Renate Förch

In Situ, Label-Free DNA Detection Using Organic Transistor Sensors

Rapid and highly sensitive PNA-DNA hybridization assays have attracted enormous attention for a wide variety of applications ranging from genotyping to molecular diagnosis. [ 1 , 2 ] Conventional optical detection systems based on microarrays and real-time PCR involve expensive detection protocols, typically requiring a fl uorescent dye and optical sources/detectors; however, this method has become the standard technique for quantifying the extent of hybridization between surface immobilized probes and fl uorophore-labeled DNA targets. Recent advances in chemical detection research, in part benefi ting from the overwhelming progress made in organic electronics, have shown great promise for a viable, low-cost alternative to current optical detection systems. [ 3 , 4 ] The utilization of organic transistor technology in chemical sensors is particularly encouraging. This simple platform allows for the fabrication of low-cost, large-area, and fl exible devices with air stability, low-power consumption, biocompatibility, and facile surface modifi cation for the detection of a wide range of analyte species. [ 5 , 6 ] Many examples exist for the detection of analyte vapors using an OTFT platform, with numerous reports addressing the ability to identify particular analytes either through the use of a fi ngerprint response [ 7 , 8 ] or by incorporating selective detection layers on functional OTFTs. [ 4 , 9 ] Few examples of chemical detection in aqueous systems have been demonstrated; however, these devices were not selective toward a particular analyte. [ 3 , 10 ] Selective in situ detection with OTFTs requires a versatile method for the immobilization of various selective molecular probes within proximity to the active transport channel. Here, we report a real-time, in situ selective detection scheme for short-chain DNA targets by employing organic transistors as the electrical read-out platform. The surfaces of the OTFTs were modifi ed with a thin maleic anhydride (MA) polymer layer

Surface design : applications in bioscience and nanotechnology

1. Tutorial Reviews 1.1 Coupling Chemistries for the Modification and Functionalization of Surfaces to Create Advanced Bio-interfaces, H. Schonherr 1.2 Surface Plasmon Resonance-Based Biosensors, J. Dostalek, Chun Jen Huang and W. Knoll 1.3 Surface Modification and Adhesion, R. Forch 1.4 Modern Biological Sensors, A.T.A. Jenkins 2. Functional Thin Film Architectures and Platforms Based on Polymers 2.1 Controlled Block Copolymer Thin Film Architectures, M. Roerdink, M. A. Hempenius, G. J. Vancso 2.2 Stimuli Responsive Polymer Brushes, E. Benetti, M. Navarro, S. Zapotoczny, G. J. Vancso 2.3 Cyanate Ester Resins as Thermally Stable Adhesives for PEEK, B. Yameen, M. Tamm, N. Vogel, A. Echler, R. Forch, U. Jonas and W. Knoll 2.4 Structured and Functionalized Polymer Thin Film Architectures, H. Schonherr, C. L. Feng, A. Embrechts, G. J. Vancso 3. Biointerfaces, Biosensing, and Molecular Interactions 3.1 Surface Chemistry in Forensics, K. Bender 3.2 Modification of Surfaces by Photosensitive Silanes, X.S. Li, S. Pradhan-Kadam, M. Alvarez-Chamorro, U. Jonas 3.3 Solid Supported Bilayer Lipid Membranes, I. Koper, I. Vockenroth 3.4 Interaction of Structured and Functionalized Polymers with Cancer Cells, A. Embrechts, C. L. Feng, I. Bredebusch, J. Schnekenburger, Wolfram Domschke, G. J. Vancso, and H. Schonherr 3.5 Fabrication and Application of Surface Tethered Vesicles, A.T.A. Jenkins and T. L. Williams 3.6 Plasma Polymerized Allylamine Thin Films for DNA Sensing, L. Q. Chu, W. Knoll, R. Forch 4. Nanoparticles and -containers 4.1 Defined Colloidal 3D Architectures, N. V. Dziomkina, M. A. Hempenius, G. J. Vancso 4.2 Nanoparticles at the Interface: The Properties of Nanoparticles Assembled into 2-D and 3-D Structures at Planar Electrode Surfaces, P. J. Cameron 4.3 Surface Engineering of Quantum Dots with Designer Ligands, N. Tomczak, D. Janczewsk, O. Tagit, M. Y. Han, G. J. Vancso 4.4 Stimuli Responsive Capsules, Y. Ma, M. A. Hempenius, E. S. Kooij, W.-F. Dong, H. Mohwald, and G. J. Vancso 4.5 Nanoporous Thin Films as Highly Versatile and Sensitive Waveguide Biosensors, K.H. Aaron Lau, P. J. Cameron, H. Duran, A. I. Abou-Kandil, W. Knoll 5. Surface and Interface Analysis 5.1 Stretching and Rupturing Single Covalent and Associating Macromolecules by AFM-based Single Molecule Force Spectroscopy, M. I. Giannotti, W. Q. Shi, S. Zou, H. Schonherr, G. J. Vancso 5.2 Quantitative Lateral Force Microscopy, H. Schonherr, E. Tocha, J. Song, G. J. Vancso 5.3 Long Range Surface Plasmon-enhanced Fluorescence Spectroscopy as a Platform for Biosensors, A. Kasry, J. Dostalek, W. Knoll 6. Glossary of Surface Analytical Tools, R. Forch, H. Schonherr, and A. T. A. Jenkins 6.1 Atomic Force Microscopy 6.2 Contact Angle Goniometry 6.3 Ellipsometry 6.4 Infra Red Spectroscopy 6.5 Impedance Spectroscopy 6.6 Scanning Electron Microscopy 6.7 Surface Plasmon Resonance Spectroscopy 6.8 Optical Waveguide Mode Spectroscopy (OWS) 6.9 Waveguide Mode Spectroscopy (WaMS) 6.10 X-Ray Photoelectron Spectroscopy

