Rewritable DNA Microarrays

VUV Photodeposition of Thiol-Terminated Films: A Wavelength-Dependent Study

Photoinitiated chemical vapor deposition (PICVD) has become attractive for selective and specific surface functionalization, because it relies on a single energy source, the photons, to carry out (photo-) chemistry. In the present wavelength (λ)-dependent study, thiol (SH)-terminated thin film deposits have been prepared from gas mixtures of acetylene (C₂H₂) and hydrogen sulfide (H₂S) via PICVD using four different vacuum-ultraviolet (VUV) sources, namely, KrL (λ_peak = 123.6 nm), XeL (λ_peak = 147.0 nm), XeE (λ_peak = 172.0 nm), and Hg (λ = 184.9 nm) lamps. Different λ influence the deposition kinetics and film composition, reflecting that photolytic reactions are governed by the gases' absorption coefficients, k(λ). Thiol concentrations, [SH], up to ∼7.7%, were obtained with the XeL source, the highest reported in the literature so far. Furthermore, all films showed islandlike surface morphology, regardless of λ.

Surface Engineering of Bromine-Based Plasma Polymer Films: A Step toward High Thiol Density Containing Organic Coatings

Nowadays, the development of synthetic methods regarding the fabrication of -SH containing organic coatings continues to attract a considerable attention. Among the potential techniques, the plasma polymerization appears as one of the most promising method but the difficulty to control the chemical composition of the layers is highly limiting. In this context, in this work, we report on an original method combining dry and wet chemistry approaches in view of selectively incorporating -SH functions in organic coatings. Our strategy is based on the (i) synthesis of a bromine-containing plasma polymer film, followed by (ii) a selective grafting of dithiol-based molecule on C-Br bond. Investigating the plasma polymerization process has revealed that, in our experimental window, the load of energy in the discharge has little influence on the chemical composition as well as on the cross-linking degree of the layers. This behavior is explained by considering the concomitant influence of the gas-phase reactions and the supply of energy to the growing film through ion bombardment. With regard to the functionalization strategy, based on comparative X-ray photoelectron spectroscopy measurements, it has been unambiguously demonstrated that a selective reaction between propanedithiol and the C-Br bond acting as the reactive center takes place resulting in the removing of the bromine atom and the incorporation of -SH groups in the PPF. Depending on the grafting reaction duration, the relative proportion of carbon bearing the -SH group is found to evolve from 4 to 6%. On the other hand, the dissolution of unbounded bromine-based species in the liquid medium during the grafting procedure is also evidenced. The whole set of our results clearly demonstrates the attractiveness of our strategy paving the way for new development in the fabrication of -SH-rich-containing organic thin films.

Plasmachemical Double Click Thiol-ene Reactions for Wet Electrical Barrier

Click thiol-ene chemistry is demonstrated for the reaction of thiol containing molecules with surface alkene bonds during electrical discharge activation. This plasmachemical reaction mechanism is shown to be 2-fold for allyl mercaptan (an alkene and thiol group containing precursor), comprising self-cross-linked nanolayer deposition in tandem with interfacial cross-linking to the surface alkene bonds of a polyisoprene base layer. A synergistic multilayer structure is attained which displays high wet electrical barrier performance during immersion in water.

Use of plasma polymerization to improve adhesion strength in carbon fiber composites cured by electron beam

Maleic anhydride plasma polymer was deposited at the surface of carbon fibers and functionalized with vinyl and thiol groups to improve its adhesion strength with an acrylate matrix cured by an electron beam. A characterization of the fiber surface properties was done before and after coating (topography, surface chemistry, and surface energy). Sharp improvements of the interfacial shear strength (+ 120%), measured by a micromechanical test derived from the pull-out test, were obtained and, to the best of our knowledge, never reported before. The values were close to the ones obtained with a thermal cure. The comparison of this approach with other types of surface treatments (oxidation, grafting of coupling agents) enabled the establishment of a general strategy for the improvement of the interfacial adhesion in carbon fiber composites cured by an electron beam and potentially the improvement of their mechanical properties. This strategy is based on a high surface density of functionalities that are generating covalent bonding during the polymerization of the matrix and on the insertion of a polymer layer strongly attached to the fiber surface and acting as a buffer between the fiber surface and the matrix to counteract the generation of stress in the interphase.

Site-specific immobilization of DNA on silicon surfaces by using the thiol–yne reaction

Covalent immobilization of ssDNA fragments onto silicon-based materials was performed using the thiol–yne reaction.

