Synthesis and cytotoxic activities of chloropyridylimineplatinum(II) and chloropyridyliminecopper(II) surface-functionalized poly(amidoamine) dendrimers

Dendritic Pyridine-Imine Copper Complexes as Metallo-Drugs

Since the discovery of cisplatin in the 1960s, the search for metallo-drugs that are more efficient than platinum complexes with negligible side effects has attracted much interest. Among the other metals that have been examined for potential applications as anticancer agents is copper. The interest in copper was recently boosted by the discovery of cuproptosis, a recently evidenced form of cell death mediated by copper. However, copper is also known to induce the proliferation of cancer cells. In view of these contradictory results, there is a need to find the most suitable copper chelators, among which Schiff-based derivatives offer a wide range of possibilities. Gathering several metal complexes in a single, larger entity may provide enhanced properties. Among the nanometric objects suitable for such purpose are dendrimers, precisely engineered hyperbranched macromolecules, which are outstanding candidates for improving therapy and diagnosis. In this review article, we present an overview of the use of a particular Schiff base, namely pyridine-imine, linked to the surface of dendrimers, suitable for complexing copper, and the use of such dendrimer complexes in biology, in particular against cancers.

Identification and characterization of mercaptopyrimidine-based small molecules as inhibitors of nonhomologous DNA end joining

Mercaptopyrimidine derivatives are heterocyclic compounds with potent biological activities including antiproliferative, antibacterial, and anti-inflammatory properties. The present study describes the synthesis and characterization of several mercaptopyrimidine derivatives through condensation of 5,6-diamino-2-mercaptopyrimidin-4-ol with various heterocyclic and aromatic aldehydes. Previous studies have shown that SCR7, synthesized from 5,6-diamino-2-mercaptopyrimidin-4-ol, induced cytotoxicity by targeting cancer cells by primarily inhibiting DNA Ligase IV involved in nonhomologous end joining, one of the major DNA double-strand break repair pathways. Inhibition of DNA repair pathways is considered as an important strategy for cancer therapy. Due to limitations of SCR7 in terms of IC₅₀ in cancer cells, here we have designed, synthesized, and characterized potent derivatives of SCR7 using 5,6-diamino-2-mercaptopyrimidin-4-ol as the starting material. Several synthesized imine compounds exhibited significant improvement in inhibition of end joining and cytotoxicity up to 27-fold lower concentrations than SCR7. Among these, two compounds, SCR116 and SCR132, showed increased cancer cell death in a Ligase IV-dependent manner. Treatment with the compounds also led to reduction in V(D)J recombination efficiency, cell cycle arrest at G2/M phase, accumulation of double-strand breaks inside cells, and improved anti-cancer potential when combined with γ-radiation and radiomimetic drugs. Thus, we describe novel inhibitors of NHEJ with higher efficacy and potential, which can be developed as cancer therapeutics.

Amphiphilic Triazine-Phosphorus Metallodendrons Possessing Anti-Cancer Stem Cell Activity

Dendritic molecules bearing metal complexes in their structure (metallodendrimers and metallodendrons) are considered prospective therapeutic entities. In particular, metallodendrons raise interest as antitumor agents for the treatment of poorly curable or drug-resistant tumors. Herein, we have synthesized amphiphilic triazine-phosphorus dendrons bearing multiple copper (II) or gold (III) complexes on the periphery and a branched hydrophobic fragment at the focal point. Due to their amphiphilic nature, metallodendrons formed single micelles (mean diameter ~9 nm) or multi-micellar aggregates (mean diameter ~60 nm) in a water solution. We have tested the antitumor activity of amphiphilic metallodendrons towards glioblastoma, a malignant brain tumor with a notoriously high level of therapy resistance, as a model disease. The metallodendrons exhibit higher cytotoxic activity towards glioblastoma stem cells (BTSC233, JHH520, NCH644, and SF188 cell lines) and U87 glioblastoma cells (IC50 was 3–6 µM for copper-containing dendron and 11–15 µM for gold-containing dendron) in comparison with temozolomide (IC50 >100 µM)—the clinical standard of care for glioblastoma. Our findings show the potential of metallodendron-based nanoformulations as antitumor entities.

