ZIF-67 and Mn & Zn co-doped ZIF-67 as multifunctional therapeutic platforms: Antibacterial, antioxidant, and anticancer assessment in lung cancer cells in vitro

The present study is an attempt to delineate the biological efficacy of zinc and manganese doping on ZIF-67 MOF. Pure (ZIF-67) and zinc/manganese-doped samples were synthesised using a one-pot method. Various analytical techniques such as fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) together with elemental mapping analyses through energy dispersive spectroscopy (EDS), support that the MOF formed is a sodalite (SOD) cage type structure. The study of surface properties through Brunauer-Emmett-Teller (BET) analysis unfolded the formation of microporous pristine MOF and mesoporous bimetallic MOF compounds with a surface area of 1227.4 and 4.3 m2g-1 respectively. Additionally, thermal gravimetric analysis (TGA) depicted that the codoped sample decomposed about 20% at 700°C when compared to its precursor which only retained 20% mass at the same temperature. The X-ray Photoelectron spectroscopy (XPS) results showed effective dopant incorporation and strong interfacial interactions between the dopant ions and the MOF framework. ICP-OES studies demonstrated the incorporation of zinc and manganese into the ZIF framework Furthermore, all the doped samples displayed exceptional antimicrobial activity against Staphylococcus aureus and Escherichia coli and also exhibited enhanced antioxidant activity in comparison to their precursor. Sample Z showed the strongest antibacterial activity against E. coli (MIC 31.25 µg/mL; MBC 250 µg/mL), while Zn/Mn modification enhanced the activity against S. aureus, lowering the MIC from 500 to 250 µg/mL for ZM and ZMZ. The in-vitro anticancer study performed on human lung adenocarcinoma cells (A549) revealed the enhancement in the antiproliferative potential of bimetallic Zn/Mn doped ZIF-67 MOFs in comparison to pure ZIF-67 nanostructures. In addition, the orange-red fluorescence observed in A549 nuclei during AO-EB staining indicated late apoptosis induced by the nanocomposites, and complete nuclear condensation coupled with fragmentation, as visualized by Hoechst staining. Thus, the studies have demonstrated the superior cytotoxic and antimicrobial potential of monometal and bimetal doped ZIF-67 samples.