Induction of apoptosis by Fe(salen)Cl through caspase-dependent pathway specifically in tumor cells

Unravelling the anticancer potential of a square planar copper complex: toward non-platinum chemotherapy

Coordination compounds from simple transition metals are robust substitutes for platinum-based complexes due to their remarkable anticancer properties. In a quest to find new metal complexes that could substitute or augment the platinum based chemotherapy we synthesized three transition metal complexes C1-C3 with Cu(ii), Ni(ii), and Co(ii) as the central metal ions, respectively, and evaluated them for their anticancer activity against the human keratinocyte (HaCaT) cell line and human cervical cancer (HeLa) cell lines. These complexes showed different activity profiles with the square planar copper complex C1 being the most active with IC50 values lower than those of the widely used anticancer drug cisplatin. Assessment of the morphological changes by DAPI staining and ROS generation by DCFH-DA assay exposed that the cell death occurred by caspase-3 mediated apoptosis. C1 displayed interesting interactions with Ct-DNA, evidenced by absorption spectroscopy and validated by docking studies. Together, our results suggest that binding of the ligand to the DNA-binding domain of the p53 tumor suppressor (p53DBD) protein and the induction of the apoptotic hallmark protein, caspase-3, upon treatment with the metal complex could be positively attributed to a higher level of ROS and the subsequent DNA damage (oxidation), generated by the complex C1, that could well explain the interesting anticancer activity observed for this complex.

‘Oxygen-Consuming Complexes’–Catalytic Effects of Iron–Salen Complexes with Dioxygen

[(salen)FeIII]+MeCN complex is a useful catalyst for cyclohexene oxidation with dioxygen. As the main products, ketone and alcohol are formed. In acetonitrile, [(salen)FeII]MeCN is rapidly oxidized by dioxygen, forming iron(III) species. Voltammetric electroreduction of the [(salen)FeIII]+MeCN complex in the presence of dioxygen causes the increase in current observed, which indicates the existence of a catalytic effect. Further transformations of the oxygen-activated iron(III) salen complex generate an effective catalyst. Based on the catalytic and electrochemical results, as well as DFT calculations, possible forms of active species in c-C6H10 oxidation have been proposed.

TRPM8 channel inhibitor-encapsulated hydrogel as a tunable surface for bone tissue engineering

A major limitation in the bio-medical sector is the availability of materials suitable for bone tissue engineering using stem cells and methodology converting the stochastic biological events towards definitive as well as efficient bio-mineralization. We show that osteoblasts and Bone Marrow-derived Mesenchymal Stem Cell Pools (BM-MSCP) express TRPM8, a Ca²⁺-ion channel critical for bone-mineralization. TRPM8 inhibition triggers up-regulation of key osteogenesis factors; and increases mineralization by osteoblasts. We utilized CMT:HEMA, a carbohydrate polymer-based hydrogel that has nanofiber-like structure suitable for optimum delivery of TRPM8-specific activators or inhibitors. This hydrogel is ideal for proper adhesion, growth, and differentiation of osteoblast cell lines, primary osteoblasts, and BM-MSCP. CMT:HEMA coated with AMTB (TRPM8 inhibitor) induces differentiation of BM-MSCP into osteoblasts and subsequent mineralization in a dose-dependent manner. Prolonged and optimum inhibition of TRPM8 by AMTB released from the gels results in upregulation of osteogenic markers. We propose that AMTB-coated CMT:HEMA can be used as a tunable surface for bone tissue engineering. These findings may have broad implications in different bio-medical sectors.

Investigating the antibacterial activity of salen/salophene metal complexes: Induction of ferroptosis as part of the mode of action

The continuous increase of resistant bacteria including Staphylococcus aureus and its methicillin-resistant phenotype (MRSA) is currently one of the major challenges in medicine. Therefore, the discovery of novel lead structures for the design of drugs to fight against infections caused by these bacteria is urgently needed. In this structure-activity relationship study, metal-based drugs were investigated for the treatment of resistant pathogens. The selected Ni(II), Cu(II), Zn(II), Mn(III), and Fe(II/III) complexes differ in their salen- and salophene-type Schiff base ligands. The in vitro activity was evaluated using gram-positive (S. aureus and MRSA) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Especially the iron(III) complexes displayed promising antimicrobial effects against gram-positive bacteria, with MIC₉₀ values ranging from 0.781 to 50 μg/mL. Among them, chlorido[(N,N'-bis(salicylidene)-1,2-phenylenediamine]iron(III) (6) showed the best MIC₉₀ value (0.781 μg/mL = 1.93 μmol/L) against S. aureus and MRSA. Complex 6 was comparably potent as ciprofloxacin against S. aureus (0.391 μg/mL = 1.18 μmol/L) and only marginally less active than tetracycline against MRSA (0.391 μg/mL = 0.88 μmol/L). As part of the mode of action, ferroptosis was identified. Applying compound 6 (10 μg/mL), both gram-positive strains grown in PBS were killed within 20 min. This efficacy basically documents that salophene iron(III) complexes represent possible lead structures for the further development of antibacterial metal complexes.

A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging

Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.