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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 71-91 
    ISSN: 1572-8870
    Keywords: Ferrocene polymers ; polyaspartamide carriers ; poly(ethylene oxide)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In continuation of earlier investigations of polymer–ferrocene conjugates for biomedical applications, this article deals with conjugates prepared by N-acylation of linear, amine-functionalized polyaspartamide carriers with 4-ferrocenylbutanoic acid. Acylation is brought about both by mediation of HBTU coupling agent and by the N-hydroxysuccinimide active ester method. The polymeric carriers contain oligo- or poly(ethylene oxide) side chains introduced here for enhancement of water solubility. The longer side chains, in addition, are to impart such biomedically important properties as increased resistance to uptake by the reticuloendothelial system and to protein binding, extended circulation life time, and lowered immunogenicity. The conjugates comprise from 10 to 25 mol% ferrocenylated subunits, corresponding to ca. 2–5% Fe by mass. Freshly prepared and isolated in the solid state, they dissolve smoothly in aqueous media, with upper concentration limits (〉0.2g/ml) dictated solely by their viscosity behavior. The conjugates are of interest in biomedical applications.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8870
    Keywords: Platinum complexes ; polyaspartamide conjugates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In continuation of previous investigations aiming at the development of macromolecular metal complexes for biomedical use, this communication describes poly(alkylene oxide)-grafted polymeric platinum complexes. The platinum-containing macromolecules are obtained from presynthesized polyaspartamide carriers bearing poly(ethylene/propylene oxide) side chains and hydroxyethyl side groups as hydrosolubilizing units in addition to ethylenediamine side group terminals for metal coordination. Platination is brought about by treatment of the carriers with tetrachloroplatinate(II) ion in aqueous solution at 25–60°C. pH 4–6. The polymeric products, purified by dialysis in aqueous solution, are isolated by freeze-drying in yields of 60–80%. Platinum contents are in the range of 4–15%. The metal is bound to the carrier through chelation with the ethylenediamine ligands, forming square-planarcis-dichloroethylenediamine-platinum(II) complex species as side-chain terminals. Initially, the product polymers dissolve smoothly in water. Although on room-temperature storage in the solid state they gradually turn insoluble as a consequence of intermolecular solid-state interaction, solubility is retained on low-temperature storage and in frozen aqueous solutions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 217-231 
    ISSN: 1572-8870
    Keywords: Water-soluble platinum conjugates ; antiproliferative agents ; cytotoxicity testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Several polymer-platinum conjugates comprising the square-planar cis-diaminedichloroplatinum(II) complex system of cisplatin-type anticancer drugs are screened for antiproliferative activity in cell culture tests. The water-soluble conjugates prepared in this study or taken from preceding investigations are obtained by platination of aliphatic polyamide carriers containing ethylenediamine segments as side-group or main-chain components. These segments, coordinating to the metal as cis-diamine chelating ligands, are bound to, or into, the carrier backbone through biofissionable amide links permitting drug release from the carrier. In vitro tests are performed against a HeLa human cervix carcinoma cell line. IC50 data, expressed as the concentration of Pt in the conjugates (μg/ml), causing 50% inhibition of cell growth, show the highest activity, with IC50=14 μg/ml, to be associated with a conjugate derived from a polyaspartamide carrier that contains the platinum complex as a side group in proximity to the main chain and, additionally, contains dimethylaminopropyl side groups as solubilizing functions. At the low end of the performance spectrum is a conjugate, with IC50〉120 μg/ml, possessing a similar backbone and metal-binding structure, yet comprising long poly(ethylene oxide) grafts. The latter apparently shield the complex-binding tether from enzymatic attack and thus prevent efficient intracellular release of the monomeric complex. Selected conjugates will be submitted for toxicological evaluation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 111-119 
    ISSN: 1572-8870
