Amplified electrochemiluminescent immunosensing using apoferritin-templated poly(ethylenimine) nanoparticles as co-reactant

A novel sandwich-type electrochemiluminescent immunoassay utilizing apoferritin-templated poly(ethylenimine) (PEI) nanoparticles as labels based on the in situ release of the co-reactant of PEI was developed for sensitive detection of HCG with a low detection limit of 0.17 μIU mL(-1).     

Folate receptor-mediated gene delivery using folate-poly(ethylene glycol)-poly(L-lysine) conjugate

For efficient receptor-mediated gene transfection, a new and simple formulation method based on using PEI and FOLPEGPLL conjugate was presented. Luciferase plasmid DNA and PEI were complexed to form slightly positive-charged nanoparticles, onto which FOL-PEG-PLL conjugate was surface coated. With increasing the coating amount of FOL-PEG-PLL conjugate, the FOL-PEG-PLL/PEI/DNA complexes exhibited increased surface zeta-potential values with concomitantly increased diameters, indicating that the PLL part was physically anchored on the surface of preformed PEI/DNA complexes with FOL moieties being exposed on the outside. The formulated complexes exhibited a considerably higher transfection efficiency against FOL receptor over-expressing KB cells than FOL receptor deficient A549 cells. This was caused by an enhanced cellular uptake of the resultant complexes via a receptor-mediated endocytosis process. The formulated complexes showed a higher gene expression level, even in the presence of serum, than the PEI/DNA or Lipofectamine/DNA complexes. This was attributed to the PEG chains present on the surface of complexes that could work as a protective shield layer against aggregation caused by non-specific protein adsorption. The FOL-PEG-PLL/PEI/DNA complexes also demonstrated better cell viability than the PEI/DNA complexes.(1)H NMR spectrum of FOL-PEG-PLL conjugate.     

Phosphoester binding,DNA binding,DNA cleavage and in vitro cytotoxicity studies of simple heteroleptic copper(II) complexes with bidentate ligands

Abstract

Two mononuclear heteroleptic copper complexes, [Cu(±trans-dach)(bpy)](ClO₄)₂ 1a and [Cu(±trans-dach)(phen)](ClO₄)₂ 2a [dach?=?1,2-diaminocyclohexane, bpy?=?2,2′-bipyridine and phen?=?1,10-phenanthroline], were synthesized and analyzed by CHN analysis, electronic absorption, FT-IR spectroscopy, EPR, and SXRD. The molecular structures of 1a and 2a showed octahedral geometry around Cu(II). Both complexes interacted with phosphoesters and DNA. Their binding affinities with diphenylphosphate, di n-butylphosphate, trimethylphosphate, and triphenylphosphate were studied by UV–vis spectroscopy. For understanding the stereochemical role of dach ligand toward DNA interaction, enantiopure DACH complexes [Cu(R,R-trans-dach(bpy)](ClO₄)₂ 1b, [Cu(S,S-trans-dach)(bpy)](ClO₄)₂ 1c, [Cu(cis-dach)(bpy)](ClO₄)₂ 1d, [Cu(R,R-trans-dach)(phen)](ClO₄)₂ 2b, [Cu(S,S-trans-dach)(phen)](ClO₄)₂ 2c, and [Cu(cis-dach)(phen)](ClO₄)₂ 2d were synthesized and analyzed. All complexes interacted with calf thymus-DNA (CT-DNA) as studied by UV–vis spectroscopy. The nature of binding to CT-DNA was groove/electrostatic as supported by circular dichroism, cyclic voltammetry, and docking studies. Complexes were able to cleave plasmid DNA at 12.5 µM (1a–d) and 6 µM (2a–d), where 2d showed 64% Form II and 36% Form III. The in vitro cytotoxic studies of two different cancer cell lines showed inhibition with low IC₅₀ value in comparison to reference control (cisplatin). These complexes are efficient in inducing apoptosis in cancer cells, making them viable for potent anticancer activity.     

