Protection of HeLa cells against ROS stress by CuZnSOD mimic system

A new copper zinc complex (CZpbi), [(bipyridinyl)₂Cu-μ-pbi-Zn(pbi)](ClO₄)₂, pbi = 2-(2-pyridyl)-benzimidazole, was synthesized to mimic copper zinc superoxide dismutase (CuZnSOD). CZpbi was then encapsulated onto a dye (fluorescein isothiocyanate, FITC) functionalized mesoporous silica nanoparticles (MSN) where MSN serves as a nanofactory platform for delivering the catalytic action of the center copper complex. We examined the inhibition of oxidative damage of HeLa cells in the presence of paraquat (PQ, 1,1'-dimethyl-4,4'-bipyridylium dichloride, an oxidative stressor). We further studied the cell viability and cell cycle process under the influence of paraquat stress in the presence of the SOD-mimic FITC-MSN-CZpbi material by flow cytometry and western blot test. We found the nano-sized FITC-MSN is an excellent nano-carrier for delivering the mimic SOD complexes to HeLa cells. Here the reactants are already inside the cell and the result is a promotion of cell function. We present the methodology of encapsulating bio-inspired SOD-mimic in FITC-MSN to achieve a better drug delivery vehicle and catalytic (detoxification) activity. The potency and the stability of SOD-mimic FITC-MSN-CZpbi may provide a new avenue in the future development of artificial antioxidant enzymes.