Reactive surface micropatterning by wet stamping

Hydrogel stamps are used to reactively micropattern various types of substrates. The method, called reactive wet stamping (r-WETS), is general in nature and overcomes several limitations of conventional soft-lithographic techniques. Illustrative applications of r-WETS in surface wettability modification, deposition of metallic microstructures, preparation of supports for electrostatic self-assembly, and multistep reactive patterning are discussed.     

Graft polymerization of carbohydrates on the surface of a macroporous silica

Conclusions A graft polymerization of carbohydrates was carried out on the surface of a macro-porous glass in order to produce biocompatible materials based on macroporous silica.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2091–2094, September, 1987.     

Polymer/colloid surface micromachining: micropatterning of hybrid multilayers

Fabrication of multicomponent patterned films comprising polymer/nanoparticle multilayers using conventional lithography and bottom-up layer-by-layer nanofabrication techniques is described. The work is motivated by the potential to extend polymer surface micromachining capabilities toward construction of integrated systems by connecting discrete domains of active materials containing functional nanoparticles. Modified surfaces illustrate tunability of the physical (thickness, roughness, 3D structures) and chemical (inorganic/organic material combinations) properties of the nanocomposite micropatterns. Intriguing nanoscale phenomena were observed for the structures when the order of material deposition was changed; the final multilayer thickness and surface roughness and mechanical integrity of the patterns were found to be interdependent and related to the roughness of layers deposited earlier in the process.     

Cell surface carbohydrates evaluation via a photoelectrochemical approach

A robust and specific photoelectrochemical approach for cell surface carbohydrates evaluation was achieved firstly based on carboxylic-group-containing free-base-porphyrin bridged 3-aminophenylboronic acid and a titania biosensing interface.     

Photochemical method of silver deposition on a quartz surface modified by polybutoxytitanium

The results of silver photochemical deposition on a surface of titanium-containing coatings are presented. The formation of the particles occurs in a near-surface layer with a direct involvement of the coating which gains an anatase structure under the action of UV light. The deposition of silver begins with the formation of low-atomic clusters which reach particle sizes of 300 nm in diameter and 35–40 nm in thickness under long irradiation. The quantum yield of the reduction of Ag(I) ions is 0.001.     

Quantum dot micropatterning on si

Using InP and PbSe quantum dots, we demonstrate that the Langmuir-Blodgett technique is well-suited to coat nonflat surfaces with quantum dot monolayers. This allows deposition on silicon substrates covered by a developed patterned resist, which results in monolayer patterns with micrometer resolution. Atomic force microscopy and scanning electron microscopy reveal the formation of a densely packed monolayer that replicates predefined structures with high selectivity after photoresist removal. A large variety of shapes can be reproduced and, due to the excellent adhesion of the quantum dots to the substrate, the hybrid approach can be repeated on the same substrate. This final possibility leads to complex, large-area quantum dot monolayer structures with micrometer spatial resolution that may combine different types of quantum dots.     

Site-selective catalytic surface activation via aerosol nanoparticles for use in metal micropatterning

There is great interest in the fabrication of micro- and nanopatterned metallic structures on substrates for a wide range of electronic, photonic, and magnetic devices. One of the most widely used techniques is the electroless deposition (ELD) of metal, which requires the surface activation of the substrates with a metal catalyst. This paper introduces a method of catalytic surface activation by producing platinum aerosol nanoparticles via spark generation and then thermophoretically depositing the particles onto a flexible polyimide (PI) substrate through the pattern hole of a mask. After annealing, the catalytically activated substrate is placed into a solution for electroless silver deposition. The silver is then formed only on the activated regions of the substrate. Silver line patterns having a width of 18 microm and a height of 1 microm are created with the ability to be effectively reproduced. The average value of the resistivities is approximately 6.8 mu Omega.cm, which is almost comparable to the theoretical resistivity of bulk silver (1.6 mu Omega.cm). Other silver micropatterns containing square dot array, line, line array, Y-branched line, and tapered line using different pattern masks are also demonstrated.     

