## 3 Results and Discussion
### In Vitro Cytotoxicity Assessment  
While MgO and AuNPs individually contribute to membrane performance, their combined incorporation is expected to produce a synergistic effect, enhancing the osteogenic, antibacterial, and regenerative properties of the scaffold. The central hypothesis of this study is that integrating both nanoparticles into electrospun PLA membranes results in a multifunctional GBR scaffold with superior biomechanical performance, enhanced osteoconductivity, and improved cellular interactions. This strategy addresses the known limitations of pristine PLA membranes, including insufficient biological activity, limited osteointegration, and suboptimal surface wettability [43; 44]. Biocompatibility is a fundamental requirement for GBR membranes, as these biomaterials must promote osteoblast adhesion, proliferation, and differentiation while avoiding cytotoxic responses. To evaluate cytocompatibility, osteoblast-like MG-63 cells were cultured on the modified and unmodified electrospun membranes, and viability was assessed using the XTT assay (Figure 14). Pure PLA membranes and those containing 0.05 g MgO exhibited the highest cell viability, exceeding 100%. This result may be attributed to the highly porous nanofibrous \begin{table}
\begin{tabular}{c c c} \hline
**Sample** & **Porosity [\%]** & **Density [mg/mL]** \\ \hline
1 & 33.3 & 19 \\
2 & 33.3 & 44.3 \\
3 & 33.3 & 42 \\
4 & 33.3 & 49.6 \\
5 & 50.0 & 54.5 \\
6 & 40.0 & 30 \\
7 & 50.0 & 40.5 \\
8 & 45.5 & 52.4 \\
9 & 50.0 & 42 \\
10 & 45.5 & 47.3 \\ \hline \end{tabular}
\end{table} 
Table 15: Porosity and density. Figure 14: XTT assay (sample 11 refers to control cell culture). architecture, which mimics the extracellular matrix and allows favorable cell-surface interactions. Additionally, PLA's moderate hydrophobicity minimizes protein denaturation while maintaining a suitable interface for cellular anchorage [48]. In MgO-modified membranes, the release of Mg\({}^{2+}\) ions may further stimulate integrin-mediated signaling and enhance the expression of osteogenic markers, such as alkaline phosphatase (ALP) and osteocalcin, which contribute to early differentiation and mineralization [49; 50]. Similarly, the addition of low-concentration AuNPs also enhanced cell viability, which is consistent with evidence that AuNPs can modulate cellular responses by influencing cytoskeletal arrangement, focal adhesion assembly, and gene expression related to osteogenesis [45; 51]. Moreover, their known antioxidant and anti-inflammatory effects can create a favorable microenvironment for osteoblast proliferation [52]. However, increasing the concentration of MgO and AuNPs resulted in a slight decrease in viability. This trend may be explained by elevated ion release or surface heterogeneity at higher nanoparticle loads, which may disturb cellular homeostasis or induce mild oxidative stress, as previously reported by [53; 56]. PLA/AuNP membranes exhibited cell viability in the range of 80-90%, which, while slightly lower than MgO-containing or hybrid membranes, still falls well within the acceptable threshold for cytocompatibility. The moderate bioactivity of AuNPs has been shown to depend on particle size, surface chemistry, and dispersion, with optimal performance typically achieved at lower concentrations [12; 45]. Most notably, PLA/MgO/AuNP hybrid membranes with the lowest combined concentrations demonstrated the highest viability overall, confirming the anticipated synergistic effect. The hybrid membranes appear to combine the bioactive ionic release of MgO with the surface-modifying and signaling properties of AuNPs, resulting in a conducive environment for cell attachment and proliferation. Previous studies [7; 47] support this approach, showing that multicomponent nanostructured scaffolds offer superior osteogenic capacity compared to single-phase materials. According to ISO 10993-5 guidelines [61], a material is classified as non-cytotoxic if cell viability exceeds 70% relative to the control.