Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires.

Myocardial infarction causes 7.3 million deaths worldwide, mostly for fibrillation that electrically originates from the damaged areas of the left ventricle. Conventional cardiac bypass graft and percutaneous coronary interventions allow reperfusion of the downstream tissue but do not counteract the bioelectrical alteration originated from the infarct area. Genetic, cellular, and tissue engineering therapies are promising avenues but require days/months for permitting proper functional tissue regeneration. Here we engineered biocompatible silicon carbide semiconductive nanowires that synthetically couple, via membrane nanobridge formations, isolated beating cardiomyocytes over distance, restoring physiological cell-cell conductance, thereby permitting the synchronization of bioelectrical activity in otherwise uncoupled cells. Local in-situ multiple injections of nanowires in the left ventricular infarcted regions allow rapid reinstatement of impulse propagation across damaged areas and recover electrogram parameters and conduction velocity. Here we propose this nanomedical intervention as a strategy for reducing ventricular arrhythmia after acute myocardial infarction.

Overexpression of microRNA­486 affects the proliferation and chemosensitivity of mesothelioma cell lines by targeting PIM1.

Dysregulated levels of microRNAs (miRNAs or miRs), involved in oncogenic pathways, have been proposed to contribute to the aggressiveness of malignant pleural mesothelioma (MPM). Previous studies have highlighted the downregulation of miRNA miR­486­5p in patients with mesothelioma and the introduction of miRNA mimics to restore their reduced or absent functionality in cancer cells is considered an important therapeutic strategy. The aim of the present study was to evaluate the mechanisms through which miRNAs may influence the functions, proliferation and sensitivity to cisplatin of MPM cells. In the present study, a miR­486­5p mimic was transfected into the H2052 and H28 MPM cell lines, and cell viability, proliferation, apoptosis and mitochondrial membrane potential were monitored. miR­486­5p overexpression led to a clear impairment of cell proliferation, targeting CDK4 and attenuating cell cycle progression. In addition, transfection with miR­486­5p mimic negatively regulated the release of inflammatory factors and the expression of Provirus integration site for Moloney murine leukaemia virus 1 (PIM1). The sensitivity of the cells to cisplatin was enhanced by enhancing the apoptotic effects of the drug and impairing mitochondrial function. On the whole, the present study demonstrates that miR­486­5p may play an important role in MPM treatment by targeting multiple pathways involved in tumour development and progression. These activities may be mostly related to the downregulation of PIM1, a crucial regulator of cell survival and proliferation. Furthermore, these results provide support for the combined use of miR­486­5p with chemotherapy as a therapeutic strategy for MPM.

Exposure to nanoparticles derived from diesel particulate filter equipped engine increases vulnerability to arrhythmia in rat hearts.

Air pollution is well recognized as a central player in cardiovascular disease. Exhaust particulate from diesel engines (DEP) is rich in nanoparticles and may contribute to the health effects of particulate matter in the environment. Moreover, diesel soot emitted by modern engines denotes defective surfaces alongside chemically-reactive sites increasing soot cytotoxicity. We recently demonstrated that engineered nanoparticles can cross the air/blood barrier and are capable to reach the heart. We hypothesize that DEP nanoparticles are pro-arrhythmogenic by direct interaction with cardiac cells. We evaluated the internalization kinetics and the effects of DEP, collected from Euro III (DEPe3, in the absence of Diesel Particulate Filter, DPF) and Euro IV (DEPe4, in the presence of DPF) engines, on alveolar and cardiac cell lines and on in situ rat hearts following DEP tracheal instillation. We observed significant differences in DEP size, metal and organic compositions derived from both engines. DEPe4 comprised ultrafine particles (<100 nm) and denoted a more pronounced toxicological outcome compared to DEPe3. In cardiomyocytes, particle internalization is fastened for DEPe4 compared to DEPe3. The in-vivo epicardial recording shows significant alteration of EGs parameters in both groups. However, the DEPe4-instilled group showed, compared to DEPe3, a significant increment of the effective refractory period, cardiac conduction velocity, and likelihood of arrhythmic events, with a significant increment of membrane lipid peroxidation but no increment in inflammation biomarkers. Our data suggest that DEPe4, possibly due to ultrafine nanoparticles, is rapidly internalized by cardiomyocytes resulting in an acute susceptibility to cardiac electrical disorder and arrhythmias that could accrue from cellular toxicity. Since the postulated transfer of nanoparticles from the lung to myocardial cells has not been investigated it remains open whether the effects on the cardiovascular function are the result of lung inflammatory reactions or due to particles that have reached the heart.

