Assembly and Characterization of Polyurethane–Gold Nanoparticle Conjugates

The PU/Au‐NPs conjugates based on poly(vinyl alcohol)‐containing polyurethane microparticles coated with Au‐NPs are prepared by a heat‐treated method. The PU/Au‐NPs conjugates are characterized by FT‐IR , SEM, TEM analysis. The appearance of characteristic peaks in the FT‐IR spectra at 1574 and 1624 cm^?1, which are attributed to urethane groups, are presented for both PU and PU/Au‐NPs conjugate. The absorption band at 1716–1718 cm^?1, attributed to the hydrogen‐bonded urethane carbonyl groups of PU/Au‐NPs_(13nm)‐A is higher than that obtained for unmodified PU. The Au‐NPs_(13nm) are found to be well dispersed in the PU. The Au‐NPs_(3.5nm) tend toward agglomeration when they are entrapped within PU. It is determined, that Au‐NPs present in PU‐Au conjugates quench the luminescence of PU.     

Formation of Thermoresponsive Gold Nanoparticle/PNIPAAm Hybrids by Surface‐Initiated,Atom Transfer Radical Polymerization in Aqueous Media

Summary: We investigated the formation of thermoresponsive gold nanoparticle/poly(N‐isopropylacrylamide) (AuNP/PNIPAAm) core/shell hybrid structures by surface‐initiated, atom transfer radical polymerization (SI‐ATRP) in aqueous media and the effect of cross‐linking on the thermoresponsiveness of the AuNP/PNIPAAm hybrids. The disulfide containing an ATRP initiator was attached onto AuNPs and the monomer, NIPAAm, was polymerized from the surface of AuNPs in the absence or presence of a cross‐linker, ethylene diacrylate, in aqueous media at room temperature. The resulting brush‐type and cross‐linked AuNP/PNIPAAm hybrids were characterized by Fourier‐transform infrared spectroscopy, transmission electron microscopy, and variable temperature dynamic light scattering.

     

Multicolor Reversible Thermochromic Properties of Gallic Acid‐Cored Polydiacetylenes Appended with Poly(alkyl aryl ether) Dendrons

This study describes synthesis of zero and first generation poly(alkyl aryl ether) dendrons onto a gallic acid core, tethered with three diacetylene moieties and their photopolymerization. Resulting polydiacetylenes are studied by (i) UV–vis, IR, Raman spectroscopies, and chromoisomerism by naked eye visualization; (ii) their stabilities by differential scanning calorimetry, thermogravimetric method, and (iii) structure, morphology, and emission behavior by scanning electron, transmission electron, atomic force microscopies, powder X‐ray diffraction method, and fluorescence spectroscopy. The dendron‐appended polydiacetylenes show robust nanoribbon morphologies and exhibit multicolor, reversible chromoisomerism at temperatures up to 300 °C. Reversibility of amide bond IR frequencies, as a function of temperature, shows the polymer stabilities, in addition to the results of thermal and powder X‐ray diffraction studies. Temperature annealed polymers having red color phase exhibit emission maxima at 572 and 633 nm, that shift to higher wavelength upon heating and revert to the initial emission wavelengths on cooling.

     

Mechanism of the Formation of Amorphous Gold Nanoparticles within Spherical Polyelectrolyte Brushes

We present a comprehensive investigation on the formation of gold nanoparticles in spherical polyelectrolyte brushes. These colloidal carrier particles consist of a solid polystyrene core onto which long cationic polyelectrolyte chains are grafted. Immersed in water these polyelectrolyte chains can be used to enrich AuCl ions. The metal ions thus confined in the polyelectrolyte layer can be reduced to gold nanoparticles of approximately 1 nm diameter. Cryogenic transmission electron microscopy shows that the Au particles are located near the surface and exhibit a narrow size distribution. Measurements by dynamic light scattering demonstrate that the polyelectrolyte chains are located near the surface of the core particles. This is explained by a crosslinking of the cationic polyelectrolyte chains by the nanoparticles that carry a negative charge. If the Au nanoparticles are removed, the spherical polyelectrolyte brushes re‐expand. High‐resolution electron microscopy together with wide‐angle X‐ray scattering measurements demonstrates that the Au nanoparticles are amorphous. We demonstrate that these Au nanoparticles exhibit catalytic activity for hydrogenation reactions that is slightly below the one of Pt and Pd nanoparticles.

