## 3 Results and Discussion
### Recovery of the Substrates Properties after Interaction with Cells  
One of the objectives of this work was to evaluate the durability of the superhydrophobic character of these surfaces after interaction with cells and their possible recovery, in the event that they were modified. Determining wettability by measurement of the contact angle has allowed the evaluation of the hydrophilic/hydrophobic nature of the surfaces after their interaction with the cells. Contact angle of the water drops over the surfaces was measured offline from video frames and summarized in Figure 3.  
Figure 2: Relative viability of cell lines on unmodified and modified substrates, for 24 h, determined by MTT assay. The data corresponds to the average of three independent experiments \(\pm\) standard deviation. Letter indicates significant differences (\(p<0.001\)) between the three cell lines for the same substrate (a: 3T3; b: HaCaT and c: A431). Number indicates significant differences (\(p<0.001\)) between the four substrates for the same cell line (1: TCPS; 2: PES; 3: SHS1; and 4: SHS2). The variations in the values of the contact angle are function of treatment done on the textile substrate. Thus, small modifications were made in the case of the native PES, presenting total wettability after incubation with cells. No significant differences between contact angle values before and after the incubation with cells were found. Deposition of water on the textile substrate modified with silica nanoparticles (SHS1) showed a slight decrease on the contact angle, without alteration of their superhydrophobic properties. Indeed, the lower surface energy of the fluoropolymer blend and the smaller size of the particles address a combined effect of surface chemistry and surface morphology. This is quite evident also in the second coating where determination of the contact angle on PS modified substrate with PTFE nanoparticles (SHS2) exhibited contact angle values above 120\({}^{\circ}\), but losing their superhydrophobic characteristics after the incubation with cells. Given the structure of the coating as reported from SEM image in Figure 1 with the layer covering homogeneously the fabric yarns, the significant differences in the wettability, reported in Figure 3, account for a coating organization in which the particles are covered by the polymer. Unfortunately, due to the high heterogeneity of the fabric yarns, it was not possible to determine with reliability the surface roughness of the coated fabric and we can only report the multi scale surface roughness value of the coating deposited on glass being SHS1 for 2-5 \(\upmu\)m and SHS2 for 70-200 nm (Figure 4). For both substrates, significant differences (\(p<0.001\)) between contact angle values before and after the incubation with cells were found. With the aim of recovering the superhydrophobic properties of the SHS2 substrates, the surfaces were treated with solutions with very different characteristics in terms of their properties as solvents and pH [28]. Here pure, distilled water (dielectric constant (\(\varepsilon_{\mathrm{r}}\)) 80 and pH 7), water/acetic acid solution (1:1) (with values of \(\varepsilon_{\mathrm{r}}\) 56 and pH 5), and pure acetic acid (\(\varepsilon_{\mathrm{r}}\) 6.15 and pH 2.4) was used. The surfaces were incubated in the solutions in 5-minute sonication cycles and their wettability was determined (Figure 3). The recovery of superhydrophobic properties was observed after treatment with pure acetic acid. Differences (\(p<0.001\)) between the contact angle values for intermediate treatments (either water or water/acetic acid mixture) and either the native SHS2 or after treatment with pure acetic acid were found. The drop does not stick on the substrate and rolls off the surface as a result of the recovered low adhesion (Hysteresis < 5\({}^{\circ}\)). Figure 3: Influence of cell incubation on wettability of the substrates determined by drop shape method. The data corresponds to the average of three independent experiments \(\pm\) standard deviation.