A New Photoactivatable Ruthenium(II) Complex with an Asymmetric Bis-Thiocarbohydrazone: Chemical and Biological Investigations.

The synthesis, photoactivation and biological activity of a new piano-stool Ru(II) complex is herein reported. The peculiarity of this complex is that its monodentate ligand which undergoes the photodissociation is an asymmetric bis-thiocarbohydrazone ligand that possesses a pyridine moiety binding to Ru(II) and the other moiety contains a quinoline that endows the ligand with the capacity of chelating other metal ions. In this way, upon dissociation, the ligand can be released in the form of a metal complex. In this article, the double ability of this new Ru(II) complex to photorelease the ligand and to chelate copper and nickel is explored and confirmed. The biological activity of this compound is studied in cell line A549 revealing that, after irradiation, proliferation inhibition is reached at very low half maximal inhibitory concentration (IC50) values. Further, biological assays reveal that the dinuclear complex containing Ni is internalized in cells.

Author Correction: In-vivo vascular application via ultra-fast bioprinting for future 5D personalised nanomedicine.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

In-vivo vascular application via ultra-fast bioprinting for future 5D personalised nanomedicine.

The design of 3D complex structures enables new correlation studies between the engineering parameters and the biological activity. Moreover, additive manufacturing technology could revolutionise the personalised medical pre-operative management due to its possibility to interplay with computer tomography. Here we present a method based on rapid freeze prototyping (RFP) 3D printer, reconstruction cutting, nano dry formulation, fast freeze gelation, disinfection and partial processes for the 5D digital models functionalisation. We elaborated the high-resolution computer tomography scan derived from a complex human peripheral artery and we reconstructed the 3D model of the vessel in order to obtain and verify the additive manufacturing processes. Then, based on the drug-eluting balloon selected for the percutaneous intervention, we reconstructed the biocompatible eluting-freeform coating containing 40 nm fluorescent nanoparticles (NPs) by means of RFP printer and we tested the in-vivo feasibility. We introduced the NPs-loaded 5D device in a rat's vena cava. The coating dissolved in a few minutes releasing NPs which were rapidly absorbed in vascular smooth muscle cell (VSMC) and human umbilical vein endothelial cell (HUVEC) in-vitro. We developed 5D high-resolution self-dissolving devices incorporating NPs with the perspective to apply this method to the personalised medicine.

INSIDE Project: Individual Air Pollution Exposure, Extracellular Vesicles Signaling and Hypertensive Disorder Development in Pregnancy.

Hypertensive disorders are common complications during pregnancy (HDP) with substantial public health impact. Acute and chronic particulate matter (PM) exposure during pregnancy increases the risk of HDP, although the underlying molecular mechanisms remain unclear. Extracellular vesicles (EVs) may be the ideal candidates for mediating the effects of PM exposure in pregnancy as they are released in response to environmental stimuli. The INSIDE project aims to investigate this mechanism in pregnancy outcomes. The study population is enrolled at the Fetal Medicine Unit of Fondazione IRCCS Ca'Granda-Ospedale Maggiore Policlinico at 10-14 weeks of gestation. Exposure to PM10 and PM2.5 is assessed using the flexible air quality regional model (FARM) and Bayesian geostatistical models. Each woman provides a blood sample for EV analysis and circulating biomarker assessment. Moreover, a subgroup of recruited women (n = 85) is asked to participate in a cardiovascular screening program including a standard clinical evaluation, a non-invasive assessment of right ventricular function, and pulmonary circulation at rest and during exercise. These subjects are also asked to wear a personal particulate sampler, to measure PM10, PM2.5, and PM1. The INSIDE study is expected to identify the health impacts of PM exposure on pregnancy outcomes.

Subchronic exposure to titanium dioxide nanoparticles modifies cardiac structure and performance in spontaneously hypertensive rats.

