2D and 3D anticancer properties of C2-functionalised glucosamine-Pt (IV) prodrugs based on cisplatin scaffold.

A series of C2-functionalied Pt (IV) glycoconjugates based on glucosamine have been synthesised, characterised and tested as anticancer agents on a series of different 2D and 3D cancer cell lines. The carbohydrate will act as a targeted delivery system to improve the selectivity, exploiting the Warburg Effect and the GLUTs receptors that are overexpressed in most of the cancer cells. The hydroxyl at C2 of the carbohydrates does not participate in hydrogen bonding with the GLUTs receptors, making C2 an attractive position for drug conjugation as seen in literature. In this study, we use the amino functionality at the C2 position in glucosamine and Copper-catalysed Azide-Alkyne Cycloaddition "click" (CuAAC) reaction to connect the prodrug Pt (IV) scaffold to the carbohydrate. We have investigated complexes with different linker lengths, as well as acetyl protected and free derivatives. To the best of our knowledge, this study represents the first series of Pt (IV) glucosamine-conjugates functionalised at C2.

Novel design of dual-action Pt(IV) anticancer pro-drugs based on cisplatin and derivatives of the tyrosine kinase inhibitors imatinib and nilotinib.

Tyrosine kinases (TKs) are emerging as important targets in cancer therapy and some of their inhibitors, TKIs (e.g. imatinib and nilotinib), are FDA-approved drugs that are used as selective anti-cancer therapeutics against cell lines that overexpress TKs. Many examples of metal-based complexes functionalised with TKIs are reported in the literature but very few have been functionalised with platinum. Here we report the design, a detailed computational analysis/simulation, the complete chemical characterisation and the preliminary biological evaluation of two novel Pt(IV) anticancer pro-drugs based on cisplatin tethered with a derivative of either imatinib or nilotinib in the axial position. Pt(IV) complexes are a strategic scaffold in combination therapy due to their axial ligands that can be functionalised to form dual action drugs. The activation by reduction releases the Pt(II) core and the axial ligands upon cellular internalisation. The antiproliferative activity and the TK inhibition properties of the novel adducts are analysed with a theoretical approach and confirmed in vitro with preliminary biological assays.

Novel Biotinylated Cu(II)-Phenanthroline Complexes: 2D and 3D Cytotoxic Activity and Mechanistic Insight.

The interest in the use of copper as a metal scaffold for the development of novel chemotherapeutics has considerably grown in recent years. This is mainly due to the relatively lower toxicity of copper complexes with respect to platinum drugs (i.e., cisplatin), the different mechanisms of action, and the cheaper cost. In the last decades, hundreds of copper-based complexes were developed and screened as anticancer agents, with the antesignanus of all compounds being copper bis-phenanthroline [Cu(phen)2]2+ developed by D.S. Sigman in the late 1990s. In particular, copper(phen) derivatives have been shown high interest in their capacity to interact with DNA by nucleobase intercalation. Here, we report the synthesis and chemical characterization of four novel copper(II) complexes functionalised with phenanthroline derivatives containing biotin. Biotin, also known as Vitamin B7, is involved in a series of metabolic processes, and its receptors are often overexpressed in many tumour cells. A detailed biological analysis including cytotoxicity in 2D and 3D, cellular drug uptake, DNA interaction, and morphological studies are discussed.

Development of Novel Pt(IV)-Carbohydrate Derivatives as Targeted Anticancer Agents against Osteosarcoma.

Despite the enormous importance of cisplatin as a chemotherapeutic agent, its application is impacted by dose-limiting side effects and lack of selectivity for cancer cells. Researchers can overcome these issues by taking advantage of the pro-drug nature of the platinum(IV) oxidation state, and by modifying the coordination sphere of the metal centre with specific vectors whose receptors are overexpressed in tumour cell membranes (e.g., carbohydrates). In this paper we report the synthesis of four novel carbohydrate-modified Pt(IV) pro-drugs, based on the cisplatin scaffold, and their biological activity against osteosarcoma (OS), a malignant tumour which is most common in adolescents and young adults. The carbohydrate-targeting vectors and Pt scaffold are linked using copper-catalysed azide-alkyne cycloaddition (CuAAC) chemistry, which is synonymous with mild and robust reaction conditions. The novel complexes are characterised using multinuclear 1D-2D NMR (1H, 13C and 195Pt), IR, HR-MS, Elem. Analyses, and CV. Cytotoxicity on 2D and 3D and cell morphology studies on OS cell lines, as well as non-cancerous human foetal osteoblasts (hFOBs), are discussed.

