**3. Conclusions**

Electrospinning is a technique used worldwide that allows the fabrication of polymeric NFs in the range of micro- and nanometers. Biocompatible and biodegradable synthetic polymers are essential structures that have improved chemotherapeutic treatments in the biomedical field. During the last years they have been extensively and specifically reported as systems with important benefits in important fields, including drug delivery and cancer treatments. In this review we have summarized recent advantage for the fabrication of NFs by electrospinning focused on drug delivery applications and cancer treatments (magnetic and plasmonic hyperthermia). Two methods are principally used for the fabrication of NFs by electrospinning: blend and coaxial electrospinning. Based on these methodologies, we reported recent approaches for the fabrication of drugs-IN-NFs with drug delivery and cancer treatment applications. We not only included a direct introduction of the drug dissolved within the polymer, nowadays, a very useful strategy is the incorporation of colloidal particles used as vehicles into the NFs during electrospinning. These particles are able to increase the amount of drug into the NFs to be released in a constant and controlled manner. In this sense, in this review we have also included polymers with stimuli-responsive behavior, obtaining NFs with the ability to increase the drug delivery capability in the function of an external stimulus (temperature or pH). Indeed, electrospinning also offers the possibility to fabricate hybrid NFs, structured as polymeric NFs with systems such as CNTs, graphene oxide, or even magnetic or metallic nanoparticles. Consequently, we also pointed out in the relevance of hybrid NFs in drug delivery improvements as well as in the reduction of solid tumors through magnetic and plasmonic hyperthermia.

**Author Contributions:** Conceptualization, R.C.-C. and J.P.; revision and supervision, R.C.-C., C.M., J.M.L.-R., J.P.; contribution to the oncological application, figures and discussion, L.C. and G.P.; contribution to nanoplatform types, figures and discussion, A.D.; funding acquisition, J.M.L.-R. and C.M.

**Funding:** This research was funded by the Comunidad de Madrid, Spain fellowship "Atracción de Talento Investigador" (2018-T1/IND-10736), Consejería de Salud de la Junta de Andalucía (project PI-0476-2016 and PI-0102-2017) and CICYT, Spain (project CTQ16-76311).

**Acknowledgments:** We thank D. Antonio Ramírez (Department of Anatomy and Embryology) for his administrative assistance.

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