**4. Conclusions**

The present study intended to find an appropriate combination of magnetic nanoparticles that provide suitable targeted hyperthermia, and potentially proper conditions for being loaded with a positively-charged drug at a neutral pH while releasing it at the acid tumor environment. Both inorganic (MNPs) and biomimetic (MamC-mediated, BMNPs) nanoparticles have been proven to be superparamagnetic, having a blocking temperature lower than 300 K, therefore behaving as paramagnetic at this temperature (thus preventing magnetic agglomeration) but exhibiting a relatively high saturation magnetization in the presence of an external magnetic field, being thus able to be magnetically guided to a selected target site. BMNPs have been found to bind different molecules based on electrostatic interactions, forming stable nano-assemblies at physiological pH, based on the change in the isoelectric point (iep) of the nanoparticles induced by MamC (iep = 4.4). In contrast, MNPs are not as good candidates for that purpose, since their pHiep is around 7. The adsorption of a positively charged drug as doxorubicin on BMNPs would be favored at neutral pH, and at the same time its release would also be enhanced as the system acidifies (like in tumor microenvironments) approaching the iep of the BMNPs. However, while potentially good nanotransporters, BMNPs are not as good agents for hyperthermia as MNPs. Therefore, the present study offers a composition of nanoparticles, namely, 25% BMNPs + 75% MNPs that, while having the maximum hyperthermia response, likely related to improved stability of the sample, is also suitable as a drug nanocarrier designed to deliver the drug in response to changes in the environmental pH. Therefore, the combination of inorganic and biomimetic nanoparticles potentially allows combined targeted chemotherapy and targeted hyperthermia.

**Author Contributions:** Conceptualization, G.R.I., C.J.-L. and Á.V.D.; methodology, G.R.I, C.J.-L., Y.J., A.P., B.L.C.F and Á.V.D.; validation, G.R.I, Y.J., A.P. and B.L.C.F.; formal analysis, G.R.I, Y.J. and A.P.; investigation, G.R.I, Y.J., A.P. and B.L.C.F.; resources, G.R.I, C.J.-L. and Á.V.D.; writing—original draft preparation, G.R.I and C.J.-L.; writing—review and editing, G.R.I, C.J.-L. and Á.V.D.; visualization, G.R.I, Y.J. and C.J.-L.; supervision, G.R.I, C.J.-L. and Á.V.D.; project administration, G.R.I, C.J.-L. and Á.V.D.; funding acquisition, G.R.I, C.J.-L. and Á.V.D.

**Funding:** We wish to thank FPU2016 gran<sup>t</sup> (Ref. FPU16-04580), RYC-2014-6901 (MINECO, Spain), CGL2016-76723 (MINECO, Spain and FEDER, EU), Unidad Científica de Excelencia UCE-PP2016-05 (UGR) and Plan Propio Beca de iniciación a la investigación para estudiantes de master (UGR).

**Acknowledgments:** C.J.L. wishes to thank Alejandro Rodriguez-Navarro for assistance in the interpretation of DRX data. All the authors want to thank the editor and two anonymous reviewers whose comments have greately improved the manuscript.

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