Cytotoxicity and DNA interaction in a series of aryl terminated iminopyridine Pt(II) complexes

A series of iminopyridine complexes of platinum(II), bearing a flexible diethereal, aryl terminated residue, where the size of aryl group is varied from phenyl to 9-anthracenyl, was synthesized. The new complexes are soluble and stable in DMSO/H₂O mixtures. Besides the metal center, aryl groups are available for further interactions with DNA, due to the good side chain flexibility. The new aryl functionalized iminopyridine dichlorido platinum(II) complexes show a significant antiproliferative activity on ovarian carcinoma cells and notably, complex 13 is able to overcome cisplatin resistance. The study of the interaction mode of 13 with DNA highlighted the ability to form a molecular complex characterized by a dual (intercalative and groove binding) geometry. The complex is also able to covalently add to DNA even though interstrand cross-links appear significantly hampered with respect to cisplatin. The interactions with the macromolecule are discussed in view of the observed cell effect.

Multivalent Copper(II)-Conjugated Phosphorus Dendrimers with Noteworthy In Vitro and In Vivo Antitumor Activities: A Concise Overview

Dendrimers are macromolecules with well-defined, homogeneous, and monodispersed structures that form a branch-like structure. In general, they have a symmetric core, inner shells, and an outer shell. Over the past decade, metallodendritic architectures have developed into a new area in nanomedicine. Due to their versatility and facile customization, phosphorus dendrimers represent interesting platforms for biomedical applications. Metallo-conjugated phosphorus dendrimers have been developed within the dendrimer space, an important part of the chemical space. The first investigation was made using phosphorus dendrimers bearing copper(II) groups on their surface as the original anticancer drug candidates. The aim of this minireview is to present our powerful strategy to find and develop original multivalent copper(II)-conjugated phosphorus dendrimers. The most potent of them is G3 dendrimers with N-(pyridine-2-ylmethylene)ethanamine as the chelating motif complexed with Cu(II) (1G3-Cu), showing very good in vitro and in vivo antiproliferative efficacy. On the basis of these results, 1G3-Cu is a potential clinical candidate having progressed from hit to preclinical candidate status.

A new Schiff base copper(II) complex induces cancer cell growth inhibition and apoptosis by multiple mechanisms

A new Schiff base copper(II) complex [N,N'-bis(2'-hydroxyphenylacetone)-o-ethanediamine] copper (II) (M1) has been synthesized and characterized by single X-ray crystallography. The cytotoxicity of complex M1 was evaluated against HeLa, LoVo, A549, A549/cis cancer cell lines, and the normal cell lines LO2 and HUVEC, by MTT (3-(4,5-dimethylthiazoyl-2-yl)2,5-diphenyltetrazoliumbromide) assays. The IC₅₀ (50% inhibition concentrations) is in the range of 5.13-11.68 μM, which is somewhat lower than cisplatin on the basis of platinum molar concentration. Furthermore, anticancer mechanistic studies showed that the complex M1 inhibited cell proliferation by blocking DNA synthesis and then acted on nuclear division of HeLa cells over time. Moreover, M1 increased intracellular ROS (Reactive oxygen species) levels in a dose-dependent manner. Western blot analysis indicated M1 dramatically decrease c-Myc transcription factor and KLF5 (Krüppel-like factor 5) protein expression levels in HeLa. M1 did not inhibit proteasomal activity. Finally, M1 induced DNA damages and activated the DNA damage repair pathways.