Effect of aqueous solution on functional plasma polymerized films

Surface plasmon resonance spectroscopy has been used to study the effect of aqueous solution on plasma polymers of allylamine, di(ethylene glycol) mono vinyl ether and maleic anhydride deposited at either continuous wave or pulsed plasma conditions. The behaviour of the films in aqueous solution was found to be dependant upon the plasma conditions used and can generally be correlated to the chemical structure of the film.

Parallel Preparation of Densely Packed Arrays of 150-nm Gold-Nanocrescent Resonators in Three Dimensions

Metallic nanostructures show interesting optical properties due to their plasmonic resonances, and when arranged in three-dimensional (3D) arrays hold promise for optical metamaterials with negative refractive index. Towards this goal a simple, cheap, and parallel method to fabricate large-area, ordered arrays of 150-nm gold nanocrescents supporting plasmonic resonances in the near-infrared spectral range is demonstrated. In this process hexagonally ordered monolayers of monodisperse colloids are prepared by a simple floating technique, and subsequently the individual particles are size-reduced in a plasma process and used as a shadow mask with the initial lattice spacing. The resulting two-dimensional array of plasmonic resonators is coated with a transparent silica layer, which serves as a support for a second layer prepared by the identical process. The mutual orientation of the nanostructures between the individual layers can be freely adjusted, which determines the polarization-dependent absorption of the array and opens the possibility to introduce chirality in this type of 3D metamaterial. The iteration of this simple and efficient methodology yields 3D arrays with optical features as sharp as those of the individual nanocrescents, and shows strong potential for large-scale production of high-quality optical metamaterials.

Immobilization of biomolecules to plasma polymerized pentafluorophenyl methacrylate.

Thin films of plasma polymerized pentafluorophenyl methacrylate (pp-PFM) offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with different aminated reagents and biological molecules. The present paper follows on from previous work on the plasma deposition of pentafluorophenyl methacrylate (PFM) for optimum functional group retention (Francesch, L.; Borros, S.; Knoll, W.; Foerch, R. Langmuir 2007, 23, 3927) and reactivity in aqueous solution (Duque, L.; Queralto, N.; Francesch, L.; Bumbu, G. G.; Borros, S.; Berger, R.; Förch, R. Plasma Process. Polym. 2010, accepted for publication) to investigate the binding of a biologically active peptide known to induce cellular adhesion (IKVAV) and of biochemically active proteins such as BSA and fibrinogen. Analyses of the films and of the immobilization of the biomolecules were carried out using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The attachment of the biomolecules on pulsed plasma polymerized pentafluorophenyl methacrylate was monitored using surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the presence of immobilized biomolecules on the plasma polymer and was used to determine the mass coverage of the peptide and proteins adsorbed onto the films. The combined analysis of the surfaces suggests the covalent binding of the peptide and proteins to the surface of the pp-PFM.

