1. Synthesis of the N,N&#8217;-(alkane-1,n-diyl)diisonicotinamide
<ol>
	<li>Dry a single neck or three-neck round bottom flask in an oven (100 &#186;C, 1 hr) to ensure all moisture is removed.</li>
	<li>Add solid isonicotinic acid, or its derivative, to the flask along with a magnetic stirring bar. If the diaminoalkane ligand(s) are solids at room temperature, then 0.5 mole&#160;(to the number moles of isonicotinic acid) is added to the flask at this stage.</li>
	<li>Cap the neck(s) of the flask with rubber septa and replace the air in the flask with nitrogen either through a continuous nitrogen stream or through the use of nitrogen filled balloons.</li>
	<li>Use a hypodermic needle and a syringe to add anhydrous dimethylformamide or dimethylsulfoxide (4 ml per 500 mg of isonicotinic acid or 2-methyl-isonicotinic acid) to dissolve the solid. If the solids do not dissolve easily, then heat the solution gently.</li>
	<li>Add 7 mole equivalents (to the amount of isonicotinic acid used) of triethylamine (weak base) and 0.5 mole equivalents of the diaminoalkane. If the solution is a liquid at room temperature, then add 1.5 mole equivalents.</li>
	<li>Add one mole equivalent of 1-propylphosphonic anhydride (coupling agent) with continuous stirring and allow the reaction to complete over 5-12 hr.</li>
</ol>
2. Purification of the Ligands
<ol>
	<li>For bispyridine ligands made using diaminoalkane ligands with 10 or more methylene groups, wait for the products to precipitate from solution as the reaction progresses.</li>
	<li>For bispyridine ligands made using diaminooctane, precipitate the product by adding ~40 ml of water.</li>
	<li>For bispyridine made using diaminoalkanes of two to six methylene groups, add ~40 ml of water and allows the compounds to crystallize over 1-3 days.</li>
	<li>Collect each bispyridine ligand by vacuum filtration and recrystallize from approximately 400-500 ml of boiling water per 200 mg of ligand. Note: More water is needed for the longer bispyridine ligands due to their much reduced water solubility.</li>
	<li>Add NaOH and KOH (pH 9) to the solution to ensure that the compounds are free bases upon recrystallization.</li>
</ol>
3. Synthesis and Purification of the Dinuclear Platinum Complexes
<ol>
	<li>Fully dissolve trans-diamminodichloridoplatinum(II), transplatin, in hot (70-80 &#186;C) water (150 ml per 200 mg of transplatin) to produce a clear strongly yellow colored solution.</li>
	<li>Add a 0.5 mole equivalent of the bispyridine ligand and stir the solution at temperature until the ligand dissolves (clear solution). Wait for the solution to turn near colorless, turn off the heat, and stir at room temperature for a few additional hours.</li>
	<li>Remove the solvent by rotary evaporation, which will yield a yellow colored powder.</li>
	<li>Purify, the platinum complex(es) by dissolving in a minimum amount of warm water (~50 &#186;C). If remaining yellow or white colored solids are present, then filter these off.</li>
	<li>Add acetone to the solution until a white precipitate is formed which appears to be a polymeric form of the metal complexes and represents up to 10% of the reaction product. Continue the addition of acetone (~extra 20-30 ml) until no more precipitate appears. Note: this white precipitate is an impurity.</li>
	<li>Remove this precipitate by filtering the contents through nylon filter paper (0.2 &#181;m pore size) and rotary evaporating the remaining solution to dryness, which will yield a pure product. Note: If necessary, then additional acetone precipitation steps can be performed until the complex is pure.</li>
</ol>

<ol>
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Cancer. 43, 2631-2633 (2007).</li><li>Markman, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+features+of+hypersensitivity+reactions+to+carboplatin.">Clinical features of hypersensitivity reactions to carboplatin.</a> J Clin. Oncol. 17, 1141-1145 (1999).</li><li>Ding, D., Allman, B. 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The authors have nothing to disclose.

In this work dinuclear platinum complexes have been synthesized as potential anticancer agents. In doing so bispyridine bridging ligands were synthesized via an amide coupling reaction using isonicotinic acid and variable length diaminoalkanes. Previously the synthesis of bispyridine ligands and their methyl analogues with 2 to 8 methylene groups and their respective platinum complexes have been reported. In this paper, the synthesis and purification method has been revised making it faster and cheaper and have demonstra...

