Organo-osmium anticancer complexes with novel azo-ligands.

Piano-stool iodido Os(II) arene complexes containing AZPY (phenylazopyridine) π-acceptor bidentate ligands have been previously shown to exhibit potent anticancer activity and mechanisms of action that involve ROS generation, and differ greatly from early Os(II) arene complexes baring σ-donor bidentate ligands. The aim of this thesis was to explore Os(II) complexes containing other types of azo-ligands as well as continue our studies into AZPY complexes. Develop methods for improving the solubility of complexes, explore their intracellular activation, and further understand the mechanisms in which ROS levels are elevated inside cells. Firstly I explored Os(II) arene complexes with AZBTZ (phenylazobenzothiazole) bidentate liagnds. It was found that AZBTZ ligands can undergo unaided cyclometallation with Os(II) to form N,C-coordinated osmacycles as well as N,N-coordination. The amount of cyclo-metallation taking place seemed to be dependent on steric factors and occurred more for iodido complexes than chlorido and bromido analogues. The osmacycles were more stable than N,N-coordinated species and exhibited unique properties such as regio-specific deuteration of the aniline ring, but were too hydrophobic for biological evaluation. A total of 31 new Os(II) arene AZPY complexes were synthesised using the previously determined structure-activity relationships as a basis. The majority contained alkoxy and glycolic side chain substituents on the AZPY ligand, which was achieved via a novel synthesis protocol. Their trends in anti-cancer activity, solubility, lipophilicity and cell uptake were explored. It was found that varying the anion was the best method for improving aqueous solubility without affecting activity, lipophilicity or uptake. Key complexes were found to be very active against OE19 oesophageal cancer cells, were capable of inducing apoptosis and elevating ROS levels in A2780 cells, as well as causing cell cycle arrest in different phases of the cell cycle. Complexes [Os(ɳ6-p-cym)(5-EtO-AZPY)I]+ and [Os(ɳ6-p-cym)(AZPY-NMe2)I]+ were labelled with radioisotope 131I (β-/γ emitter, t½ 8.02 d) in Kings College London. They were relatively stable in human blood serum and cell culture medium over 24 h. However, in the presence of MCF-7 cells, rapid dissociation of the iodide monodentate ligand was observed in the supernatants. Cell uptake studies revealed a spike in 131I uptake after 5-10 min, which proceeds to steadily decline. The complexes seemed to undergo intracellular activation involving dissociation of the iodide ligand, and uptake of the complex is in competition with a rapid rate of iodide efflux, probably involving chloride transport channels. The aqua species, [Os(ɳ6-p-cym)(5-EtO-AZPY)H2O]2+, was synthesised and its pKa was determined as 4.55, meaning it exists predominantly as a +1 charged hydroxido species under physiological conditions. Using UV-Vis spectroscopy and EPR (DEPMPO spin trap), [Os(ɳ6-p-cym)(5-EtO-AZPY)OH]+, and its chlorido and iodido analogues were found to catabolise H2O2, generating HO· radicals in the process that were capable of cleaving lysozyme protein with effectiveness in the order OH>Cl>I. Interestingly it was discovered that iodide complexes are activated by iodide ligand dissociation in the presence of low concentrations of GSH (75 μM) to form the more active hydroxido species. However, in higher concentrations (7.5 mM), they formed Os-SG and Os-SOG adducts. Likewise, [Os(ɳ6-p-cym)(5-EtO-AZPY)OH]+ and its iodido analogue were both capable of oxidising NADH to NAD+ with effectiveness in the order OH>I. NADH was also capable of activating iodido species in a similar manner and generating the hydroxido species was required for NADH oxidation to proceed

NMR studies of group 8 metallodrugs : 187Os-enriched organo-osmium half-sandwich anticancer complex

Synthesis of this 187Os-enriched organo-osmium azopyridine anticancer complex, has allowed determination of 187Os NMR J-couplings to ligand 1H and 13C, and the 187Os chemical shift. The complex was also characterised by X-ray crystallography and MS

Metallation‐induced heterogeneous dynamics of DNA revealed by single‐molecule FRET

The metallation of nucleic acids is key to wide‐ranging applications, from anticancer medicine to nanomaterials, yet there is a lack of understanding of the molecular‐level effects of metallation. Here, we apply single‐molecule fluorescence methods to study the reaction of an organo‐osmium anticancer complex and DNA. Individual metallated DNA hairpins are characterized using Förster resonance energy transfer (FRET). Although ensemble measurements suggest a simple two‐state system, single‐molecule experiments reveal an underlying heterogeneity in the oligonucleotide dynamics, attributable to different degrees of metallation of the GC‐rich hairpin stem. Metallated hairpins display fast two‐state transitions with a two‐fold increase in the opening rate to ~2 s‐1, relative to the unmodified hairpin, and relatively static conformations with long‐lived open (and closed) states of 5 s to ≥ 50 s. These studies show that a single‐molecule approach can provides new insight into metallation‐induced changes in DNA structure and dynamics

