## 4 Results and Discussion
The addition of PVA increased the electrical conductivity of the PVP/PVA polymer solution to 673 \(\upmu\)s leading to a higher diameter of PVA/PVP nanofibers. Likewise, the addition of Bup to PVP led to an increase in the electrical conductivity of the polymer solution from 226 \(\upmu\)s for pure PVP to 1628 for the Bup/PVP solution. The conductivity of the PVP/PVA solution also revealed a considerable increase by the addition of Bup (from 673 \(\upmu\)s to 1261 \(\upmu\)s) due to the polarity of the drug which is the cause of higher conductivity of Bup-loaded solutions. The increased mean diameter of electrospun Bup/PVP/PVA nanofiber mats (186 nm) as compared to electrospun PVP/PVA nanofibers (104 nm) can be explained by the polarity of Bup and the increased conductivity of the solution. The contact angles analysis of electrospun Bup/PVP/PVA nanofiber mats (Figure 4c) revealed that the hydrophilicity and wettability of electrospun PVP/PVA nanofiber mats enhanced as a result of lower contact angle (70\({}^{\circ}\) as compared to the contact angle of 88\({}^{\circ}\) for Bup/PVP nanofiber mats), which can be attributed to the addition of polar PVA. The comparison of contact angle of the four nanofibrous samples in Table 1 shows that the addition of PVA led to a more polar and hydrophilic surface with a lower contact angle; however, the addition of Bup did not affect the contact angle and surface properties of nanofibers. It seems that the drug wrapped successfully with the polymers in the nanofibrous structure so, despite the polarity of drug and higher electrical conductivity of the Bup-loaded solution, the structure of polymers (polarity, hydroxyl group and PVA content) controlled the surface properties of solid nanofibrous mats. This is promising because the envelope of the polymer around the drug and the placement of a small percentage of the drug on the nanofiber structure can control the drug release rate and make it slow. This is the ultimate goal set to reach slow-release systems. Figure 4: (**a**) SEM images, (**b**) fiber diameter distribution, (**c**) contact angle, (**d**) the image of Bup/PVP/PVA nanofiber. Solution viscosity is one of the other key factors in determining the fiber morphology, which is directly correlated with the solution concentration and molecular weight of polymers [13]. The viscosity of electrospinning solutions was measured by a rotational viscometer equipped with 42 spindles and a 5-100 rpm shear rate (Figure 5). The shear rate was increased gradually with the temperature being maintained at 25 \({}^{\circ}\)C. It was found that the viscosity of the PVP solution decreased in accordance with the increase in the shear rate which is indicative of having appropriate concentration for maintaining a continuous jet stream during the electrospinning process. Also, a decrease in the viscosity accompanied by an increase in the shear rate showed the electrospinning capacity of the solution, and it was observed that the higher the gradient the thinner the nanofibers [56]. The viscosity of Bup/PVP and PVP/PVA solutions decreased as the shear rate increased. The addition of PVA raised the viscosity slope but decreased the gradient, and consequently resulted in the thicker diameter of the fibers. A similar trend was also observed in the Bup/PVP/PVA solution. Finally, the fabricated Bup/PVP/PVA nanofibers cross-linked with GTA at room temperature directly affecting the water uptake capacity (WUC) of prepared nanofiber mats. Figure 6 shows the effect of GTA cross-linking on the morphology of electrospun Bup/PVP/PVA nanofibers. The average diameter of GTA cross-linked electrospun Bup/PVP/PVA nanofiber mats boosted to 285 nm (Figure 6b), which describes the absorption of GTA vapor into nanofiber structures while maintaining the integrity and porosity of nanofibers. Moreover, after cross-linking, nanofibers appeared to have some fusion. The partial fusion and smooth surface of nanofibers indicate the cross-linking of nanofibers; the nanofibrous morphology is still observed, however.