Ultrasmall silicon nanoparticles as a promising platform for multimodal imaging.

Bimodal systems for nuclear and optical imaging are currently being intensively investigated due to their comparable detection sensitivity and the complementary information they provide. In this perspective, we have implemented both modalities on biocompatible ultrasmall silicon nanoparticles (Si NPs). Such nanoparticles are particularly interesting since they are highly biocompatible, have covalent surface functionalization and demonstrate very fast body clearance. We prepared monodisperse citrate-stabilized Si NPs (2.4 ± 0.5 nm) with more than 40 accessible terminal amino groups per particle and, for the first time, simultaneously, a near-infrared dye (IR800-CW) and a radiolabel (64Cu-NOTA = 1,4,7-triazacyclononane-1,4,7-triacetic acid) have been covalently linked to the surface of such Si NPs. The obtained nanomaterials have been fully characterized using HR-TEM, XPS, UV-Vis and FT-IR spectroscopy. These dual-labelled particles do not exhibit any cytotoxicity in vitro. In vivo studies employing both positron emission tomography (PET) and optical imaging (OI) techniques revealed rapid renal clearance of dual-labelled Si NPs from mice.

A nanoscale photothermal agent based on a metal-organic coordination polymer as a drug-loading framework for effective combination therapy.

Metallic materials are widely emerging as photothermal agents owing to their superior photothermal transduction efficiency and satisfactory photostability. In this study, an iron-based coordination polymer (Fe-CNP) loaded with doxorubicin (DOX) was assessed as a dual-function agent for photothermal therapy (PTT) and tumor-targeted chemotherapy. Fe-CNPs were synthesized by a one-step coordination reaction between Fe3+, hydrocaffeic acid, and dopamine-modified hyaluronic acid. A drug-loading method was developed to entrap DOX within Fe-CNPs through the formation of coordination bonds by Fe3+ and DOX (Scheme 1). DOX release was rapidly triggered in the cellular acidic environment and further enhanced by hyperpyrexia in the part of tumor, which will kill the remaining tumor cells after PTT. Animal experiments demonstrated complete inhibition of tumor growth without recurrence in 21 days after injection of DOX@Fe-CNPs with NIR laser irradiation. These results confirmed the enhanced anti-tumor efficiency of the chemo-photothermal nanosystem. Our work may reveal a photothermal coordination polymer as a drug-loading framework and highlight the development of metal-organic materials in combined chemo-photothermal therapy. STATEMENT OF SIGNIFICANCE: Photothermal therapy (PTT), which could directly act on tumors, has been considered as a promising treatment method for cancer. The combination of PTT with chemotherapy is attracting tremendous attention because such advanced application can achieve personalized precise medicine. Unfortunately, most PTT materials have photobleaching property, which results in reduced photothermal efficiency. Furthermore, their clinical applications also suffer from low loading capacity of chemotherapeutic drugs or nonbiodegradability in the biological system. In this study, we hypothesized that iron-based coordination polymers (Fe-CNPs) could function dually as agents to deliver both PTT and tumor-targeted chemotherapy by coordination loading of the chemotherapeutic drug doxorubicin (DOX). Our work may open up new avenues to rationally design versatile platforms for photothermal-chemotherapy to obtain synergistically enhanced therapeutic efficacy.

Copper complexes for biomedical applications: Structural insights, antioxidant activity and neuron compatibility.