Graphene Oxide Nanoplatforms to Enhance Cisplatin-Based Drug Delivery in Anticancer Therapy.

Chemotherapeutics such as platinum-based drugs are commonly used to treat several cancer types, but unfortunately, their use is limited by several side effects, such as high degradation of the drug before entering the cells, off-target organ toxicity and development of drug resistance. An interesting strategy to overcome such limitations is the development of nanocarriers that could enhance cellular accumulation in target cells in addition to decreasing associated drug toxicity in normal cells. Here, we aim to prepare and characterize a graphene-oxide-based 2D nanoplatform functionalised using highly branched, eight-arm polyethylene-glycol, which, owing to its high number of available functional groups, offers considerable loading capacity over its linear modalities and represents a highly potent nanodelivery platform as a versatile system in cancer therapy. The obtained results show that the GO@PEG carrier allows for the use of lower amounts of Pt drug compared to a Pt-free complex while achieving similar effects. The nanoplatform accomplishes very good cellular proliferation inhibition in osteosarcoma, which is strictly related to increased cellular uptake. This enhanced cellular internalization is also observed in glioblastoma, although it is less pronounced due to differences in metabolism compared to osteosarcoma. The proposed GO@PEG nanoplatform is also promising for the inhibition of migration, especially in highly invasive breast carcinoma (i.e., MDA-MB-231 cell line), neutralizing the metastatic process. The GO@PEG nanoplatform thus represents an interesting tool in cancer treatment that can be specifically tailored to target different cancers.

Click Pt(IV)-Carbohydrates Pro-Drugs for Treatment of Osteosarcoma.

The selectivity vs. cancer cells has always been a major challenge for chemotherapeutic agents and in particular for cisplatin, one of the most important anticancer drugs for the treatment of several types of tumors. One strategy to overtake this challenge is to modify the coordination sphere of the metallic center with specific vectors whose receptors are overexpressed in the tumoral cell membrane, such as monosaccharides. In this paper, we report the synthesis of four novel glyco-modified Pt(IV) pro-drugs, based on cisplatin scaffold, and their biological activity against osteosarcoma (OS), a malignant tumor affecting in particular adolescents and young adults. The sugar moiety and the Pt scaffold are linked exploiting the Copper Azide Alkyne Cycloaddition (CUAAC) reaction, which has become the flagship of click chemistry due to its versatility and mild conditions. Cytotoxicity and drug uptake on three different OS cell lines as well as CSCs (Cancer Stem Cell) are described.

Antimicrobials offered from nature: Peroxidase-catalyzed systems and their mimics.

The control of antimicrobial resistance requires the development of novel antimicrobial alternatives and naturally occurring peroxidase-catalyzed systems may be of great value in this era of emerging antimicrobial resistance. In the peroxidase system, a peroxidase enzyme catalyzes the oxidation of a halide/pseudohalide, at the expense of hydrogen peroxide, to generate reactive products with broad antimicrobial properties. The appropriate use of peroxidase systems needs a better understanding of the identities and properties of the generated antimicrobial oxidants, specific targets in bacterial cells, their mode of action and the factors favoring or limiting their activity. Here, the ABCs (antibacterial activity, bacterial "backtalk" and cytotoxicity) of these systems and their mimics are discussed. Particular attention is paid to the concomitant use of thiocyanate and iodide dual substrates in peroxidase/peroxidase-free systems with implications on their antimicrobial activity. This review also provides a summary of actual applications of peroxidase systems as bio-preservatives in oral healthcare, milk industry, food/feed specialties and related products, mastitis and wound treatment; lastly, this review points to opportunities for further research and potential applications.

Pt(IV) pro-drugs with an axial HDAC inhibitor demonstrate multimodal mechanisms involving DNA damage and apoptosis independent of cisplatin resistance in A2780/A2780cis cells.

