Formation of gold nanoparticles in microreactor composed of helical peptide assembly in water

A novel microreactor was prepared by self-assembly of an amphiphilic block copolymer composed of a hydrophobic helical peptide unit with a naphthyl group at the C terminal and a hydrophilic poly(ethylene glycol) unit. The copolymer formed a self-assembly in water, taking a vesicular structure. Noticeably, when the copolymer was dispersed in an Au(3+) aqueous solution, gold nanoparticles were formed without addition of any reducing reagent. The naphthyl groups, which are located at the inner surface of the vesicular assembly, promoted the reduction of Au(3+) ions with accompanying pH decrease.     

Amphiphilic polymers as pseudotemplates in the synthesis of metal sols

The effects of poly(ethylene glycol) and its amphiphilic polymers on the products of copper ion reduction in aqueous solutions are studied. Whereas coarse metal dispersions are formed in poly(ethylene glycol) solutions, stable sols of metal nanoparticles with diameters of 2 nm and above are produced in the presence of poly(ethylene glycol monolaurate) and poly(ethylene glycol monostearate). A poly(ethylene glycol)-poly(propylene glycol) block copolymer (Pluronic) also stabilizes copper nanoparticles; however, the interaction product of this copolymer with nanoparticles forms a precipitate. According to the electron microscopy data, sol particles comprise polymer micelles containing included copper nanoparticles.     

Bioactive Polymeric Metallosomes Self-Assembled through Block Copolymer-Metal Complexation

Spontaneous formation of polymeric metallosomes with uniform size (～100 nm) was found to occur in aqueous medium through the reaction of an anticancer agent, (1,2-diaminocyclohexane)platinum(II) (DACHPt), with a Y-shaped block copolymer of ω-cholesteroyl-poly(l-glutamic acid) and two-armed poly(ethylene glycol) (PEGasus-PLGA-Chole). Circular dichroism spectrum measurements revealed that the PLGA segment forms an α-helix structure within the metallosomes, suggesting that secondary-structure formation of metallocomplexed PLGA segment may drive the self-assembly of the system into vesicular structure. These metallosomes can encapsulate water-soluble fluorescent macromolecules into their inner aqueous phase and eventually deliver them selectively into tumor tissues in mice, owing to the prolonged blood circulation. Accordingly, fluorescent imaging of the tumor was successfully demonstrated along with an appreciable antitumor activity by DACHPt moieties retained in the vesicular wall of the metallosomes, indicating the potential of metallosomes as multifunctional drug carriers.     

苯胺四聚体-PEG两亲性嵌段共聚物的合成、表征及自组装行为

以二环己基碳二亚胺（DCC）为缩合剂与聚乙二醇单甲基醚（mPEG）反应的产物再与苯胺四聚体（AT）反应得到了两嵌段共聚物. 采用1H-NMR和FTIR分析方法确认了共聚物的结构,UV-Vis及CV的测试结果表明该共聚物具有良好的电活性特征. 用扫描电镜与光散射的方法对粒径大小进行了测量,共聚物在水溶液中可形成直径125 nm左右的均匀球形组装体,并通过透射电镜确定了组装体的实心结构. 当嵌段共聚物处于中间氧化态时,组装体的尺寸会随着溶液pH值的不同而变化. 对组装体的形成及pH敏感性的可能机理进行了讨论.     

Synthesis and characterization of poly(vinyl pyrrolidone)-capped bismuth nanospheres

Poly(vinyl pyrrolidone)-capped bismuth nanospheres were synthesized by a simple and convenient wet chemical method. In the process, bismuth nitrate was reduced by ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) at 185 °C in air. PVP was used as a protecting agent to prevent oxidation of the sperical bismuth particles. PVP molecules were absorbed on the surface of bismuth nanospheres through the interaction of O–Bi bond which was confirmed by Fourier transform infrared (FT-IR) measurement. The thermal analysis shows the samples contained about 73 wt.% metallic bismuth. The optical absorption spectrum of poly(vinyl pyrrolidone)-capped bismuth nanosphere shows a strong absorption band at 275 nm.     