Poly(amidoamine) Dendrimer-Coordinated Copper(II) Complexes as a Theranostic Nanoplatform for the Radiotherapy-Enhanced Magnetic Resonance Imaging and Chemotherapy of Tumors and Tumor Metastasis

The development of a powerful nanoplatform to realize the simultaneous therapy and diagnosis of cancer using a similar element for theranostics remains a critical challenge. Herein, we report such a theranostic nanoplatform based on pyridine (Pyr)-functionalized generation 5 (G5) poly(amidoamine) dendrimers complexed with copper(II) (Cu(II)) for radiotherapy-enhanced T₁-weighted magnetic resonance (MR) imaging and the synergistic radio-chemotherapy of both tumors and tumor metastasis. In this study, amine-terminated G5 dendrimers were covalently linked with 2-pyridinecarboxylic acid, acetylated to neutralize their remaining terminal amines, and complexed with Cu(II) through both the internal tertiary amines and the surface Pyr groups to form the G5.NHAc-Pyr/Cu(II) complexes. We show that the complexes are able to inhibit the proliferation of different cancer cell lines with half-maximal inhibitory concentrations ranging from 4 to 10 μM and induce significant cancer cell apoptosis. Due to the presence of Cu(II), the G5.NHAc-Pyr/Cu(II) complexes display an r₁ relaxivity of 0.7024 mM^-1 s^-1, enabling effective in vivo MR imaging of tumor xenografts and lung metastatic nodules. Further, under radiotherapy (RT) conditions, the tumor MR imaging sensitivity can be significantly enhanced, and the G5.NHAc-Pyr/Cu(II) complexes enable the enhanced chemotherapy of both a xenografted tumor model and a blood-vessel metastasis model. With the demonstrated theranostic potential of the dendrimer-Cu(II) nanocomplexes without additional agents or elements for RT-enhanced MR imaging and chemotherapy of tumor and tumor metastasis, this novel Cu(II)-based nanohybrids may hold great promise for the theranostics of different cancer types and metastases.

Poly(alkylidenimine) Dendrimers Functionalized with the Organometallic Moiety [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ as Promising Drugs Against Cisplatin-Resistant Cancer Cells and Human Mesenchymal Stem Cells

Here and for the first time, we show that the organometallic compound [Ru(η⁵-C₅H₅)(PPh₃)₂Cl] (RuCp) has potential to be used as a metallodrug in anticancer therapy, and further present a new approach for the cellular delivery of the [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragment via coordination on the periphery of low-generation poly(alkylidenimine) dendrimers through nitrile terminal groups. Importantly, both the RuCp and the dendrimers functionalized with [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragments present remarkable toxicity towards a wide set of cancer cells (Caco-2, MCF-7, CAL-72, and A2780 cells), including cisplatin-resistant human ovarian carcinoma cell lines (A2780cisR cells). Also, RuCp and the prepared metallodendrimers are active against human mesenchymal stem cells (hMSCs), which are often found in the tumor microenvironment where they seem to play a role in tumor progression and drug resistance.

EPR Characterization of Copper(II) Complexes of PAMAM-Py Dendrimers for Biocatalysis in the Absence and Presence of Reducing Agents and a Spin Trap

Polyamidoamine (PAMAM) dendrimers at different generations (from G2 to G6) were functionalized with pyridine (Py) groups at the external surface, and their complexation behavior with Cu(II) at increasing molar ratios between the ions and the Py groups was analyzed in the absence and presence of reducing agents and a spin trap. These Cu(II)-dendrimer complexes may be used as antitumor and antiamyloidogenesis drugs, similarly to other Cu(II)-dendrimer complexes, and as biocatalysts. Indeed, they have revealed to selectively catalyze molecular oxygen reduction to generate reactive oxygen species (ROS). A computer-aided electron paramagnetic resonance (EPR) study of these complexes allowed us to identify different complexes by increasing the Cu(II)/Py molar ratio for the different generations. Binuclear EPR-silent complexes were formed at the highest generations. The differently complexed Cu(II) ions showed a different capability to be reduced, starting from the most exposed at the dendrimer surface bearing a stable Cu(II)-Py₂ coordination. Cu(II)-G5 showed peculiar structural properties which probably favored its activity as biocatalyst. The spin trap was able to capture hydroxyl radicals, which became clearly EPR visible after all Cu(II) ions were reduced to Cu(I). This method may be used as a platform to study interactions of Cu(II) in nanosized macromolecules for biomedical purposes, mainly in biocatalysis involving redox reactions and formation of ROS.