Synthesis of linear poly(ethylenimine) containing nucleic acid pendants as polynucleotide analogs

Polynucleotide analogs with a linear poly(ethylenimine) (PEI) backbone and adenine, cytosine, and hypoxanthine pendants were synthesized. Linear PEI was synthesized by the cationic ring-opening polymerization of 2-H-2-oxazoline, followed by acid hydrolysis. 2-(Adenin-9-yl)- and 2-(N⁶-benzyladenin-9-yl)-, 2-(cytosin-1-yl)propanoic acids in addition to 2-(adenin-9-yl)-3-methyland 3-(cytosin-1-yl)butanoic acids were synthesized from their respective nucleic acid bases. 2-(Hypoxanthin-9-yl)propanoic acid and 3-(hypoxanthin-9-yl)butanoic acid were converted from the corresponding adenine derivatives by reaction with nitrous acid. Grafting reactions of pendant groups onto various molecular weight PEI backbones were carried out at room temperature, using the coupling agent norborn-5-ene-2,3-carboximido diphenyl phosphate (PPONB), generally resulting in percent graft values greater than 90%. PPONB showed selectivity against the amino group of adenine and cytosine rings. The appropriate model compounds were also prepared.     

Chemo-physical and biological evaluation of poly(L-lysine)-grafted chitosan copolymers used for highly efficient gene delivery

For the success of non-viral gene delivery, it is of great importance to develop gene vectors with high efficiency but low toxicity. We demonstrate that PLL-grafted chitosan copolymers combine the advantages of PLL with its good pDNA-binding ability and of chitosan with its good biocompatibility. The chemo-physical properties of the prepared Chi-g-PLL copolymers are thoroughly characterized. The in vitro transfection study shows that the copolymers have a much higher gene transfer ability than the starting materials chitosan and PLL. A positive correlation between PLL chain lengths and transfection efficiency of the copolymers is found. Our results suggest that these novel Chi-g-PLL copolymers are good candidates for gene delivery in vivo.     

Self-assembly of poly(ethylenimine)-capped Au nanoparticles at a toluene-water interface for efficient surface-enhanced raman scattering

Branched poly(ethylenimine) (PEI)-capped Au nanoparticles are prepared at room temperature using PEI as the reductant of hydrogen tetrachloroaurate (HAuCl4). The size of Au nanoparticles, ranging from 10 to 70 nm, is readily controlled by varying the relative amount of PEI used initially versus HAuCl4. The PEI-capped Au nanoparticles are further demonstrated to be assembled into a large area of 2-D aggregates at a toluene-water interface either by heating the mixture or by adding benzenethiol to the toluene phase at room temperature. Both films are quite homogeneous, but Au nanoparticles appear to be more closely packed in the film assembled via the mediation of benzenethiol. The optical property of the PEI-capped Au films is controlled by the amount of benzenethiol added to the toluene phase. The obtained large area of PEI-capped Au film exhibits strong SERS activity of benzenethiol and also exhibits a very intense SERS spectrum of 4-nitrobenzenethiol via a place-exchange reaction that takes place between benzenethiol and 4-nitrobenzenethiol. Because the proposed method is cost-effective and is suitable for the mass production of diverse Au films irrespective of the shapes of the underlying substrates, it is expected to play a significant role in the development of optical nanotechnology especially for surface plasmon-based analytical devices.     

Tailor-made poly(amidoamine)s for controlled complexation and condensation of DNA

A set of polymer carriers for DNA delivery was synthesized by combining monodisperse, sequence-defined poly(amidoamine) (PAA) segments with poly(ethylene oxide) (PEO) blocks. The precise definition of the PAA segments provides the possibility of correlating the chemical structure (monomer sequence) with the resulting biological properties. Three different PAA-PEO conjugates were synthesized by solid-phase supported synthesis, and the cationic nature of the PAA segments was systematically varied. This allows for the tailoring of interactions with double-stranded plasmid DNA (dsDNA). The potential of the PAA-PEO conjugates as non-viral vectors for gene delivery is demonstrated by investigating the dsDNA complexation and condensation properties. Depending on the applied carrier, a transition in polyplex (polymer-DNA ion complex) structures is observed. This reaches from extended ring-like structures to highly compact toroidal structures, where supercoiling of the DNA is induced. An aggregation model is proposed that is based on structural investigations of the polyplexes with atomic force microscopy (AFM) and dynamic light scattering (DLS). While the cationic PAA segment mediates primarily the contact of the carrier to the dsDNA, the PEO block stabilizes the polyplex and generates a "stealth" aggregate, as was suggested by Zeta potentials that were close to zero. The controlled aggregation leads to stable, single-plasmid complexes, and stabilizes the DNA structure itself. This is shown by ethidium bromide intercalation assays and DNase digestion assays. The presented PAA-PEO systems allow for the formation of well-defined single-plasmid polyplexes, preventing hard DNA compression and strongly polydisperse polyplexes. Moreover carrier polymers and the resulting polyplexes exhibit no cytotoxicity, as was shown by viability tests; this makes the carriers potentially suitable for in vivo delivery applications.     

