## 3 Results and Discussion  
### Morphology of the Samples  
Prepared samples were first examined by visual inspection in order to determine the presence of visible defects like drops, and when it was confirmed that all of the samples had satisfying macro-characteristics, they were further examined using a scanning electron microscope.  
In the beginning, it was necessary to confirm the fiber morphology of pure polymers, so PLA- and PVP-based nonwovens were examined by SEM (Figure 1), and after that samples with active compounds were prepared.  
As it can be seen in Figure 1a,b, electrospinning parameters for pure polymers were well established as no irregularities like drops or beads along the fibers were not detected. Fibers were nicely shaped, smooth, and with regular morphology. PLA fibers had slightly higher diameters than pure PVP fibers.  
The addition of active compounds changed the morphology compared to pure polymer fibers, especially in the case of PLA-based samples, where significant change in the shape of the fibers was observed. With the addition of PSO (Figure 2a), fibers within the sample had high differences regarding fiber's diameter (Table 2), where very thin and very thick fibers were present in the structure, which increase standard deviation of the diameter values. It seems that one fiber was actually divided into two, which might be due to lower compatibility of PLA and PSO. In the case of the mixture of PLA with SB (Figure 2b), fibers were flatter with thicker domains along them, which looked like reservoirs for oil. It seems that sea-buckthorn oil was not well dispersed within PLA matrix. Possible reason for this behavior within the PLA mixtures with PSO and SB can be the fact that PLA is approved for contact with food which contains fats and oils, pointing at good barrier properties of PLA against fatty matter. PSO and SB oils have high content of fatty acids, both saturated and unsaturated, which might be immiscible with PLA when added in higher concentrations.  
The main effect of the addition of active compounds into PVP on the fiber morphology is the increase in the diameter of the fibers (Table 2). Fibers look more voluminous and rounder in shape, whereby bead-less structure without drops was maintained (Figure 2c,d). In the case of the encapsulation of mixture of PSO and extract of fermented pomegranate juice (which is in the form of the powder), small particles of the extract were detected on the fibers' surface as light dots (Figure 2e). The addition of the EP did not affect regular morphology of the fibers.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sample Name** & **Fiber Diameter (\(\mu\)m)** \\ \hline PLA & 0.88 \(\pm\) 0.22 \\ PVP & 0.755 \(\pm\) 0.067 \\ PLA-5 SB & 0.92 \(\pm\) 0.37 \\ PLA-10 SB & 0.98 \(\pm\) 0.45 \\ PVP-5 SB & 0.788 \(\pm\) 0.083 \\ PVP-10 SB & 0.93 \(\pm\) 0.15 \\ PLA-5 PSO & 1.05 \(\pm\) 0.22 \\ PLA-10 PSO & 1.6 \(\pm\) 0.3 \\ PVP-5 PSO & 0.82 \(\pm\) 0.15 \\ PVP-10 PSO & 0.91 \(\pm\) 0.09 \\ PLA-5 PSO5 EP & 0.9 \(\pm\) 0.15 \\ PVP-5 PSO5 EP & 0.87 \(\pm\) 0.15 \\ PVP-10 EP & 0.83 \(\pm\) 0.12 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Diameters of the Fibers.  
Figure 1: SEM micrographs of (**a**) PLA nanofibers, (**b**) poly(vinyl-pyrrolidone) (PVP) nanofibers.