Mutations in the metallo-protein Cu/Zn-superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS) in humans and

The molecules known as bis(thiosemicarbazones) derived from 1,2-diones can act as tetradentate ligands for Cu(II), forming stable, neutral complexes. As a family, these complexes possess fascinating biological activity. This critical review presents an historical perspective of their progression from potential chemotherapeutics through to more recent applications in nuclear medicine. Methods of synthesis are presented followed by studies focusing on their potential application as anti-cancer agents and more recent investigations into their potential as therapeutics for Alzheimer's disease. The Cu(II) complexes are of sufficient stability to be used to coordinate copper radioisotopes for application in diagnostic and therapeutic radiopharmaceuticals. Detailed understanding of the coordination chemistry has allowed careful manipulation of the metal based properties to engineer specific biological activities. Perhaps the most promising complex radiolabelled with copper radioisotopes to date is Cu(II)(atsm), which has progressed to clinical trials in humans (162 references).

We report the engineering of poly(ethylene glycol) (PEG) hydrogel particles using a mesoporous silica (MS) templating method via tuning the PEG molecular weight, particle size, and the presence or absence of the template and investigate the cell association and biodistribution of these particles. An ex vivo assay based on human whole blood that is more sensitive and relevant than traditional cell-line based assays for predicting in vivo circulation behavior is introduced. The association of MS@PEG particles (template present) with granulocytes and monocytes is higher compared with PEG particles (template absent). Increasing the PEG molecular weight (from 10 to 40 kDa) or decreasing the PEG particle size (from 1400 to 150 nm) reduces phagocytic blood cell association of the PEG particles. Mice biodistribution studies show that the PEG particles exhibit extended circulation times (>12 h) compared with the MS@PEG particles and that the retention of smaller PEG particles (150 nm) in blood, when compared with larger PEG particles (>400 nm), is increased at least 4-fold at 12 h after injection. Our findings highlight the influence of unique aspects of polymer hydrogel particles on biological interactions. The reported PEG hydrogel particles represent a new class of polymer carriers with potential biomedical applications.

A range of macrocyclic and acyclic chelators have been reacted with the PET isotope, gallium-68, and their radiolabelling efficiencies have been compared. Structural data for complexes of HBED with Ga3+ are reported.

The therapeutic efficacy of two bis(thiosemicarbazonato) copper complexes, glyoxalbis[N4-methylthiosemicarbazonato]Cu(II) [Cu(II)(gtsm)] and diacetylbis[N4-methylthiosemicarbazonato]Cu(II) [Cu(II)(atsm)], for the treatment of prostate cancer was assessed in cell culture and animal models. Distinctively, copper dissociates intracellularly from Cu(II)(gtsm) but is retained by Cu(II)(atsm). We further demonstrated that intracellular H2gtsm [reduced Cu(II)(gtsm)] continues to redistribute copper into a bioavailable (exchangeable) pool. Both Cu(II)(gtsm) and Cu(II)(atsm) selectively kill transformed (hyperplastic and carcinoma) prostate cell lines but, importantly, do not affect the viability of primary prostate epithelial cells. Increasing extracellular copper concentrations enhanced the therapeutic capacity of both Cu(II)(gtsm) and Cu(II)(atsm), and their ligands (H2gtsm and H2atsm) were toxic only toward cancerous prostate cells when combined with copper. Treatment of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model with Cu(II)(gtsm) (2.5 mg/kg) significantly reduced prostate cancer burden (∼70%) and severity (grade), while treatment with Cu(II)(atsm) (30 mg/kg) was ineffective at the given dose. However, Cu(II)(gtsm) caused mild kidney toxicity in the mice, associated primarily with interstitial nephritis and luminal distention. Mechanistically, we demonstrated that Cu(II)(gtsm) inhibits proteasomal chymotrypsin-like activity, a feature further established as being common to copper-ionophores that increase intracellular bioavailable copper. We have demonstrated that increasing intracellular bioavailable copper can selectively kill cancerous prostate cells in vitro and in vivo and have revealed the potential for bis(thiosemicarbazone) copper complexes to be developed as therapeutics for prostate cancer.