Platinum anticancer drugs remain one of the most widely used family of agents in the treatment of human cancer1. Despite their success, they are limited in their application by severe dose-limiting side effects2-4. The limited doses that can be administered to patients also means that tumors can develop resistance5. As such, new drugs continue to be developed to improve the side effect profile and overcome acquired resistance, like phenanthriplatin6 and phosphaplatin7.
In the late 1990s, a trinuclear platinum drug was developed, BBR3464 (Scheme 1)8, that is up to 1,000x&#160;more cytotoxic in vitro than the leading platinum drug, cisplatin. BBR3464 is also able to overcome acquired resistance in a panel of human cancer cell lines9. Unfortunately, the increased activity of BBR3464 is matched by 50- to 100- fold higher toxicity, which limits its use10-12. It is also easily degraded in the body, meaning little of the drug reaches cancer nuclei intact9.
Picoplatin is a mononuclear platinum-based drug that contains a 2-methyl-pyridine ligand (Scheme 1)13. The methyl group of this drug protects it from attack by biological nucleophiles; in particular cysteine and methionine containing peptides/proteins14-16. As such, the drug is quite stable and has a much higher concentration that reaches cancer nuclei compared with both BBR3464 and cisplatin17. Its reduced reactivity also means picoplatin has a higher maximum tolerated dose compared with BBR3464 and cisplatin10,18,19.
This project therefore sought to combine the properties of BBR3464 and picoplatin to produce new drugs that are able to overcome acquired resistance that display improved biological stability and less severe side-effects (e.g., Figure 1). In doing so, a range of dinuclear platinum complexes were prepared with bispyridine bridging ligands20. The ligands are made using amide coupling reactions with isonicotinic acid, or its derivatives like 2-methyl-isonicotinic acid, variable length diaminoalkanes. Reaction of one mole equivalent of the ligands with two mole equivalents of transplatin yields the desired platinum complexes (Scheme 1).

<table border="0" cellpadding="0" cellspacing="0" width="782">
	<tbody>
		<tr height="24">
			<td height="24" style="height:24px;width:297px;">D2O</td>
			<td style="width:175px;">Aldrich</td>
			<td align="right" style="width:159px;">151882</td>
			<td style="width:152px;">99.9% D</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:297px;">DMSO-d6</td>
			<td style="width:175px;">Aldrich</td>
			<td align="right" style="width:159px;">156914</td>
			<td style="width:152px;">99.96% D</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:297px;">1,8-diaminooctane</td>
			<td style="width:175px;">Aldrich</td>
			<td style="width:159px;">D22401</td>
			<td align="right" style="width:152px;">98%</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:297px;">1,10-diaminodecane</td>
			<td style="width:175px;">Aldrich</td>
			<td style="width:159px;">D14204</td>
			<td align="right" style="width:152px;">98%</td>
		</tr>
		<tr height="80">
			<td height="80" style="height:80px;width:297px;">1,12-diaminododecane</td>
			<td style="width:175px;">Aldrich</td>
			<td style="width:159px;">D1,640-1</td>
			<td align="right" style="width:152px;">98%</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:297px;">Isonicotinic acid</td>
			<td style="width:175px;">Aldrich</td>
			<td style="width:159px;">I17508</td>
			<td align="right" style="width:152px;">99%</td>
		</tr>
		<tr height="120">
			<td height="120" style="height:120px;width:297px;">1-Propylphosphonic anhydride solution</td>
			<td style="width:175px;">Aldrich</td>
			<td align="right" style="width:159px;">431303</td>
			<td style="width:152px;">50 wt% in ethyl acetate</td>
		</tr>
		<tr height="100">
			<td height="100" style="height:100px;width:297px;">Trans-diaminodichloridoplatinum(II)</td>
			<td style="width:175px;">Aldrich</td>
			<td style="width:159px;">P1525</td>
			<td style="width:152px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Dimethylsulfoxide</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:159px;">Z76855</td>
			<td style="width:152px;">&#62;99.9%, anhydrous</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">N,N&#8217;-dimethylformamide</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td align="right" style="width:159px;">227056</td>
			<td style="width:152px;">99.8%, anhydrous</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Triethylamine</td>
			<td style="width:175px;">Sigma-Aldrich</td>
			<td style="width:159px;">T0886</td>
			<td style="width:152px;">&#62;99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Nylon filter membranes</td>
			<td style="width:175px;">Whatman</td>
			<td style="width:159px;">7402-004</td>
			<td style="width:152px;">Pore size, 0.2 &#181;m</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Equipment</td>
			<td style="width:175px;"></td>
			<td style="width:159px;"></td>
			<td style="width:152px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Magnetic stirring hotplate</td>
			<td style="width:175px;"></td>
			<td style="width:159px;"></td>
			<td style="width:152px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Magnetic stirring bar&#160;</td>
			<td style="width:175px;"></td>
			<td style="width:159px;"></td>
			<td style="width:152px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Round bottom or three neck flask</td>
			<td style="width:175px;"></td>
			<td style="width:159px;"></td>
			<td style="width:152px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:297px;">Rubber septums of sufficient size for chosen round bottom or three neck flask</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">5 mL hypodermic syringes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Hypodermic needles</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Rubber party ballons</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Rubber bands</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:297px;">A source of N2 gas</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Rotary evaporator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Drying oven</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">NMR tubes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">NMR spectrometer</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">500 mL beakers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:297px;">Glass or plastic pipettes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

amide coupling reaction for the synthesis of bispyridine-based ligands and their complexation to platinum as dinuclear anticancer agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

The bispyridine ligands and their respective dinuclear platinum complexes are characterized by 1H, 13C and 195Pt NMR (Tables 1 and 2), and electrospray ionization mass spectroscopy. Accurate melting points can be determined using differential scanning calorimetry and purity is best determined by elemental analysis for C, H and N percentage content. Of most use is 1H NMR as it is quick and easy to use, giving results within minutes of isolation ...

