**5. Conclusions**

In summary, our results indicate that thermally stable ZrO2 nanoceramic was successfully synthesized via the hydrothermal method with an average size of 10 to 35 nm. The air-jet spinning technique allowed the design of a nanocomposite scaffold of PLA/ZrO2 composed of fiber morphology, with an average diameter of 395 nm, with random distribution. The biocompatibility of osteoblasts analyzed in the function of cellular adhesion and cellular viability onto the PLA/ZrO2 fiber nanocomposite did not show any cytotoxic effects. Moreover, 0.5 g of the PLA/ZrO2 nanocomposite influenced a good cell functionality, providing a microenvironment correlated to the nanometric and interconnectivity of the fiber scaffold that increased the cell bioactivity over the topography, shown by the mineral-like deposit. However, further studies may be focused on the structural properties of the 0.5 g PLA/ZrO2 fiber nanocomposite in critical-size bone models as a future potential to be applied in bone tissue engineering.

**Author Contributions:** Conceptualization, R.O.-A., O.A.-F. and M.A.A.-P.; investigation, R.O.-A. and M.G.-H.; methodology, R.O.-A. and M.G.-H.; validation, R.O.-A., O.A.-F. and M.A.A.-P.; data curation and formal analysis, R.O.-A. and M.G.-H.; writing—original draft preparation, R.O.-A., M.G.-H. and M.A.A.-P.; writing—review and editing, O.A.-F. and M.A.A.-P.; funding acquisition, M.A.A.-P. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors are grateful for the financial support of the DGAPA-UNAM: PAPIIT IN213821 project and the CONACYT by the particular program of Fondo Sectorial de Investigación para la Educación A1-S-9178 project.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data generated for this study are included in the manuscript.

**Acknowledgments:** We appreciate the support provided by the CONACYT through its scholarship (number: 613415 and CVU: 745379) to Rodrigo Osorio Arciniega during his Doctoral studies in the Programa de Maestría y Doctorado en Ciencias Médicas, Odontológicas y de la Salud at UNAM. The authors want to thank Raul Reyes Ortíz and Adriana Tejeda Cruz from IIM-UNAM for their technical assistance and support.

**Conflicts of Interest:** The authors declare that the research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.