Pulsed plasma polymerized di(ethylene glycol) monovinyl ether coatings for nonfouling surfaces

BSA and fibrinogen adsorption to ultrathin nonfouling coatings was investigated using surface plasmon resonance spectroscopy. The nonfouling coatings were prepared by pulsed plasma polymerization (pp) of di(ethylene glycol) monovinyl ether (EO2). The pp-EO2 coatings were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. The nonfouling properties of the pp-EO2 coatings were found to correlate with details of the surface chemistry and with the film thickness. BSA and fibrinogen exhibited different adsorption behaviors. We identified the threshold value of the thickness of pp-EO2, above which the films showed excellent antifouling properties. The mechanism by which these films resist protein adsorption is discussed.

Surface Initiated Polymerization on Pulsed Plasma Deposited Polyallylamine: A Polymer Substrate-Independent Strategy to Soft Surfaces with Polymer Brushes

The deposition of polyallylamine (PAA) adlayers by pulsed plasma polymerization on various types of polymeric substrates has been explored as a general route to amino functionalized polymeric surfaces. These amino groups are highly suitable for anchoring an atom transfer radical polymerization (ATRP) initiator via a robust amide linkage. Subsequent surface initiated ATRP (SI-ATRP) of monomethoxy oligo(ethylene glycol) methacrylate (MeOEGMA) resulted in polyMeOEGMA brush grafted polymer surfaces. This combined strategy of pulsed plasma polymerization with SI-ATRP was demonstrated for five different polymeric substrates namely polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), and polytetrafluoroethylene (PTFE). Analysis of brush layers by attenuated total reflection infrared (ATR-IR) spectroscopy as well as X-ray photoelectron spectroscopy (XPS) fully corroborated the success of the proposed strategy for all substrate types.

Plasma polymerized epoxide functional surfaces for DNA probe immobilization

The development of functional surfaces for the immobilization of DNA probe is crucial for a successful design of a DNA sensor. In this report, epoxide functional thin films were achieved simply by pulsed plasma polymerization (PP) of glycidyl methacrylate (GMA) at low duty cycle. The presence of epoxide groups in the resulting ppGMA films was confirmed by Fourier transform infrared spectroscopy. The ppGMA coatings were found to be resistant to the non-specific adsorption of DNA strands, while the epoxide groups obtained could react with amine-modified DNA probes in a mild basic environment without any activation steps. A DNA sensor was made, and was successfully employed to distinguish different DNA sequences with one base pair mismatch as seen by surface plasmon enhanced fluorescence spectroscopy (SPFS). The regeneration of the present DNA sensor was also discussed. This result suggests that surface modification with ppGMA films is very promising for the fabrication of various DNA sensors.

Polymer-Tethered Bimolecular Lipid Membranes

This contribution describes the assembly and structural and functional characterization of various types of polymer-supported lipid bilayer membranes.We start with the description of the polymer-cushioned membrane that can be prepared by first attaching (covalently) polymer coils (as tethers or cushions) from solution to a reactive solid support, followed by the covalent coupling of a lipid monolayer containing reactive anchor lipids. Alternatively, a lipopolymer monolayer (if needed mixed with “normal” lipids) is pre-organized at the water-air interface in a Langmuir trough and then transferred to a solid substrate which is again pre-functionalized by a reactive coating. A special case discussed is the use of glycolipopolymers for the assembly of the proximal tethered monolayer. From all these interfacial architectures the final structure, the supported bilayer, is obtained by the fusion of vesicles forming the distal monolayer of the membrane.

Pulsed plasma polymerized maleic anhydride films in humid air and in aqueous solutions studied with optical waveguide spectroscopy

Optical waveguide spectroscopy (OWS) was employed to monitor the swelling behavior of pulsed plasma polymerized maleic anhydride (PPPMA) films in humid air and in aqueous solutions by measuring the film thicknesses and refractive indices. With the relative humidity of air increasing, both the thickness and the refractive index of the PPPMA films increased, indicating water penetration into and uptake by the films. The swelling of the hydrated PPPMA films in humid air is reversible. In aqueous media, the thickness and the refractive index of the washed PPPMA film increased with an increase of pH and ionic strength, respectively. On the basis of the present data, a hypothesis concerning the structure of the PPPMA film is proposed. Our model suggests that the unique structure of the PPPMA films originates from the cyclic structure of maleic anhydride and depends on parameters of the plasma deposition process, and the interaction between H(2)O and the carboxylic groups.