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.