Photochemical activation of a polycarbonate surface for covalent immobilization of a protein ligand

Polycarbonate—a thermostable polymer is activated by a simple and rapid method using a photolinker, 1-fluoro-2-nitro-4-azidobenzene (FNAB) for covalent immobilization of a biomolecule. Horseradish peroxidase (HRP) is used as a model enzyme to check the efficacy of the activated surface. HRP is immobilized on the activated polycarbonate surface without addition of any reagent or catalyst and is found to give 2-2.5-fold increase in absorbance with the substrate as compared to the directly adsorbed enzyme. Photochemical attachment of FNAB to the PC surface is confirmed by X-ray photoelectron spectroscopy (XPS), which shows the presence of nitrogen and fluorine in the ratio of 2:1 in the activated polycarbonate. Disappearance of fluorine peak in the XP spectra of PC bound enzyme further confirms the covalent binding of HRP, through displacement of fluorine moiety of the activated PC by the amino group of the protein. Optimized concentration of the photolinker is found as 6 μmol of FNAB per well and time of photo irradiation is 8 min for activation of a PCR polycarbonate plate. PC bound HRP has shown enhanced thermal and storage stability. Kinetic studies of the immobilized HRP shows improved catalytic activity. The potential application of activated polycarbonate surface includes immobilization of biomolecules for biosensors, immunoassays, and protein and DNA micro-arrays. Due to the stability of the polycarbonate at high temperature, the activated polycarbonate has an advantage for immobilization of thermostable biomolecule such as thermostable enzyme for reaction at elevated temperature.     

A simple approach to micropatterning and surface modification of poly(dimethylsiloxane)

Ozone treatment is an efficient economical, alternative method for surface activation of poly(dimethylsiloxane) (PDMS). This is illustrated by the derivatization of a PDMS surface with (3-aminopropyl)triethoxysilane (APTES). The apparent surface concentration of amino groups was found to be ca. 10(-8) mol/cm2 using UV/visible spectroscopy of the product from the reaction of the amino groups and fluorescamine. Potential application for micropatterning of biologically active interfaces was demonstrated by the covalent immobilization of oligonucleotides. A simple process for photolithographic patterning on PDMS surfaces has been developed.     

Photochemical modification of polyethylene surface with aryl azides

It has been shown that the formation of a covalently grafted modifying layer takes place during the photolysis of polycrystalline layers of 2-azidoanthraquinone and 4-azidobenzoyl azide on the surface of polyethylene. Its thickness is determined by the amount of the azide applied, and phenyl isocyanate groups formed by the photolysis of 4-azidobenzoyl azide are prone to further functionalization of the modified surface with primary amines.     

Photochemical cycloaddition on the pore surface of a porous coordination polymer impacts the sorption behavior

Photochemical [2+2] cycloaddition reactions in a two-dimensional interdigitated porous crystalline framework proceed in a single-crystal-to-single-crystal manner, and one-dimensional channels show structural changes that have a significant impact on the CO(2) sorption.     

Photochemical precipitation of copper particles on the quartz surface modified with polybutoxytitanium

Results of photochemical precipitation of copper nanoparticles on the surface of polybutoxytitanium film applied to the surface of quartz sublayer and modified by the UV irradiation with the excitation wavelength 254 nm are presented. Photocatalytic activity of polybutoxytitanium film modified by the UV light was confirmed. It was established that photoprecipitated copper nanoparticles form a uniform stable coating consisting of tightly packed particles of 50 nm diameter and 8 nm height.     

Mimicry of tandem repeat peptides against cell surface carbohydrates

Our approach to multivalent peptide construction relies on tentacle peptides, also known as a multiple antigenic peptides, which contain two and four repeats of a selected peptide. In this communication, we report the results of preliminary studies aimed at (1) the selection of short peptides against the carbohydrate, sLeX, (2) the synthesis of tentacle dimers and tetramers of the selected peptides, and (3) the determination of affinities and specificities of the peptides to several related carbohydrates by using the surface plasmon resonance (SPR) and the equilibrium dialysis techniques. Binding affinity studies, as well as assays of in vitro binding of the peptides to a sLeX-specific cell line, have shown that the tetrameric peptides bind to the cell surface sugars.     

Protein micropatterning on bifunctional organic-inorganic sol-gel hybrid materials

Active protein micropatterns and microarrays made by selective localization are popular candidates for medical diagnostics, such as biosensors, bioMEMS, and basic protein studies. In this paper, we present a simple fabrication process of thick (approximately 20 microm) protein micropatterning using capillary force lithography with bifunctional sol-gel hybrid materials. Because bifunctional sol-gel hybrid material can have both an amine function for linking with protein and a methacryl function for photocuring, proteins such as streptavidin can be immobilized directly on thick bifunctional sol-gel hybrid micropatterns. Another advantage of the bifunctional sol-gel hybrid materials is the high selective stability of the amine group on bifunctional sol-gel hybrid patterns. Because amine function is regularly contained in each siloxane oligomers, immobilizing sites for streptavidin are widely distributed on the surface of thick hybrid micropatterns. The micropatterning processes of active proteins using efficient bifunctional sol-gel hybrid materials will be useful for the development of future bioengineered systems because they can save several processing steps and reduce costs.     

