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ABSTRACT: We report the tumor cell-selective prodrugs based on the arsonic acid-presenting iron oxide nanoparticles. We synthesized the well-dispersed nanoparticles having arsonoacetic acid which is composed of the low toxic As(V) form. From the analyses of the reaction products, it is suggested that the reduction by dithiothreitol with arsonoacetic acid and the modified nanoparticles could generate the highly-toxic As(III) species. In the MTT assays, it was found that the cell viabilities of HeLaS3 and especially HepG2 were reduced in the presence of the modified nanoparticles. In contrast, a slight effect on viability was observed with primary mouse hepatocytes. The viabilities showed good agreements with the amounts of intracellular reduced glutathione concentrations. Furthermore, the valid concentrations of the modified nanoparticles for tumor-specific cytotoxicity were similar level in MRI measurements. These results indicate that arsonic acid-presenting nanoparticles should be a good platform for developing highly-sensitive tumor-specific prodrugs.
Bioorganic & medicinal chemistry 06/2012; 20(15):4675-9. · 2.82 Impact Factor
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ABSTRACT: We report the synthesis and characterization of the arsonic acid-presenting superparamagnetic iron oxide (SPIO). We used arsonoacetic acid as the ligand for SPIOs in aqueous media. The surface modification of the SPIOs was accomplished via the ligand exchange from undecanoic acid to the carboxyl moiety of arsonoacetic acid. Consequently, the well-dispersed arsonic acid-presenting SPIOs in water were obtained. We found that the dispersion state of the arsonic acid-presenting SPIOs can be sharply regulated by pH changes in the biological significant region. The well dispersion state of the arsonic acid-presenting SPIOs can be maintained at the neutral pH region. In contrast, the arsonic acid-presenting SPIOs can sensitively form the aggregation below pH 6.1. Moreover, these dispersion states can be controlled reversibly by the pH alteration in the narrow region.
Bioorganic & medicinal chemistry 02/2011; 19(7):2282-6. · 2.82 Impact Factor
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ABSTRACT: Mono- and dinuclear trans-dichloroplatinum(II) complexes, i.e., trans-PtCl2(cis-DHDAtBu)2 and trans,trans-Pt2Cl4(cis-DHDAtBu)2, respectively, using cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(tert-butoxycarbonyl)-1,4-diarsinine (cis-DHDAtBu), which was prepared by the radical reaction of pentamethylcyclopentaarsine (cyclo-(MeAs)5) and di-tert-butyl acetylenedicarboxylate, were obtained individually as only products by stoichiometric addition of cis-bis(benzonitrile)dichloroplatinum to cis-DHDAtBu. Replacement of chloride with iodide by adding KI into acetone solutions of trans-PtCl2(cis-DHDAtBu)2 and trans,trans-Pt2Cl4(cis-DHDAtBu)2 gave trans-PtI2(cis-DHDAtBu)2 and trans,trans-Pt2I4(cis-DHDAtBu)2, respectively. The structures of all the obtained compounds were confirmed by 1H and 13C NMR spectra, X-ray crystallography, and elemental analysis. The interior angles around the arsenic and the As−C═C bond angle were significantly varied in a series of the present platinum(II) complexes. These observations suggest that the flexibility of the bond angles around the arsenic center is an inherent property in the present organoarsenic compounds. The intermetallic interaction was induced in the dinuclear platinum(II) “face-to-face” complex using cis-DHDAtBu by the replacement of chloride with iodide. The distance of the Pt−Pt of trans,trans-Pt2I4(cis-DHDAtBu)2 was shortened compared with that of trans,trans-Pt2Cl4(cis-DHDAtBu)2, and the new broad absorption band at around 562 nm was observed in the solution of trans,trans-Pt2I4(cis-DHDAtBu)2. Density functional theory calculations indicate that the frontier molecular orbitals in trans,trans-Pt2Cl4(cis-DHDAOH)2, in which H atom surrogates were used in place of the tBu group, show no d−d interaction orbitals. On the other hand, the HOMO level in trans,trans-Pt2I4(cis-DHDAOH)2 has mainly dxz contributions in the π*-antibonding MO.