    Keywords: Monoamineplatinum(II) complexes ; polyaspartamides ; water-soluble conjugates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In continuation of earlier work in this laboratory comprising the synthesis of water-soluble polyaspartamide-monoamineaquadichloroplatinum conjugates as potential antineoplastic agents, the presently described project is concerned with related conjugates in which the same type of monoamineplatinum complex unit is bound to polyaspartamide carriers via main chain-attached poly(ethylene oxide) (PEO) spacers introduced here in order to improve certain biomedical performance features. The conjugates are synthesized by aqueous-phase platination of amine terminals on the PEO side chains of the carriers, brought about by treatment with tetrachloroplatinate(II) anion under closely controlled conditions of time, temperature, and acidity, followed by dialysis. The target polymers, separated by freeze-drying, are completely water soluble upon isolation, yet undergo slow intermolecular interaction in the solid state with a gradual loss of solubility unless stored in (frozen) aqueous solution at −30°C.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 8 (1998), S. 225-236 
    ISSN: 1572-8870
    Keywords: Polymer–ferrocene conjugates ; N-succinimidyl 4-ferrocenylbutanoate ; polyamide carriers ; intrachain anchoring sites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is the objective of this project to synthesize polymer–ferrocene conjugates from macromolecular carriers in which the “anchoring” sites are main-chain constituents, thus contrasting with previously described conjugates featuring side-chain terminals as anchoring sites. To this end, earlier-developed polyamide carriers containing secondary amino groups in the main chain are treated with the active N-succinimidyl ester of 4-ferrocenylbutanoic acid in DMF solution. Molar feed ratios are chosen so as to favor the incorporation of a single ferrocenyl group per recurring unit. The water-soluble, microanalytically and spectroscopically characterized conjugates are of interest as antiproliferative agents in cancer research.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 7 (1997), S. 163-181 
    ISSN: 1572-8870
    Keywords: cis-Diaminedichloroplatinum(II) ; polyamide carriers ; main-chain platination ; water-solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As a follow-up study to previous work involving the platination of polyamide carriers through metal chelation by side group-incorporated ethylenediamine ligands, the present investigation is concerned with the synthesis of platinum-containing polymers in which the metal-coordinating ethylenediamine segments are components of the main chain. Two chloro groups in cis geometry are attached to each Pt atom as additional ligands, complementing a square-planar cis-diaminedichloroplatinum(II) complex system. The water-soluble polymeric carriers are synthesized by Michael-type addition polymerization, interfacial polymerization, and high-temperature solution polycondensation techniques and are crudely fractionated by stepwise aqueous dialysis, ultimately in tubing with a molecular mass cutoff of 25,000. Carrier platination is brought about by treatment with tetrachloroplatinate(II) anion in aqueous solution, care being taken to exercise strict control of reaction variables and workup conditions in an effort to restrict platination to the given ligands and avoid metal aquation or hydroxylation. The platinum conjugates, with Pt contents ranging from about 11 to 23% by mass, are completely soluble in aqueous media when freshly prepared, although long-term storage at room temperature in the solid state is conducive to gradual loss of solubility. The conjugates are of interest as carcinostatic agents.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 9 (1999), S. 221-230 
    ISSN: 1572-8870
    Keywords: Polymer–ferrocene conjugates ; ester link ; bioactivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ferrocene, the parent of the metallocene family of organotransition metal compounds, has come to occupy a significant niche in cancer research. Developmental work in the authors' laboratory has been focused on the synthesis of antiproliferative ferrocene conjugates in which the bioactive ferrocene unit is covalently, yet bioreversibly bound (anchored) to water-soluble carrier polymers designed in accordance with requisite biomedical specifications. The anchoring link in most of these conjugates has been an aliphatic spacer containing the biofissionable amide group. In this communication the synthesis of a class of ferrocene conjugates is reported in which the ferrocene group is carrier-anchored through spacers containing an ester link, of interest here because of potentially different drug release behavior. The carriers are polyamides equipped with variously spaced hydroxyl side groups, to which the ferrocenylation agent, 4-ferrocenylbutanoic acid, is connected through esterification. The coupling reactions, mediated by carbodiimide agent and catalyzed by 4-(dimethylamino)pyridine, are carried out in DMF at temperatures not exceeding 65°C, and the water-soluble product polymers are isolated in yields of typically 70–85% by precipitation, aqueous dialysis, and freeze-drying. With the molar feed ratios chosen in these coupling experiments, the incorporation of ferrocene, assessed by 1H NMR spectroscopy, corresponds to iron contents of roughly 2.5–5.5%, by mass. The conjugates will be included in a forthcoming bioactivity screening program.