Original Multivalent Gold(III) and Dual Gold(III)-Copper(II) Conjugated Phosphorus Dendrimers as Potent Antitumoral and Antimicrobial Agents

Original metallophosphorus dendrimers (generation 3, 48 terminal groups) have been prepared via the complexation of phosphorus dendrimers bearing imino-pyridino end groups with Au(III) or with both Au(III) and Cu(II). The complexation of the dendrimer with Au(III), leading to 1G3-[Au₄₈][AuCl₄]₄₈, strongly increased the antiproliferative activities against both KB and HL-60 tumoral cell lines, showing IC₅₀s in the low nanomolar range. It can be noticed also that this gold conjugated phosphorus dendrimer displayed low activity on the quiescent cell line EPC versus its potent antiproliferative activity against actively dividing cells. In order to evaluate the potential synergistic effect between Au(III) and Cu(II) and the influence of the number of Au(III) moieties on the surface of dendrimer against the proliferative activities, nine other original dendrimers with several surface modifications have been prepared. Whatever the number of Au(III) moieties introduced on the surface of dendrimers, all the dendrimers prepared displayed similar potency (nanomolar range) to 1G3-[Au₄₈][AuCl₄]₄₈ against KB and HL60. In marked contrast synergistic effects on the antimicrobial activity of some of these phosphorus dendrimers are observed when both Au(III) and Cu(II) are present on the dendritic structure.

Carbosilane metallodendrimers based on copper (II) complexes: Synthesis, EPR characterization and anticancer activity

A series of new organometallic carbosilane dendrimers functionalized with Copper(II) complex on the surface were synthesized and characterized as potential anticancer agents. These metallodendrimers were synthesized through the reaction of dendritic ligands containing N,N- and N,O- donor atoms able to act as chelating agents with CuCl₂ as metallic ion precursor. The structural characterization of these complexes was addressed through the use of different analytical and spectroscopical techniques. Particularly, an electron paramagnetic resonance study was performed to corroborate the coordination properties of these dendritic ligands. A preliminary study was carried out to establish the cytotoxicity of the new synthesized compounds in human prostate (PC3) and human cervical (HeLa) cancer cell lines in order to evaluate their potential as anticancer agents and compare their activity with other copper or analogous ruthenium metallodendrimers.

Synthetic methodologies and spatial organization of metal chelate dendrimers and star and hyperbranched polymers

The synthetic methodologies, physico-chemical peculiarities, properties, and structure of metal chelate dendrimers and star and hyperbranched polymers are considered.

Advances in combination therapies based on nanoparticles for efficacious cancer treatment: an analytical report

The main objective of nanomedicine research is the development of nanoparticles as drug delivery systems or drugs per se to tackle diseases as cancer, which are a leading cause of death with developed nations. Targeted treatments against solid tumors generally lead to dramatic regressions, but, unfortunately, the responses are often short-lived due to resistant cancer cells. In addition, one of the major challenges of combination drug therapy (called "cocktail") is the crucial optimization of different drug parameters. This issue can be solved using combination nanotherapy. Nanoparticles developed in oncology based on combination nanotherapy are either (a) those designed to combat multidrug resistance or (b) those used to circumvent resistance to clinical cancer drugs. This review provides an overview of the different nanoparticles currently used in clinical treatments in oncology. We analyze in detail the development of combinatorial nanoparticles including dendrimers for dual drug delivery via two strategic approaches: (a) use of chemotherapeutics and chemosensitizers to combat multidrug resistance and (b) use of multiple cytotoxic drugs. Finally, in this review, we discuss the challenges, clinical outlook, and perspectives of the nanoparticle-based combination therapy in cancer.

Comparative EPR studies of Cu(ii)-conjugated phosphorous-dendrimers in the absence and presence of normal and cancer cells

EPR analysis revealed peculiar structural and dynamical properties of anticancer-activeG3B–Cu(ii) in absence and presence of normal and cancer cells.