Epigenetic agents such as histone deacetylase (HDAC) inhibitors are widely investigated for use in combined anticancer therapy and the co-administration of Pt drugs with HDAC inhibitors has shown promise for the treatment of resistant cancers. Coordination of an HDAC inhibitor to an axial position of a Pt(IV) derivative of cisplatin allows the combination of the epigenetic drug and the Pt chemotherapeutic into a single molecule. In this work we carry out mechanistic studies on the known Pt(IV) complex cis,cis,trans-[Pt(NH3)2Cl2(PBA)2] (B) with the HDAC inhibitor 4-phenylbutyrate (PBA) and its derivatives cis,cis,trans-[Pt(NH3)2Cl2(PBA)(OH)] (A), cis,cis,trans-[Pt(NH3)2Cl2(PBA)(Bz)] (C), and cis,cis,trans-[Pt(NH3)2Cl2(PBA)(Suc)] (D) (Bz = benzoate, Suc = succinate). The comparison of the cytotoxicity, effect on HDAC activity, reactive oxygen species (ROS) generation, γ-H2AX (histone 2A-family member X) foci generation and induction of apoptosis in cisplatin-sensitive and cisplatin-resistant ovarian cancer cells shows that A - C exhibit multimodal mechanisms involving DNA damage and apoptosis independent of cisplatin resistance.

Anticancer activity, DNA binding and cell mechanistic studies of estrogen-functionalised Cu(II) complexes.

Four estrogen-functionalised copper complexes were synthesised and investigated as electrochemical active DNA binding and cleavage agents. These complexes strategically contain a biocompatible metal centre [Cu(II)], a planar aromatic ligand as DNA intercalative agent and an estradiol-derivative moiety which acts as delivery vector to target estrogen-receptor-positive (ER+) cancer cells. Cytotoxic activity was studied over a panel of estrogen-receptor-positive (ER+) and negative (ER-) human cancer cell lines by means of both 2D and 3D cell viability studies. The complexes showed high in vitro intercalative interaction with nuclear DNA and demonstrated to be strong DNA cleaving agents. This series of Cu compounds are potent anticancer agents with low and sub-micromolar IC50 values and the cellular uptake follows the lipophilicity order meaning that the internalisation mainly happened via passive diffusion. Finally, the estrogen-complexes are involved in the cellular redox stress by stimulating the production of ROS (reactive oxygen species).

Stability of antibacterial Te(IV) compounds: A combined experimental and computational study.

Inorganic Te(IV) compounds are important cysteine protease inhibitors and antimicrobial agents; AS-101 [ammonium trichloro (dioxoethylene-O,O')tellurate] is the first compound of a family with formula NH4[C2H4Cl3O2Te], where a Te(IV) centre is bound to a chelate ethylene glycol, and showed several protective therapeutic applications. This compound is lacking in stability performance and is subjected to hydrolysis reaction with displacement of the diol ligand. In this paper, we report the stability trend of a series of analogues complexes of AS-101 with generic formula NH4[(RC2H3O2)Cl3Te], where R is an alkyl group with different chain length and different electronic properties, in order to find a correlation between structure and stability in aqueous-physiological conditions. The stability was studied in solution via multinuclear NMR spectroscopy (1H, 13C, 125Te) and computationally at the Density Functional Theory level with an explicit micro solvation model. The combined experimental and theoretical work highlights the essential role of the solvating environment and provides mechanistic insights into the complex decomposition reaction. Antimicrobial activity of the compounds was assessed against different bacterial strains.

A Pt(IV) Prodrug Combining Chlorambucil and Cisplatin: a Dual-Acting Weapon for Targeting DNA in Cancer Cells.

In this study, two DNA-targeting agents, cisplatin and chlorambucil, were combined in a Pt(IV) prodrug, 1, which was thoroughly characterized by means of spectroscopic and spectrometric techniques. Tested towards a panel of various human tumor cell lines, this compound showed superior in vitro antitumor potential than the reference drug cisplatin. In addition, an antitumor potential of 1 was found, which is comparable to that of oxaliplatin in 3D spheroid models of colon cancer cells. Mechanistic studies performed in colon cancer cells confirmed that the conjugation of chlorambucil to Pt(IV) cisplatin-based scaffold tunes the lipophilicity of the prodrug, consequently improving the ability of the compound to accumulate into cancer cells and to target DNA, ultimately leading to apoptotic cancer cell death.

A phosphate-targeted dinuclear Cu(II) complex combining major groove binding and oxidative DNA cleavage.

Free radical generation is an inevitable consequence of aerobic existence and is implicated in a wide variety of pathological conditions including cancer, cardiovascular disease, ageing and neurodegenerative disorder. Free radicals can, however, be used to our advantage since their production is catalysed by synthetic inorganic molecules-termed artificial metallonucleases-that cut DNA strands by oxidative cleavage reactions. Here, we report the rational design and DNA binding interactions of a novel di-Cu2+ artificial metallonuclease [Cu2(tetra-(2-pyridyl)-NMe-naphthalene)Cl4] (Cu2TPNap). Cu2TPNap is a high-affinity binder of duplex DNA with an apparent binding constant (Kapp) of 107 M(bp)-1. The agent binds non-intercalatively in the major groove causing condensation and G-C specific destabilization. Artificial metallonuclease activity occurs in the absence of exogenous reductant, is dependent on superoxide and hydrogen peroxide, and gives rise to single strand DNA breaks. Pre-associative molecular docking studies with the 8-mer d(GGGGCCCC)2, a model for poly[d(G-C)2], identified selective major groove incorporation of the complex with ancillary Cu2+-phosphate backbone binding. Molecular mechanics methods then showed the d(GGGGCCCC)2 adduct to relax about the complex and this interaction is supported by UV melting experiments where poly[d(G-C)2] is selectively destabilized.