     

Gold Nano-Structures for Transduction of Biomolecular Interactions into Micrometer Scale Movements

Microfabricated cantilevers, similar to those commonly used in scanning probe microscopies, have recently become increasingly popular as transducers in chemical and biological sensors. Surface stress changes that accompany intermolecular interactions on the cantilever surfaces offer an attractive means to develop new generations of microfabricated sensors and actuators that respond directly to chemical stimuli. In the present study, we demonstrate that interfacial molecular recognition events can be converted into mechanical responses much more efficiently when quasi 3-dimensional interfaces with nano-size features are used. Some of the particularly useful approaches to creating such interfaces are surface immobilization of gold nano-spheres and dealloying of co-evaporated Au:Ag films. Preliminary evaluation of these nanostructured surfaces was performed by measuring mechanical stresses generated by receptor modified nano-structures and smooth gold surfaces in response to gas-phase hydrocarbon compounds. The most efficient chemi-mechanical transduction was achieved when the cantilevers were modified with 50 to 75 nm thick dealloyed gold nanostrutures. Cantilevers of this type were selected for liquid phase experiments. These cantilevers were found to undergo several micron deflections upon adsorption of protein A and biotin-labeled albumin on nanostructured gold surfaces. Additional micrometer scale movements of the cantilevers were observed upon interaction of the surface bound bioreceptors with, respectively, immunoglobulin G and avidin from the aqueous phase.     

The Influences of Cooperative Swelling and Coordination on Patterned Decoration of Gold on Block Copolymer Nanospheres

Ordered nanoring arrays are a new pattern of block copolymer thin films generated by spin‐coating of block copolymer reverse micelles on silicon substrates, which can further direct the formation of gold nanoring arrays on block copolymer thin films. Here, it is reported that the cooperation of swelling and coordination can influence the surface pattern of the block copolymer nanospheres. A hexagonally arranged dot pattern can be transformed into a ring pattern on polystyrene‐block‐poly(2‐vinylpyridine) nanospheres, and the new pattern can further direct the decoration of gold nanoparticles by balancing the swelling of the poly(2‐vinylpyridine) chains and the coordination effect between gold ions and the pyridine units.

     

Tunable Arrangement of Gold Nanoparticles in Epoxidated Poly(styrene‐block‐butadiene) Diblock Copolymer Matrices

A new approach to synthesize block‐copolymer‐mediated/gold nanoparticle (Au NP) composites is developed. Stable and narrowly distributed Au NPs modified with a 2‐phenylethanethiol ligand are prepared by a two‐phase liquid–liquid method. A new epoxidation of a poly(styrene‐block‐butadiene) diblock copolymer, to form poly(styrene‐block‐vinyl oxirane) (PS‐b‐PBO), is achieved through chemical modification. It is found that the Au NPs disperse well in the PS block segment by partially crosslinking the PBO block segment with poly(ethylene oxide bisamine) (D230), a curing agent. The aggregation of Au NPs leads to a red‐shift of the plasmon absorption with the increase in the D230 content. However, without crosslinking the PBO block segment with D230, Au NPs distributes in both the PS and PBO segments.     

Well‐Defined Glycopolymers via RAFT Polymerization: Stabilization of Gold Nanoparticles

Well‐defined glycopolymers of poly(2‐{[(d ‐glucosamin‐2‐N‐yl)carbonyl]oxy}ethyl meth(acry­late)) (PHEMAGl and PHEAGl, respectively) are first synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization in green solvents such as water and dimethyl sulfoxide (DMSO). The biomolecular recognition of the synthesized glycopolymers bearing glucose residues toward Concanavalin A lectin is confirmed by turbidimetric assays. Subsequently, HEMAGl glycopolymer is mixed with gold nanoparticles in the presence of sodium borohydride, which reduces the terminal groups to thiol and yields the preparation of synthetic carbohydrate polymer‐stabilized gold nanoparticles showing enhanced colloidal stability. The resulting glyco‐nanoparticles are characterized by dynamic light scattering (DLS) and field‐emission electron microscopy (FE‐SEM), whereas the molecular recognition abilities are investigated using UV–vis spectroscopy by analyzing the shift in the plasmon band as a consequence of the aggregation variation with the addition of Concanavalin A.

     

Clathrin‐Mediated Endocytosis of Gold Nanoparticles In Vitro

Gold nanoparticles (AuNPs) have potential biomedical and scientific applications. In this study, we evaluated the uptake and internalization of FBS‐coated 20 nm AuNPs into lung fibroblasts and liver cells by different microscopy techniques. AuNP aggregates were observed inside MRC5 lung fibroblasts and Chang liver cells under light microscopy, especially after enhancement with automegallography. Clusters of AuNPs were observed to be adsorbed on the cell surface by scanning electron microscopy. Ultrathin sections showed that AuNPs were mainly enclosed within cytoplasmic vesicles when viewed under transmission electron microscopy. We also investigated the mechanism of uptake for AuNPs, using endocytosis inhibitors and quantification of Au with inductively coupled plasma mass spectrometry. Cells treated with concanavalin A and chlorpromazine showed significant decrease of Au uptake in MRC5 lung fibroblasts and Chang liver cells, respectively, implying that the uptake of AuNPs was facilitated by clathrin‐mediated endocytosis. It would therefore appear that uptake of 20 nm AuNPs in both cell types with different tissues of origin, was dependent upon clathrin‐mediated endocytosis. Anat Rec, 298:418–427, 2015. © 2014 Wiley Periodicals, Inc.     

