**5. Conclusions**

Silver-doped nanoscale hydroxyapatite may be incorporated into electrospun PCL scaffolds to fabricate a device that is both nontoxic to cultured mammalian cells and capable of inhibiting the growth of pathogenic microorganisms. The scaffold demonstrated antibacterial activity against both Gram-positive and Gram-negative bacterial strains commonly found in bone infections. The material

was shown to release silver in an initial burst followed by a more sustained bulk degradation release. Silver appeared to enhance MSC di fferentiation down an osteogenic path when used in nontoxic concentrations. Silver-doped nHA containing sca ffolds exhibited antimicrobial activity while stimulating bone tissue regeneration, which shows promise as a dual-action medical device to address unmet clinical needs in orthopedic and dental bone surgery.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2079-4983/11/3/58/s1, Figure S1: EDX elemental mapping of 10 Ag mol.% samples detecting oxygen, phosphorus, calcium and silver. TEM image of the analysed material is also shown for comparison along with an overlay image of all elements in a single frame.

**Author Contributions:** Conceptualization, T.E.P., R.S., P.V.H., and I.O.; Formal analysis, M.d.S.M.; Funding acquisition, T.E.P, R.S., and P.V.H.; Investigation, T.E.P. and J.T.; Methodology, T.E.P., J.T., and C.J.H.; Resources, P.V.H., Z.L., and I.O.; Supervision, R.S., Z.L., and I.O.; Validation, C.J.H.; Writing—original draft, T.EP. and J.T.; Writing—review & editing, R.S., C.J.H., P.V.H., Z.L., and I.O. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was funded by MeDe Innovation (the UK EPSRC Centre for Innovative Manufacturing in Medical Devices, gran<sup>t</sup> number EP/K029592/1). UK-China lab placement was made possible by Newton Trust funding, with further support from the National Natural Science Foundation of China (51673029 and 61875015), Beijing Talent Fund (2016000012113ZK34), and Beijing Municipal Health Commission (PXM2018026275000001, BMC2018-4).

**Acknowledgments:** Mass spectrometry analyses were performed by the biOMICS/chemMS Facility of the Faculty of Science Mass Spectrometry Centre at the University of She ffield.

**Conflicts of Interest:** The authors have no competing or conflicted interests to declare.