An innovative and efficient route to the synthesis of metal-based glycoconjugates: proof-of-concept and potential applications.

With a view to developing more efficient strategies to the functionalization of metallodrugs with carbohydrates, we here report on an innovative and efficient synthetic route to generate gold(iii) glycoconjugates in high yields and purity. The method is based on the initial synthesis of the zinc(ii)-dithiocarbamato intermediate [ZnII(SSC-Inp-GlcN)2] (Inp = isonipecotic moiety; GlcN = amino-glucose) followed by the transfer of the glucoseisonipecoticdithiocarbamato ligand to the gold(iii) center via transmetallation reaction between the zinc(ii) intermediate and K[AuIIIBr4] in 1 : 2 stoichiometric ratio, yielding the corresponding glucose-functionalized gold(iii)-dithiocarbamato derivative [AuIIIBr2(SSC-Inp-GlcN)]. No protection/deprotection of the amino-glucose scaffold and no chromatographic purification were needed. The synthetic protocol was optimized for glucose precursors bearing the amino function at either the C2 or the C6 position, and works in the case of both α and ß anomers. The application of the synthetic strategy was also successfully extended to other metal ions of biomedical interest, such as gold(i) and platinum(ii), to obtain [AuI(SSC-Inp-GlcN)(PPh3)] and [PtII(SSC-Inp-GlcN)2], respectively. All compounds were fully characterized by elemental analysis, mid- and far-IR, mono- and multidimensional NMR spectroscopy, and, where possible, X-ray crystallography. Results and potential applications are here discussed.

Increased immune cell infiltration in patient-derived tumor explants treated with Traniplatin: an original Pt(iv) pro-drug based on Cisplatin and Tranilast.

Elevated intra-tumoral immune infiltrate is associated with an improved prognosis in cancer of distinct origins. Traniplatin (TPT) is a novel platinum(iv) pro-drug based on Cisplatin (CDDP) and the marketed drug Tranilast. When compared in vitro to Cisplatin, TPT showed increased cytotoxic activity against colon and lung cancer cells but decreased activity against immune cells. In addition, TPT efficiency was evaluated in tumor explants derived from colorectal cancer samples from patients subjected to intended curative surgery. TPT induced strong intra-tumoral cytotoxic activity yet was associated with an elevated presence of immune cell infiltrate, suggesting a reduced cytotoxic activity against immune cells in colorectal cancer.

Development of an Efficient Dual-Action GST-Inhibiting Anticancer Platinum(IV) Prodrug.

The cytotoxicity of cisplatin (cDDP) is enhanced when co-administered with ethacrynic acid (EA), a glutathione S-transferase (GST) inhibitor. A PtIV -EA conjugate containing a cDDP core and two axial ethacrynate ligands (compound 1) was shown to be an excellent inhibitor of GST, but did not readily release a PtII species to exert a synergistic cytotoxic effect. In this study, a redesigned PtIV construct composed of a cDDP core with one axial ethacrynate ligand and one axial hydroxido ligand (compound 2) was prepared and shown to overcome the limitations of compound 1. The EA ligand in 2 is readily released in vitro together with a cytotoxic PtII species derived from cisplatin, working together to inhibit cell proliferation in cDDP-resistant human ovarian cancer cells. The in vitro activity translates well in vivo with 2, showing effective (∼80 %) inhibition of tumor growth in a human ovarian carcinoma A2780 tumor model, while showing considerably lower toxicity than cisplatin, thus validating the new design strategy.

Antitumor platinum(IV) derivatives of carboplatin and the histone deacetylase inhibitor 4-phenylbutyric acid.