Spectroscopic examination of linear poly(ethylenimine) containing nucleic acid pendants as polynucleotide analogs

The NMR spectra and UV absorptions of polynucleotide analogs with a poly(ethylenimine) (PEI) backbone containing adenine, cytosine, and hypoxanthine pendants have been examined. As has been shown in single-stranded polynucleotides, these polymers also exhibited base stacking behavior in aqueous solution as well as in 2,2,2-trifluoroethanol. Such stacking resulted in significant UV hypochromicities and observed differences in the NMR spectra compared to the corresponding model compounds. From continuous variation mixing experiments, well-defined base pairing interactions were observed between complementary graft polymers in aqueous solutions. Enhanced UV hypochromicity due to such interactions was also observed.     

Photochromic inorganic-organic multilayer films based on polyoxometalates and poly(ethylenimine)

Novel photochromic inorganic-organic multilayers composed of polyoxometalates and poly(ethylenimine) have been prepared by the layer-by-layer (LbL) self-assembly method. The growth process, composition, surface topography, and photochromic properties of the multilayer films were investigated by UV-visible and Fourier transform infrared spectroscopy, atomic force microscopy, electrospin resonance (ESR), and X-ray photoelectron spectroscopy (XPS). Irradiated with ultraviolet light, the transparent films changed from colorless to blue. Moreover, the blue films showed good reversibility of photochromism and could recover the colorless state gradually in air, where oxygen plays an important role in the bleaching process. On account of the ESR and XPS results, parts of W6+ in multilayers were reduced to W5+, which exhibited a characteristic blue; a possible photochromic mechanism can be speculated. This work provides basic guideline for the assembly of multilayers with photochromic properties.     

Water soluble poly(histamine acrylamide) with superior buffer capacity mediates efficient and nontoxic in vitro gene transfection

Water‐soluble cationic polymers, poly(histamine acrylamide)s (PHAs), with superior buffer capacity at the endosomal pH range were designed, prepared, and investigated for non‐viral gene transfection. PHAs were obtained with molecular weights ranging from 9.2 to 28.7 kDa through controlled radical polymerization of histamine acrylamide (HA). Acid–base titration results displayed that all PHA polymers had a remarkably high buffer capacity of about 70% at pH 5.1–7.2. 12.7–28.7 kDa PHAs were able to effectively condense DNA into nano‐sized (<220 nm) polyplexes with moderate positive surface charges (+13–+19 mV) at N/P ratios ≥10/1. CCK assays indicated that polyplexes of 12.7 and 17.5 kDa PHAs were non‐toxic to COS‐7 cells up to a tested N/P ratio of 20/1. Interestingly, the in vitro transfection using pCMV‐Luc and pEGFP‐C1 plasmid DNA as reporter genes showed that polyplexes of 12.7 kDa PHA formed at an N/P ratio of 20/1 mediated efficient transfection in COS‐7 cells under 10% serum conditions, with transfection efficiencies comparable to that of 25 kDa polyethylenimine control. Their versatile design of structures, controlled synthesis, low cytotoxicity, and high transfection activity render PHA‐based cationic polymers particularly interesting for the development of safe and efficient non‐viral gene delivery systems. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Syntheses of poly[N-(1-pyrenyl)acetyl ethylenimine] [pyrene-substituted linear poly(ethylenimine)] and poly[methyl 2-(1-pyrenyl)acetamidopropenoate] [pyrene-substituted poly(dehydroalanine methyl ester)]

The syntheses of two new pyrene-containing monomers—2-(1-pyrenyl)methyl-2-oxazoline ( 6 ) and methyl 2-(1-pyrenyl)acetamidopropenoate ( 12 )—and their polymerization are described. Cationic isomerization polymerization of 6 with ethylene glycol ditosylate initiator gave poly[N-(1-pyrenyl)acetyl ethylenimine] ( 7 ) and free-radical polymerization of 12 with AIBN initiator gave poly[methyl 2-(1-pyrenyl)acetamidopropenoate] ( 15 ). The monomer model compounds of the two polymers, namely, N,N-diethyl(1-pyrenyl)acetamide ( 9 ) and methyl 2-methyl-2-(1-pyrenyl)acetamidopropanoate ( 14 ), were also synthesized. The polymers were characterized by elemental analysis, IR spectroscopy, and a comparison of their ¹H-NMR spectra with those of the respective monomer model compounds.     