Radiolabeleddiacetylbis4-methylthiosemicarbazonatocopper II [Cu II atsm] is an effective positron-emission tomography imaging agent for myocardial ischemia, hypoxic tumors, and brain disorders with regionalized oxidative stress, such as mitochondrial myopathy, encephalopathy, and lactic acidosis with stroke-like episodes (MELAS) and Parkinson's disease. An excessively elevated reductive state is common to these conditions and has been proposed as an important mechanism affecting cellular retention of Cu from Cu II atsm. However, data from whole-cell models to demonstrate this mechanism have not yet been provided. The present study used a unique cell culture model, mitochondrial xenocybrids, to provide whole-cell mechanistic data on cellular retention of Cu from Cu II atsm. Genetic incompatibility between nuclear and mitochondrial encoded subunits of the mitochondrial electron transport chain (ETC) in xenocybrid cells compromises normal function of the ETC. As a consequence of this impairment to the ETC we show xenocybrid cells upregulate glycolytic ATP production and accumulate NADH. Compared to control cells the xenocybrid cells retained more Cu after being treated with Cu II atsm. By transfecting the cells with a metal-responsive element reporter construct the increase in Cu retention was shown to involve a Cu II atsminduced increase in intracellular bioavailable Cu specifically within the xenocybrid cells. Parallel experiments using cells grown under hypoxic conditions confirmed that a compromised ETC and elevated NADH levels contribute to increased cellular retention of Cu from Cu II atsm. Using these cell culture models our data demonstrate that compromised ETC function, due to the absence of O 2 as the terminal electron acceptor or dysfunction of individual components of the ETC, is an important determinant in driving the intracellular dissociation of Cu II atsm that increases cellular retention of the Cu.sodium arsenite | energy metabolism | radiopharmaceutical P

One of the pathological hallmarks of Alzheimer's disease is the presence of amyloid-β plaques in the brain and the major constituent of these plaques is aggregated amyloid-β peptide. New thiosemicarbazone-pyridylhydrazine based ligands that incorporate functional groups designed to bind amyloid-β plaques have been synthesized. The new ligands form stable four coordinate complexes with a positron-emitting radioactive isotope of copper, (64)Cu. Two of the new Cu(II) complexes include a functionalized styrylpyridine group and these complexes bind to amyloid-β plaques in samples of post-mortem human brain tissue. Strategies to increase brain uptake by functional group manipulation have led to a (64)Cu complex that effectively crosses the blood-brain barrier in wild-type mice. The new complexes described in this manuscript provide insight into strategies to deliver metal complexes to amyloid-β plaques.

The use of copper radioisotopes in cancer diagnosis and radionuclide therapy is possible using chelators that are capable of binding Cu(II) with sufficient stability in vivo to provide high tumour-to-background contrast. Here we report the design and synthesis of a new bifunctional chelator, 5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid (MeCOSar), that forms copper complexes of exceptional stability by virtue of a cage amine (sarcophagine) ligand and a new conjugate referred to as SarTATE, obtained by the conjugation of MeCOSar to the tumour-targeting peptide Tyr(3)-octreotate. Radiolabeling of SarTATE with (64)Cu(II), a radioisotope suitable for positron emission tomography (PET), was fast (~20 min), easily performed at room temperature and consistently resulted in high radiochemical purity (>99%). In vitro and in vivo evaluation of (64)CuSarTATE demonstrated its high selectivity for tumour cells expressing somatostatin receptor 2 (sstr2). Biodistribution and PET imaging comparisons were made between (64)CuSarTATE and (64)Cu-labeled DOTA-Tyr(3)-octreotate ((64)CuDOTATATE). Both radiopharmaceuticals showed excellent uptake in sstr2-positive tumours at 2 h post-injection. While tumour uptake of (64)CuDOTATATE decreased significantly at 24 h, (64)CuSarTATE activity was retained, improving contrast at later time points. (64)CuSarTATE accumulated less than (64)CuDOTATATE in the non-target organs, liver and lungs. The uptake of (64)CuSarTATE in the kidneys was high at 2 h but showed significant clearance by 24 h. The new chemistry and pre-clinical evaluation presented here demonstrates that MeCOSar is a promising bifunctional chelator for Tyr(3)-octreotate that could be applied to a combined imaging and therapeutic regimen using a combination of (64)Cu- and (67)CuSarTATE complexes, owing to improved tumour-to-non-target organ ratios compared to (64)CuDOTATATE at longer time points.