Biomimetic approach to the formation of gold nanoparticle/silica core/shell structures and subsequent bioconjugation

The encapsulation of individual nanoparticles has gained great attention as a method for both stabilizing nanoparticles and tailoring their surface properties. In particular, the encapsulation of nanoparticles with silica shells is advantageous for bioconjugation and applications to (nano)biotechnology. Herein we report a method for constructing gold nanoparticle (AuNP)/silica core/shell hybrid structures by biomimetic silicification of silicic acids. The procedure consists of surface-initiated, atom transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from AuNPs and biomimetic polycondensation of silicic acids by using poly(DMAEMA) as a synthetic counterpart for silaffins that are found in diatoms. The resulting AuNP/silica hybrids were characterized by Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy, UV-vis spectroscopy and transmission electron microscopy. In addition, the immobilization of biological ligands onto the hybrids was investigated for potential applications to biotechnology. As a model ligand, biotin was attached onto the AuNP/silica hybrids through substitution reaction and Michael addition reaction, and the attachment was confirmed by fluorescence microscopy after complexation with fluorescein-conjugated streptavidin.     

基于微接触印刷法的PbS微图案的制备

以聚二甲基硅氧(PDMS)弹性体为印模,十八烷基三氯硅烷(OTS)为"墨水",采用微接触印刷法分别在平整的玻璃基片表面和弯曲的玻璃棒表面进行印刷操作,将印刷后的基片浸入到PbS化学浴液中沉积得到微图案化的PbS薄膜.交叉印刷和光学显微观察结果表明,所沉积的PbS微图案边界清晰规整,并且PbS会选择性沉积在基片表面没有被OTS覆盖的区域.     

Shaping Metallic Nanolattices: Design by Microcontact Printing from Wrinkled Stamps

A method for the fabrication of well‐defined metallic nanostructures is presented here in a simple and straightforward fashion. As an alternative to lithographic techniques, this routine employs microcontact printing utilizing wrinkled stamps, which are prepared from polydimethylsiloxane (PDMS), and includes the formation of hydrophobic stripe patterns on a substrate via the transfer of oligomeric PDMS. Subsequent backfilling of the interspaces between these stripes with a hydroxyl‐functional poly(2‐vinyl pyridine) then provides the basic pattern for the deposition of citrate‐stabilized gold nanoparticles promoted by electrostatic interaction. The resulting metallic nanostripes can be further customized by peeling off particles in a second microcontact printing step, which employs poly(ethylene imine) surface‐decorated wrinkled stamps, to form nanolattices. Due to the independent adjustability of the period dimensions of the wrinkled stamps and stamp orientation with respect to the substrate, particle arrays on the (sub)micro‐scale with various kinds of geometries are accessible in a straightforward fashion. This work provides an alternative, cost‐effective, and scalable surface‐patterning technique to fabricate nanolattice structures applicable to multiple types of functional nanoparticles. Being a top‐down method, this process could be readily implemented into, e.g., the fabrication of optical and sensing devices on a large scale.     

(Bio)functional surface structural design of substrate materials based on self-assembled monolayers from aminocellulose derivatives and amino(organo)polysiloxanes

Practical procedures according to the self-assembling principle are used to modify a number of substrate materials such as glass, silicon, gold, metals/oxides, polymers (e.g. polystyrene), implant materials (polydimethylsiloxane, polyhydroxyethylmethacrylate, polymethylacrylate, poly-l-lactate) for a wide range of (bio)functional applications based on self-assembled monolayers of structural-designed derivatives of a novel aminocellulose type with varying (bio)functional surface properties and special amino(organo)polysiloxanes.By microcontact printing, lateral structural patterns are stamped onto the substrate material surfaces in the form of monolayer composites of aminocellulose chains and amino(organo)polysiloxanes.     

