**5. Conclusions**

This work supports the rationale for targeting uPAR-positive breast cancer cells, using *N*-AI-loaded PAI-2-functionalized liposomes, and provides a basis for the further development of liposomes that can target heterogeneous tumor cells within the TNBC subtype, in which uPAR was shown to play a key role in driving metastasis. Further research is needed to clarify if and how the potency of *N*-AI as a cytotoxin could be translated into an anti-tumor growth effect by targeting uPAR-positive tumors. The utilization of advanced preclinical models and methods will enable an enhanced evaluation of *N*-AI PAI-2 liposomes in the in vivo context. Future studies assessing the efficacy of *N*-AI PAI-2 liposomes in TNBC are therefore warranted.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1999-4923/12/7/641/s1. Figure S1: Liposome phospholipid interference with *N*-AI absorption spectrum. Figure S2: HPLC standard curve for quantifying *N*-AI encapsulated in liposomes. Figure S3: Cytotoxicity of *N*-AI PAI-2 liposomes. Figure S4: Toxicology testing of empty and *N*-AI-loaded liposomes in mice. Figure S5: Stability of *N*-AI-loaded liposomes over time.

**Author Contributions:** Conceptualization, K.L.V.; methodology, L.B. and K.L.V.; validation, L.B.; formal analysis, L.B. and K.L.V.; investigation, L.B. and K.L.V.; resources, M.R. and K.L.V.; writing—original draft preparation, L.B. and K.L.V.; writing—review and editing, L.B., D.N.S, M.R. and K.L.V.; visualization, L.B., K.L.V.; supervision, M.R., D.N.S. and K.L.V.; project administration, K.L.V.; funding acquisition, K.L.V. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Cure Cancer Australia Foundation with the award of Young Investigator Project Grant to K.L.V., administered by Cancer Australia as part of the Priority-driven Collaborative Cancer Research Scheme, APP1045831. The APC was funded by Molecular Horizons, University of Wollongong.

**Acknowledgments:** This research was conducted with the support of an Australian Government Research Training Program Scholarship, and a Jayne Wilson Cancer Research PhD Top-Up Scholarship (UOW) awarded to L.B.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