05/2010;
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Applied Organometallic Chemistry 01/2010; 24(8):573 - 575. · 2.06 Impact Factor
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ABSTRACT: We prepared and characterized a new class of fluorophore-labeled magnetic nanoparticles (MNPs) possessing a hypoxia-responsive unit to construct a hypoxia-selective emission system. The indolequinone derivative as a hypoxia-response unit bearing biotin was synthesized and immobilized on Fe(3)O(4) MNP. Subsequent complexation of this functionalized MNP with fluorescein-labeled avidin formed fluorophore-labeled nanoparticles (AF-QB@MNP). The fluorescence intensity of AF-QB@MNP was suppressed because of the adjacent quenching function of the indolequinone moiety and MNP. Upon hypoxic treatment by NADPH:cytochrome P450 reductase, AF-QB@MNP was activated to liberate a fluorescence unit, leading to the significant enhancement of fluorescence emission, while a smaller enhancement in fluorescence emission occurred upon aerobic treatment. The AF-QB@MNP has a indispensable properties as a fluorescent probe for imaging of disease relevant hypoxic microenvironments.
Bioorganic & medicinal chemistry 07/2009; 17(11):3775-81. · 2.82 Impact Factor
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ABSTRACT: We report a new method for the synthesis of block copolymers with a pentasilane core by the polymerization of alkyl methacrylate monomers using the pentasilyl dianion as an initiator. The polymerization proceeded with living features and yielded the corresponding block copolymers with controlled molecular weights. The amphiphilic block copolymer was obtained by the polymer reaction, and it formed sphere-like aggregates in MeOH/H(2) O solution.
Macromolecular Rapid Communications 06/2009; 30(11):948-53. · 4.60 Impact Factor
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ABSTRACT: We describe here the facile preparation of conductive casting films consisting of mixed-valence tetrathiafulvalene (TTF) nanofibers. Self-assembled nanofibers of mixed-valence TTF with organic acid anions were grown during film deposition, and the conductivities of the resulting films were significantly altered by the type of the anion. In particular, the casting films containing heptafluorobutyrate, propanesulfonate, and undecanesulfonate work as semiconductors (10(-2) S/cm). It was revealed that anion species played a crucial role in the formation of the nanofibers and the morphology of the film was varied.
Langmuir 04/2009; 25(12):6929-33. · 4.19 Impact Factor
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ABSTRACT: The establishment of (19)F NMR signal regulation and the application of this strategy to develop a multi-modal (19)F NMR probe for monitoring enzymatic activity using nanoparticles as a signal regulator is described; water-soluble perfluorinated cubic silsesquioxane was synthesized and immobilized onto the silica nanoparticles for suppressing the signals; (19)F NMR signals of the probes were recovered by releasing from nanoparticles.
Chemical Communications 01/2009; · 6.17 Impact Factor
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ABSTRACT: Metal nanoparticles have various unusual chemical and physical properties compared with those of metal atoms or bulk metal
due to the quantum size effect and their large superficial area, which make them attractive for applications such as optics,
electronics, catalysis, and biology [1, 2]. The catalytic properties of metal nanoparticles have generated great interest
over the past decade. Among various metal nanoparticles, gold nanoparticles have tremendously high molar absorptivity in the
visible region. Particle aggregation results in further color changes of gold nanoparticles solutions due to mutually induced
dipoles that depend on interparticle distance and aggregate size. This phenomenon can be applied to various sensing systems
[3–7]. The assembly of gold, silver, or copper nanoparticle monolayers is one of the ideal substrate for surfaced-enhanced
Raman scattering (SERS) [8, 9].
12/2008: pages 3-40;
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ABSTRACT: We report that a polyhedral oligomeric silsesquioxane (POSS) core can enhance the entrapping ability of dendrimers. Compared to the G2 PAMAM dendrimer, the G2 POSS-core dendrimer can entrap a larger amount of guest molecules without loss of affinity, and consequently, the water solubility of the entrapped guest molecules can be increased. In addition, we demonstrated that a fluorophore entrapped in the G2 POSS-core dendrimer was prevented from undergoing fluorescence photobleaching.