Palladium as a substrate for self-assembled monolayers used in biotechnology

This paper describes self-assembled monolayers (SAMs) on palladium that resist the nonspecific adsorption of proteins and the adhesion of mammalian cells. These SAMs form when thin films of palladium are exposed to solutions of alkanethiol with the general structure HS(CH(2))(m)()(OCH(2)CH(2))(n)()OH (m = 2, 11; n = 3, 6, 7). Ellipsometry and surface plasmon resonance spectroscopy (using a palladium-on-gold substrate) showed that these SAMs resist adsorption of all proteins present in bovine serum. Microislands of SAMs of octadecanethiol on palladium allowed patterned adhesion and growth of mammalian cells (in a "sea" of oligo(ethyleneglycol)-terminated SAM). The oligo(ethyleneglycol)-terminated SAM resisted the invasion of cells for over four weeks under standard conditions of cell culture; similar SAMs on gold remained patterned for only two weeks.     

Edge transfer lithography using alkanethiol inks

Edge lithographic patterning techniques are based on the utilization of the edges of micrometer-sized template features for the reproduction of submicrometer structures. Edge transfer lithography (ETL) permits local surface modification in a single step by depositing self-assembled monolayers onto a metal substrate selectively along the feature edges of an elastomeric stamp. In this report two stamp designs are described that now allow for the use of alkanethiol inks in ETL and their use as etch resists to reproduce submicrometer structures in gold. Anisotropically modified stamps are shown to combine the potential for very high-resolution patterning with the versatility and simplicity of microcontact printing.     

Co-patterning chitosan and bovine serum albumin on an aldehyde-enriched glass substrate by microcontact printing

Chitosan and bovine serum albumin were co-patterned onto a glass substrate by microcontact printing technique. The process uses a microfabricated polydimethylsiloxane stamp to transfer chitosan on an aldehyde functionalized glass substrate, followed by adding a drop of albumin solution to the patterned side and holding for 30 min. After being washed with phosphate-buffered saline and cleaned by ultrasonic, the co-patterns of chitosan and albumin, each with their own micropatterns, were formed on the same surface. In this procedure, ultrasonic cleaning takes an important role to obtain clear patterns, whereas the printing/adding sequence has less influence. Moreover, patterns printed could give higher contrast than those assembled from solution. These co-patterns could find applications in cell localization and cell growth guidance.     

Metal-mesh lithography

Metal-mesh lithography (MML) is a practical hybrid of microcontact printing and capillary force lithography that can be applied over millimeter-sized areas with a high level of uniformity. MML can be achieved by blotting various inks onto substrates through thin copper grids, relying on preferential wetting and capillary interactions between template and substrate for pattern replication. The resulting mesh patterns, which are inverted relative to those produced by stenciling or serigraphy, can be reproduced with low micrometer resolution. MML can be combined with other surface chemistry and lift-off methods to create functional microarrays for diverse applications, such as periodic islands of gold nanorods and patterned corrals for fibroblast cell cultures.     

A (-)-menthyl bonded silica phase for chiral separations: synthesis and solid state NMR characterization

A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH(3))(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 μmol/m(2)) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state (13)C and (29)Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.     

Patterning Hydrophobic Surfaces by Negative Microcontact Printing and Its Applications

Here, a negative microcontact printing method is developed to form hydrophilic polydopamine (PDA) patterns with micrometer resolution on hydrophobic including perfluorinated surfaces. In the process of the negative microcontact printing, a uniform PDA thin film is first formed on the hydrophobic surface. An activated polydimethylsiloxane (PDMS) stamp is then placed in contact with the PDA‐coated hydrophobic surface. Taking advantage of the difference in the surface energy between the hydrophobic surface and the stamp, PDA is removed from the contact area after the stamp release. As a result, a PDA pattern complementary to the stamp is obtained on the hydrophobic surface. By using the negative microcontact printing, arrays of liquid droplets and single cells are reliably formed on perfluorinated surfaces. Microlens array with tunable focal length for imaging studies is further created based on the droplet array. The negative microcontact printing method is expected to be widely applicable in high‐throughput chemical and biological screening and analysis.     