叶酸和聚乙二醇接枝作基因载体用壳聚糖的合成与表征

本研究将叶酸和聚乙二醇接枝到四种不同分子量的壳聚糖氨基侧链上,以改善壳聚糖的靶向性和水溶性作基因载体。用FTIE、1HNMR、UV-Vis、DSC和TEM对产物进行了表征,结果表明,叶酸和聚乙二醇被成功地接枝到壳聚糖上,所制得的载体有望作为潜在的肿瘤细胞靶向基因载体。     

Synthesis of poly(ethylene glycol methyl ether)-b-poly(ethylenimine) and its derivatives containing thymine and amino acids as pendants

Poly(ethylene glycol methyl ether)tosylate was prepared and used to initiate the polymerization of 2-methyl-2-oxazoline. The resulting poly(ethylene glycol methyl ether)-b-poly(N-acetyl ethylenimine) was hydrolyzed and neutralized to give poly(ethylene glycol methyl ether)-b-poly(ethyl-enimine) (PEO–PEI). 2-(thymin-1-yl)propionic acid, N-Cbz-alanine, N-Cbz-proline, N-Cbz-O-t-Bu-serine. and N-FMOC-proline were grafted onto the PEO–PEI copolymer; attempts were then made to remove the Cbz and FMOC protecting groups.     

Layer-by-layer self-assembly and electrocatalytic properties of poly(ethylenimine)-silicotungstate multilayer composite films

Hybrid multilayer films composed of poly(ethylenimine) and the Keggin-type polyoxometalates [ SiW₁₁O₃₉ ]^{8 -} ( SiW₁₁ ) {\left[ {{\hbox{Si}}{{\hbox{W}}_{{11}}}{{\hbox{O}}_{{39}}}} \right]^{{8} - }}\left( {{\hbox{Si}}{{\hbox{W}}_{{11}}}} \right) and [ SiW₁₁Co^II( H₂O )O₃₉ ]^{6 -} ( SiW₁₁Co ) {\left[ {{\hbox{Si}}{{\hbox{W}}_{{11}}}{\hbox{C}}{{\hbox{o}}^{\rm{II}}}\left( {{{\hbox{H}}_2}{\hbox{O}}} \right){{\hbox{O}}_{{39}}}} \right]^{{6} - }}\left( {{\hbox{Si}}{{\hbox{W}}_{{11}}}{\hbox{Co}}} \right) were prepared on glassy carbon electrodes by layer-by-layer self-assembly, and were characterized by cyclic voltammetry and scanning electron microscopy. UV-vis absorption spectroscopy of films deposited on quartz slides was used to monitor film growth, showing that the absorbance values at characteristic wavelengths of the multilayer films increase almost linearly with the number of bilayers. Cyclic voltammetry indicates that the electrochemical properties of the polyoxometalates are maintained in the multilayer films, and that the first tungsten reduction process for immobilized SiW₁₁ and SiW₁₁Co is a surface-confined process. Electron transfer to [ Fe( CN )₆ ]^{3 - /4 -} {\left[ {{\hbox{Fe}}{{\left( {\hbox{CN}} \right)}_6}} \right]^{{3} - /{4} - }} and [ Ru( NH₃ )₆ ]^{3 + /2 +} {\left[ {{\hbox{Ru}}{{\left( {{\hbox{N}}{{\hbox{H}}_3}} \right)}_6}} \right]^{{3} + /{2} + }} as electrochemical probes was also investigated by cyclic voltammetry. The (PEI/SiW₁₁Co)_n multilayer films showed excellent electrocatalytic reduction properties towards nitrite, bromate and iodate.     

Synthesis of N-methylene phosphonic chitosan （NMPCS） and its potential as gene carder

N-Methylene phosphoulc chitosan (NMPCS),an amphiphilic macromolecule with powerful chelating ability of Ca~(2 ) ions,was synthesized and characterized.The physicochemical properties of NMPCS and the interactions between NMPCS and plasmid DNA were investigated by FTIR,~(13)C NMR,X-ray,agarose gel electrophorcsis retardation assay,atomic force microscopy (AFM) and circular dichroism (CD).The results suggest that at charge ratio 2:1 or above,DNA could be completely entrapped and spherical complexes with mean size of 80-210 nm were formed.Taking HeLa as host cell,luciferase expression mediated by NMPCS improved about 100 times compared to the expression mediated by chitosan.     

