## 3 Results
### Antibacterial Properties  
_Escherichia coli, Pseudomonas aeruginosa_ (Gram-negative), _Staphylococcus aureus,_ and _Staphylococcus epidermidis_ (Gram-positive) are the primary bacteria responsible for infections linked to prosthetic implants and medical devices, according to [PERSON] and colleagues [41]. Therefore, we chose one Gram-negative (_E. coli_) and one Gram-positive (_S. aureus_) strain to employ for in vitro antibacterial assays. The bactericidal effect of Cu-containing TiO\({}_{2}\) coatings on the adhesion and growth of both _E. coli_ and _S. aureus_ colony-forming units (CFUs) over an exposure period of 24 h is quantitatively demonstrated in Figure 10. The samples coated at a \(-100\) V bias were not tested because of their mechanical instability and almost similar copper content to that of the \(-75\) V biased specimens. By inhibiting microbial growth and lowering bacterial numbers, the application of a Cu-containing TiO\({}_{2}\) coating might indicate a decreased risk of infections linked to implants. The tests on the antibacterial activity of the \(-25\) V biased films revealed a noteworthy decrease in the _E. coli_ and _S. aureus_ colonies, reaching \(86\%\) and \(98\%\) inhibition throughout 24 h when compared with the bare alloy. The data also indicated that the \(-50\) V film exhibited a strong bactericidal effect against _S. aureus_ and a lack of bactericidal effect against _E. coli_. These outcomes demonstrated how important copper-containing surfaces are to the antibacterial qualities of the coatings. The antibacterial efficacy of the \(-75\) V biased sample against _S. aureus_ and _E. coli_ is low and not readily apparent. The less hydrophilic surface and insufficient Cu content within the surface are likely the causes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **E\({}_{\text{corr}}\)** & **j\({}_{\text{corr}}\)** & **R\({}_{\text{p}}\)** & **P.E** \\
**(mV)** & **(10\({}^{-6}\) A/cm\({}^{2}\))** & **(kOhms)** & **(\%)** \\ \hline T6 Al4V & \(-118\) & \(10.1\) & \(18.2\) & - \\ Substrate & \(-25\) V & \(-145\) & \(5.4\) & \(33.5\) & \(46.5\) \\ Coated \(-50\) V & \(-122\) & \(2.7\) & \(93.6\) & \(73.3\) \\ Coated \(-75\) V & \(-140\) & \(3.8\) & \(4.0\) & \(62.4\) \\ Coated \(-100\) V & \(-159\) & \(3.9\) & \(36.3\) & \(61.4\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Corrosion potential (E\({}_{\text{corr}}\)), corrosion current density (j\({}_{\text{corr}}\)), polarization resistance (R\({}_{\text{p}}\)), and protection efficacy (P.E.) values obtained for the substrate and coated samples. Figure 9: Potentiodynamic polarization curves in SBF solution at 37 \({}^{\circ}\)C of the substrate and coated samples at different bias values. The higher bactericidal activity against _S. aureus_ on the examined surfaces can be attributed to the dissimilarity in the cell wall structure between the two strains. Gram-negative _E. coli_ possesses an outer membrane, which is important in functioning as a permeability barrier and inhibiting biocide diffusion to the inner plasma membrane, in contrast to Gram-positive _S. aureus_. Furthermore, the reason why _S. aureus_ exhibits a greater inhibition of copper than _E. coli_ is the existence of copper tolerance mechanisms in _E. coli_, such as activation transmembrane copper export and copper sequestration by metallothioneeins [42]. There are a few theories, but the precise mechanisms underlying the copper antibacterial activity are still unknown. One explanation is that copper ions released by the film generate antibacterial activity by their capacity to produce reactive oxygen species (ROS), which harm bacteria [43]. On the one hand, copper ions can alter or disrupt the permeability of the cell membrane, which can cause cell lysis and the release of internal contents. The copper ions can interfere with the processes of DNA replication and protein synthesis. Nevertheless, it has also been noted, that the total cytotoxicity that copper oxide produced was only partially attributable to dissolved copper ions [44].