## 3 Results and Discussion
### Cell Interactions with Surfaces  
The interactions between the biological systems and the new materials are of fundamental importance for the study of biomaterials. In vitro cell culture assays are of principal interest to assess the biocompatibility of materials. Also, such initial in vitro analyses provide an excellent way to screen materials before performing in-depth _in vivo_-based analyses. Among the putative cell lines suitable to perform the present study, commercially available cell lines that include representative cells of the different layers of the skin were chosen. The function of the skin includes acting a barrier providing protection from physical, chemical and microbiological agents [23]. Keratinocytes represent 95% of the epidermal cells, acting as structural and barrier function of the epidermis. Their role on the skin inflammatory and immunological responses, and wound repair are well recognized. The spontaneously immortalized human keratinocytes HaCaT cell line from adult skin has been proposed as a model for the study of keratinocytes functions [24]. This work includes another keratinocytes with tumoral characteristics such as squamous cell carcinoma (SCC) through the A431 cell line, considering that SCC is by far the most common skin cancer, and actually is more common than any other form of cancer [25]. Fibroblasts (3T3 cell line) have become one of the most common non-epithelial cell line used in in vitro studies on general cytotoxicity and biocompatibility studies. Swiss albino mouse fibroblasts are readily available, show a well-defined protocol, and are representative of a physiologic model cell line [26]. Modified surfaces should not be toxic in nature due to the properties of both PES fabric as well as coating materials. However, the induced superhydrophobicity aims to the decrease of cells adhesion and spreading. Most adherent cells, like fibroblasts and epithelial cells are anchorage dependent, requiring integrin-mediated signaling to stimulate cell-cycle progression and promote cell survival. Loss of integrin-mediated signaling can cause cell death, which can be determined by using the conventional MTT colorimetric method as a measure of the changes on the metabolic activity of cells upon incubation in the presence of the different substrates [13; 21]. Cellular viability was reduced in any textile substrate, either in the absence or presence of coating, compared to standard TCPs conditions, which constitutes the 100% of cellular viability (Figure 2). In all cases, differences (\(p<0.001\)) were found between TCPs and the other substrates, independently of the cell type. Experiments carried out in native PES substratum, as well as other modifications provide feasibility values ranging from 7.1 to 8.0% (3T3), 6.8 to 8.3% (HaCaT), and 5.4-8.1% (A431) with mean values ranged between 7.6 (3T3), 7.1 (HaCaT), and 6.4 (A431). In vitro cell viability and cytotoxicity assays with cultured cell have demonstrated to be useful for the drug screening or cytotoxicity tests of chemicals. These in vitro assays are based on the alteration of some fundamental cell functions such as membrane permeability, enzymatic activity, ATP production, and cell adherence and morphology, among others [27]. Due to the biocompatible properties of both the compounds used to modify fabrics as well as the own substrate, the lack of cell viability may be related to some limitations in adhesion, restrictions of cell attachment, and spreading under the assayed conditions. Figure 1: Surface morphology (1000\(\times\)) of uncoated and coated PES and contact angle (degrees), and EDS maps for F (green), O (purple) and Si (red) of PES fabrics with 2 different superhydrophobic (SH) treatments. Taking into account cell viability values using native PES substrate, significant differences between non-tumoral cell lines (3T3 and HaCaT cell lines) and both types of keratinocytes (HaCaT and A431 cell lines) were found.