Since the growth environment can have a significanteffect on the cells, the measurement of cell activityand proliferation is needed to evaluate the biocompatibility and toxicity of the proposed nanocomposite. HEK 293 cells culture experiments wereconducted on the E20M0 and E20M10 films; cellswere cultured on glass slides as normal growthcontrols for comparison. The states of the cells as afunction of incubation time are shown in Fig. 8; noresults are shown for the E20M0 film because noliving cells were detected on this substrate (Fig. S1).This effect may have been caused by poor celladhesion to the cross-linked casein as the presence ofhydroxyl groups on EGDE creates a very hydrophilicsurface, preventing cells from attaching [15]. However, cells adhered normally and grew on the E20M10nanocomposite. This implies that the OMMT greatlyimproved the biocompatibility of the casein-basedcomposite. The presence of Si element in thenanocomposite surface and higher surface area arebeneficial to the cell attachment [42]. The structureand morphology of cells were observed when thecells were removed from the E20M10 film andtransferred to a 96-well plate, as shown in Fig. 8c andd. The cells maintained their normal spindle-shapedmorphology after 5 days in culture on the E20M10film. Thus, it can be concluded that the surface of thecasein nanocomposite facilitated cell adhesion without having a cytotoxic effect.Figure 9 shows the growth of the HEK 293 cellsafter culturing on E20M10 for 1 day, 3 days, and5 days. The relative cell viability is defined as thepercentage change in the absorbance value afterincubation relative to the original value. After incubation, the cells from all samples proliferated. Thereis no difference in the measured growth activitybetween the treated cells and control cells after 24 hof incubation (ANOVA, p[0.05). After another 24 h,the proliferation rate of all cells accelerated. Theseresults further confirmed that the prepared caseinnanocomposite is suitable for cell adhesion and proliferation so that can serve as substrates for cellgrowth for application in tissue engineering orwound healing [43].