**4. Conclusions**

In this study, PEO were mainly applied to form a well-distributed porous TiO2 surface, and HiPIMS was further adopted to deposit Ta2O5 and Ta(Zn)O coatings on the porous surface of Ti to discuss the material properties, antibacterial performance, and biocompatibility of the thin films.

The conclusions are shown as follows:


and they had improved antibacterial abilities against *S. aureus* and *A. actinomycetemcomitans*. The Ta(Zn)O deposited by HiPIMS exhibited the lowest intensity in both of the *S. aureus* and *A. actinomycetemcomitans* bacterial colonies, and it showed the best antibacterial performance.

3) The results of the ISO-10993-5 cell cytotoxicity and cell viability MTT assay tests revealed that the Ta2O5 or Ta(Zn)O coated Ti had better cell viability and lower cytotoxicity in HSF cells, and both coatings possessed high biocompatibilities in this study. The cell activity of Ta(Zn)O coated Ti decreased slightly when reacting to the MG63 cells. The result showed that the Ta2O5 coating on Ti surface with porous structure improved adhesion, migration, and proliferation for the osteoblastic cell. Due to the di fferent properties of cells, HSF and MG-63 cells represented di fferent behaviors of cell cytoxicity and cell viability in each kind of coating specimens on Ti.

**Author Contributions:** Conceptualization: Y.-Y.C., H.-L.H.; methodology: Y.-Y.C., H.-L.H.; validation: Y.-Y.C.; formal analysis: Y.-Y.C., H.-L.H., M.-T.T.; investigation: Y.-Y.C.; resources: Y.-Y.C.; data Ccration: Y.-Y.C., H.-L.H.; writing—original draft preparation: Y.-Y.C., Y.-J.L.; writing—review and editing: Y.-Y.C., H.-L.H., M.-T.T.; visualization: J.-T.H.; supervision: Y.-Y.C.; project administration: Y.-Y.C., H.-L.H.; funding acquisition: Y.-Y.C., J.-T.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Ministry of Science and Technology (MOST 107-2218-E-131 -001 and MOST 108-2221-E-150-020-MY3) of Taiwan. This work was also financially supported by the "High Entropy Materials Center" from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) and from the Project MOST 108-3017-F-007-002- by Ministry of Science and Technology (MOST) in Taiwan.

**Acknowledgments:** The instrumental assistance from the Common Lab. for Micro/Nano Sci. and Tech. of National Formosa University is sincerely appreciated.

**Conflicts of Interest:** The authors declare no conflict of interest.