Copper coordinated with amino acid residues is essential for the function of many proteins. In addition, copper complexed to free l-Histidine, as [Cu(His)2], is used in the treatment of the neurodegenerative Menkes disease and of cardioencephalomyopathy. This study was aimed to coordinate copper(II) with four small ligands (l-Serine, l-Histidine, Urea and Biuret) and to evaluate structural features, stability, antioxidant activity and neuronal compatibility of the resulting complexes. All complexes were synthesized with CuCl2 and purified by precipitation in alcohol. Elemental composition, X-rays diffraction and FTIR indicated that the complexes were in form of [Cu(ligand)2] and exhibited tridentate (l-Histidine), bidentate (l-Serine and Biuret) or monodentate (Urea) coordination with copper. UV-Vis absorbance profiles in physiologically relevant solutions and cyclic voltammetry revealed that, contrarily to [Cu(Urea)2Cl2] and [Cu(Biuret)2Cl2], the [Cu(Ser)2] and [Cu(His)2Cl2] complexes were stable in different media including water, physiological saline and intestinal-like solutions. All complexes and their ligands had antioxidant capacity as evaluated by DPPH (1,1-diphenyl-2,2-picrylhydrazyl) and DPD (N,N-diethyl-p-phenylenediamine) methods, and the [Cu(His)2Cl2] complex was the most potent. Neuronal compatibility was assessed through cell viability measurements using cultured neurons derived from mouse P19 stem cells. Although only [Cu(His)2Cl2] showed a good neurocompatibility (about 90% at concentrations up to 200 µM), the cytotoxicity of the other copper complexes was lower compared to equivalent concentrations of CuCl2. These findings open new perspectives for the use of these copper complexes as antioxidants and possibly as therapeutic agents for neurodegenerative diseases. Furthermore, study of these complexes may help to improve chelation therapy for copper dysfunctions.

In-vitro evaluation studies of 7-chloro-4-aminoquinoline Schiff bases and their copper complexes as cholinesterase inhibitors.

Alzheimer's disease (AD) is one of the most common age-related neurodegenerative disorders. Aggregation of amyloid-ß peptide into extracellular plaques with incorporation of metal ions, such as Cu2+, and reduction of the neurotransmitter acetylcholine levels are among the factors associated to the AD brain. Hence, a series of 7-chloro-4-aminoquinoline Schiff bases (HLa-e) were synthesized and their cytotoxicity and anti-cholinesterase activity, assessed for Alzheimer's disease. The intrinsic relationship between Cu2+ and the amyloidogenic plaques encouraged us to investigate the chelating ability of HLa-e. Dimeric tetracationic compounds, [Cu2(NHLa-e)4]Cl4, containing quinoline protonated ligands were isolated from the reactions with CuCl2·2H2O and fully characterized in the solid state, including an X ray diffraction study, whereas EPR data showed that the complexes exist as monomers in DMSO solution. The inhibitory activity of all compounds was evaluated by Ellman's spectrophotometric method in acetylcholinesterase (AChE) from Electrophorus electricus and butyrylcholinesterase (BChE) from equine serum. HLa-e and [Cu(NHLd)2]Cl2 were selective for AChE (IC50 = 4.61-9.31 µM) and were not neurotoxic in primary brain cultures. Docking and molecular dynamics studies of HLa-e inside AChE were performed and the results suggested that these compounds are able to bind inside AChE similarly to other AChE inhibitors, such as donepezil. Studies of the affinity of HLd for Cu2+ in DMSO/HEPES at pH 6.6 and pH 7.4 in µM concentrations showed formation of analogous 1:2 Cu2+/ligand complexes, which may suggest that in the AD-affected brain HLd may scavenge Cu2+ and the complex, also inhibit AChE.

Image-guided thermosensitive liposomes for focused ultrasound drug delivery: Using NIRF-labelled lipids and topotecan to visualise the effects of hyperthermia in tumours.

Image guided drug delivery using imageable thermosensitive liposomes (iTSLs) and high intensity focused ultrasound (FUS or HIFU) has attracted interest as a novel and non-invasive route to targeted delivery of anti-cancer therapeutics. FUS-induced hyperthermia is used as an externally applied "trigger" for the release of a drug cargo from within thermosensitive drug carriers. It is suggested that sub-ablative hyperthermia significantly modifies the permeability of tumour vasculature and enhances nanoparticle uptake. Here we describe the preparation and use of magnetic resonance imaging (MRI) and near infrared fluorescence (NIRF) labelled thermosensitive liposomes for imaging and tracking of biodistribution and drug release in a murine cancer model. We prepared iTSLs to encapsulate topotecan (Hycamtin®), a chemotherapeutic agent which when released in tumours can be monitored by an increase in its intrinsic drug fluorescence. FUS was applied using feedback via subcutaneously placed fine-wire thermocouples to maintain and monitor hyperthermic temperatures. iTSL accumulation was detected within tumours using NIRF imaging immediately after liposome administration. Mild FUS-induced hyperthermia (3 min at 42 °C, 30 min post i.v. administration) greatly enhanced iTSLs uptake. A co-localised enhancement of topotecan fluorescence emission was also observed immediately after application of FUS indicating rapid triggered drug release. The phenomena of increased iTSL accumulation and concomitant topotecan release appeared to be amplified by a second mild hyperthermia treatment applied one hour after the first. MRI in vivo also confirmed enhanced iTSLs uptake due to the FUS treatments. Our imaging results indicate the effects of hyperthermia on the uptake of carriers and drug. FUS-induced hyperthermia combined with real time imaging could be used as a tool for tumour targeted drug delivery.