The Janus‐SAM Approach for the Flexible Functionalization of Gold and Titanium Oxide Surfaces

A novel approach is developed to address the requirement of multiple stamps and inks for microcontact printing (µCP) onto different substrate surfaces. This approach relies on µCP one divalent molecule, which is able to form Janus self‐assembled monolayers (JSAMs) with a labile cleavable centre, thus providing a facile method for the chemical derivatization of different substrate surfaces. This study presents an answer to the challenges presented within a highly versatile application, µCP. N‐(3‐diethylphosphatoxy)propyl‐11‐mercaptoundecanamide is used for the first time as an ink for µCP onto both gold and titanium oxide surfaces, utilizing the same polydimethylsiloxane stamp. Following printing, the JSAMs are enzymatically treated on these two different substrates to reveal different functional groups. The newly formed surfaces are subjected to additional surface reactions and used for the chemisorption of bovine serum albumin. At each stage, these JSAMs are characterized by X‐ray photoelectron spectroscopy and dynamic water‐contact‐angle measurements. Confocal laser scanning microscopy is used for the characterization of the adsorbed proteins.     

Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica

Amino functional mesoporous silica SBA-15 materials have been prepared to develop efficient adsorbents of heavy metals in wastewater. Functionalization with amino groups has been carried out by using two independent methods, grafting and co-condensation. Three organic moieties have been selected to incorporate the active amino sites: aminopropyl (H(2)N-(CH(2))(3)-), [2-aminoethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(3)-) and [(2-aminoethylamino)-ethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(2)-NH-(CH(2))(3)-). Materials have been characterized by XRD, nitrogen sorption measurements and chemical analysis. We have found that all materials preserve the mesoscopic order and exhibit suitable textural properties and nitrogen contents to act as potential adsorbents. Metal removal from aqueous solution has been examined for Cu(II), Ni(II), Pb(II), Cd(II), and Zn(II); adsorption performances of materials prepared by the two functionalization methods have been compared. In addition, copper adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for some selected materials. Aqueous Cu(II) adsorption rates show that the overall process is fast and the time evolution can be successfully reproduced with a pseudo-second-order kinetic model. Whole copper adsorption isotherms have been obtained at 25 degrees C. Significant maximum adsorption capacities have been found with excellent behavior at low concentration.     

Microcontact printing-based fabrication of digital microfluidic devices

Digital microfluidics is a fluid manipulation technique in which discrete droplets are actuated on patterned arrays of electrodes. Although there is great enthusiasm for the application of this technique to chemical and biological assays, development has been hindered by the requirement of clean room fabrication facilities. Here, we present a new fabrication scheme, relying on microcontact printing (microCP), an inexpensive technique that does not require clean room facilities. In microCP, an elastomeric poly(dimethylsiloxane) stamp is used to deposit patterns of self-assembled monolayers onto a substrate. We report three different microCP-based fabrication techniques: (1) selective etching of gold-on-glass substrates; (2) direct printing of a suspension of palladium colloids; and (3) indirect trapping of gold colloids from suspension. In method 1, etched gold electrodes are used for droplet actuation; in methods 2 and 3, colloid patterns are used to seed electroless deposition of copper. We demonstrate, for the first time, that digital microfluidic devices can be formed by microCP and are capable of the full range of digital microfluidics operations: dispensing, merging, motion, and splitting. Devices formed by the most robust of the new techniques were comparable in performance to devices formed by conventional methods, at a fraction of the fabrication time. These new techniques for digital microfluidics device fabrication have the potential to facilitate expansion of this technology to any research group, even those without access to conventional microfabrication tools and facilities.     

Micropatterning of Ag and Au nanoparticles by microcontact printing and block copolymer micelles

Micropatterns of gold and silver nanoparticles were successfully obtained by combining microcontact printing and poly(2-vinylpyridine)-block-poly(cyclohexyl metharylate) (P2VP-b-PCHMA) diblock copolymer micelles with metal precursors. The metal ions were incorporated into poly(2-vinylpyridine) blocks and located into the core area of micelles. Then the metal-loaded micellar solutions were used as inks which were spin coated as thin layers onto polydimethylsiloxane stamps and transferred onto the substrates by stamping. Different morphologies of micellar aggregates were formed on the substrates depending on the stamp morphologies, and single layers of nanoparticles in the micropattern were obtained by the reducing process.     