Organic & Biomolecular Chemistry 12/2008; 6(21):3899-901. · 3.70 Impact Factor
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ABSTRACT: Spherical aggregates of palladium nanoparticles were produced by stirring palladium(II) acetate with dendritic molecules (i.e., octa(3-aminopropyl)silsesquioxane octahydrochloride (POSS-NH3+) or the amine-terminated G1.0 poly(amidoamine) dendrimer (G1-NH2)) in methanol at room temperature via self-organized spherical templates of Pd(OAc)2 and the dendritic molecule. The mixing ratio of the terminal amino groups of the dendritic molecule and palladium ions (Z=[Pd2+]/[-NH2]) affected the formation of the spherical aggregates of palladium nanoparticles. Maximum Z values with no reduction of palladium ions (the solution remained yellow) were 1.0 for POSS-NH3+ and 1.6 for G1-NH2, respectively. TEM observations suggested that the density of the palladium nanoparticles in the aggregates using POSS-NH3+ as a template was higher than that using G1-NH2. From tapping mode atomic force microscopy, shapes of the aggregates using POSS-NH3+ and G1-NH2 were a spherical form and an oval form on plates, respectively. Increasing the rigidity of the silsesquioxane core of the dendritic molecules increased the stability of the spherical form in the dry state.
Langmuir 04/2008; 24(6):2719-26. · 4.19 Impact Factor
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ABSTRACT: We have investigated the self-assembly formed by palladium acetate (Pd(OAc)2) and polyamidoamine dendrimers (GN-NH2) in a mixed solvent of methanol and N,N-dimethylformamide. We aim to explore effects of the generation number (GN) and concentration of the dendrimers, [GN-NH2], on the self-assembly of the dendrimers (defined hereafter as “templates”) and the Pd nanoparticles inside the templates in order to clarify physical factors controlling the self-assembling mechanisms. For this purpose, we changed GN from 0 to 4 and [GN-NH2] from 0.03 to 2.7 mM, keeping the concentration of Pd(OAc)2, [Pd(OAc)2], at a fixed value of 3.6 mM. The self-assemblies of the templates and the Pd nanoparticles were investigated by means of a combined method of small-angle neutron and X-ray scattering, ultra-small-angle X-ray scattering, dynamic light scattering, and transmission electron microscopy. We elucidated the following two facts concerning the effects of increasing GN on the self-assembly under a fixed value of [−NH2] such that [Pd(OAc)2]/[−NH2] = 3.33, where [−NH2] is molar concentration of the peripheral amine group of dendrimers having varying GN. (i) The size of the templates becomes smaller, while the number density of the templates increases. This trend is well explained from the viewpoint that the effective binding force between the templates via attractive interactions of Pd(OAc)2 and amine groups of the dendrimers, which belong to different templates, becomes weak relatively to the random thermal force acting on the templates. (ii) The size of Pd nanoparticles becomes larger with increasing GN. This result can be rationalized by the following two effects: (a) increasing number fraction of Pd(OAc)2 molecules, which are easily reduced to Pd(0) atoms; (b) increasing number density of Pd(OAc)2 per single template as detailed in the text (section 4.2.1. and 4.2.3.). As for the effect of [GN-NH2], we found that the templates are formed only when [GN-NH2] falls below a critical value and thereby a sufficient amount of Pd(OAc)2 exists as the binders between the dendrimers. Otherwise dendrimers are molecularly dispersed in solution.