Flexible Modulation of CO-Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation.

Utilizing the size-dependent adsorption properties of ruthenium carbonyl clusters (Ru-carbon monoxide (CO)) onto graphene oxide (GO), a facile CO-release platform for in situ vasodilation as a treatment for stroke-related vascular diseases is developed. The rate and amount of formation of the CO-release-active RuII (CO)2 species can be modulated by a simple mixing procedure at room temperature. The subsequent thermally induced oxidation of RuII (CO)2 to RuO2 on the GO surface results in the release of CO. Further modulation of thermal and CO-release properties can be achieved via a hybridization of medium- and high-nuclearity of Ru-CO clusters that produces a RuO2 /RuII (CO)2 /6 Ru-CO-GO composite, where 6 Ru-CO-GO provides a photothermally activated reservoir of RuII (CO)2 species and the combined infrared absorption properties of GO and RuO2 provides photothermal response for in situ CO-release. The RuO2 /RuII (CO)2 /6 Ru-CO-GO composite does not produce any cytotoxicity and the efficacy of the composite is further demonstrated in a cortical photothrombotic ischemia rat model.

Characterization of zinc amino acid complexes for zinc delivery in vitro using Caco-2 cells and enterocytes from hiPSC.

Zn is essential for growth and development. The bioavailability of Zn is affected by several factors such as other food components. It is therefore of interest, to understand uptake mechanisms of Zn delivering compounds to identify ways to bypass the inhibitory effects of these factors. Here, we studied the effect of Zn amino acid conjugates (ZnAAs) on the bioavailabilty of Zn. We used Caco-2 cells and enterocytes differentiated from human induced pluripotent stem cells from a control and Acrodermatitis enteropathica (AE) patient, and performed fluorescence based assays, protein biochemistry and atomic absorption spectrometry to characterize cellular uptake and absorption of ZnAAs. The results show that ZnAAs are taken up by AA transporters, leading to an intracellular enrichment of Zn mostly uninhibited by Zn uptake antagonists. Enterocytes from AE patients were unable to gain significant Zn through exposure to ZnCl2 but did not show differences with respect to ZnAAs. We conclude that ZnAAs may possess an advantage over classical Zn supplements such as Zn salts, as they may be able to increase bioavailability of Zn, and may be more efficient in patients with AE.

Higher iron bioavailability of a human-like collagen iron complex.

Iron deficiency remains a public health problem around the world due to low iron intake and/or bioavailability. FeSO4, ferrous succinate, and ferrous glycinate chelate are rich in iron but have poor bioavailability. To solve the problem of iron deficiency, following previous research studies, a thiolated human-like collagen-ironcomplex supplement with a high iron content was prepared in an anaerobic workstation. In addition, cell viability tests were evaluated after conducting an MTT assay, and a quantitative analysis of the thiolated human-like collagen-iron digesta samples was performed using the SDS-PAGE method coupled with gel filtration chromatography. The iron bioavailability was assessed using Caco-2 cell monolayers and iron-deficiency anemia mice models. The results showed that (1) one mole of thiolated human-like collagen-iron possessed approximately 35.34 moles of iron; (2) thiolated human-like collagen-iron did not exhibit cytotoxity and (3) thiolated human-like collagen- iron digesta samples had higher bioavailability than other iron supplements, including FeSO4, ferrous succinate, ferrous glycine chelate and thiolated human-like collagen-Fe iron. Finally, the iron bioavailability was significantly enhanced by vitamin C. These results indicated that thiolated human-like collagen-iron is a promising iron supplement for use in the future.

Complex formation equilibria of Cu2+ and Zn2+ with Irbesartan and Losartan.

