Loading the Anionic [Pd(dipic)₂]^2- Complex into the Cavities of Magnetic and Non Magnetic Halloysite Nanotubes Conjugated with Folic Acid and Investigating the in vitro Therapeutic Effects

Abstract

To overcome the non-specific entry of cisplatin and other transition metal complexes into both normal and cancer cells, we developed folic acid-modified halloysite nanotubes (HNTs-FA) and magnetic halloysite nanotubes (MHNTs-FA) as targeted drug carriers. These carriers were loaded with an anionic palladium complex, [Pd(dipic)₂]^2- (dipic: dipicolinic acid), and tested on colon cancer cells. On folate receptors (FRs)-positive HT29 cells, MHNTs-FA-[Pd(dipic)₂]^2- showed significant cytotoxicity, reducing cell viability below 50% at low concentrations. While free [Pd(dipic)₂]^2- and cisplatin were ineffective at these concentrations, MHNTs-FA performed better due to enhanced folate receptor targeting and the presence of Fe₃O₄ nanoparticles. On FR-negative LoVo cells, results suggested the transferrin receptor-1 (TfR1) provided an alternate entry path for MHNTs-FA. Real-time polymerase chain reaction (PCR) confirmed the increased apoptosis via the mitochondrial pathway, with MHNTs-FA-[Pd(dipic)₂]^2- boosting the Bak1/Bclx ratio by 1500-fold and raising Caspase-3 expression. Additionally, it suppressed AKT1 gene expression, lowering drug resistance. Flow cytometric analysis also confirmed the ability of MHNTs-FA-[Pd(dipic)₂]^2- to induce apoptosis in HT29 cells. Importantly, modified HNTs did not cause oxidative stress in erythrocytes. These findings highlight MHNTs-FA as an efficient, targeted delivery system that enhances the therapeutic effects of palladium complexes while minimizing harm to healthy cells.

Keywords:
colon cancer; oxidative stress; AKT1; caspase-3; Bak1/Bclx ratio; erythrocytes