02/2008;
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ABSTRACT: Stable amorphous calcium carbonate (ACC) composite particle with a size-controlled monodispersed sphere was obtained by a new simple carbonate controlled-addition method by using poly(acrylic acid) (PAA) (Mw = 5000), in which an aqueous ammonium carbonate solution was added into an aqueous solution of PAA and CaCl2 with a different time period. The obtained ACC composite products consist of about 50 wt % of ACC, 30 wt % of PAA, and H2O. Average particle sizes of the ACC spheres increased from (1.8 +/- 0.4) x 102 to (5.5 +/- 1.2) x 102 nm with an increase of the complexation time of the PAA-CaCl2 solution from 3 min to 24 h, respectively. The ACC formed from the complexation time for 3 min was stable for 10 days with gentle stirring as well as 3 months under a quiescent condition in the aqueous solution. Moreover, the ACC was also stable at 400 degrees C. Stability of the amorphous phase decreased with an increase of the complexation time of the PAA-CaCl2 solution. No ACC was obtained when the lower molar mass PAAs (Mw = 1200 and 2100) were used. In the higher molar mass case (Mw = 25 000), a mixture of the amorphous phase and vaterite and calcite crystalline product was produced. The present results demonstrate that the interaction and the reaction kinetics of the PAA-Ca2+-H2O complex play an important role in the mineralization of CaCO3.
Langmuir 12/2007; 23(24):12086-95. · 4.19 Impact Factor
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ABSTRACT: A series of optically active P-chiral oligophosphines (S,R,R,S)-2, (S,R,S,S,R,S)-3, (S,R,S,R,R,S,R,S)-4, and (S,R,S,R,S,R,R,S,R,S,R,S)-5 with four, six, eight, and 12 chiral phosphorus atoms, respectively, were successfully synthesized by a step-by-step oxidative-coupling reaction from (S,S)-1. The corresponding optically inactive oligophosphines 1'-5' were also prepared. Their properties were characterized by DSC, XRD, and optical-rotation analyses. While optically active bisphosphine (S,S)-1 and tetraphosphine (S,R,R,S)-2 behaved as small molecules, octaphosphine (S,R,S,R,R,S,R,S)-4 and dodecaphosphine (S,R,S,R,S,R,R,S,R,S,R,S)-5 exhibited the features of a polymer. Furthermore, DSC and XRD analyses showed that hexaphosphine (S,R,S,S,R,S)-3 is an intermediate between a small molecule and a polymer. Comparison of optically active oligophosphines 1-5 with the corresponding optically inactive oligophosphines 1'-5' revealed that the optically active phosphines have higher crystallinity than the optically inactive counterparts. It is considered that the properties of oligophosphines depend on the enantiomeric purity as well as the oligomer chain length.
Chemistry - An Asian Journal 10/2007; 2(9):1166-73. · 4.50 Impact Factor
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ABSTRACT: A carboxylic acid-terminated polyhedral oligosilsesquioxane (POSS)-core dendrimer (POSS-CO2H) was synthesized from octa(3-ammoniumpropyl)octasilsesquioxane octachloride (POSS-NH3+) via a t-butyl ester-terminated POSS-core dendrimer that was prepared from neutralized POSS-NH3+ and t-butyl acrylate. Complexing properties of the sodium salts of POSS-CO2H (POSS-CO2Na) with Cu2+ were studied in comparison with those of the G1.5 poly(amidoamine) (PAMAM) dendrimer (G1.5-CO2Na) by spectroscopic approach and isothermal titration calorimetry. In the case of G1.5-CO2Na, Cu2+-N4 and Cu2+-N2O2 complexes are possible coordination modes, and only a Cu2+-N2O2 complex can be formed for POSS-CO2Na. In the case of POSS-CO2Na, upon increasing the concentration of Cu2+, the values of the binding constants decreased. However, the values of binding constants in the regions of the Cu2+-N2O2 coordination mode for G1.5-CO2Na increased with increasing concentration of Cu2+. This observation suggests that the uptake of Cu2+ is inhibited by increasing binding numbers of Cu2+ due to the rigid structure of the POSS-core dendrimer.
