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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
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inorganic and organometallic polymers and materials 10 (2000), S. 177-188 
    ISSN: 1572-8870
    Keywords: toxicology ; polymer–ferrocene conjugates ; polymer–platinum conjugates ; cisplatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Prompted by early observations of the cytotoxic and antineoplastic properties of certain ferrocene and ferricenium derivatives, efforts in this laboratory were focused on the synthesis of carrier-bound ferrocene compounds. Subsequent cell culture tests carried out with selected conjugates obtained in that program showed these polymers to be highly active antiproliferative agents. In the present project toxicological work has been performed in vivo on several ferrocene conjugates in an effort to assess their toxic effects in experimental animals (CD-1 mice). The conjugates, all based on an α,β-DL-polyaspartamide backbone structure, comprise the ferrocene drug model as a terminal on short side chains containing biofissionable amide or ester links for intracellular drug release. The polymers, dissolved in phosphate-buffered saline, have been injected in predetermined concentrations into the vein of the mice, and the maximum tolerated dose (MTD) levels have been determined, the latter referring to the highest dose levels administered that would allow long-term survival of the test animals. For the five conjugates tested, MTD levels range from about 3 to 30 mg Fe/kg or 0.05–0.66 mmol Fe/kg. Compared on a molar metal-to-metal basis with similarly structured platinum conjugates tested previously (MTD, ∼0.14–2.66 mmol Pt/kg), these values are indicative of comparatively high toxicity of the ferrocene polymers. Some implications of these findings are discussed.
    Type of Medium: Electronic Resource
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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    ISSN: 1572-8870
    Keywords: antiproliferative activity ; water-soluble polymer–platinum complexes ; LNCaP human metastatic prostate adenocarcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemotherapeutic treatment of secondary, i.e., disseminated cancers, has until now remained an unsatisfactory modality. The LNCaP human metastatic prostate adenocarcinoma cell line lends itself as a useful tool to probe the efficaciousness of novel antineoplastic agents for the control of metastatic cell growth. In this paper we report on a series of cell culture tests assessing the antiproliferative activity of several water-soluble polymer–platinum conjugates in which the metal is tied (anchored) to various polymeric carriers through coordination by a single carrier-attached primary amine ligand. The conjugates are based on polyaspartamide carriers composed, within the backbone, of a majority fraction of subunits bearing water-solubilizing tertiary amine side-group functions and a minority fraction of subunits featuring side chain-terminating primary amino groups for metal binding. Two similarly structured conjugates in which the platinum center is coordinated by two amine ligands in cisoid orientation mimicking the structural skeleton of cisplatin are included in the study for comparison. In all structures cleavage of a side-chain segment is required for release of the monomeric bioactive platinum complex. The growth of LNCaP human metastatic prostate adenocarcinoma cells in RPMI 1640 medium in the presence and absence of the conjugates in a range of concentrations is assessed by a protein assay, and the IC50 values, representing the drug concentrations required for 50% cell growth inhibition relative to untreated control, are determined. The results show both classes of conjugates, those comprising monoamine-coordinated platinum and those featuring cis-diamine-coordinated metal, to be well comparable in antiproliferative activity. A major program of synthesis and evaluation of polymer-bound monoamineplatinum complexes, prompted by these findings, is forthcoming in this laboratory.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-8870
    Keywords: ferrocene polymers ; polyaspartamide carriers ; carboxamide ; LNCaP cell line
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In continuation of earlier studies probing the cytotoxic properties of polymer-bound ferrocene against the HeLa cell line, the present communication presents the results of cell culture tests performed on a number of polymer–ferrocene conjugates against the LNCaP human metastatic prostate adenocarcinoma line. The water-soluble substrates are polyaspartamide carriers containing primary amine functions as side-group terminals to which the ferrocenylation agent, 4-ferrocenylbutanoic acid, is covalently bound (anchored) through N-acylation, the carboxamide groups so generated in the tether acting as the biofissionable links for release of the monomeric ferrocene compound from the conjugate in the lysosomal compartment. The carrier backbone structures are of the α, β-DL-peptide type preferred in our ongoing work, as this structural configuration allows ultimate chain degradation for efficacious excretion yet prevents fast and premature, α-peptidase-mediated “unzipping” of the peptidic chain. The screens are performed by exposing the selected conjugates 1–7 at various concentrations to cultured LNCaP cells in RPMI medium over a period of 7 days and assessing cell viability by a protein assay. From cell growth data relative to control, plotted against conjugate concentration, the IC50 values, expressed as metal concentrations required for 50% cell growth inhibition, are found to be in the narrow range of 1–10 μg Fe/ml. This compares well with earlier results obtained on selected ferrocene conjugates against the HeLa cell line and, more strikingly still, on analogous, previously tested conjugates containing the square-planar structural skeleton of the cisplatin-type anticancer drug system as the bioactive agent. The present findings, hence, should provide a healthy motivation for more extended studies of polymer-anchored ferrocenes in the biomedical realm.
    Type of Medium: Electronic Resource
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  • 9
    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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  • 10
    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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