Core-shell-corona au-micelle composites with a tunable smart hybrid shell

Micelles having a core of polystyrene and a mixed shell of poly(ethylene glycol) and poly(4-vinylpyridine) were formed through self-assembly of a triblock copolymer poly(ethylene glycol)- block-polystyrene- block-poly(4-vinylpyridine) in acidic water (pH 2). Reducing the HAuCl(4)-treated micelle solution leads to the formation of the Au-micelle composites with a core of polystyrene, a hybrid shell of poly(4-vinylpyridine)/Au/poly(ethylene glycol), and a corona of poly(ethylene glycol). The gold nanoparticles with controlled sizes were anchored to poly(4-vinylpyridine) to form the physically cross-linked hybrid shell. In aqueous solution, the hybrid shell is swollen and the swollen degree is sensitive to the pH condition. Under basic conditions, the channel in the hybrid shells of the composite is produced, which renders the composites a good catalytic activity. In addition, the composites also show good stability, unchanged hydrodynamic diameter, and surface plasmon absorption under different pH conditions.     

Enhanced stability and bioconjugation of photo-cross-linked polystyrene-shell, Au-core nanoparticles

Encapsulating Au nanoparticles within a shell of photo-cross-linked block copolymer surfactant dramatically improves the physical and chemical stability of the nanoparticles, particularly when they are applied as bioconjugates. Photo-cross-linkable block copolymer amphiphiles [polystyrene-co-poly(4-vinyl benzophenone)]-block-poly(acrylic acid) [(PS-co-PVBP)-b-PAA] and [poly(styrene)-co-poly(4-vinyl benzophenone)]-block-poly(ethylene oxide) [(PS-co-PVBP)-b-PEO] were assembled around Au nanoparticles ranging from 12 to 108 nm in diameter. UV irradiation cross-linked the PVBP groups on the polymer to yield particles that withstood extremes of temperature, ionic strength, and chemical etching. Streptavidin was attached to [PS-co-PVBP]-b-PAA-coated particles using the same noncovalent and covalent conjugation protocols used to bind biomolecules to divinylbenzene-cross-linked PS microspheres. We expect that these particles will be useful as plasmonic, highly light-scattering and light-absorbing analogs to fluorescently labeled PS nanospheres.     

Facile synthesis of core‐shell organic–inorganic hybrid nanoparticles with amphiphilic polymer shell by one‐step sol–gel reactions

Organic–inorganic hybrid core‐shell nanoparticles with diameters ranging from 100 to 1000 nm were prepared by a one‐pot synthesis based on base catalyzed sol–gel reactions using tetraethoxysilane and a triethoxysilane‐terminated polyethylene‐b‐poly(ethylene glycol) as reactants. Data from TEM, TGA, and solid‐state NMR analysis are in agreement with the formation of core‐shell nanoparticles with an inorganic‐rich core and an external shell consisting of an amphiphilic block copolymer monolayer. The influence of the organic–inorganic ratio, solution concentration, and postcuring temperature on core and shell dimensions of the nanospheres were investigated by TEM microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1699–1709, 2008     

Synthesis of a triblock copolymer: Poly(ethylene glycol)‐poly(alkylene phosphate)‐poly(ethylene glycol) as a modifier of CaCO3 crystallization

Triblock copolymer poly(ethylene glycol)‐poly(alkylene phosphate)‐poly(ethylene glycol) was prepared by first reacting hexamethylene glycol with dimethyl‐H‐phosphonate at conditions of transesterification and then replacing the CH₃OP(O)(H)O‐… end‐groups by monomethyl ether of poly(ethylene glycol). The course of reaction was studied by ³¹P NMR indicating complete conversion. After oxidation the poly(alkylene H‐phosphonate was converted into the final triblock polyphosphate. This triblock copolymer was used as a modifier of CaCO₃ crystallization. Unusual semi open empty spheres resulted, composed of small crystallites of the size (diameter) equal to 40–90 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 650–657, 2005     