A New Polymeric pH Sensor Based on Photophysical Property of Gold Nanoparticle and pH Sensitivity of Poly(sulfadimethoxine methacrylate)

A new pH sensor, which consists of a fluorophore and gold nanoparticle (AuNP) attached to each chain end of a pH‐sensitive polysulfonamide, respectively, is synthesized, and its pH sensitivity is investigated in terms of the fluorescent quenching efficiency of AuNP. Since the pH‐sensitive polymeric linker exhibits a pH‐induced coil–globule transition that is rapid enough to show a typical two‐state transition, it shows drastic on‐and‐off quenching efficiency with variation of pH due to the change in the distance between fluorophore and AuNP. This AuNP‐based pH sensor exhibits a well‐defined on‐and‐off behavior at a small change in pH, and therefore can be used for an ideal alarm‐type sensor.

     

Preparation of Gold Nanoparticle– Poly(L‐menthyl methacrylate) Conjugates via ATRP Polymerization

Poly(L ‐menthyl methacrylate) (PMenMA) is synthesized by atom transfer radical polymerization (ATRP) of methyl L ‐mentholacrylate using bis[2‐(2‐bromoisobutyrooxy)ethyl]disulfide] ((BiBOE)₂)S₂) as the ATRP coinitiator. Reduction of hydrogen tetrachloroaureate(III) (HAuCl₄ ·3 H₂O) by Super‐Hydride in the presence of PMenMA yields gold nanoparticles (AuNP)–PMenMA conjugates in the size range of 2–20 nm, depending on the ratio of PMenMA and HAuCl₄. AuNP–PMenMA is characterized by TEM, NMR, IR‐, and UV‐spectroscopy. The correlation of the ratio of (AuNP)–PMenMA conjugates and free PMenMA is analyzed by gel permeation chromatography (GPC).     

Electrospun Bacteria‐Gold Nanoparticle/Polymer Composite Mesofiber Nonwovens for Catalytic Application

Polymer composite nonwovens with living Micrococcus luteus (ML), a very common gram‐positive bacterium present on human skin, are prepared by electrospinning followed by coating via the chemical vapor deposition (CVD) of poly(p‐xylylene) (PPX). The encapsulated living ML convert Au(III) ions to gold nanoparticles (AuNPs) when the composite nonwovens are dipped in an aqueous chloroauric acid solution. As a result of this process, AuNPs are formed on the ML. The ML‐immobilized AuNPs can be used for catalytic reactions with acetone as the solvent at a very low gold concentration. Despite the presence of acetone, ML survive the catalytic reaction. Interestingly, the catalytic reactions are possible only when the ML in the nonwovens are alive. In contrast, nonwovens with dead ML do not show any significant catalytic activity.     

Ultrafine Gold Nanoparticles Anchored on Pyridine-Inner-Functionalized Hollow Porous Organic Nanospheres for Highly Efficient Heterogeneous Catalysis

The development of metal nanoparticles (MNPs) loaded on porous materials with high efficiency and stability is significant importance for heterogeneous catalysis. Herein, ultrafine Au NPs are prepared and anchored on hollow porous organic nanospheres (Au@HPONs) with polylactide-b-poly(4-vinylpyridine)-b-polystyrene (PLA-b-P4VP-b-PS) triblock copolymers as precursors and pyridine as the coordination group. In this strategy, pyridine functional groups can coordinate with the Au NPs and uniformly disperse them in the carrier. Due to its hollow porous structure, high specific surface area, and physicochemical stability, the obtained Au@HPONs nanocomposite shows excellent catalytic performance and cycling ability for the oxidation of benzyl alcohol and the reduction of 4-nitrophenol.     

Light‐Tunable Thermosensitivity of Polymer‐Coated Gold Nanoparticles Achieved by Light‐Controlled Molecular Recognition

Thermo‐ and photosensitive gold nanoparticles (AuNPs) coated with an azobenzene‐contained P(DMA‐PAPA‐MAEL) copolymer are prepared by ligand exchange reactions. The photoisomerization of azobenzene moiety on the surface of P(DMA‐PAPA‐MAEL)‐coated AuNPs is detected by means of UV‐Vis spectroscopy with the presence or absence of free α‐cyclodextrin. When subjected to visible and UV light irradiation alternately, P(DMA‐PAPA‐MAEL)‐coated AuNPs in the presence of free α‐CD display a light‐tunable lower critical solution temperature through light‐controlled molecular recognition between the azobenzene moiety on the surface of AuNPs and free α‐CD.

