The current study paves the way for improved chemotherapy by creating pH-responsive nanogels (NGs) (GC1 and GC2) loaded with synthetic ruthenium(II) arene complexes to increase biological potency. NGs are fabricated by the conjugation of chitosan (CTS)-biotin biopolymers that selectively target the cancer cells as CTS has the pH-responsive property, which helps in releasing the drug in cancer cells having pH ∼ 5.5, and biotin provides the way to target the cancer cells selectively due to the overexpression of integrin. The synthesized compounds and NGs were thoroughly characterized using various spectroscopic and analytical techniques such as NMR, electrospray ionization-mass spectrometry, Fourier transform infrared, UV-vis, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, rheology, Brunauer-Emmett-Teller, and others. NGs displayed exceptional increased efficacy toward cancerous cells with IC50 values ranging from 7.50 to 18.86 μM via induced apoptosis in three human cancer cell lines. Apart from its potency, NGs were found to be highly selective toward cancer cells. Moreover, based on the results of immunoblot analysis, it was observed that the synthesized compounds exhibit a significant increase in the expression of cleaved caspase-3 and a decrease in the expression of the antiapoptotic protein BCL-XL. Interestingly, the complexes were discovered to have the additional capability of catalyzing the conversion of NADH to NAD+, leading to the generation of radical oxygen species within the cells. Additionally, it was discovered that NG-induced apoptosis depends on ROS production and DNA binding. A narrower range of LD50 values (1185.93 and 823.03 μM) was seen after administering NGs to zebrafish embryos in vivo. The results support the use of drug-loaded NGs as potential chemotherapeutic and chemopreventive agents for human cancer cells.
Keywords: NADH catalysis; Ru(II) arene complexes; in vivo toxicity; nanogels (NGs); pH-responsive drug delivery.