**4. Conclusions**

In this study, we used full-thickness ex vivo human skin and a wound infection model to investigate the e fficacy and tolerability of ciprofloxacin-loaded PVP foils and nanofiber mats. The model allowed us to test the antimicrobial e fficacy of these materials and to correlate it to their delivery properties. Ciprofloxacin was representative of a poorly water-soluble drug to be loaded in PVP-based drug delivery systems. The use of a solubilizer (acetic acid) increased the loading capacity and drug delivery properties of nanofibers and foils. This was in turn a crucial point for the accomplishment of high local drug concentrations that were required for the successful prevention and eradication of the PAO1 biofilm infections.

This strategy can be used to load PVP-based delivery systems with di fferent types of drugs or disinfectants, including high molecular weight moieties. Besides their sustained drug release properties, such matrixes allow for a more precise dosing of the active ingredient in comparison to ointments or creams. Foils and nanofiber mats are flexible and can be easily applied in less accessible skin areas, e.g., the lower back or between the toes, which is an advantage, especially for old and disabled patients. Thus, we conclude that the combination of drug delivery systems and solubilizing agents is a promising strategy to create attractive new pharmaceutical forms for topical drug delivery to treat or prevent wound infections.

**Author Contributions:** Conceptualization, F.R., M.C., I.S.B. and C.S.; methodology, F.R. and C.S.; formal analysis, F.R., J.J. and M.C.; investigation, M.C., J.J. and C.S.; resources, U.B.-P., A.V. and C.S.; writing—original draft preparation, F.R.; writing—review and editing, F.R., M.C., I.S.B., U.B.-P., A.V. and C.S.; visualization, F.R. and M.C.; funding acquisition, F.R. and C.S.

**Funding:** This research was partially funded by the German Federal Ministry of Economics (grants: KF2928204MD4 and KF2088119MD4). We acknowledge support from the German Research Foundation (DFG) and the Open Access Publication Fund of Charité—Universitätsmedizin Berlin.

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