Photochemical modification of diamond films: introduction of perfluorooctyl functional groups on their surface

Photolysis of perfluoroazooctane with diamond films led the chemical modification of the surface to introduce perfluorooctyl functional groups, confirmed by means of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and time-of-flight secondary ion mass spectrometry measurements. Diamond films modified with fluorine moieties showed improved frictional property and reduction of surface energy, as evaluated by contact angle to water, compared with a pristine diamond film. The contact angle and friction coefficient of chemically modified diamond film are 118 degrees and 0.1, respectively. The results of the value of the contact angle depending on irradiation times are consistent with those of the F/C ratio of fluorinated diamond films by monitoring with XPS.     

DNA micropatterning on polycrystalline diamond via one-step direct amination

We report a novel method of one-step direct amination on polycrystalline diamond to produce functionalized surfaces for DNA micropatterning by photolithography. Polycrystalline diamond was exposed to UV irradiation in ammonia gas to generate amine groups directly. After patterning, optical microscopy confirmed that micropatterns covered with an Au mask were regular in size and shape. The regions outside the micropatterns were passivated with fluorine termination by C3F8 plasma, and the chemical changes on the two different surfaces--the amine groups inside the patterned regions by one-step direct amination and fluorine termination outside the patterned regions--were characterized by spatially resolved X-ray photoelectron spectroscopy (XPS). The patterned areas terminated with active amine groups were then immobilized with probe DNA via a bifunctional molecule. The sequence specificity was conducted by hybridizing fluorescently labeled target DNA to both complementary and noncomplementary probe DNA attached inside the micropatterns. The fluorescence micropatterns observed by epifluorescence microscopy corresponded to those imaged by optical microscopy. DNA hybridization and denaturation experiments on a DNA-modified diamond show that the diamond surfaces reveal superior stability. The influence of a different amination time on fluorescence intensity was compared. Different terminations as passivated layers were investigated, and as a result, fluorine termination points to the greatest signal-to-noise ratio.     

Biocompatible micropatterning of two different cell types

The spatial arrangement of individual cell types can now be routinely controlled using soft-lithography-based micropatterning of complementary cell-adhesive and cell-resistant patterns. However, the application of these tools in tissue engineering to recreate tissue complexity in vitro has been hampered by the challenge of finding noncytotoxic procedures for converting complementary cell-resistant regions that define the arrangement of the first cell type into cell-adhesive regions to allow for the attachment of other cell types. A polyelectrolyte assembly approach is presented here for the first time, which allows for this noncytotoxic conversion and, thus, micropatterning of two different cell types, for example, endothelial cells and fibroblasts, on biodegradable substrates. The flexibility of this approach is further demonstrated by inducing organized capillary formation by endothelial cells on micropatterned lines followed by subsequent assembly of fibroblasts.     

Cell surface carbohydrates of preimplantation embryos as assessed by lectin binding

Preimplantation embryos were obtained from the uteri and oviducts of 2 strains of mice, Swiss CD-1 and B6CBA. After removal of the zona pellucida by treatment with pronase, FITC-lectins were bound to the embryonic cell surfaces at either 4 degrees C or 37 degrees C. Both morula and blastocyst stage embryos bound the following lectins, FITC-ConA, FITC-WGA, FITC-RCAII and FITC-RCAI. No difference in binding was observed between the morula stage and the blastocyst stage within each mouse strain for each specific lectin. However B6CBA embryos bound less FITC-ConA and FITC-WGA than the corresponding Swiss CD-1 embryos. The topographical arrangement of the lectin receptors was observed to differ between 4 degrees C and 37 degrees C for FITC-ConA, FITC-RCAII, and FITC-RCAI. While lectins bound at 4 degrees C showed a pattern of continuous labeling, the same lectin at 37 degrees C showed aggregation of lectin receptors into patches indicating lateral mobility of these receptors within the embryonic cell membranes. In contrast FITC-WGA bound at 4 degrees C and 37 degrees C demonstrated continuous labeling of embryos at both temperatures. FITC-fucose binding protein did not bind to Swiss CD-1 embryos. The invasiveness of trophoblastic cells of mouse blastocysts was studied by culturing isolated embryos without prior enzyme treatment on reconstituted collagen gels. After 4 days in BME containing only glutamine and bovine serum albumin as supplements, the embryos shed their zona pellucida and implanted into the collagen gel as indicated by zones of lysis in proximity to the embryonic cells when analyzed by scanning electron microscopy.