We conducted a thorough study of Cu2+ complex formation equilibria with Irbesartan and Losartan, the two primary drugs for the cure of cardiovascular diseases, with the aim of recognising if these drugs could exert a chelating action towards Cu2+. We used different complementary techniques to gain a clear picture of the involved protonation and complexation equilibria. The low solubility in water of the ligands and of the formed metal complexes prevented the use of water as solvent, so we had to perform the measurements in mixed methanol-water solvents. Further, we studied the related equilibria with Zn2+ for evaluating a potential interference of this essential metal ion, largely present in biological fluids. Our study provided a strong evaluation of the formed complexes and of the relative stability constants. The binding of both metal ions takes place through the tetrazole moiety except for the Zn2+-Irbesartan system. In this last case, NMR measurements gave evidence of a tautomeric equilibrium involving the imidazole ring and the aliphatic chain. The estimated complexation model, and the related stability constants, allowed a speciation study in human plasma, based on a number of simplifying assumptions, which remarked that both drugs, Losartan and Irbesartan, could exert a chelating action, scavenging non-negligible amounts of Cu2+ from the organism.

Development of 4-hexadecyl-4,7-diaza-1,10-decanedithiol (HDD) kit for the preparation of the liver cancer therapeutic agent Re-188-HDD/lipiodol.

INTRODUCTION: A lipiodol solution of (188)Re-4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol (HTDD) has been successfully developed for liver cancer therapy; however, its preparation requires a multi-step synthesis and it is characterized by a low labeling yield. METHODS: We synthesized a new compound, 4-hexadecyl-4,7-diaza-1,10-decanedithioacetate (AHDD), without gem dimethyl groups to address these issues. AHDD was formulated into a kit and was labeled with (188)Re. Biodistribution study was performed using normal BALB/c mice. RESULTS: The kit was labeled with (188)Re with a high efficiency (98.8±0.2%). After extraction with lipiodol, the overall yield of (188)Re-HDD/lipiodol was as high as 90.2±2.6%. A comparative biodistribution study of (188)Re-HTDD and (188)Re-HDD was performed in normal mice after intravenous injection. The lungs were identified as the main uptake site due to capillary-blockage. (188)Re-HDD/lipiodol showed a significantly higher lung uptake than that of (188)Re-HTDD/lipiodol (p<0.05). CONCLUSION: The newly synthesized (188)Re-HDD/lipiodol showed improved radiolabeling yield and biodistribution results compared to (188)Re-HTDD/lipiodol, and may therefore be more suitable for liver cancer therapy.

Synthesis and biological evaluation of bisphosphonate compound labeled with (99m)Tc(CO)3(+).

In this study, radiolabeling of a bisphosphonate, alendronate (Alendronate sodium), was performed with the help of a bifunctional chelating agent. For that purpose, DTPA-NHS (Diethylenetriaminepentaacetic acid dianhydride-N-hydroxysuccinimide) was synthesized with an esterification between DTPA and NHS. Combining the DTPA-NHS ester with alendronate yields the DTPA-Alendronate compound. The structure of synthesized compound was analyzed by (1) H/(13) C/(31) P-NMR and HPLC. After then, the labeling with [(99m) Tc(CO)3 ](+) core of synthesized compound was provided. Performing quality controls of newly synthesized [(99m) Tc(CO)3 -DTPA-Alendronate] complex with thin layer radiochromatography (TLRC) and high-performance liquid radiochromatography (HPLRC), the labeling yield was found as 99%. It was observed that the compound conserves its stability for 24 h in serum media. Biodistribution of the radiolabeled complex was performed on Wistar Albino rats to determine radiopharmaceutical potential of the [(99m) Tc(CO)3 -DTPA-Alendronate] complex. It is thought that the data gained from this study will contribute to the development of complexes with bisphosphonate.

In vitro and in vivo evaluation of water-soluble iminophosphorane ruthenium(II) compounds. A potential chemotherapeutic agent for triple negative breast cancer.