Watch this Scientific Journal Video about Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents at JoVE.com

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

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JoVE Journal

Chemistry

13.9K 조회수.  The University of Sydney.  이 프로토콜은 항암제와 BBR3464 picoplatin의 양태를 결합 다핵 백금 착체의 합성에 사용하기에 적합한 가교 리간드를 형성하기 위해 이소 니코틴산 및 디아 미노 알칸의 아미드 커플 링 반응을 사용하는 방법을 설명한다. 

비디오: Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance imaging (MRI). Their purpose is to enhance the relaxation rate of water protons in tissue, thus increasing the MR image contrast and the specificity of the MRI measurements. Current clinically approved contrast agents are low molecular weight molecules that are rapidly cleared from the body. The use of dendrimers as carriers of paramagnetic chelators can play an important role in the future development of more efficient MRI contrast agents. Specifically, the increase in local concentration of the paramagnetic species results in a higher signal contrast. Furthermore, this CA provides a longer tissue retention time due to its high molecular weight and size. Here, we demonstrate a convenient procedure for the preparation of macromolecular MRI contrast agents based on poly(amidoamine) (PAMAM) dendrimers with monomacrocyclic DOTA-type chelators (DOTA &#8211; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate). The chelating unit was appended by exploiting the reactivity of the isothiocyanate (NCS) group towards the amine surface groups of the PAMAM dendrimer to form thiourea bridges. Dendrimeric products were purified and analyzed by means of nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. Finally, high resolution MR images were recorded and the signal contrasts obtained from the prepared dendrimeric and the commercially available monomeric agents were compared.

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

This protocol describes the preparation and characterization of a dendrimeric magnetic resonance imaging (MRI) contrast agent that carries cyclen-based macrocyclic chelates coordinating paramagnetic gadolinium ions. In a series of MRI experiments in vitro, this agent produced an amplified MRI signal when compared to the commercially available monomeric analogue.

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the aziridine ring. The utility of bicyclic aziridinium ions, specifically 1-azoniabicyclo[3.1.0]hexane and 1-azoniabicyclo[4.1.0]heptane tosylate highlighted in the aziridine ring openings by the nucleophile with the release of the ring strain to yield the corresponding ring-expanded azaheterocycles such as pyrrolidine, piperidine and azepane with diverse substituents on the ring in regio- and stereospecific manner. Herein, we report a simple and convenient method for the preparation of the stable 1-azabicyclo[4.1.0]heptane tosylate followed by selective ring opening via a nucleophilic attack either at the bridge or at the bridgehead carbon to yield piperidine and azepane rings, respectively. This synthetic strategy allowed us to prepare biologically active natural products containing piperidine and azepane motif including sedamine, allosedamine, fagomine and balanol in highly efficient manner.

Bicyclic aziridinium ions such as 1-azoniabicyclo[4.1.0]heptane tosylate were generated from 2-[4-tolenesulfonyloxybutyl]aziridine, which was utilized for the preparation of substituted piperidines and azepanes via regio- and stereospecific ring-expansion with various nucleophiles. This highly efficient protocol allowed us to prepare diverse azaheterocycles including natural products such as fagomine, febrifugine analogue and balanol.

Bicyclic aziridinium ions were generated by the removal of an appropriate leaving group through internal nucleophilic attack by nitrogen atom in the ...

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 clusters have been observed as intermediates in the synthesis of InP quantum dots from molecular precursors (In(O2CR)3, HO2CR, and P(SiMe3)3) and may be isolated as a pure reagent for subsequent study and use as a single-source precursor. These clusters readily convert to crystalline and relatively monodisperse samples of quasi-spherical InP quantum dots when subjected to thermolysis conditions in the absence of additional precursors above 200 &#176;C. The optical properties, morphology, and structure of both the clusters and quantum dots are confirmed using UV-Vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The molecular symmetry of the clusters is additionally confirmed by solution-phase 31P NMR spectroscopy. This protocol demonstrates the preparation and isolation of atomically-precise InP clusters, and their reliable and scalable conversion to InP QDs.

Synthesis of In37P20O2CR51 Clusters and Their Conversion to InP Quantum Dots

A protocol for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots is presented.

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 ...