Cutaneous metastatic melanoma (CMM) is the most aggressive form of skin cancer with a poor prognosis. Drugs-induced secondary tumorigenesis and the emergency of drug resistance worsen the already worrying scenario, thus rendering urgent the development of new treatments, not dealing with mutable cellular processes. Triphenyl phosphonium salts (TPPSs), in addiction to act as cytoplasmic membrane disruptors, are reported to be mitochondria-targeting compounds, exerting anticancer effects mainly by damaging their membranes and causing depolarization, impairing mitochondria functions and their DNA, triggering oxidative stress (OS), and priming primarily apoptotic cell death. TPP-based bola-amphiphiles are capable to self-form nanoparticles (NPs) with enhanced biological properties, as commonly observed for nanomaterials. Already employed in several other biomedical applications, only recently the per se selective potent antibacterial effects of a TPP bola-amphiphile has been demonstrated on 50 multidrug resistant (MDR) clinical superbugs, as well as its exceptional and selective anticancer properties, on sensitive and MDR neuroblastoma cells. Here, aiming at finding new molecules possibly developable as new treatments for counteracting CMM, the effects of this TPP-based bola-amphiphile (BPPB) have been investigated against two BRAF mutants CMM cell lines (MeOV and MeTRAV) with excellent results (even IC50 = 49 nM on MeOV after 72 h treatment). Upon these findings and considered the low cytotoxicity of BPPB against different mammalian not tumoral cell lines and red blood cells (RBCs, selectivity indexes up to 299 on MeOV after 72 h treatment), the possible future development of BPPB as topical treatment for CMM lesions was presumed. In this sight, a biodegradable hyaluronic acid (HA)-based hydrogel formulation (HA-BPPB-HG) was prepared without using any potentially toxic crosslinking agents, but simply dispersing suitable amounts of the two ingredients in water and sonicating under gentle heating. HA-BPPB-HA was completely characterized with promising outcomes, such as high swelling capability, high porosity and viscous elastic rheological behavior.

Neuroblastoma (NB) is a solid tumor occurring in infancy and childhood, whose high-risk form has currently a survival rate < 50 %, despite aggressive treatments. Additionally, drugs-induced secondary tumorigenesis and the emergency of drug resistance worsen the already worrying scenario, calling for an urgent development of new extra-genomic treatments. Quaternary phosphonium salts (QPSs) possess both antimicrobial and anticancer effects. Triphenyl phosphonium salts (TPPs) are mitochondria-targeting compounds, exerting anticancer effects, impairing mitochondria functions and damaging DNA, at the same time. TPP-based bola-amphiphiles, previously proven to self-assemble nanoparticles (NPs) in water and successfully assayed as possible antibacterials, were never tested as suitable antitumor agents. Here, aiming at the development of new antitumor devices to counteract resistant forms of NB, the anticancer effects of a TPP-based amphiphile molecule have been investigated for the first time. To this end, we considered the water-soluble sterically hindered quaternary phosphonium salt (BPPB) encompassing two triphenyl phosphonium groups linked by a C12 alkyl chain, thus embodying both the characteristics of mitochondria-targeting compounds and those of bola-amphiphiles. The anticancer effects of BPPB were assessed against HTLA-230 human stage-IV NB cells and their counterpart resistant to etoposide (ETO), doxorubicin (DOX) and to many other therapeutics (HTLA-ER). Determined IC50 values were very low on both cell populations, already after 24 hours of treatment, when cells viability did not significantly differ from that observed for the longest exposure timing. Moreover, to investigate a putative future inclusion of BPPB in a chemotherapeutic cocktail for NB, its cytotoxic effects were assessed against mammalian cell lines. These included monkey kidney cells (Cos-7), human hepatic cells (HepG2), a lung-derived fibroblast cell line (MRC-5) and red blood cells. From appreciable to very high selectivity indices have been determined after 24 hours treatments, an exposure time after which both NB cell populations tested appeared already fully exterminated.