pH-sensitive tangeretin-ZnO quantum dots exert apoptotic and anti-metastatic effects in metastatic lung cancer cell line

Abstract

Most cancer patients die as a consequence of distant metastases, which are frequently unresponsive to cancer therapy. This study focuses on the anti-tumorigenic and anti-metastatic properties of tangeretin-zinc oxide quantum dots (Tan-ZnO QDs) against the NCI-H358 cell line. Tan-ZnO QDs are pH-sensitive and capitalize on the acidic pH maintained in the tumor microenvironment; therefore, targeted drug delivery is directed specifically to cancer cells, leaving the normal cells less affected. Tan was loaded into synthesized ZnO QDs, and drug loading was analyzed using Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV-Vis) spectrometry. Crystalline phase and particle size were measured using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Drug release was evaluated in buffered solutions with differing pH for up to 15 h. The results confirmed stable drug release (80%) in an acidic pH. Tan-ZnO QDs induced significant cytotoxicity in NCI-H358 metastatic cells, while not markedly affecting HK-2 human normal cells. Morphology of treated H358 cells analyzed via atomic force microscopy (AFM) showed an increased surface roughness and pores. Further, the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells increased after treatment with Tan-ZnO QDs. DNA fragmentation was also induced after treatment with increasing concentrations of Tan-ZnO QDs in H358 cells. We also confirmed regulation of apoptosis via expression levels of Bax and Bcl-2 proteins; G2/M phase cell cycle arrest was observed. Additionally, cell proliferation and migration drastically decreased, and cell invasion and migration, hallmarks of metastasis, were significantly inhibited in H358 cells. Matrix metalloproteinase (MMP)2 and MMP9, markers of metastasis, as well as vascular endothelial growth factor (VEGF), a marker of angiogenesis, were significantly downregulated upon treatment with Tan-ZnO QDs. In conclusion, our novel formulation destabilized H358 cells by using its acidic tumor microenvironment, thereby regulating cell apoptosis, proliferation, and metastatic properties.

Keywords: Anti-metastatic; Apoptosis; Lung cancer; Quantum dots; Tangeretin; Zinc oxide; pH responsive.