductivity of the resulting fibers caused the diameters of the fibers to be thicker than expected [54]. Previous research shows that extremely thin nanofibers with more PVP and high surface-to-volume ratio can lead to a fast drug release [24; 25]. This issue is improved by a relative increase in the diameter of nanofiber and a slower release. Also, the incorporation of PVP in PVA makes these membranes maintain the moisture of environment [46]. The context angle of electrospun PVP/PVA nanofibers is shown in Figure 2c. As observed in Figure 2c, the contact angle was below 90\({}^{\circ}\) (71\({}^{\circ}\)), indicating the spreading of the liquid on the solid surface, hence a wettability in the medium range suggesting potential applicability of this nanofiber that for transdermal drug delivery systems.