Self-optimization of binding sites by Ni(II) ion on carboxypyrazine-containing poly(ethylenimine)

To test the concept of self-optimization of own binding site by a metal ion, host molecules for Ni(II) ion were built on poly(ethylenimine) (PEI) by using the ethylenediamine portions of PEI and 2-carboxypyrazinyl (CP) group. Two derivatives of PEI containing CP were prepared: one by random acylation of PEI with pyrazine-2,5-dicarboxylic acid mono-(2,5-dioxo-pyrrolidin-1-yl) ester (PC-DP), and the other by acylation of PEI with PC–DP in the presence of Ni(II) ion. Between these two CP derivatives of PEI, Ni(II) binding ability was more than 10³ times greater for the latter. Optimization by Ni(II) ion of its own binding site built on the polymer was attributed to the preassemblage of PC–DP and PEI with Ni(II) ion and the subsequent attack at PC–DP by an amino group of PEI located in an optimal position. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 533–537, 1997.     

Mesomorphous structure and properties of non-equimolar complexes of poly(ethylenimine) and perfluorooctanoic acid

A series of solid complexes, PEI-PFAO, made of poly(ethylenimine) (PEI) and perfluorooctanoic acid (PFOA) with different compositions were prepared through a "starving addition" method, where PFOA was fed into PEI solution at the molar ratio, phi(feed), of acid group to the amino group of PEI, never beyond unity. Wide-angle X-ray diffraction diagrams confirmed amorphous structure of these complexes. Small-angle X-ray scattering indicated two ordered mesomorphous structures of alpha and beta lamellar phases, with respective long periods of 2.29 and 1.15 nm in the complexes. By increasing the actual molar ratio, phi, of PFOA to the amino group of PEI, the complex structure was altered from alpha-phase dominant to beta-phase dominant. All complexes exhibited two thermal degradation processes induced by decomposition of the bound PFOA below 230 degrees C and PEI backbone at about 350 degrees C. The initiating degradation temperature, Tid, decreases with increasing phi due to the preferential degradation of the PFOA chain bound to the tertiary amino groups. The glass transition temperature, Tg, of the complex increases with phi up to the degradation of the complex of phi = 1. This increase in Tg with phi also supports an ordered alignment of the bound PFOA chains, which greatly restricts the PEI mobility. The solid surface tension, gammaS, and critical surface tension, gammac, of the complex are between 15.4 and 16.8 mN/m and between 13.5 and 15.4 mN/m, respectively. The latter is very close to or even smaller than gammac of PTFE (15 mN/m), suggesting the enrichment of CF2 and CF3 groups at the complex surfaces. The fact that the PEI-POFA complex combines high hydrophobicity with selective thermal degradation of bound fluorinated chains promises a potential of selective change and local functionalization of the surface in a well-controlled manner.     

Binding of uranyl ion by poly(ethylenimine) containing a salicylate derivative

Three molecules of 5-(bromoacetyl)salicylate ( 1 ) complexed to uranyl UO ion were crosslinked with branchy poly(ethylenimine) (PEI) in DMSO by alkylation of amino groups of PEI with 1, leading to the formation of UO₂(Sal) PEI. Upon demetalation of UO₂(Sal) PEI with HCl, apo(Sal) PEI was obtained. Based on the pH dependence of log K_f for UO₂(Sal) PEI, it was concluded that each uranyl binding site in UO₂(Sal) PEI or apo(Sal) PEI contains three salicylate moieties. In terms of the equilibrium constant for formation of the uranyl complex, apo(Sal) PEI was found to be comparable to or better than the previously reported effective uranophiles. In terms of the rates for the formation of the uranyl complex, however, apo(Sal) PEI was far superior to those other uranophiles. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2935–2942, 1997     

Isolation and identification of cyclic oligomers of the poly(ethylene terephthalate)–poly(ethylene isophthalate) copolymer

New cyclic oligomers of the copolymer of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) were isolated and identified. A condensation polymerization was carried out at a high temperature, and the solid‐state polymerization that followed yielded the high molecular weight polymer. The oligomers were extracted from the high molecular weight PET–PEI copolymer and separated with preparative high performance liquid chromatography techniques. Their chemical structures and properties were analyzed and determined by ¹H NMR, differential scanning calorimetry, and mass spectroscopy. The oligomers observed at early retention times were a cyclic dimer and cyclic trimers and consisted of [GT]₃, [GI]₂, [GI]₃, [GT]₂[GI]₁, and [GT]₁[GI]₂. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 881–889, 2003