Gold(i) complexes based on six-membered phosphorus heterocycles as bio-active molecules against brain cancer

Versatile Palladium-catalyzed intramolecular cyclization to access new luminescent azaphosphaphenalene motifs

Using a straightforward sequence of diphosphonylation and a Pd-catalysed concerted-metalation-deprotonation (CMD), a synthetic strategy towards polyaromatic phosphorus containing heterocycles was developed. Herein, we report the synthesis and characterization of new azaphosphaphenalenes, using easily accessible palladium catalysts and starting materials. The key tetrahydroquinoline intermediates of the reaction were synthesised via a fast and effective procedure and could be isolated as such, or further reacted towards the target polyaromatic structures. The obtained products showed interesting luminescent properties and their emission, excitation and quantum yields were evaluated.

Synthesis, Post-Functionalization and Properties of Diphosphapentaarenes

Linearly-fused polyarenes are an important class of compounds with high relevance in materials science. While modifying the shape and size represents a common means to fine-tune their properties, the precise placement of heteroatoms is a strategy that is receiving an increasing deal of attention to overcome the intrinsic limitations of all-carbon structures. Thus, linearly-fused diphosphaarenes recently emerged as a novel family of molecules with striking optoelectronic properties and outstanding stability. However, the properties of diphosphaarenes are far from being benchmarked. Herein, we report the synthesis, phosphorus post-functionalization and properties of new diphosphapentaarene derivatives. We describe their synthetic limitations and unveil their potential for optoelectronic applications.

The anti-breast cancer stem cell properties of gold(i)-non-steroidal anti-inflammatory drug complexes

The anti-breast cancer stem cell (CSC) properties of a series of gold(i) complexes comprising various non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine 1-8 are reported. The most effective gold(i)-NSAID complex 1, containing indomethacin, exhibits greater potency for breast CSCs than bulk breast cancer cells (up to 80-fold). Furthermore, 1 reduces mammosphere viability to a better extent than a panel of clinically used breast cancer drugs and salinomycin, an established anti-breast CSC agent. Mechanistic studies suggest 1-induced breast CSC death results from breast CSC entry, cytoplasm localisation, an increase in intracellular reactive oxygen species levels, cyclooxygenase-2 downregulation and inhibition, and apoptosis. Remarkably, 1 also significantly inhibits tumour growth in a murine metastatic triple-negative breast cancer model. To the best of our knowledge, 1 is the first gold complex of any geometry or oxidation state to demonstrate anti-breast CSC properties.

Boron- and phosphorus-containing molecular/nano platforms: exploiting pathological redox imbalance to fight cancer

Cancer is currently the second leading cause of death globally. Despite multidisciplinary efforts, therapies to fight various types of cancer still remain inefficient. Reducing high recurrence rates and mortality is thus a major challenge to tackle. In this context, redox imbalance is an undervalued characteristic of cancer. However, it may be targeted by boron- and phosphorus-containing materials to selectively or systemically fight cancer. In particular, boron and phosphorus derivatives are attractive building blocks for rational drug discovery due to their unique and wide regioselective chemistry, high degree of tuneability and chemical stability. Thus, they can be meticulously employed to access tunable molecular platforms to selectively exploit the redox imbalance of cancer cells towards necrosis/apoptosis. This field of research holds a remarkable potential; nevertheless, it is still in its infancy. In this mini-review, we underline recent advances in the development of boron- or phosphorus-derivatives as molecular/nano platforms for rational anticancer drug design. Our goal is to provide comprehensive information on different methodologies that bear an outstanding potential to further develop this very promising field of research.

Luminescent Pyrrole‐Based Phosphaphenalene Gold Complexes: Versatile Anticancer Tools with Wide Applicability

Brain cancer, one of the most lethal diseases, urgently requires the discovery of novel theranostic agents. In this context, molecules based on six‐membered phosphorus heterocycles – phosphaphenalenes – are especially attractive; they possess unique characteristics that allow precise chemical engineering. Herein, we demonstrate that subtle structural modifications of the phosphaphenalene‐based gold(I) complexes lead to modify their electronic distribution, endow them with marked photophysical properties and enhance their efficacy against cancer. In particular, phosphaphenalene‐based gold(I) complexes containing a pyrrole ring show antiproliferative properties in 14 cell lines including glioblastomas, brain metastases, meningiomas, IDH‐mutant gliomas and head and neck cancers, reaching IC₅₀ values as low as 0.73 μM. The bioactivity of this new family of drugs in combination with their photophysical properties thus offer new research possibilities for both the fundamental investigation and treatment of brain cancer.

Saponins -Uptake and Targeting issues for brain-specific delivery for enhanced cell death induction in glioblastoma

Abstract:

Saponins represent a category of diverse, natural glycoside molecules that belong to the triterpenoid or the steroid class. They vary in terms of their solubility and permeability characteristics and are classifiable based on the biopharmaceutics classification system. They have drug delivery potential as surfactants that can solubilize cholesterol in the plasma membrane of tumorigenic cells. Glioblastoma is an important malignancy that can aggressively afflict the brain of humans with a poor prognosis. Glioblastoma Stem Cells (GSCs), are an important subset of cancer cells and are major determinants for drug resistance and tumour relapse. These cells are quiescent and have been known to survive current therapeutic strategies. Certain saponins have shown potential to eliminate glioblastoma cells in a variety of model systems and hence provide a sound scientific basis for their development as a “stand-alone” drug or as part of a drug combination (from the existing arsenal of drugs) developed for the treatment of glioblastoma. However, due to their reactogenicity towards the immune system and hemolytic potential, selective delivery to the tumorigenic site is essential. Hence, nano-formulations (liposome/emulsion-based delivery systems/nano-structured lipid and calix[n]arenes-based carriers) and variants that are resistant to saponin may serve as delivery tools that can be functionalized to improve the selectivity. It is necessary to develop/validate/refine in vitro higher order models that replicate the features of the glioma microenvironment (BBB/BTB). Reproducible validation of the model as well as the drug/delivery system will help in the development of formulations that can augment cell death in this recalcitrant brain tumour.