BACKGROUND: Non-communicable diseases, intended as the results of a combination of inherited, environmental and biological factors, kill 40 million people each year, equivalent to roughly 70% of all premature deaths globally. The possibility that manufactured nanoparticles (NPs) may affect cardiac performance, has led to recognize NPs-exposure not only as a major Public Health concern, but also as an occupational hazard. In volunteers, NPs-exposure is problematic to quantify. We recently found that inhaled titanium dioxide NPs, one of the most produced engineered nanomaterials, acutely increased cardiac excitability and promoted arrhythmogenesis in normotensive rats by a direct interaction with cardiac cells. We hypothesized that such scenario can be exacerbated by latent cardiovascular disorders such as hypertension. RESULTS: We monitored cardiac electromechanical performance in spontaneously hypertensive rats (SHRs) exposed to titanium dioxide NPs for 6 weeks using a combination of cardiac functional measurements associated with toxicological, immunological, physical and genetic assays. Longitudinal radio-telemetry ECG recordings and multiple-lead epicardial potential mapping revealed that atrial activation times significantly increased as well as proneness to arrhythmia. At the third week of nanoparticles administration, the lung and cardiac tissue encountered a maladaptive irreversible structural remodelling starting with increased pro-inflammatory cytokines levels and lipid peroxidation, resulting in upregulation of the main pro-fibrotic cardiac genes. At the end of the exposure, the majority of spontaneous arrhythmic events terminated, while cardiac hemodynamic deteriorated and a significant accumulation of fibrotic tissue occurred as compared to control untreated SHRs. Titanium dioxide nanoparticles were quantified in the heart tissue although without definite accumulation as revealed by particle-induced X-ray emission and ultrastructural analysis. CONCLUSIONS: The co-morbidity of hypertension and inhaled nanoparticles induces irreversible hemodynamic impairment associated with cardiac structural damage potentially leading to heart failure. The time-dependence of exposure indicates a non-return point that needs to be taken into account in hypertensive subjects daily exposed to nanoparticles.

New CeF3-ZnO nanocomposites for self-lighted photodynamic therapy that block adenocarcinoma cell life cycle.

AIM: To synthesize and characterize the performances of a new all-inorganic nanocomposite (NC) for self-lighted photodynamic therapy against cancer. This NC could allow radiotherapy doses to be reduced, as it enhances the effects of x-rays, generating cytotoxic reactive oxygen species as singlet oxygen. MATERIALS & METHODS: The proposed NC combines CeF3 and ZnO; CeF3 absorbs 6-MeV x-rays and activates the photosensitizer ZnO. Characterization is performed by transmission electron microscopy (TEM), scanning-TEM, energy dispersive x-ray spectrometry and fluorescence spectroscopies. Efficiency on human adenocarcinoma cells (A549) was tested by fluorescence spectroscopy, cytofluorimetry, viability assays, clonogenic assays, cell cycle progression assays. RESULTS: NC blocks A549's cell cycle before mitosis in the dark. Upon low-dose x-ray irradiation (2 Gy), reactive oxygen species/singlet oxygen are generated, further blocking cell cycle and reducing viability by 18% with respect to the sum of x-ray irradiation and NC dark activity. CONCLUSION: These novel NCs promise to reduce doses in radiotherapy, helping to reduce unwanted side effects.

Biomarkers of exposure to stainless steel tungsten inert gas welding fumes and the effect of exposure on exhaled breath condensate.

The respiratory tract is the main target organ of the inhaled hexavalent chromium (Cr-VI) and nickel (Ni) contained in stainless steel (SS) welding fumes (WFs). The aim of this study was to investigate the Cr and Ni content of the exhaled breath condensate (EBC) of SS tungsten inert gas (TIG) welders, and relate their concentrations with oxidative stress and inflammatory biomarkers. EBC and urine from 100 SS TIG welders were collected pre-(T0) and post-shift (T1) on a Friday, and pre-shift (T2) on the following Monday morning. Both EBC and urinary Cr concentrations were higher at T1 (0.08 µg/L and 0.71 µg/g creatinine) and T0 (0.06 µg/L and 0.74 µg/g creatinine) than at T2 (below the limit of detection [LOD] and 0.59 µg/g creatinine), and EBC Ni concentrations generally remained

Inhalation of peptide-loaded nanoparticles improves heart failure.

Peptides are highly selective and efficacious for the treatment of cardiovascular and other diseases. However, it is currently not possible to administer peptides for cardiac-targeting therapy via a noninvasive procedure, thus representing scientific and technological challenges. We demonstrate that inhalation of small (<50 nm in diameter) biocompatible and biodegradable calcium phosphate nanoparticles (CaPs) allows for rapid translocation of CaPs from the pulmonary tree to the bloodstream and to the myocardium, where their cargo is quickly released. Treatment of a rodent model of diabetic cardiomyopathy by inhalation of CaPs loaded with a therapeutic mimetic peptide that we previously demonstrated to improve myocardial contraction resulted in restoration of cardiac function. Translation to a porcine large animal model provides evidence that inhalation of a peptide-loaded CaP formulation is an effective method of targeted administration to the heart. Together, these results demonstrate that inhalation of biocompatible tailored peptide nanocarriers represents a pioneering approach for the pharmacological treatment of heart failure.

