Folate receptor-targeted indomethacin-loaded gold nanoparticles enhance drug chemotherapeutic efficacy in glioblastoma cells and spheroids

Glioblastoma is a highly malignant brain cancer with a poor survival rate. Increasing evidence demonstrates the anticancer activity, including anti-glioma activity, of indomethacin (IND), a non-steroidal anti-inflammatory drug. However, due to the IND's poor aqueous solubility, nano-based drug delivery systems, especially gold nanoparticles (AuNPs), are great tools for increasing solubility and therapeutic efficacy. Herein, glutathione (GSH)-coated folic acid (FA)-modified AuNPs were used for the first time to generate IND-loaded AuNPs (55 nm), which were successfully synthesized according to DLS, TEM, FTIR, NMR, and TGA results. IND/AuNPs were found to have spherical morphology, nanoscale particle size, narrow size distribution, and good stability. Fluorescence and confocal imaging demonstrated that the nanoparticles penetrated folate receptor (FR)+ U-87MG human glioblastoma monolayer and sphere-forming cells. Remarkably, short-term exposure (4h) to IND/AuNPs significantly increased IND cytotoxicity in U-87MG cells after post-44h and -68h (>35- and >120-fold, respectively). Even against prolonged exposure of cells to IND for 24h, 48h, and 72h, IND/AuNP treatment revealed a marked result: glioma proliferation slowed by 7.38-fold, 6.8-fold, and 17-fold, respectively. No significant effect was observed on the FR- cell lines. The increased antitumoral activity was accompanied by efficient increased apoptosis in glioblastoma cells due to the IND/AuNP treatments. Moreover, compared to free-drug and control groups, IND/AuNP treatments markedly reduced glioblastoma growth in 3D spheroids (in vitro system that mimics in vivo tumors). Therefore, these findings suggest that the new spherical IND/Au-GSH-FA NP conjugate has the potential to be a beneficial therapeutic agent in glioblastoma therapy by targeting FRs.