Optically active micelles from self-assembly of MPEG-b-PMALM copolymer in water

Reported here is fabrication of optically active micelles with broad range of morphologies in water,such as spheres,cylinders, and vesicles,from self-assembly of poly(ethylene glycol)monomethyl ether-b-poly-(methacryloyl-L-leucine methyl ester) (MPEG-b-PMALM)copolymer,which was prepared via atom transfer radical polymerization(ATRP)from vinyl monomer bearing chiral amino acid moieties,N-methacryloyl L-leucine methyl ester(MALM),using bromine(Br)end-capped poly(ethylene golycol)monomethylether(MPEG-Br)as ...     

The Synthesis of Special Block Copolymers Using a Reaction Calorimeter

Summary : The paper provides experimental results about an easy and versatile method to produce amphiphilic block copolymers, block copolymer particles, and even inorganic – polymeric nano-composites via aqueous heterophase polymerization. Special emphasis is placed on the morphology and colloidal properties of some non-ionic di- and triblock copolymer particles with poly(ethylene glycol) of 10⁶ g/mol molecular weight as hydrophilic block as well as di-stimuli-responsive block copolymers containing both a poly(N-isopropyl acrylamide) and a poly(ionic liquid) block.     

Formation of block copolymer-protected nanoparticles via reactive impingement mixing

Reactive impingement mixing was employed to produce polymer-protected nanoparticles. Amphiphilic block copolymer was formed in situ by reactive coupling of hydrophobic and hydrophilic blocks. Simultaneously, a hydrophobic compound and the copolymer coprecipitated to form nanoparticles in the range of 100 nm. Specifically, beta-carotene was stabilized by the amphiphilic diblock copolymer, formed from the reaction of an amino-terminated hydrophilic block, poly(ethylene glycol) (PEG-NH2), with an acid chloride-terminated hydrophobic block, either poly(epsilon-caprolactone) (PCL-COCl) or polystyrene (PS-COCl). Spherical particles were observed by scanning and cryogenic transmission electron microscopy. Process conditions, including feed concentration of beta-carotene and feed concentrations of polymeric stabilizers, had little or no effect on average particle sizes over the range studied. Further, for Reynolds numbers greater than 500 the feed flow rates also had no effect. The effect of glass transition temperature (Tg) of the hydrophobic polymer on morphology and particle formation mechanism is discussed.     

One-step advanced preparation of surface-functional peptide nanospheres by the polymerization of L-phenylalanine N-carboxyanhydride with dual initiators

Surface-grafted peptide nanospheres consisting of hydrophobic poly(L-phenylalanine) with hydrophilic poly(ethylene glycol) (PEG) grafts were successfully prepared by the one-step polymerization of L-phenylalanine N-carboxyanhydride with the dual initiators of hydrophobic n-butylamine and hydrophilic NH2-monoterminated PEG (NH2-PEG). The monodispersed peptide nanospheres were stably self-assembled during polymerization in a mixture of water/dimethyl sulfoxide to create a colloidal solution, but only aggregated in water or organic solvents. When n-butylamine or NH2-PEG was used as a solitary initiator, the peptide nanospheres were not formed. The peptide nanospheres showed high dispersion-stability in water, and their diameter was approximately 300 nm. Furthermore, the peptide nanospheres were well-redispersed in water, retaining the same diameter and monodispersity even after lyophilization. Peptide nanospheres with the functional carboxylic acid on their graft layer were also successfully prepared by the one-step preparation method. This one-step preparation method of surface-grafted peptide nanospheres will be useful as an advanced technology to develop biodegradable functional nanospheres.     