Langmuir 09/2007; 23(17):9057-63. · 4.19 Impact Factor
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ABSTRACT: Organic-metal hybrid nanowires were synthesized by cooperative self-organization of the one-dimensional stacking of tetrathiafulvalene (TTF) via charge-transfer interaction with metallic gold originating from the redox reaction between TTF and gold ions. The nanowires can be easily obtained as purple precipitates just by mixing TTF and HAuCl4 in a CH3CN solution at room temperature. The feed molar ratio of TTF to HAuCl4 was 4.4. The average diameter and length of the observed nanowires were 90 +/- 36 nm and 15 +/- 3 microm, respectively. The formation was facilitated by the arrangement of the neutral and oxidized TTF along the one direction in a mix-valence state, which was confirmed by a broad absorption that appeared in the region of 2000 nm and the composition of the nanowires of [(TTFCl(0.78))Au(0.12)].
Langmuir 04/2007; 23(6):3450-4. · 4.19 Impact Factor
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ABSTRACT: The crystallization of CaCO3 was examined by changing the addition time of poly(acrylic acid) (PAA) to an aqueous solution of calcium carbonate by selectively interacting with the crystal at different stages during the crystal-forming process. The precipitation of CaCO3 was carried out by a double jet method to prevent heterogeneous nucleation on glass walls, and the sodium salt of PAA was added by a delayed addition method. In the initial presence of PAA in an aqueous solution of calcium carbonate, PAA acted as an inhibitor for the nucleation and growth of crystallization. However, it was found that stable vaterite particles were successfully obtained by delaying the addition of PAA from 1 to 60 min. The vaterite particles were stable in the aqueous solution for more than 30 days, and the CaCO3 particles were formed by a spherulitic growth mechanism. It is suggested that PAA strongly binds with the Ca2+ ion on the surface of CaCO3 particles to stabilize the unstable vaterite form effectively. Upon changing the addition time of PAA, we found that CaCO3 particles were formed through different formation mechanisms in selectively controlled crystallization at different stages during the crystallization process.
Langmuir 09/2006; 22(18):7760-7. · 4.19 Impact Factor
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ABSTRACT: Microporous nanocomposites of Pd and Au nanoparticles were generated by utilizing electrostatic interaction between oppositely charged Au nanoparticles coated with carboxylate groups (Au-COO-) and spherical aggregates of Pd nanoparticles (Pd- NH3+) with a mean diameter of 80+/-20 nm stabilized and cross linked by octa(aminopropyl)silsesquioxane octahydrochloride (POSS-NH3+). Amide bonds were formed between the reactive ion couples that are well defined in the Pd-Au colloidal nanocomposites during a subsequent chemical reaction to generate more stable nanocomposites with improved chemical and physical properties.
Langmuir 01/2006; 21(26):12395-8. · 4.19 Impact Factor
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ABSTRACT: Cross-linked poly(vinylene-arsine)s (4) were synthesized by a free-radical terpolymerization of phenylacetylene (2), hexaphenylcyclohexaarsine (l), and p- or m-diethynylbenzene (p- or m-3) at different compositions in the presence of a catalytic amount of AIBN. The number-average molecular weights of the resulting polymers were a few thousands estimated by gel permeation chromatography (GPC) analysis. By gas chromatography (GC) analysis p-3 was found to be more reactive during the polymerization than m-3 and the resulting cross-linked polymer (p-4) showed lower solubility than that of m-4. The cross-linked poly(vinylene-arsine)s showed higher glass transition temperature in the measurement of differential scanning calorimetry (DSC) and more red-shifted emission in chloroform solution than that of the linear poly(vinylene-arsine). These properties could be tuned by varying the monomer feed ratio.
Polymer Bulletin 09/2004; 52(3):191-199. · 1.53 Impact Factor
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ABSTRACT: The synthesis and processing of nanoparticles consisting of metallic nanocrystal cores and organic monolayer shells promise interesting technological applications. Here, we report the synthesis of gold nanoparticles modified with ionic liquids based on the imidazolium cation. Aggregation-induced color changes of the gold nanoparticles in an aqueous solution were used as an optical sensor for anions via anion exchange of ionic liquid moiety. We also demonstrated the phase transfer of the gold nanoparticles from aqueous media to ionic liquid.
Journal of the American Chemical Society 04/2004; 126(10):3026-7. · 9.91 Impact Factor