MicroRNA Expression in Malignant Pleural Mesothelioma and Asbestosis: A Pilot Study.

BACKGROUND: The identification of diagnostic/prognostic biomarkers for asbestos-related diseases is relevant for early diagnosis and patient survival and may contribute to understanding the molecular mechanisms underlying the disease development and progression. AIMS: To identify a pattern of miRNAs as possible diagnostic biomarkers for patients with malignant pleural mesothelioma (MPM) and asbestosis (ASB) and as prognostic biomarkers for MPM patients. METHODS: miRNA-16, miRNA-17, miRNA-126, and miRNA-486 were quantified in plasma and formalin-fixed paraffin-embedded samples to evaluate their diagnostic and prognostic roles compared to patients with other noncancerous pulmonary diseases (controls). Results. The expression of all the miRNAs was significantly lower in patients with MPM and ASB than that in controls. miRNA-16, miRNA-17, and miRNA-486 in plasma and tissue of MPM patients were significantly correlated. Furthermore, the expression of miRNA-16 in plasma and tissue, and miRNA-486 only in tissue, was positively related with cumulative survival in MPM patients. CONCLUSIONS: All the miRNA levels were decreased in patients with MPM or ASB, supporting the role of circulating miRNAs as a potential tool for diseases associated with exposure to asbestos fibers. miRNA-16 was directly related to MPM patient prognosis, suggesting its possible use as a prognostic marker in MPM patients.

Titanium dioxide aggregating nanoparticles induce autophagy and under-expression of microRNA 21 and 30a in A549 cell line: A comparative study with cobalt(II, III) oxide nanoparticles.

The toxicity of TiO2 nanoparticles (NPs) is controversial, while it is widely accepted for Co3O4 NPs. We present a comparative study concerning the uptake of these NPs and their effect on cytoplasmic organelles and autophagy in a human lung carcinoma cell line (A549), including assays on the expression of autophagy-related microRNAs. The NP accumulation caused a fast dose- and time-dependent change of flow cytometry physical parameters particularly after TiO2 NP exposure. The intracellular levels of metals confirmed it, but the Co concentration was ten times higher than that of Ti. Both NPs caused neither necrosis nor apoptosis, but cytotoxicity was mainly evident for Co3O4 NPs in the first 72h. TiO2 NPs caused autophagy, contrarily to Co3O4 NPs. Furthermore, a significant and persistent downregulation of miRNA-21 and miRNA-30a was observed only in TiO2 NPs-treated cultures. The expression of miRNA-155 was similar for both NPs. Oxidative stress was evident only for Co3O4 NPs, while both NPs perturbed endoplasmic reticulum and p-53 expression. In conclusion, the oxidative stress caused by Co3O4 NPs can influence energy homeostasis and hamper the ability to detoxify and to repair the resulting damage, thus preventing the induction of autophagy, while TiO2 NPs elicit autophagy also under sub-toxic conditions.

Autophagy and apoptosis: studies on the effects of bisthiosemicarbazone copper(ii) complexes on p53 and p53-null tumour cell lines.

A comparative study between two bisthiosemicarbazones, 2,3-butanedione bis(4,4-dimethyl-3-thiosemicarbazone) and 2,3-butanedione bis(2-methyl-3-thiosemicarbazone), and their copper(ii) complexes is reported. The four compounds have been tested on a leukemia cell line U937 (p53-null) and on an adenocarcinoma cell line A549. The study includes cell viability, cell cycle, morphological changes, assessment of apoptosis, analysis of autophagy, measurement of reactive oxygen species (ROS) and of lipid peroxidation, protein determination, assessment of the expression of p53 and cellular uptake of metal complexes. Tests about the copper uptake under normoxic and hypoxic conditions were also carried out on a solid tumour cell line A549. The four compounds under study elicit different effects on the two lines adopted as representatives of p53 and p53-null cells. The role of the metal is relevant and it is likely that the metal-mediated oxidative stress plays an essential role in the whole process. The mechanisms induced by these molecules differ not only as a function of the cell line but also of dose. The responses include two distinct self-destructive processes, autophagy and apoptosis.