Polystyrene nanoparticles based on poly(butyl methacrylate-g-methoxypoly(ethylene glycol)) and poly(methyl methacrylate-g-methoxypoly(ethylene glycol)) graft copolymers

The solubilization of styrene by poly(butyl methacrylate-g-methoxypoly(ethylene glycol)) and poly(methyl methacrylate-g-methoxypoly(ethylene glycol)) graft copolymers has been examined. From turbidity measurements the solubility limit of the monomer in the micelles was obtained and the distribution coefficients were evaluated. Dynamic light scattering revealed that below the solubility limit, solubilization leads to a slight increase in micelle size, while above the solubility limit, there is a dramatic increase in particle size and turbidity as oil-in-water emulsions are formed through coalescence of monomer-swollen micelles. Polymerizations carried out below the solubility limit using the graft copolymer micelles as templates resembled microemulsion polymerizations in nature and led to very fine sterically stabilized polystyrene latex particles. Through careful control of the monomer concentration and the polymerization temperature it was possible to obtain spherical nanosize latex particles with similar size to those of the micelle precursors (10 nm) up to 11% monomer by weight. Polymerizations above the solubility limit, on the other hand, showed similarities with emulsion polymerizations and resulted in larger particles with higher polydispersity.     

Novel antifouling oligo(ethylene glycol) methacrylate particles via surfactant-free emulsion polymerization

The use of particle formulations with antifouling surface properties attracts increasing interest in several biotechnological applications. Majority of these studies utilize a poly(ethylene glycol) coating to render the corresponding surface nonrecognizable to biological macromolecules. Herein, we report a simple way to prepare novel antifouling colloids composed of oligo(ethylene glycol) backbones via surfactant-free emulsion polymerization. Monodisperse cross-linked poly(ethylene glycol) ethyl ether methacrylate particles were characterized by dynamic light scattering and transmission electron microscopy. The effects of monomer, cross-linker and initiator on particle characteristics were investigated. More importantly, a prominent blockage of bovine serum albumin adsorption was obtained for the poly(ethylene glycol)-based sub-micron (~200 nm) particles when compared with similar-sized poly(methyl methacrylate) counterparts.     

化学酶法合成五嵌段聚合物及其自组装行为的研究

用酶促开环聚合与ATRP方法相结合,制备了聚甲基丙烯酸六氟丁酯-聚己内酯-聚乙二醇-聚己内酯-聚甲基丙烯酸六氟丁酯(PHFMA-b-PCL-b-PEG-b-PCL-b-PHFMA)五嵌段聚合物.首先用Novozym e 435作为催化剂合成了聚己内酯-聚乙二醇-聚己内酯三嵌段聚合物,然后通过端基官能化法合成了大分子引发剂,并用其引发甲基丙烯酸六氟丁酯(HFMA)的ATRP反应,合成了五嵌段聚合物.通过核磁和GPC证明了大分子引发剂和五嵌段共聚物的结构,五嵌段共聚物的GPC分析表明这种合成方法的可行.共聚物胶束的直径和大小通过动态光散射方法和原子力显微镜测试,五嵌段共聚物在水中的的自组装行为也被研究.结果证明胶束是球形,其平均直径为77 nm.聚合物在四氢呋喃中的浓度对聚合物的聚集形貌有很大的影响.     

Fabrication of virus-like particles with strip-pattern surface: A two-step self-assembly approach

Spherical nanostructures with striped patterns on the surfaces resembling the essential structures of natural virus particles were constructed through a two-step self-assembly approach of polystyrene-boligo(acrylic acid)(PS-b-oligo-AA) and poly(γ-benzyI L-glutamate)-b-poly(ethylene glycol)(PBLG-bPEG) copolymer mixtures in solution.On the basis of difference in hydrophilicity and self-assembly properties of the two copolymers,the two-step self-assembly process is realized.It was found that PS-boligo-AA copolymers formed spherical aggregates by adding a certain amount of water into polymer solutions in the first step.In the second step,two polymer solutions were mixed and water was further added,inducing the self-assembly of PBLG-b-PEG on the surfaces of PS-b-oligo-AA spheres to form striped patterns.In-depth study was conducted for the indispensable defects of striped patterns which are dislocations and +1/2 disclinations.The influencing factors such as the mixing ratio of two copolymers and the added water content in the first step on the morphology and defects of the striped patterns were investigated.This work not only presents an idea to interpret mechanism of the cooperative self-assembly behavior,but also provides an effective approach to construct virus-like particles and other complex structures with controllable morphology.     

