Targeted Fluoxetine Delivery Using Folic Acid-Modified PLGA Nanoparticles for Selective Uptake by Glioblastoma Cells

Background/Objectives: The conventional treatment of glioblastoma (GBM) with alkylating agents is not curative. The protein O6-methylguanine DNA methyltransferase (MGMT) is a significant limitation, being able to repair drug-induced DNA damage. Thus, exploring non-alkylating agents already approved by the FDA is imperative. The antidepressant fluoxetine (FL) has been explored due to its anti-cancer properties. However, its first-pass effect and its non-targeted distribution to brain tissue are major limitations of FL's administration, which is conventionally orally administered. Thus, the primary objective of this work was the development of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) tailored with folic acid (FA) for FL delivery to GBM cells. Methods: A Central Composite Design (CCD) was applied to optimize the NPs. Results: The developed FA-functionalized PLGA NPs exhibited physicochemical properties suitable for brain-targeted delivery. The final formulation presented an average diameter of 167 ± 8 nm, a polydispersity index (PdI) of 0.23 ± 0.07, and a zeta potential of -22.2 ± 0.3 mV. The encapsulation efficiency (EE) and loading capacity (LC) values were 44.4 ± 3.8% and 3.1 ± 0.3%, respectively. In vitro studies demonstrated that the NPs are stable in storage and simulated physiological conditions and can maintain a controlled and slow-release profile of FL for 17 days. In vitro cell uptake experiments demonstrated that conjugation with FA enhances the NPs' internalization in GBM cells overexpressing folate receptors through endocytosis mediated by this receptor. Furthermore, in vitro cytotoxicity experiments demonstrated that the FL encapsulation in the developed NPs maintains drug efficacy, as well as it was able to increase cell sensitivity to treatment with an alkylating agent. Conclusions: These results suggest that the developed NPs are effective nanocarriers, either as a standalone therapy or as a chemosensitizer in combination with the standard GBM treatment.