Remarkable Stability of Glutathione-Based Supramolecular Gel in the Presence of Oxidative Stress from Hydrogen Peroxide

Low molecular weight 7-methoxy-3-(p-nitrophenyl)iminocoumarin (MNI) with donor and acceptor groups has been synthesized. The molecule shows typical π-stacking geometry in the crystal structure. In this study, MNI, an achiral small organic molecule, forms a nanostructured supramolecular gel along with a short peptide sequence glutathione (GSH). The self-assembly of the achiral organic coumarin component and chiral biomolecule produces a chiral gel with helical fiber structures. Interestingly, the helicities of chiral gels are controlled by the solvent ratio, where MNI in DMSO and GSH in water has been used. Variation of the solvent ratio from 6:4 to 1:9 for DMSO:H2O results in six gels (4, 5, 6, 7, 8 and 9), where the gel numbers signify the water content ratio. FE-SEM analysis shows gel fibers with right-handed helical structures, which have been further confirmed by circular dichroism (CD) with notable helicity in 4 to 6. This is the first report of controlled chiral helical nanostructured supramolecular gel formation by a solvent mixture with an organic small molecule and biomolecule. Interestingly, storage modulus (G') initially decreases from 4 to 6 and further increases up to 9. An opposite strain (%) trend was observed among these six gels. These unusual solvent-dependent gel properties have been further applied to monitor the stability of the gels in the presence of hydrogen peroxide (H2O2), which converts GSH to oxidized glutathione (GSSG) in general. The oxidative stress from H2O2 disrupts 4 to 6 gels, and precipitation occurs. It is noteworthy to mention that GSSG alone cannot form a gel with the MNI molecule and forms a precipitate. Remarkably, on the other hand, 7 to 9 remain as strong gels even after H2O2 treatment. Among all six gels, 9 shows extraordinary stability of gels even after H2O2 treatment.

Enantioselective Cytotoxicity of Chiral Diphosphine Ruthenium(II) Complexes Against Cancer Cells

The chiral cationic complex [Ru(η1 -OAc)(CO)((R,R)-Skewphos)(phen)]OAc (2R ), isolated from reaction of [Ru(η1 -OAc)(η2 -OAc)(R,R)-Skewphos)(CO)] (1R ) with phen, reacts with NaOPiv and KSAc affording [RuX(CO)((R,R)-Skewphos)(phen)]Y (X=Y=OPiv 3R ; X=SAc, Y=OAc 4R ). The corresponding enantiomers 2S -4S have been obtained from 1S containing (S,S)-Skewphos. Reaction of 2R and 2S with (S)-cysteine and NaPF6 at pH=9 gives the diastereoisomers [Ru((S)-Cys)(CO)(PP)(phen)]PF6 (PP=(R,R)-Skewphos 2R -Cys; (S,S)-Skewphos 2S -Cys). The DFT energetic profile for 2R with (S)-cysteine in H2 O indicates that aquo and hydroxo species are involved in formation of 2R -Cys. The stability of the ruthenium complexes in 0.9 % w/v NaCl solution, PBS and complete DMEM medium, as well as their n-octanol/water partition coefficient (logP), have been evaluated. The chiral complexes show high cytotoxic activity against SW1736, 8505 C, HCT-116 and A549 cell lines with EC50 values of 2.8-0.04 μM. The (R,R)-Skewphos derivatives show higher cytotoxicity compared to their enantiomers, 4R (EC50 =0.04 μM) being 14 times more cytotoxic than 4S against the anaplastic thyroid cancer 8505 C cell line.

Redox-Responsive Self-Assembled Nanoparticles for Cancer Therapy

Chemotherapy, combined with other treatments, is widely applied in the clinical treatment of cancer. However, deficiencies inherited from the traditional route of administration limit its successful application. With the development of nanotechnology, a series of smart nanodelivery systems have been developed to utilize the unique tumor environment (pH changes, different enzymes, and redox potential gradients) and exogenous stimuli (thermal changes, magnetic fields, and light) to improve the curative effect of anticancer drugs. In this review, endogenous and exogenous stimuli are briefly introduced. Among these stimuli, various redox-sensitive linkages are primarily described in detail, and their application with self-assembled nanoparticles is recounted. Finally, the application of redox-responsive self-assembled nanoparticles in cancer therapy is summarized.