Brush-type amphiphilic diblock copolymers from "living"/controlled radical polymerizations and their aggregation behavior

Two brush-type amphiphilic diblock copolymers, poly(poly(ethylene glycol)methyl ether methacrylate-block-polystyrene) (P(PEGMA)-b-PS) and poly(glycidyl methacrylate)-block-poly(poly(ethylene glycol)methyl ether methacrylate) (P(GMA)-b-P(PEGMA)) were synthesized, respectively, via consecutive atom-transfer radical polymerizations (ATRPs) and reversible addition-fragmentation chain-transfer (RAFT) polymerizations. The diblock copolymers were characterized by gel permeation chromatography (GPC), (1)H nuclear magnetic resonance (NMR) spectroscopy, and FT-IR spectroscopy. The aggregation behavior of the two amphiphilic diblock copolymers in water was also studied. Scanning electron and transmission electron microscopic images revealed that spherical micelles (40-80 nm in diameter) from self-assembly of the P(PEGMA)-b-PS copolymers and wormlike micelles (60-120 nm in length and 20-30 nm in diameter) from self-assembly of the P(GMA)-b-P(PEGMA) copolymers were prevalent. The spherical P(PEGMA)-b-PS micelles could self-assemble gradually into giant aggregates of several micrometers in diameter.     

醇/水介质对PEG大分子单体与BMA分散共聚反应的影响

通过端基反应法合成了苯乙烯单封端的聚乙二醇(St- PEG)大分子单体,使其与甲基丙烯酸丁酯(BMA)在乙醇 水混合介质中进行分散共聚,得到了聚乙二醇接枝的聚甲基丙烯酸丁酯(PBMA- g -PEG)高分子微球.PBMA- g -PEG共聚物的亲溶剂 疏溶剂平衡将影响微球的形成,反应结束时,体系随BMA浓度和介质中水含量的变化呈现出4种不同的状态,透明清液、乳液、伴有沉淀或凝胶的乳液和凝胶.用透射电子显微镜(TEM)和激光光散射(LLS)对乳液体系的粒径及其形态进行了表征,表明所得接枝高分子微球形态规整具有较好的单分散性.通过控制介质中水的含量和BMA的浓度可得粒径在4 0～5 0 0nm范围的PBMA -g -PEG微球.     

Synthesis of double hydrophilic graft copolymer containing poly(ethylene glycol) and poly(methacrylic acid) side chains via successive ATRP

A well‐defined double hydrophilic graft copolymer, with polyacrylate as backbone, hydrophilic poly(ethylene glycol) and poly(methacrylic acid) as side chains, was synthesized via successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl methacrylate) side chains. The grafting‐through strategy was first used to prepare poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer. The obtained comb copolymer was transformed into macroinitiator by reacting with lithium diisopropylamine and 2‐bromopropionyl chloride. Afterwards, grafting‐from route was employed for the synthesis of poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methoxymethyl methacrylate) amphiphilic graft copolymer. The molecular weight distribution of this amphiphilic graft copolymer was narrow. Poly(methoxymethyl methacrylate) side chains were connected to polyacrylate backbone through stable C? C bonds instead of ester connections. The final product, poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methacrylate acid), was obtained by selective hydrolysis of poly(methoxymethyl methacrylate) side chains under mild conditions without affecting the polyacrylate backbone. This double hydrophilic graft copolymer was found be stimuli‐responsive to pH and ionic strength. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4056–4069, 2008