**5. Conclusions**

The obtained membranes, composed of recycled PET nanofibers obtained by electrospinning at four different flow rates, decorated with silver nanoparticles, were characterized by GIXRD, FT-IR, SEM, TEM, and SAED. Results proved the formation of the silver nanoparticles on the surface of the fibers, with a slight tendency of agglomeration at the nodes. The dimensions of the fibers varied between 30 and 100 nm, while the silver nanoparticles ranged in size between 8 and 20 nm. Furthermore, the antimicrobial properties of the materials showed good antimicrobial and antibiofilm activity against Gram-positive and Gram-negative bacteria, as well as fungal strains. The biocompatibility tests were performed both in vitro, on human AFSC cells, and in vivo, through the subcutaneous implantation of the fibrous networks in CD1 mice. Results showed acceptable levels of toxicity in the in vitro and in vivo assays, with lower cytotoxic and inflammatory effects for the silver nanoparticle-decorated fibers. These results recommend the obtained materials for different antimicrobial applications, both in industry and in the biomedical field, opening promising new perspectives for the PET materials.

**Author Contributions:** A.M.G., A.H., M.C.C., A.F., B.S.V., and E.A. conceived and designed the experiments; A.E.S., M.-S.D.-B., performed the synthesis of PET fibers; A.F., A.E.S., M.-S.D.-B., A.M.G., and B.S.V. performed the physico-chemical characterization; A.M.H., C.C., and M.C.C. performed the in vitro experiments; S.G., C.B., M.R., H.H., and A.H. performed the in vivo experiments; all authors analyzed the obtained data; E.A., A.F., M.C.C., A.M.H., A.H., and C.C. wrote the paper.

**Acknowledgments:** This research was supported by the Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), by the National research gran<sup>t</sup> no. 61/2018, project code: PN-III-P1-1.1-PD2016-0605, Romania.

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