A series of organometallic ruthenium(II) complexes containing iminophosphorane ligands have been synthesized and characterized. Cationic compounds with chloride as counterion are soluble in water (70-100 mg/mL). Most compounds (especially highly water-soluble 2) are more cytotoxic to a number of human cancer cell lines than cisplatin. Initial mechanistic studies indicate that the cell death type for these compounds is mainly through canonical or caspase-dependent apoptosis, nondependent on p53, and that the compounds do not interact with DNA or inhibit protease cathepsin B. In vivo experiments of 2 on MDA-MB-231 xenografts in NOD.CB17-Prkdc SCID/J mice showed an impressive tumor reduction (shrinkage) of 56% after 28 days of treatment (14 doses of 5 mg/kg every other day) with low systemic toxicity. Pharmacokinetic studies showed a quick absorption of 2 in plasma with preferential accumulation in the breast tumor tissues when compared to kidney and liver, which may explain its high efficacy in vivo.

Complementary strategies for developing Gd-free high-field T1 MRI contrast agents based on Mn(III) porphyrins.

Mn(III) porphyrin (MnP) holds the promise of addressing the emerging challenges associated with Gd-based clinical MRI contrast agents (CAs), namely, Gd-related adverse effect and decreasing sensitivity at high clinical magnetic fields. Two complementary strategies for developing new MnPs as Gd-free CAs with optimized biocompatibility were established to improve relaxivity or clearance rate. MnPs with distinct and tunable pharmacokinetic properties can consequently be constructed for different in vivo applications at clinical field of 3 T.

Formation of oxo-centered trinuclear chromium carboxylate complexes and hydrolysis of Cr3 as established by paramagnetic (2)H NMR spectroscopy.

Paramagnetic (2)H NMR techniques have been utilized to study the mechanism of formation of the oxo-bridged trinuclear Cr(III) carboxylate assembly [Cr3O(O2CCD3)6(H2O)3](+) from [Cr(H2O)6](3+) and d4-acetic acid. These studies reveal a complex mechanism dominated by the involvement of dinuclear intermediates. The oxo-bridged trinuclear Cr(III) carboxylate assembly [Cr3O(O2CCH2CH3)6(H2O)3](+) has been suggested for use as a chromium nutritional supplement and therapeutic agent as it is readily absorbed and has been proposed to enter cells intact. The paramagnetic (2)H NMR technique has been utilized to follow the stability of this Cr(III) carboxylate assembly in biologically relevant media; its stability is consistent with the assembly being able to enter cells intact.

Delivery of curcumin and medicinal effects of the copper(II)-curcumin complexes.

Curcumin, a yellow pigment extracted from the rhizome of Curcuma longa, commonly known as turmeric, is the most active agent of this herbal medicine. The therapeutic activities of curcumin are exemplified not only by its enhancement in wound healing but also in the treatment of inflammation, cystic fibrosis, Alzheimer's disease and cancer. There are two critical issues involving low aqueous stability and solubility that limit the bioavailability and application of curcumin as a therapeutic agent. To address these issues, delivery systems of curcumin including surfactant micelles, liposomes, polymer nanoparticles, casein micelles, plasma proteins and cyclodextrins have been developed and characterized. From a biochemical perspective, the medicinal activities of curcumin are proposed to be related to an elevated level of transition metals including copper, zinc and iron in many disease sites, especially those in cancer and Alzheimer's disease. Previous studies have demonstrated the importance of copper(II)-curcumin complexes in DNA damage owing to the strong interaction between curcumin and copper(II). Curcumin, as an anti-oxidant, possesses the abilities to scavenge radicals and maintain the levels of anti-oxidant enzymes in the presence of copper. On the other hand, copper(II)-curcumin complexes show pro-oxidant effects by generating reactive oxygen species at a high free copper level in a reducing environment. This condition results in DNA damage and inhibition of vital signaling pathways in cancer cells, leading to apoptosis. In short, curcumin has dual roles as an anti-oxidant and a prooxidant in the presence of copper and these fascinating phenomena contribute greatly to its multiple medicinal effects.

Synthesis and application of 188Re-MN-16ET/Lipiodol in a hepatocellular carcinoma animal model.