Osmium–arene complexes with high potency towards Mycobacterium tuberculosis

The treatment of tuberculosis (TB) poses a major challenge as frontline therapeutic agents become increasingly ineffective with the emergence and spread of drug-resistant strains of Mycobacterium tuberculosis (Mtb). To combat this global health problem, new antitubercular agents with novel modes of action are needed. We have screened a close family of 17 organometallic half-sandwich Os(II) complexes [(arene)Os(phenyl-azo/imino-pyridine)(Cl/I)]+Y– containing various arenes (p-cymene, biphenyl, or terphenyl), and NMe2, F, Cl, or Br phenyl or pyridyl substituents, for activity towards Mtb in comparison with normal human lung cells (MRC5). In general, complexes with a monodentate iodido ligand were more potent than chlorido complexes, and the five most potent iodido complexes (MIC 1.25–2.5 µM) have an electron-donating Me2N or OH substituent on the phenyl ring. As expected, the counter anion Y (PF6–, Cl–, I–) had little effect on the activity. The pattern of potency of the complexes towards Mtb is similar to that towards human cells, perhaps because in both cases intracellular thiols are likely to be involved in their activation and their redox mechanism of action. The most active complex against Mtb is the p-cymene Os(II) NMe2-phenyl-azopyridine iodido complex (2), a relatively inert complex that also exhibits potent activity towards cancer cells. The uptake of Os from complex 2 by Mtb is rapid and peaks after 6 h, with temperature-dependence studies suggesting a major role for active transport. Significance to Metallomics Antimicrobial resistance is a global health problem. New advances are urgently needed in the discovery of new antibiotics with novel mechanisms of action. Half-sandwich organometallic complexes offer a versatile platform for drug design. We show that with an appropriate choice of the arene, an N,N-chelated ligand, and monodentate ligand, half-sandwich organo–osmium(II) complexes can exhibit potent activity towards Mycobacterium tuberculosis (Mtb), the leading cause of death from a single infectious agent. The patterns of activity of the 17 azo- and imino-pyridine complexes studied here towards Mtb and normal lung cells suggest a common redox mechanism of action involving intracellular thiols

Dose and time-dependent tolerability and efficacy of organo-osmium complex FY26 and its tissue pharmacokinetics in hepatocarcinoma-bearing mice

The organo-osmium complex [OsII(ɳ6-p-cym)(PhAzPy-NMe2)I]+ (FY26) exhibits promising in vitro antitumour activity against mouse hepatocarcinoma Hepa1-6 and other mouse or human cancer cell lines. Here, we drastically enhance water solubility of FY26 through the replacement of the PF6-counter-anion with chloride using a novel synthesis method. FY26.PF6 and FY26.Cl displayed similar in vitro cytoxicity in two cancer cell models. We then show the moderate and late anticancer efficacy of FY26.PF6 and FY26.Cl in a subcutaneous murine hepatocarcinoma mouse model. Both efficacy and tolerability varied according to FY26 circadian dosing time in hepatocarcinoma tumour-bearing mice. Tumour and liver uptake of the drug were determined over 48 h following FY26.Cl administration at Zeitgeber 6 (ZT6), when the drug is least toxic (in the middle of the light span when mice are resting). Our studies suggest the need to administer protracted low doses of FY26 at ZT6 in order to optimize its delivery schedule, for example through the use of chrono-releasing nanoparticles

“It Is Me Who Endures but My Family That Suffers”: Social Isolation as a Consequence of the Household Cost Burden of Buruli Ulcer Free of Charge Hospital Treatment

Despite free of charge biomedical treatment, the cost burden of Buruli ulcer disease (Bu) hospitalisation in Central Cameroon accounts for 25% of households' yearly earnings, surpassing the threshold of 10%, which is generally considered catastrophic for the household economy, and calling into question the sustainability of current Bu programmes. The high non-medical costs and productivity loss for Bu patients and their households make household involvement in the healing process unsustainable. 63% of households cease providing social and financial support for patients as a coping strategy, resulting in the patient's isolation at the hospital. Social isolation itself was cited by in-patients as the principal cause for abandonment of biomedical treatment. These findings demonstrate that further research and investment in Bu are urgently needed to evaluate new intervention strategies that are socially acceptable and appropriate in the local context

Cultural preferences for formal versus intuitive reasoning

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91932/1/cultural_preferences.pd

Assessing access barriers to tuberculosis care with the tool to Estimate Patients' Costs: pilot results from two districts in Kenya

<p>Abstract</p> <p>Background</p> <p>The poor face geographical, socio-cultural and health system barriers in accessing tuberculosis care. These may cause delays to timely diagnosis and treatment resulting in more advanced disease and continued transmission of TB. By addressing barriers and reasons for delay, costs incurred by TB patients can be effectively reduced. A Tool to Estimate Patients' Costs has been developed. It can assist TB control programs in assessing such barriers. This study presents the Tool and results of its pilot in Kenya.</p> <p>Methods</p> <p>The Tool was adapted to the local setting, translated into Kiswahili and pretested. Nine public health facilities in two districts in Eastern Province were purposively sampled. Responses gathered from TB patients above 15 years of age with at least one month of treatment completed and signed informed consent were double entered and analyzed. Follow-up interviews with key informants on district and national level were conducted to assess the impact of the pilot and to explore potential interventions.</p> <p>Results</p> <p>A total of 208 patients were interviewed in September 2008. TB patients in both districts have a substantial burden of direct (out of pocket; USD 55.8) and indirect (opportunity; USD 294.2) costs due to TB. Inability to work is a major cause of increased poverty. Results confirm a 'medical poverty trap' situation in the two districts: expenditures increased while incomes decreased. Subsequently, TB treatment services were decentralized to fifteen more facilities and other health programs were approached for nutritional support of TB patients and sputum sample transport. On the national level, a TB and poverty sub-committee was convened to develop a comprehensive pro-poor approach.</p> <p>Conclusions</p> <p>The Tool to Estimate Patients' Costs proved to be a valuable instrument to assess the costs incurred by TB patients, socioeconomic situations, health-seeking behavior patterns, concurrent illnesses such as HIV, and social and gender-related impacts. The Tool helps to identify and tackle bottlenecks in access to TB care, especially for the poor. Reducing delays in diagnosis, decentralization of services, fully integrated TB/HIV care and expansion of health insurance coverage would alleviate patients' economic constraints due to TB.</p