Kinetics of the degradation of sulfur mustard on ambient and moist concrete

The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using (13)C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 degrees C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 degrees C ranged from 75 to 350h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 degrees C and weeks to months on concrete at 35 degrees C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane.     

Advances in single-molecule magnet surface patterning through microcontact printing

We present an implementation of strategies to deposit single-molecule magnets (SMMs) using microcontact printing microCP). We describe different approaches of microCP to print stripes of a sulfur-functionalized dodecamanganese (III, IV) cluster on gold surfaces. Comparison by atomic force microscopy profile analysis of the patterned structures confirms the formation of a chemically stable single layer of SMMs. Images based on chemical contrast, obtained by time-of-flight secondary ion mass spectrometry, confirm the patterned structure.     

Features of photopolymerization of Langmiur–Blodgett thin films of acetylenic acids

UV-induced polymerization of thin (1–4 monolayers) Langmuir–Blodgett films of acetylenic carboxylic acids with triple bonds in different positions (terminal: 23-tetracosinic acid HC≡C(CH2)21COOH, and internal: 2-docosinic CH3(CH2)18C≡CCOOH) and their lead salts is investigated. It is shown by means of IR spectroscopy that the topochemical reaction proceeds with the participation of carboxylic groups. The differences in the structure of mono- and bilayers are demonstrated. The mechanism of the topochemical reaction depends on the method of film transfer onto the substrate. It is shown by means of UV spectroscopy that short conjugated polyenes (containing 7 to 9 carbon atoms) are formed as the product of polymerization. The mechanism of the formation of these polyene chains is proposed on the basis of the experimental data and semi-empirical calculations.     

SiO2含量对新型PA6/EP/SiO2纳米材料体系聚合反应的影响

采用廉价的环氧树脂(EP)与正硅酸乙酯(TEOS)反应生成改性前驱体,然后水解,再将水解液与熔融己内酰胺混匀,通过原位生成法制备出新型PA6/EP/SiO2纳米复合材料。研究了SiO2无机粒子的加入对PA6聚合反应的影响。端基分析和高效液相色谱仪(HPLC)测试结果表明:随SiO2加入量的增加,PA6分子量及低聚物含量有下降趋势。     

Microcontact Printing of Proteins

The direct patterning of biomolecules on a solid substrate can be achieved using microcontact printing, a method that has been very successfully adopted for the precise and gentle transfer of proteins and lipid bilayers from stamp to substrate in 1 s, without loss of biological activity. The image shown was produced by patterning 16 different proteins onto the polystyrene surface of a cell culture dish using a stamp inked by means of a microfluidic network.     

Ordered nanostructure of PS-b-PEO copolymer by solvent annealing with mixture of benzene/water vapor and its micropattern fabrication

We investigate the effect of water/benzene co-solvent vapor on the ordering of poly(styrene-b-ethylene oxide) (PS-b-PEO) copolymer thin film on silicon substrate upon solvent annealing. In-plane cylindrical PEO microdomains were observed after exposure of benzene vapor. The addition of water vapor dominantly produced the cylindrical PEO domains aligned perpendicular to the substrate. The best ordering of the cylinders was obtained at the water fraction of approximately 0.05. The degree of ordering decreases while the periodicity of haxagonally packed PEO cylinders increases with the amount of water in the vapor mixture. The average center-to-center distance of hexagonally packed cylindrical PEO microdomains increases with the water fraction from approximately 25 nm to 40 nm. As one way of utilizing the dewetting of thin films inevitable during solvent annealing, PS-b-PEO micropatterns prepared by microcontact printing were treated with co-solvent vapor, which allows us to fabricate the controlled dewet structures guided by the micropatterns. Cylinder-to-sphere phase transition of PEO microdomains also occurred upon solvent annealing in the micropatterned PS-b-PEO films.