## 3 Results
### Pre-Test Characterization
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Number** & **Position (cm\({}^{-1}\))** & **Assignments** & **References** \\ \hline
**1** & 843 & CH\({}_{2}\) rocking & [38] \\
**2** & 900 & wagging (C-H) & [28] \\
**3** & 934 & Si-O stretching & [28] \\
**4** & 958 & CH\({}_{2}\) rocking of methylene group & [38] \\
**5** & 999 & CO group & [39] \\
**6** & 1029 (1034) & stretching C-O, (Si-O stretching) & [28; 30; 36] \\
**7** & 1066 & symmetric and asymmetric stretching (C-O) & [28; 30] \\
**8** & 1110 & Asymmetric stretching (C-O-C) & [29] \\
**9** & 1146 & Symmetric stretching (C-O-C) & [28] \\
**10** & 1159 & (carbonyl bands) bridge C-O-C & [28; 30] \\
**11** & 1241 & Symmetric twisting CH\({}_{2}\) & [31] \\
**12** & 1287 & Asymmetric twisting CH\({}_{2}\) & [32] \\
**13** & 1315 & C-N stretching, C-H symmetric stretching (CH\({}_{3}\)) & [28] \\
**14** & 1348 & CH\({}_{2}\) wagging (C-H) & [31] \\
**15** & 1374 & CH\({}_{3}\) bending & [28; 30] \\
**16** & 1420 & CH\({}_{2}\) bending & [28; 30] \\
**17** & 1456 & Asymmetric and symmetric CH\({}_{2}\) bending & [29] \\
**18** & 1470 & Asymmetric CH\({}_{2}\) bending & [38] \\
**19** & 1518 & N-H deformation and C-N stretching of amide II & [34] \\
**20** & 1557 & N-H bending (amide II) & [35] \\
**21** & 1595 & N-H bending & [33] \\
**22** & 1634 & N-H bending of NH\({}_{2}\), C=N stretching (Schiff base) & [40] \\
**23** & 1663 & Stretching C=O (amide I) & [34] \\
**24** & 1713 & Carboxyl band (C=O) & [35] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of FTIR band assignments related to CS/PEO and CS/PEO/BG. Laser micrographs of the three tested surfaces are shown in Figure 5a-c as obtained at two different magnifications. Images collected at 10X revealed the how the fiber coatings are distributed on all the Ti-alloy surfaces. Some raised clusters are clearly visible and related to the drying of polymer droplets on the tip of the needle during the electrospinning. These areas influenced the Rz parameters for each of the types of substrates coated by electrospinning. Analyzing the topology of the Ti-alloy, the surface appeared affected by long grooves with a depth in the micrometer order clearly visible at both magnifications. Average roughness value, \(Ra\), and mean Roughness depth, \(Rz\), were obtained by laser profilometry and their differences statistically validated. Figure 4: FTIR spectra of CS/PEO (a) and CS/PEO/BG (b) nanofibers. The numbers correspond to the positions of bands whose assignments are listed in Table 1.  
Figure 5: 3D laser micrographs of the three different substrates (Ti-alloy (**a**), CS/PEO (**b**) and CS/PEO/BG (c)) obtained before bacterial and osteoblast treatments at two different magnifications (10X and 150X). The graphs reported in Figure 6 display the same trend. The Ti-alloy uncoated showed statistically relevant differences (\(p<0.05\)) with both of the other two fiber-coated substrates possessing the lowest average roughness and mean roughness depth, \(0.23\pm 0.01\)\(\upmu\)m and \(3.73\pm 0.41\)\(\upmu\)m, respectively. About CS/PEO (Ra 0.85 \(\pm\) 0.18 \(\upmu\)m and Rz 17.48 \(\pm\) 4.26 \(\upmu\)m) and CS/PEO/BG (Ra 0.84 \(\pm\) 0.17 \(\upmu\)m and Rz 16.01 \(\pm\) 1.69 \(\upmu\)m), no statistical differences were identified between each other. The fiber distribution and size was measured by using SEM (Figure 7). CS/PEO fibers (Figure 7a) were smooth and randomly oriented with a narrow distribution of diameters (Figure 7b), \(294\pm 64\) nm. The average fiber diameter for CS/PEO/BG was bigger (\(493.21\pm 77.11\) nm) (Figure 7d) and some groups presented the same orientations adhering together (Figure 7c). Another important feature regards the formation of nanowebs within the nanofibers, clearly visible especially in the CS/PEO, with a diameter varying from 50 to 90 nm. These ultrathin nanowire formations are attributed to the phase separation of charged droplets generated during electrospinning under high electric forces, including electrostatic force, drag force, and gravity.