Original multivalent copper(II)-conjugated phosphorus dendrimers and corresponding mononuclear copper(II) complexes with antitumoral activities

Novel multivalent copper(II)-conjugated phosphorus dendrimers and their corresponding mononuclear copper(II) complexes were synthesized, characterized, and screened for antiproliferative activity against human cancer cell lines. Selected copper ligands were grafted on the surface of phosphorus dendrimers of generation G(n) (n = 1 to 3): N-(pyridin-2-ylmethylene)ethanamine for dendrimers 1G(n), N-(di(pyridin-2-yl)methylene)ethanamine for dendrimers 2G(n), and 2-(2-methylenehydrazinyl)pyridine for dendrimers 3G(n). The results indicated that the most potent derivatives are 1G(n) and 1G(n)-Cu versus 2G(n), 2G(n)-Cu, and 3G(n), 3G(n)-Cu. A direct relationship between the growth inhibitory effect and the number of terminal moieties or the amount of copper complexed to the dendrimer was observed in copper-complexed 1 series and noncomplexed 1 series. These data clearly suggested that cytotoxicity increased with the number of terminal moieties available and was boosted by the presence of complexed Cu atoms. Importantly, no cytotoxic effect was observed with CuCl2 at the same concentrations. Finally, 1G3 and 1G3-Cu have been selected for antiproliferative studies against a panel of tumor cell lines: 1G3 and 1G3-Cu demonstrated potent antiproliferative activities with IC50 values ranging 0.3-1.6 μM. Interestingly, the complexation of the terminal ligands of 1G3 dendrimers by copper(II) metal strongly increased the IC50 values in noncancer cells lines referred to as "safety" cell lines.

Development of copper based drugs, radiopharmaceuticals and medical materials

Copper is one of the most interesting elements for various biomedical applications. Copper compounds show vast array of biological actions, including anti-inflammatory, anti-proliferative, biocidal and other. It also offers a selection of radioisotopes, suitable for nuclear imaging and radiotherapy. Quick progress in nanotechnology opened new possibilities for design of copper based drugs and medical materials. To date, copper has not found many uses in medicine, but number of ongoing research, as well as preclinical and clinical studies, will most likely lead to many novel applications of copper in the near future.

Evaluation of anionic half generation 3.5-6.5 poly(amidoamine) dendrimers as delivery vehicles for the active component of the anticancer drug cisplatin

Aquated cisplatin was added to half-generation PAMAM dendrimers and the resultant complexes were purified by centrifuge. The drug-dendrimer complexes were then characterised by 1-D and diffusion (1)H NMR and ICP-AES. The amount of drug bound was found to increase in proportion with dendrimer size: G3.5, 22 cis-{Pt(NH(3))(2)} molecules per dendrimer; G4.5, 37; G5.5, 54; and G6.5, 94, which represent only a fraction of the available binding sites on each dendrimer (68, 58, 42 and 37%, respectively). Drug release studies showed that some drug remains bound to the dendrimer even after prolonged incubation with 5'-GMP at temperatures of 60°C for over a week (percentage of drug released 18, 30, 35 and 63%, respectively). Attachment of the drug was found to decrease the radius of the dendrimers. Finally, the effect of the dendrimer on drug cytotoxicity was determined using in vitro assays with the A2780, A2780cis and A2780cp ovarian cancer cell lines. The free dendrimers display no cytotoxicity whilst the drug-dendrimer complexes showed moderate activity. In vivo activity was examined using an A2780 tumour xenograft. Cisplatin, at its maximum tolerated dose of 6 mg/kg, reduced tumour size by 33% compared to an untreated control group. The G6.5 cisplatin-dendrimer complex was administered at two doses (6 and 8 mg/kg equivalent of cisplatin). Both were well tolerated by the mice. The lower dose displayed comparable activity to cisplatin with a tumour volume reduction of 32%, but the higher dose was significantly more active than free cisplatin with a tumour reduction of 45%.