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Jang J.-W.,Northwestern University | Jang J.-W.,NanoInk Inc. | Zheng Z.,Northwestern University | Zheng Z.,Hong Kong Polytechnic University | And 5 more authors.
Nano Letters | Year: 2010

Poly(ethylene glycol) (PEG) polymer lens arrays are made by using dip-pen nanolithography to deposit nanoscale PEG features on hydrophobically modified quartz glass. The dimensions of the PEG lenses are controlled by tuning dwell time and polymer molecular weight. The PEG polymer lenses on the quartz substrate act as a phase-shift photomask for fabricating subwavelength scale features, ∼100 nm in width. Depending upon UV irradiation time during the photolithography, the photoresist nanostructures can be transitioned from well-shaped (short time) to ring-shaped (long time) features. The technique can be used to pattern large areas through the use of cantilever arrays. © 2010 American Chemical Society. Source

Carbonell C.,Catalan Institute of Nanoscience and Nanotechnology | Stylianou K.C.,Catalan Institute of Nanoscience and Nanotechnology | Hernando J.,Autonomous University of Barcelona | Evangelio E.,Catalan Institute of Nanoscience and Nanotechnology | And 5 more authors.
Nature Communications | Year: 2013

Chemical reactions at ultrasmall volumes are becoming increasingly necessary to study biological processes, to synthesize homogenous nanostructures and to perform high-throughput assays and combinatorial screening. Here we show that a femtolitre reaction can be realized on a surface by handling and mixing femtolitre volumes of reagents using a microfluidic stylus. This method, named microfluidic pen lithography, allows mixing reagents in isolated femtolitre droplets that can be used as reactors to conduct independent reactions and crystallization processes. This strategy overcomes the high-throughput limitations of vesicles and micelles and obviates the usually costly step of fabricating microdevices and wells. We anticipate that this process enables performing distinct reactions (acid-base, enzymatic recognition and metal-organic framework synthesis), creating multiplexed nanoscale metal-organic framework arrays, and screening combinatorial reactions to evaluate the crystallization of novel peptide-based materials. © 2013 Macmillan Publishers Limited. All rights reserved. Source

Bett C.K.,Louisiana State University | Ngunjiri J.N.,NanoInk Inc. | Serem W.K.,Louisiana State University | Fontenot K.R.,Louisiana State University | And 3 more authors.
ACS Chemical Neuroscience | Year: 2010

Neuronal cytotoxicity observed in Alzheimer's disease (AD) is linked to the aggregation of β-amyloid peptide (Aβ) into toxic forms. Increasing evidence points to oligomeric materials as the neurotoxic species, not Aβ fibrils; disruption or inhibition of Aβ self-assembly into oligomeric or fibrillar forms remains a viable therapeutic strategy to reduce Aβ neurotoxicity. We describe the synthesis and characterization of amyloid aggregation mitigating peptides (AAMPs) whose structure is based on the Aβ "hydrophobic core" Aβ17?20, with α,α- disubstituted amino acids (ααAAs) added into this core as potential disrupting agents of fibril self-assembly. The number, positional distribution, and side-chain functionality of ααAAs incorporated into the AAMP sequence were found to influence the resultant aggregate morphology as indicated by ex situ experiments using atomic force microscopy (AFM) and transmission electron microscopy (TEM). For instance, AAMP-5, incorporating a sterically hindered ααAA with a diisobutyl side chain in the core sequence, disrupted Aβ1?40 fibril formation. However, AAMP-6, with a less sterically hindered ααAA with a dipropyl side chain, altered fibril morphology, producing shorter and larger sized fibrils (compared with those of Aβ1?40). Remarkably, ααAA-AAMPs caused disassembly of existing Aβ fibrils to produce either spherical aggregates or protofibrillar structures, suggesting the existence of equilibrium between fibrils and prefibrillar structures. © 2010 American Chemical Society. Source

George S.,University of Illinois at Urbana - Champaign | Chaudhery V.,University of Illinois at Urbana - Champaign | Lu M.,University of Illinois at Urbana - Champaign | Takagi M.,University of Illinois at Urbana - Champaign | And 5 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2013

Enhancement of the fluorescent output of surface-based fluorescence assays by performing them upon nanostructured photonic crystal (PC) surfaces has been demonstrated to increase signal intensities by >8000×. Using the multiplicative effects of optical resonant coupling to the PC in increasing the electric field intensity experienced by fluorescent labels ("enhanced excitation") and the spatially biased funneling of fluorophore emissions through coupling to PC resonances ("enhanced extraction"), PC enhanced fluorescence (PCEF) can be adapted to reduce the limits of detection of disease biomarker assays, and to reduce the size and cost of high sensitivity detection instrumentation. In this work, we demonstrate the first silicon-based PCEF detection platform for multiplexed biomarker assay. The sensor in this platform is a silicon-based PC structure, comprised of a SiO2 grating that is overcoated with a thin film of high refractive index TiO2 and is produced in a semiconductor foundry for low cost, uniform, and reproducible manufacturing. The compact detection instrument that completes this platform was designed to efficiently couple fluorescence excitation from a semiconductor laser to the resonant optical modes of the PC, resulting in elevated electric field strength that is highly concentrated within the region <100 nm from the PC surface. This instrument utilizes a cylindrically focused line to scan a microarray in <1 min. To demonstrate the capabilities of this sensor-detector platform, microspot fluorescent sandwich immunoassays using secondary antibodies labeled with Cy5 for two cancer biomarkers (TNF-α and IL-3) were performed. Biomarkers were detected at concentrations as low as 0.1 pM. In a fluorescent microarray for detection of a breast cancer miRNA biomarker miR-21, the miRNA was detectable at a concentration of 0.6 pM. © The Royal Society of Chemistry 2013. Source

Jang J.-W.,Pukyong National University | Collins J.M.,NanoInk Inc. | Nettikadan S.,NanoInk Inc.
Advanced Functional Materials | Year: 2013

A new method for subcellular-sized protein patterning on a SiOx substrate is demonstrated by dip-pen nanolithography printed aldehyde-terminated alkylsilane template. The aldehyde-silane template is stable and durable; for example, subcellular scaled IgG protein array can be obtained using one-year old aldehyde-silane template. Moreover, single cell patterning is successfully carried out by extracellular material (ECM) protein microarray and nanoarray fabricated on an aldehyde-silane template. With more than half of chance, single- or double-cells are successfully attached on fibronectin protein nanoarrays in 21 × 21 μm 2 (7 × 7 dot array) and 42 × 42 μm2 (14 × 14 dot array). The fibronectin nanoarray with small area (21 × 21 μm2) shows the more rate of single cell attachment. Therefore, it is also demonstrated that cell patterning can be controlled by adjusting the nanostructure of ECM materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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