Despite
being the most common component of numerous metalloenzymes
in the human body, zinc complexes are still under-rated as chemotherapeutic
agents. Herein, the present study opens up a key route toward enhanced
chemotherapy with the help of two ZnII complexes (ZnMBC)
synthesized alongside Mannich base ligands to upsurge biological potency.
Further, well-established mesoporous silica nanoparticles (MSNs) have
been chosen as carriers of the titled metallodrugs in order to achieve
anticancer drug delivery. A pH-sensitive additive, namely, chitosan
(CTS) conjugated with biotin is tagged to MSNs for the targeted release
of core agents inside tumors selectively. In general, CTS blocks ZnMBC
inside the mesopores of MSNs, and biotin acts as a targeting ligand
to improve tumor-specific cellular uptake. CTS–biotin surface
decoration significantly enhanced the cellular uptake of ZnMBC through
endocytosis. A panel of four human cancer cell lines has revealed
that ZnMBC (1/2)@MSNs–CTS–biotin
nanoparticles (NPs) exhibits unprecedented enhanced cytotoxicity toward
cancer cells with IC50 values ranging from 6.5 to 28.8
μM through induction of apoptosis. NPs also possess great selectivity
between normal and cancer cells despite this potency. Two-photon-excited in vitro imaging of normal (HEK) and cancer (HeLa) cells
has been performed to confirm the biased drug delivery. Also, NP-induced
apoptosis was found to be dependent on targeting DNA and ROS generation.
Moreover, a lower range of LD50 values (153.6–335.5
μM) were observed upon treatment zebrafish embryos with NPs in vivo. Because of the anatomical similarity to the human
heart, the heart rate of NP-treated zebrafish has been analyzed in
assessing the cardiac functions, which is in favor of the early clinical
trials of ZnMBC (1/2)@MSNs–CTS–biotin
candidates for their further evaluation as a chemotherapeutic and
chemopreventive agent toward human cancers, especially adenocarcinoma.
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