A new rhodium(I) NHC complex inhibits TrxR: In vitro cytotoxicity and in vivo hepatocellular carcinoma suppression

Thioredoxin reductase (TrxR) is often overexpressed in different types of cancer cells including hepatocellular carcinoma (HCC) cells and regarded as a target with great promise for anticancer drug research and development. Here, we have synthesized and characterized nine new designed rhodium(I) N-heterocyclic carbene (NHC) complexes. All of them were effective towards cancer cells, especially complex 1e was more active than cisplatin and manifested strong antiproliferative activity against HCC cells. In vivo anticancer studies showed that 1e significantly repressed tumor growth in an HCC nude mouse model and ameliorated liver lesions in a chronic HCC model caused by CCl₄. Notably, a mechanistic study revealed that 1e can strongly inhibit TrxR system both in vitro and in vivo. Furthermore, 1e promoted intracellular ROS accumulation, damaged mitochondrial membrane potential, promoted cancer cell apoptosis and blocked the cells in the G1 phase.

In-Cell Activation of Organo-Osmium(II) Anticancer Complexes

The family of iodido OsII arene phenylazopyridine complexes [Os(η6 -p-cym)(5-R1 -pyridylazo-4-R2 -phenyl))I]+ (where p-cym=para-cymene) exhibit potent sub-micromolar antiproliferative activity towards human cancer cells and are active in vivo. Their chemical behavior is distinct from that of cisplatin: they do not readily hydrolyze, nor bind to DNA bases. We report here a mechanism by which they are activated in cancer cells, involving release of the I- ligand in the presence of glutathione (GSH). The X-ray crystal structures of two active complexes are reported, 1-I (R1 =OEt, R2 =H) and 2-I (R1 =H, R2 =NMe2 ). They were labelled with the radionuclide 131 I (β- /γ emitter, t1/2 8.02 d), and their activity in MCF-7 human breast cancer cells was studied. 1-[131 I] and 2-[131 I] exhibit good stability in both phosphate-buffered saline and blood serum. In contrast, once taken up by MCF-7 cells, the iodide ligand is rapidly pumped out. Intriguingly, GSH catalyzes their hydrolysis. The resulting hydroxido complexes can form thiolato and sulfenato adducts with GSH, and react with H2 O2 generating hydroxyl radicals. These findings shed new light on the mechanism of action of these organo-osmium complexes.

M2L4 coordination capsules with tunable anticancer activity upon guest encapsulation

Guest encapsulation can modulate the cytotoxicity of anthracene-based nano-capsules and broaden their applications from metallodrugs to biocompatible delivery systems.

Current applications and future potential for bioinorganic chemistry in the development of anticancer drugs

This review illustrates notable recent progress in the field of medicinal bioinorganic chemistry as many new approaches to the design of innovative metal-based anticancer drugs are emerging. Current research addressing the problems associated with platinum drugs has focused on other metal-based therapeutics that have different modes of action and on prodrug and targeting strategies in an effort to diminish the side-effects of cisplatin chemotherapy.

Tuning heavy metal compounds for anti-tumor activity: is diversity the key to ruthenium’s success?

This review aims to bring the reader up to date with the more recent ruthenium compounds that have been synthesized and tested for their cytotoxicity. The chemistry of these transition metal complexes will be introduced and the basic principles that govern their common behavior outlined. The recent history of established compounds within this field will be presented alongside those that now represent the cutting-edge. The inherent variety within this class of compounds will lead the reader to appreciate their diversity and pose questions as to their similarities aside from the presence of a shared metal ion. This review aims to discuss and contextualize the state-of-the-art research within the context of the speculative advancement of this developing field. There is an evident need to specify the molecular and cellular targets of these drug molecules in order to ultimately elucidate their mode or modes of action. The evidence presented herein suggests that new avenues of research require novel analytical probes and methods for tracing the fate of ruthenium complexes in cells in order to understand their very promising cytotoxic activity.