Development of electrochemical microbiochip for the biological diagnosis of Neisseria gonorrhoeae

A sexually transmitted disease is an illness that has a high probability of transmission between humans or animals who have sexual contact. Our research is based on the development of a microbiochip for Neisseria gonorrhoeae (N.G.). In our study, we have employed fusion technology between microarray technology and a microfluidic system for quantitative analysis of N.G. A great deal of attention has been focused on electrochemical detection by using a DNA probe, which is a specific DNA sequence and binds to a target biomolecule, because of high affinity, ease of usage, and fast measurement. The microbiochip consisted of two electrode systems and microchannel based PDMS. Our detection principles use electrochemical detection. Consequently, our microbiochip detected 5 ng/mL of N.G. and the correlation rate was over 0.95. We can produce a microbiochip, which could bind to a DNA probe and detect sample of interest. We expect that our electrobiochemical chip will be used for the development of a portable device.

Establishment of a derivatization method to quantify thiol function in sulfur-containing plasma polymer films

Thiol-supported surfaces draw more and more interest in numerous fields of applications from biotechnology to catalysis. Among the various strategies to generate such surfaces, the plasma polymerization of a thiol-containing molecule appears to be one of the ideal candidates. Nevertheless, considering such an approach, a careful characterization of the material surface chemistry is necessary. In this work, an original chemical derivatization method aiming to quantitatively probe the -SH functions in plasma polymers was established using N-ethylmaleimide as a labeling molecule. The method was qualitatively and quantitatively validated on self-assembled monolayers of 3-mercaptopropyltrimethoxysilane exhibiting a -SH-terminated group used as "model" surface. For a quantitative determination of the -SH content in propanethiol plasma polymers, the kinetics of the reaction was investigated. The latter is described as a two-step mechanism, namely a fast surface reaction followed by a diffusion-limited one. The density of -SH groups deduced from the derivatization method (~4%) is in good agreement with typical values measured in some other plasma polymer families. The whole set of our data opens up new possibilities for optimizing the -SH content in thiol-based plasma polymer films.

Pulsed plasmachemical deposition of highly proton conducting composite sulfonic acid-carboxylic acid films

Graft polymerization of sulfonic acid monomers onto structurally well-defined pulsed plasma poly(maleic anhydride) layers yields a composite carboxylic acid-sulfonic acid network. These bifunctional films are shown to exhibit high proton conductivity (125 mS cm(-1)) as well as good stability in water.

Immobilization of oligonucleotides onto zirconia-modified filter paper and specific molecular recognition

A morphologically complex cellulosic substance (e.g., commercial filter paper) was employed as a substrate for DNA immobilization and successive recognition. A uniform ultrathin zirconia gel film was first deposited on each cellulose nanofiber in bulk filter paper by a facile sol-gel process. Relying on the large surface area of filter paper and the strong affinity of zirconia for the phosphate group, terminal-phosphate probe DNA was abundantly immobilized on the zirconia-modified filter paper so as to convert the composite to a biofunctional material for the sensitive and repetitive recognition of the corresponding complementary target DNA on the nanomolar level. By contrast, in spite of the viability of the immobilization of the probe DNA and the recognition of target DNA on the quartz plate, the amount of captured probe DNA or recognized target DNA on such a flat substrate was much less than that captured or recognized on filter paper, resulting in a relatively insensitive recognition event. Moreover, control experiments on bare filter paper (without a zirconia nanocoating) suggested that the zirconia gel film was essential to probe DNA immobilization and subsequent target DNA recognition.

Controlled fragrant molecule release from surface-tethered cyclodextrin host-guest inclusion complexes

β-cyclodextrin barrels can be tethered to solid surfaces using the Williamson ether synthesis reaction via an intermediate pulsed plasma deposited poly(4-vinylbenzyl chloride) linker layer. The loading and release of perfume molecules through host-guest inclusion complex formation with surface tethered β-cyclodextrin has been followed by infrared spectroscopy and quartz crystal microbalance measurements. Fragrance release lasts for several months and can be easily recharged.

A substrate-independent lift-off approach for patterning functional surfaces

A lift-off method for creating multifunctional patterned surfaces has been devised. It entails consecutive pulsed plasmachemical deposition of a reactive bottom layer and a protective top release layer. By way of example, a bottom/top layer combination comprising pulsed plasma deposited poly(glycidyl methacrylate)/poly(pentafluorostyrene) has been shown to display selective adhesive lift-off of the latter. Application of a prepatterned adhesive template yields well-defined arrays of reactive epoxide functionality surrounded by a passive fluoropolymer background or vice versa.

Controlling cell growth on titanium by surface functionalization of heptylamine using a novel combined plasma polymerization mode

A novel bio-interface, produced by a combined plasma polymerization mode on a titanium (Ti) surface, was shown to enhance osteoblast growth and reduce fibroblast cell growth. This new method can securely attach a tailored interface to difficult materials such as Ti or ceramics. Here a more stable and higher density of NH₂ functional groups is able to withstand sterilization in ethanol. The biocompatibility, in terms of cell attachment and actin cytoskeleton development, was markedly improved in vitro, compared with untreated Ti surfaces and samples treated by other plasma modes. It gave a boosted (approximately six times higher) cellular response of osteoblasts in their initial adhesion stage. These factors should increase the formation of new bone around implants (reducing healing time), promoting osseointegration and thereby increasing implantation success rates.