Five new platinum(IV) derivatives of carboplatin each incorporating the histone deacetylase inhibitor 4-phenylbutyrate in axial position were synthesized and characterized by 1H and 195Pt NMR spectroscopy, electrospray ionization mass spectrometry and elemental analysis, namely cis,trans-[Pt(CBDCA)(NH3)2(PBA)(OH)] (1), cis,trans-[Pt(CBDCA)(NH3)2(PBA)2] (2), cis,trans-[Pt(CBDCA)(NH3)2(PBA)(bz)] (3), cis,trans-[Pt(CBDCA)(NH3)2(PBA)(suc)] (4) and cis,trans-[Pt(CBDCA)(NH3)2)(PBA)(ac)] (5) (PBA=4-phenylbutyrate, CBDCA=1,1-cyclobutane dicarboxylate, bz=benzoate, suc=succinate and ac=acetate). The reduction behavior in the presence of ascorbic acid was studied by high performance liquid chromatography. The cytotoxicity against a panel of human tumor cell lines, histone deacetylase (HDAC) inhibitory activity, cellular accumulation and the ability to induce apoptosis were evaluated. The most effective complex, compound 3, was found to be up to ten times more effective than carboplatin and to decrease cellular basal HDAC activity by approximately 18% in A431 human cervical cancer cells.

Steroid-AuI -NHC Complexes: Synthesis and Antibacterial Activity.

A series of gold(I) pioneer complexes bearing N-heterocyclic carbenes and steroid derivatives (ethynylestradiol and ethisterone) with the generic formula [Au(R2 -imidazol-2-ylidene)(steroid)] (where R=CH3 or CH2 CH2 OCH3 ) were synthesized, and the X-ray structure of a rare of gold(I)-estradiol derivative is discussed. Toxicity studies reveal notable antibacterial activity of the gold-based compounds, which is significantly increased in vivo by the presence of the estradiol unit. Toxicity profiling was estimated in vitro versus Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, and in vivo on Galleria mellonella larvae against E. coli.

Oxidative Stress Induced by Pt(IV) Pro-drugs Based on the Cisplatin Scaffold and Indole Carboxylic Acids in Axial Position.

The use of Pt(IV) complexes as pro-drugs that are activated by intracellular reduction is a widely investigated approach to overcome the limitations of Pt(II) anticancer agents. A series of ten mono- and bis-carboxylated Pt(IV) complexes with axial indole-3-acetic acid (IAA) and indole-3-propionic acid (IPA) ligands were synthesized and characterized by elemental analysis, ESI-MS, FT-IR, (1)H and (195)Pt NMR spectroscopy. Cellular uptake, DNA platination and cytotoxicity against a panel of human tumor cell lines were evaluated. All the complexes are able to overcome cisplatin-resistance and the most potent complex, cis,cis,trans-[Pt(NH3)2Cl2(IPA)(OH)] was on average three times more active than cisplatin. Mechanistic studies revealed that the trend in cytotoxicity of the Pt(IV) complexes is primarily consistent with their ability to accumulate into cancer cells and to increase intracellular basal reactive oxygen species levels, which in turn results in the loss of mitochondrial membrane potential and apoptosis induction. The role of the indole acid ligand as a redox modulator is discussed.

DNA damage and induction of apoptosis in pancreatic cancer cells by a new dinuclear bis(triazacyclonane) copper complex.

The dinuclear copper(II) complex [Cu2{bcmp(-H)}(µ-OH)](NO3)2·H2O (1, bcmp=2,6-bis(1,4,7-triazacyclonon-1-ylmethyl)-4-methylphenol) has been synthesized and characterized by electrospray ionization mass spectrometry, potentiometric titration and cyclovoltammetry. The X-ray structure of the analogous perchlorate salt [Cu2{bcmp(-H)}(µ-OH)](ClO4)2·2.5H2O (2) was determined. Cytotoxicity studies showed very promising activity of 1 against various pancreatic tumor cell lines with IC50 values comparable or even lower than those of cisplatin. The Cu complex displayed low toxicity against a human non-tumor cell line (HEK 293) demonstrating selectivity for cancer cells. 1 converts supercoiled pUC19 plasmid DNA into the nicked form at micromolar concentrations in the absence of added reductants. A detailed kinetic study on the hydrolysis of the DNA model bis(2,4-dinitrophenyl) phosphate (BDNPP) has been performed. 1 hydrolyses BDNPP with a second order rate constant of 0.047 M s(-1) at pH 8 and 40 °C. Finally, single cell electrophoresis (comet assay) and fluorescence microscopy analysis showed that 1 interacts with cellular DNA and induces apoptotic cell death of Capan-1 pancreatic cancer cells. Western blotting analysis indicated that the Cu complex activates the p53 dependent pathway of apoptosis.