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary cis-Dichlorocyclopentylamine(dimethyl sulphoxide)-platinum(II) is obtained, in addition to small quantities of the corresponding trans compound, by reaction of K2PtCl4 with cyclopentylamine in DMSO solution, where it is formed as the thermodynamically favoured isomer. An X-ray crystal structure analysis confirms the cis configuration. Coordination around the metal centre is square planar, and the ligand bond angles at the Pt atom are close to the expected values of 90 and 180°. The DMSO ligand is S-coordinated to Pt. The Pt-Cl bond lengths, 2.299(2) and 2.317(2) Å, are normal for structures of this type, as are the Pt-N and Pt-S bond distances, 2.059(5) and 2.191(2) Å, respectively.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 793-799 
    ISSN: 0268-2605
    Keywords: anticancer ; antineoplastic ; ferrocene/ferricenium ; biological redox ; free radical ; polyaspartamide ; tumor ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ferrocene/ferricenium redox system plays a significant role in biological oxidation, reduction and free-radical reactions. Of particular interest are the findings of earlier investigations which showed certain water-soluble ferricenium salts to possess appreciable antiproliferative activity against various murine tumor lines and a xenografted human colorectal adenocarcinoma. Solubility in water, a prerequisite for efficacious transport and dissipation in central circulation, was then proposed as a principal requirement for the ferrocene complex system to exert antineoplastic activity irrespective of the oxidation state in which it is administered. In order to shed more light on this question, we decided to investigate the antiproliferative properties of polymer-ferrocene conjugates containing the metal complex in the non-oxidized (ferrocene) form while fulfilling the critical requirement of water solubility. To this end, five selected, water-soluble conjugates, synthesized by reversible coupling of 4-ferrocenylbutanoic acid to variously structured polyaspartamides featuring pendant primary amino groups as coupling sites, were tested in vitro against cultured HeLa cells at concentrations up to 50 µg Fe ml-1. Optimal antiproliferative activities, with IC50 in the range of 2-7 µg Fe ml-1, were determined for three compounds possessing tertiary-amine functions susceptible to protonation at physiological pH. Lower activities (IC50 = 45-60 µg Fe ml-1) were demonstrated for two poly(ethylene oxide)-containing conjugates. However, no reasonable structure-performance relationships can be derived at this stage from the small number of compounds tested. Copyright © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 7 (1996), S. 867-872 
    ISSN: 1042-7147
    Keywords: polymeric drug carriers ; water solubility ; oligo(ethylene oxide) segments ; cis-diaminedichloroplatinum(II) conjugates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Following a brief discussion of the concept of polymer-drug conjugation and the use of platinum drugs in cancer therapy, the paper presents recent results in the synthesis of water-soluble polymeric carriers designed for the binding of antineoplastic coordination compounds of the cisplatin type. The target polymers, specifically, are linear aliphatic polyamides comprising the ethylenediamine ligand system in the main chain as the potential metal binding site. With solubility in aqueous media a key requirement for intravenously injectable conjugates, the polymers also contain hydrosolubilizing oligo(ethylene oxide) units in the chain, which serve the additional purpose of imparting resistance to serum protein binding and capture by the reticuloendothelial system. The synthesis methods include interfacial polymerization, high-temperature solution polycondensation in polyphosphoric acid and Michael addition polymerization, with 1,2-bis(2-aminoethylamino)ethane and 1,2-bis(3-aminopropylamino)ethane used as the amine comonomers providing the ethylenediamine ligand segment. The target polymers, crudely fractionated by dialysis in 25,000 molecular-mass cult-off tubing, are isolated by freeze-drying as water-soluble solids possessing inherent viscosities of 10-20 ml/g. A selected carrier polymer is converted to the corresponding water-soluble cis-diaminedichloroplatinum(II) conjugate by treatment with tetrachloroplatinate(II) anion in aqueous solution.
    Type of Medium: Electronic Resource
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