Quinoline-2-carboxaldehyde thiosemicarbazones and their Cu(II) and Ni(II) complexes as topoisomerase IIa inhibitors.

A series of quinoline-2-carboxaldehyde thiosemicarbazones and their copper(II) and nickel(II) complexes were synthesized and characterized. In all complexes the ligands are in the E configuration with respect to the imino bond and behave as terdentate. The copper(II) complexes form square planar derivatives with one molecule of terdentate ligand and chloride ion. A further non-coordinated chloride ion compensates the overall charge. Nickel(II) ions form instead octahedral complexes with two ligands for each metal ion, independently from the stoichiometric metal:ligand ratio used in the synthesis. Ligands and complexes were tested for their antiproliferative properties on histiocytic lymphoma cell line U937. Copper(II) derivatives are systematically more active than the ligands and the nickel complexes. All copper derivatives result in inhibiting topoisomerase IIa in vitro. Computational methods were used to propose a model to explain the different extent of inhibition presented by these compounds. The positive charge of the dissociated form of the copper complexes may play a key role in their action.

Effects of TiO2 and Co3O4 nanoparticles on circulating angiogenic cells.

BACKGROUND AND AIM: Sparse evidence suggests a possible link between exposure to airborne nanoparticles (NPs) and cardiovascular (CV) risk, perhaps through mechanisms involving oxidative stress and inflammation. We assessed the effects of TiO2 and Co3O4 NPs in human circulating angiogenic cells (CACs), which take part in vascular endothelium repair/replacement. METHODS: CACs were isolated from healthy donors' buffy coats after culturing lymphomonocytes on fibronectin-coated dishes in endothelial medium for 7 days. CACs were pre-incubated with increasing concentration of TiO2 and Co3O4 (from 1 to 100 µg/ml) to test the effects of NP ­ characterized by Transmission Electron Microscopy ­ on CAC viability, apoptosis (caspase 3/7 activation), function (fibronectin adhesion assay), oxidative stress and inflammatory cytokine gene expression. RESULTS: Neither oxidative stress nor cell death were associated with exposure to TiO2 NP (except at the highest concentration tested), which, however, induced a higher pro-inflammatory effect compared to Co3O4 NPs (p<0.01). Exposure to Co3O4 NPs significantly reduced cell viability (p<0.01) and increased caspase activity (p<0.01), lipid peroxidation end-products (p<0.05) and pro-inflammatory cytokine gene expression (p<0.05 or lower). Notably, CAC functional activity was impaired after exposure to both TiO2 (p<0.05 or lower) and Co3O4 (p<0.01) NPs. CONCLUSIONS: In vitro exposure to TiO2 and Co3O4 NPs exerts detrimental effects on CAC viability and function, possibly mediated by accelerated apoptosis, increased oxidant stress (Co3O4 NPs only) and enhancement of inflammatory pathways (both TiO2 and Co3O4 NPs). Such adverse effects may be relevant for a potential role of exposure to TiO2 and Co3O4 NPs in enhancing CV risk in humans.

Oxidative and pro-inflammatory effects of cobalt and titanium oxide nanoparticles on aortic and venous endothelial cells.

Ultra-fine particles have recently been included among the risk factors for the development of endothelium inflammation and atherosclerosis, and cobalt (CoNPs) and titanium oxide nanoparticles (TiNPs) have attracted attention because of their wide range of applications. We investigated their toxicity profiles in two primary endothelial cell lines derived from human aorta (HAECs) and human umbilical vein (HUVECs) by comparing cell viability, oxidative stress, the expression of adhesion molecules and the release of chemokines during NP exposure. Both NPs were very rapidly internalised, and significantly increased adhesion molecule (ICAM-1, VCAM-1, E-selectin) mRNA and protein levels and the release of monocyte chemoattractant protein-1 (MCP-1) and interleukin 8 (IL-8). However, unlike the TiNPs, the CoNPs also induced time- and concentration-dependent metabolic impairment and oxidative stress without any evident signs of cell death or the induction of apoptosis. There were differences between the HAECs and HUVECs in terms of the extent of oxidative stress-related enzyme and vascular adhesion molecule expression, ROS production, and pro-inflammatory cytokine release despite the similar rate of NP internalisation, thus indicating endothelium heterogeneity in response to exogenous stimuli. Our data indicate that NPs can induce endothelial inflammatory responses via various pathways not involving only oxidative stress.