INTRODUCTION: Hepatocellular carcinoma is the most common form of primary hepatic carcinoma. A new N(2)S(2) tetradentate ligand, N-[2-(triphenylmethyl)thioethyl]-3-aza-19-ethyloxycarbonyl-3-[2-(triphenylmethyl)thioethyl]octadecanoate (H(3)MN-16ET), was introduced and labeled with (188)Re to create (188)Re-MN-16ET in the Lipiodol phase. The potential of (188)Re-MN-16ET/Lipiodol for hepatoma therapy was evaluated in a hepatocellular carcinoma animal model of Sprague-Dawley rats implanted with the N1S1 cell line. METHODS: Synthesis of H(3)MN-16ET was described, and characterization was identified by infrared, nuclear magnetic resonance and mass spectra. We compared the effects of transchelating agents (glucoheptonate or tartaric acid) and a reducing agent (stannous chloride) on the complexing of (188)Re-perrhenate and H(3)MN-16ET. Twenty-four rats implanted with hepatoma were injected with 3.7 MBq/0.1 ml of (188)Re-MN-16ET/Lipiodol or (188)Re-MN-16ET via transcatheter arterial embolization. Biodistribution experiments and single-photon emission computed tomography imaging were performed to investigate tumor accumulation. RESULTS: H(3)MN-16ET was proved to easily conjugate with the Re isotope and showed good solubility in Lipiodol. The radiochemical purity of (188)Re-MN-16ET/Lipiodol with 10 mg tartaric acid and stannous chloride was shown to be more than 90%. The major distribution sites of (188)Re-MN-16ET in Sprague-Dawley rats were hepatoma and the liver. However, the radioactivity at the tumor site postadministered with (188)Re-MN-16ET was quickly decreased from 9.15±0.23 (at 1 h) to 2.71%±0.18% of injected dose/g (at 48 h). The biodistribution and micro-single-photon emission computed tomography/computed tomography image data showed that (188)Re-MN-16ET/Lipiodol was selectively retained at the tumor site, with 11.55±1.44, 13.16±1.46 and 10.67%±0.95% of injected dose/g at 1, 24 and 48 h postinjection, respectively. The radioactivity in normal liver tissue was high but significantly lower than that of the tumors. CONCLUSION: H(3)MN-16ET is a suitable tetradentate ligand for (188)Re labeling. From the animal data, we suggest that (188)Re-MN-16ET/Lipiodol has the potential to be a therapeutic radiopharmaceutical for hepatoma treatment.

Novel transition metal complexes of 4-hydroxy-coumarin-3-thiocarbohydrazone: pharmacodynamic of Co(III) on rats and antimicrobial activity.

A new series of stable transition metal complexes of the formula M(L)X·S, where M = Cu(II), Ni(II), Co(III), Cr(III) and Fe(III) and L is the deprotonated ligand of 4-hydroxy-coumarin-3-thiocarbohydrazone, X = Cl(-), NO(3)(-) or CH(3)COO(-) and S = H(2)O and/or EtOH. The HL ligand was prepared by the reaction of 3-formyl-4-hydroxy-coumarine with thiocarbohydrazide in the molar ratio 1:1. The HL ligand and its metal complexes were characterized by elemental analysis, (1)H NMR, IR and electronic spectra, and molar conductance and magnetic measurements and thermal gravimetric analysis (TGA). The HL ligand acts as a monobasic tridentate ONS donor in all metal complexes, and coordinated through the phenolic OH, azomethine nitrogen and thione sulfur. Electronic spectra with magnetic moments suggested varieties of geometries around the central metal atoms. Thermal gravimetric analysis indicates that the complexes are stable up to 300°C, and release the uncoordinated and/or coordinated H(2)O/solvent molecules, which is accompanied by a color change. The formed complexes after releasing the solvent were investigated and their structures are suggested to have square planar or octahedral arrangement. Pharmacodynamic of cobalt(III) complex on some biochemical parameters and histological studies in serum and heart tissue in rats have been studied. Although the complexes demonstrated a significant effect at low dose than the high dose, the ligand showed significant good effects in both high and low doses on the biochemical analysis in serum and heart tissue. Cobalt complex was screened in order to evaluate its antifungal activity against the filamentous fungi Aspergillus niger, Aspergillus fumigatus, and Aspergillus flavus, and antibacterial activity against the Candida albicans, Escherichia coli, Klebseilla pneumoniae and Pseudomonas aeruginosa.