Recycling and reusing patterned self-assembled monolayers for cell culture

Patterned self-assembled monolayers (SAMs) have been widely utilized for the study of cellular growth and behavior. While microcontact printing is a straightforward method of producing patterned substrates, the process is time consuming and requires the use of many techniques and specialized equipment. Here we present a method by which patterned substrates can be reused up to 15 times, saving both time and valuable resources.

Surface actuation of smart nanoshutters

Patterned polymer brush surfaces have been fabricated using the molecular scratchcard lithography technique, where a functional top nanolayer (acting also as a resist) is selectively removed using a scanning probe tip to expose underlying atom-transfer radical polymerization (ATRP) initiator sites. The lateral spreading of grafted polymer brush patterns across the adjacent functional resist surface can be reversibly actuated via solvent exposure. Effectively, this methodology provides a means for hiding/unveiling functional surfaces on the nanoscale.

Chemical vapor deposition of conformal, functional, and responsive polymer films

Chemical vapor deposition (CVD) polymerization utilizes the delivery of vapor-phase monomers to form chemically well-defined polymeric films directly on the surface of a substrate. CVD polymers are desirable as conformal surface modification layers exhibiting strong retention of organic functional groups, and, in some cases, are responsive to external stimuli. Traditional wet-chemical chain- and step-growth mechanisms guide the development of new heterogeneous CVD polymerization techniques. Commonality with inorganic CVD methods facilitates the fabrication of hybrid devices. CVD polymers bridge microfabrication technology with chemical, biological, and nanoparticle systems and assembly. Robust interfaces can be achieved through covalent grafting enabling high-resolution (60 nm) patterning, even on flexible substrates. Utilizing only low-energy input to drive selective chemistry, modest vacuum, and room-temperature substrates, CVD polymerization is compatible with thermally sensitive substrates, such as paper, textiles, and plastics. CVD methods are particularly valuable for insoluble and infusible films, including fluoropolymers, electrically conductive polymers, and controllably crosslinked networks and for the potential to reduce environmental, health, and safety impacts associated with solvents. Quantitative models aid the development of large-area and roll-to-roll CVD polymer reactors. Relevant background, fundamental principles, and selected applications are reviewed.

Construction of protein-resistant pOEGMA films by helicon plasma-enhanced chemical vapor deposition

This paper describes the formation of protein-resistant, poly(ethylene glycol) methyl ether methacrylate (pOEGMA) thin films by helicon plasma-enhanced chemical vapor deposition (helicon-PECVD). pOEGMA was successfully grafted onto a silicon substrate, as a model substrate, without any additional surface initiators, by plasma polymerization of OEGMA. The resulting pOEGMA films were characterized by ellipsometry, FT-IR spectroscopy, X-ray photoelectron spectroscopy and contact angle goniometry. To investigate the protein-resistant property of the pOEGMA films, four different proteins, bovine serum albumin, fibrinogen, lysozyme and ribonuclease A, were tested as model proteins for ellipsometric measurements. The ellipsometric thickness change for all the model proteins was less than 3 A, indicating that the formed pOEGMA films are protein-resistant.

A substrate-independent approach for bactericidal surfaces

Existing methods for imparting antibacterial performance to solid surfaces tend to either be substrate-specific or rely upon leaching modes of action that cause ecological damage. An alternative approach is outlined comprising plasmachemical functionalization of solid surfaces with poly(4-vinyl pyridine) moieties and their subsequent activation (quaternization) with bromobutane to yield bactericidal activity. These bioactive surfaces can be applied to a host of different substrate materials and are easily regenerated by rinsing in water.

Rewritable glycochips

We describe microarraying of carbohydrates for protein screening using either disulfide bridge or Schiff base imine immobilization chemistries on plasmachemical deposited functional nanolayers. The commonly observed issue of nonspecific background binding of proteins is overcome by spotting carbohydrates through a protein-resistant overlayer yielding spatially localized interaction with a reactive functional underlayer.

Electroless metallization onto pulsed plasma deposited poly(4-vinylpyridine) surfaces

Pulsed plasma-chemical deposition of poly(4-vinylpyridine) is found to be a highly effective way of functionalizing solid surfaces with pyridine ring centers. These surfaces can be metallized via complexation to Pd2+ ions from solution, followed by autocatalytic electroless deposition of either copper or nickel films.

A Substrate-Independent Approach for Cyclodextrin Functionalized Surfaces

6-Amino-6-deoxy-beta-cyclodextrin can be immobilized onto a range of solid surfaces via reaction with a predeposited pulsed plasma poly(glycidyl methacrylate) layer. X-ray photoelectron spectroscopy, infrared spectroscopy, and quartz crystal microbalance measurements have been employed to monitor guest-host interactions between N,N-dimethylformamide or cholic acid and surface-tethered 6-amino-6-deoxy-beta-cyclodextrin barrels.