Titanium dioxide nanoparticles promote arrhythmias via a direct interaction with rat cardiac tissue.

BACKGROUND: In light of recent developments in nanotechnologies, interest is growing to better comprehend the interaction of nanoparticles with body tissues, in particular within the cardiovascular system. Attention has recently focused on the link between environmental pollution and cardiovascular diseases. Nanoparticles <50 nm in size are known to pass the alveolar-pulmonary barrier, enter into bloodstream and induce inflammation, but the direct pathogenic mechanisms still need to be evaluated. We thus focused our attention on titanium dioxide (TiO2) nanoparticles, the most diffuse nanomaterial in polluted environments and one generally considered inert for the human body. METHODS: We conducted functional studies on isolated adult rat cardiomyocytes exposed acutely in vitro to TiO2 and on healthy rats administered a single dose of 2 mg/Kg TiO2 NPs via the trachea. Transmission electron microscopy was used to verify the actual presence of TiO2 nanoparticles within cardiac tissue, toxicological assays were used to assess lipid peroxidation and DNA tissue damage, and an in silico method was used to model the effect on action potential. RESULTS: Ventricular myocytes exposed in vitro to TiO2 had significantly reduced action potential duration, impairment of sarcomere shortening and decreased stability of resting membrane potential. In vivo, a single intra-tracheal administration of saline solution containing TiO2 nanoparticles increased cardiac conduction velocity and tissue excitability, resulting in an enhanced propensity for inducible arrhythmias. Computational modeling of ventricular action potential indicated that a membrane leakage could account for the nanoparticle-induced effects measured on real cardiomyocytes. CONCLUSIONS: Acute exposure to TiO2 nanoparticles acutely alters cardiac excitability and increases the likelihood of arrhythmic events.

Cinnamaldehyde and cuminaldehyde thiosemicarbazones and their copper(II) and nickel(II) complexes: a study to understand their biological activity.

This paper reports the synthesis and characterization of trans-cinnamaldehyde thiosemicarbazone (Htcin), cuminaldehyde thiosemicarbazone (Htcum) and their copper and nickel complexes. All the compounds, which on healthy cells (human fibroblasts) show a neglectable cytotoxicity, were screened in vitro in cell line U937 for their antileukemic activity. These compounds, in spite of their molecular similarity, present variegated behaviors. Htcin shows no inhibition activity in U935 cells, while both its metal complexes inhibit proliferation with IC50 at µM concentrations. The other ligand, Htcum, and its metal complexes, besides inhibiting proliferation, induce apoptosis. The cell cycle analysis highlights a G2/M checkpoint stop suggesting a possible direct action on DNA or on topoisomerase IIa. From CD and UV spectroscopy experiments, the DNA results to be not the main target of all these molecules, while both copper complexes are effective topoisomerase IIa inhibitors. All of these molecules activate caspase-9 and caspase-3, while caspase-8 activity is significantly induced by both cinnamaldehyde metal complexes. Tests on PgP and intracellular metal concentrations (determined by mean of atomic absorption spectrometry) show that the compounds tend to accumulate in the cytoplasm and that the cells do not manage to pump out copper and nickel ions.

Unravelling mechanisms behind the biological activity of bis(S-citronellalthiosemicarbazonato)nickel(II).

Bis(S-citronellalthiosemicarbazonato)nickel(II), [Ni(tcitr)2], is a compound that inhibits proliferation of tumour line U937 by inducing a G2/M block and leading the cancer cells to apoptosis. This nickel derivative shows no activity on non proliferating healthy cells. In this paper we report our studies on the action mechanisms of [Ni(tcitr)2]. Apoptosis in U937 cells exposed to [Ni(tcitr)2] takes place through activation of caspase-9, and therefore through an intrinsic triggering mechanism. Given the DNA damage observed in the Comet assay, the mutagenic activity of the metal complex was tested, including with the Ames test, micronuclei and DNA damage recovery, but neither mutagenicity nor recovery were detected. Nickel-complex-DNA interactions were analyzed by direct action of the compound on plasmidic and linear DNA by UV-vis and CD spectroscopy, gel electrophoresis and Atomic Force Microscopy. These experiments reveal that [Ni(tcitr)2] does not cause DNA breaks and does not intercalate, but significantly alters the DNA conformation creating knot-like structures and hairpins.