Gold nanohole arrays for biochemical sensing fabricated by soft UV nanoimprint lithography
ABSTRACT We report on results of fabrication and optical characterisation of sub-250 nm periodic gold nanohole arrays on glass by using UV nanoimprint lithography (UV-NIL) combined with both reactive ion etching (RIE) and Cr/Au lift-off processes. The transmission spectra of the fabricated nanohole gratings were measured for different hole diameters and periods. We also show preliminary results of chemical sensing after surface modification of the gold hole arrays. In agreement with the theoretical prediction, we found that any change in the dielectric index of the surrounding environment of the metallic array produces a transmission peak red shift.
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ABSTRACT: Microcontact printing (μCP) is a widely used technique for depositing proteins in micro patterns. The investigation of protein-protein interactions in small cells like T-cells (5-10μm), however, require feature sizes in the nanometer range which could be created by nanocontact printing (nCP). The main intention of our work was to develop functionalized Polyhedral Oligomeric Silsesquioxane (POSS) materials as an alternative for poly(dimethylsiloxane) (PDMS) which are commonly used as stamp material for micro-contact printing. POSS materials combine many desirable properties of conventional organic and inorganic components and provide an exemplary core system for developing versatile functional resist materials. Their properties are easily tunable by molecular design to suit the desired application. Used as stamp material POSS combines the advantages of hard stamps for high resolution printing and the possibility to tune the surface chemistry to enable a proper transfer of proteins.In this work, epoxy as well as carboxylic acid functionalized POSS were synthesized and epoxy-carboxylic acid bi-functionalized POSS materials have been developed for nCP stamp applications. The POSS polymers were designed by incorporating the necessary functional groups onto the silsesquioxane cage via platinum catalyzed hydrosilylation chemistry. The presence of epoxy groups allows the resists to polymerize at room temperature under UV-light exposure, while carboxylic acid groups ensure the presence of anionic species (COO-) at the surface of the stamps to facilitate protein transfer. The as-synthesized materials were characterized and supposed structures of the cured materials were confirmed by spectroscopic methods. Via nCP a monolayer of nanoscale avidin patterns have been deposited on epoxy-functionalized glass substrates.European Polymer Journal 11/2014; 65:221-231. DOI:10.1016/j.eurpolymj.2014.11.015 · 3.24 Impact Factor
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ABSTRACT: Lipopolysaccharide (LPS) is a known trigger in the pathogenesis of sepsis, lipid A being the toxic component. One of several adjuvant therapeutic approaches for severe sepsis is currently focusing on the neutralization of LPS. In order to obtain the components from traditional Chinese herbs that can neutralize the endotoxin, aqueous extractions were tested using affinity biosensor technology. From amongst 42 herbs, eight were found to possess lipid A-binding abilities. Radix Paeoniae Rubras had the highest lipid A-binding ability; therefore an aqueous extraction from this plant was investigated further. After preparation using standard methods, including silica gel chromatography and HPLC, we obtained 1, 2, 3, 4, 6-beta-d-pentagalloylglucose (PGG), with lipid A-binding ability. It was found that in vitro, PGG directly bound to lipid A, with a Kd of 32 microM, and that it neutralized the endotoxin both in the Limulus Amebocyte Lysate (LAL) assay and in a TNF-alpha release experiment, in a dose-dependent manner. In in vivo experiments, PGG was found to protect mice from a lethal challenge by LPS, and significantly decreased the plasma endotoxin level both in endotoxemic mice and rats, the reduction of the endotoxin level in rats being tightly associated with the TNF-alpha level. In conclusion, we demonstrate the effectiveness of affinity biosensor technology in discovering useful agents amongst traditional Chinese herbs and using this approach we found a new anti-endotoxin agent.International Immunopharmacology 07/2005; 5(6):1007-17. DOI:10.1016/j.intimp.2005.01.013 · 2.71 Impact Factor
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ABSTRACT: We present a simple and massively parallel nanofabrication technique to produce self-assembled periodic nanohole arrays over a millimeter-sized area of metallic film, with a tunable hole shape, diameter, and periodicity. Using this method, 30 x 30 microm(2) defect-free areas of 300 nm diameter or smaller holes were obtained in silver; this area threshold is critical because it is larger than the visible wavelength propagation length of surface plasmon waves ( approximately 27 microm) in the silver film. Measured optical transmission spectra show highly homogeneous characteristics across the millimeter-size patterned area, and they are in good agreement with FDTD simulations. The simulations also reveal intense electric fields concentrated near the air/silver interface, which was used for surface-enhanced Raman spectroscopy (SERS). Enhancement factors (EFs) measured with different hole shape and excitation wavelengths on the self-assembled nanohole arrays were 10(4)-10(6). With an additional Ag electroless plating step, the EF was further increased up to 3 x 10(6). The periodic nanohole arrays produced using this tunable self-assembly method show great promise as inexpensive SERS substrates as well as surface plasmon resonance biosensing platforms.Langmuir 10/2009; 25(23):13685-93. DOI:10.1021/la9020614 · 4.38 Impact Factor