     

Thermoresponsive Gold Nanoparticles with Positive UCST‐Type Thermoresponsivity

Trithiocarbonate end‐functionalized poly(N‐acryloylglycinamide) (PNAGA), synthesized via reversible addition–fragmentation transfer (RAFT) polymerization of different molecular weights, is grafted onto gold nanoparticles (AuNPs) by ligand exchange in phosphate‐buffered saline. The PNAGA‐grafted AuNPs display upper critical solution temperature (UCST)‐type transitions: stable colloidal distribution and aggregation above and below the cloud points, respectively. Cloud points of PNAGA are not affected by the grafting procedure, and PNAGA@AuNPs show similar cloud points as that of the trithiocarbonate end‐functionalized free‐PNAGAs used for grafting. The UCST‐type phase transition is reversible for many cycles. The reversible control of the phase transition is proved by turbidity measurements and UV–vis spectroscopy, as well as by transmission electron microscopy (TEM).

     

Nanoparticle therapeutics for prostate cancer treatment

The application of nanotechnology in medicine is offering many exciting possibilities in healthcare. Engineered nanoparticles have the potential to revolutionize the diagnosis and the therapy of several diseases, particularly by targeted delivery of anticancer drugs and imaging contrast agents. Prostate cancer, the second most common cancer in men, represents one of the major epidemiological problems, especially for patients in the advanced age. There is a substantial interest in developing therapeutic options for treatment of prostate cancer based on use of nanodevices, to overcome the lack of specificity of conventional chemotherapeutic agents as well as for the early detection of precancerous and malignant lesions. Herein, we highlight on the recent development of nanotechnology strategies adopted for the management of prostate cancer. In particular, the combination of targeted and controlled-release polymer nanotechnologies has recently resulted in the clinical development of BIND-014, a promising targeted Docetaxel-loaded nanoprototype, which can be validated for use in the prostate cancer therapy. However, several limitations facing nanoparticle delivery to solid tumours, such as heterogeneity of intratumoural barriers and vasculature, cytotoxicity and/or hypersensitivity reactions to currently available cancer nanomedicines, and the difficult in developing targeted nanoparticles with optimal biophysicochemical properties, should be still addressed for a successful tumour eradication.     

“One‐Pot” In Situ Formation of Gold Nanoparticles within Poly(acrylamide) Hydrogels

This paper focuses on two different strategies to incorporate gold nanoparticles (AuNPs) into the matrix of polyacrylamide (PAAm) hydrogels. Poly(ethyleneimine) (PEI) is used as both reducing and stabilizing agent for the formation of AuNPs. In addition, the influence of an ionic liquid (IL) (i.e., 1‐ethyl‐3‐methylimidazolium ethylsulfate) on the stability of the nanoparticles and their immobilization in the hydrogel is investigated The results show that AuNPs surrounded by a shell containing PEI and IL, synthesized according to the “one‐pot” approach, are much better immobilized within the PAAm hydrogel. Hereby, the IL is responsible for structural changes in the hydrogel as well as the improved stabilization and embedding of the AuNPs into the polymer gel matrix.

     

Highly Monodisperse Sub‐microspherical Poly(glycidyl methacrylate) Nanocomposites with Highly Stabilized Gold Nanoparticles

Sub‐micrometer spheres of poly(glycidyl methacrylate) (PGMA) with a layer of poly(allylamine hydrochloride) (PAH) film are prepared by an easily controlled assembly method. The gold nanoparticles (Au NPs) exhibit a discontinuous structure on the PGMA@PAH particle surface, exhibiting a surface interaction between the PGMA spheres and the Au NPs. PAH not only modifies the surface of the PGMA particles but also affirmatively affects the crystallite of the PGMA particles. The real permittivity of the nanocomposite spheres is much higher than that of pure PGMA spheres. An improved thermal stability is observed in the nanocomposite spheres. The calculated bandgap (0.91 eV) of the nanocomposite spheres is observed to be lower than that (4.92 eV) of pure PGMA spheres.

     

白蛋白纳米颗粒的制备研究进展

由于可以增强药物的靶向性、降低游离药物的毒副作用,基于纳米颗粒的药物递送系统在医学领域具有广泛应用。白蛋白是血浆中含量最多的蛋白质, 具有生物相容性好、无免疫原性、可生物降解等特性, 是制备纳米颗粒的理想材料。现有白蛋白纳米颗粒的制备方法主要有去溶剂化法、自组装法、乳化法、双乳化法、热凝胶、喷雾干燥、nab^TM技术、pH凝聚法等。由于制备原理及制备条件的差异,各方法表现出的优缺点也不尽相同。综述近年来白蛋白纳米颗粒的制备研究进展, 按照制备方法分类进行介绍, 并对当前白蛋白纳米颗粒研究领域所面临的困境及未来的发展方向进行探讨。