InterNano Nanomanufacturing Repository
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Homogeneous immunoassays based on fluorescence emission intensity variations of zinc selenide quantum dot sensors
No full textThe fluorescence emission intensity of ZnSe quantum dots (QDs) conjugated to proteins to form QD-based biomolecular sensors increases significantly upon binding of the sensors to target proteins in solution. This phenomenon enables the development of homogeneous, separation-free immunoassays for rapid quantitative detection of proteins in solution. Proof-of-principle assays were developed by dosing a solution containing a biomolecular target with a solution containing the corresponding QD-based sensor and monitoring the changes in the peak fluorescence emission intensity of the QDs. Direct immunoassays for detecting basic fibroblast growth factor (bFGF) and prostate-specific antigen (PSA) in solution were demonstrated using QD-anti-bFGF and QD-anti-PSA sensors. A competitive immunoassay for detecting human serum albumin (HSA) was also demonstrated by dosing samples containing HSA with QD-HSA sensors and free anti-HSA antibodies. The QD-HSA sensors were tested in 1000 x diluted human serum and found to be unaffected by interference from other proteins. The lower limit of detection of the assays was equal to the lowest sensor concentration in the solution that can be unambiguously detected, typically less than 1 nM. The dynamic range of the assays was determined by identifying the sensor concentration above which optical interference between QDs affected adversely the observed fluorescence emission intensity. The upper limit of this concentration was 2.5 mu M for 4 nm QDs. The ZnSe QD-based sensors were stable and preserved similar to 80% of their initial peak emission intensity after two months in refrigerated storage. These biosensors have potential applications in rapid sensing of target proteins for emergency and point-of-care diagnostic applications. (C) 2012 Elsevier B.V. All rights reserved
Electrostatic Control of Peptide Side-Chain Reactivity Using Amphiphilic Homopolymer-Based Supramolecular Assemblies
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Synthesis of nanogel-protein conjugates
No full textThe covalent conjugation of bovine serum albumin (BSA) to disulfide cross-linked polymeric nanogels is reported. Polymeric nanogel precursors were synthesized via a reversible addition-fragmentation chain transfer (RAFT) random copolymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and pyridyl disulfide methacrylate (PDSMA). Reaction of the p(PEGMA-co-PDSMA) with dithiothreitol resulted in the formation of nanogels. PDSMA serves as both a crosslinking agent and a reactive handle for the surface modification of the nanogels. Lipophilic dye, DiI, was sequestered within the nanogels by performing the crosslinking reaction in the presence of the hydrophobic molecule. Thiol-enriched BSA was conjugated to nanogels loaded with DiI via a thiol-disulfide exchange reaction between the BSA and the surface exposed nanogel pyridyl disulfides. Conjugation was confirmed by fast protein liquid chromatography, dynamic light scattering, and agarose and polyacrylamide gel electrophoresis. We expect that this methodology is generally applicable to the preparation of nanogel-protein therapeutics
Nanomanufacturing Accelerates Body-Worn Electronic Monitoring Systems
No full textAs we continue to promote the economic and societal benefits of nanotechnology, advanced nanomanufacturing techniques are paving the road towards more integrated systems with increased functionality, scaled production platforms, and lower cost that will impact a broad range of industries. Nanomanufacturing has arguably had the largest impact in the area of flexible electronics and systems, affecting a range of product applications including displays, photovoltaics, lighting, energy storage, and printed electronics circuits. Perhaps the area of highest impact could be that in the area of devices interacting with the human body to extract specific biometrics for various purposes such as point-of-care health diagnostics, therapeutic treatment, or general activity monitoring. While these concepts have been around for decades, the key factors of technology push and market pull are now beginning to align in a manner that will accelerate and sustain the translational R&D necessary for these applications to grow. From a market pull perspective, the increasing cost of hospital and medical care combined with the growth of an aging population will necessitate in-home monitoring and out-patient care. Nanotechnology will most certainly provide the market push to meet these challenges
Recognition of glycosaminoglycan chemical patterns using an unbiased sensor array
No full textA sensor array composed of eight functionalized gold nanoparticles and a fluorescent polymer was utilized to identify 11 glycosaminoglycans (GAGs) by their chemical signatures. Particle ligand structure was key in differentiating analytes, with aromatic and specific sugar functionalities recognizing GAG structural parameters including sulfonation, acetylation, epimeric structure, size, and charge
Inactivation of Listeria monocytogenes on a polyethylene surface modified by layer-by-layer deposition of the antimicrobial N-halamine
No full textModification of food contact surfaces to be antimicrobial represents an approach to address the problem of cross-contamination in the food industry. The effect of increasing levels of surface modification on low density polyethylene (LDPE) through application of N-halamines on the inactivation kinetics of Listeria monocytogenes Scott A was evaluated. Increasing levels of modification were applied through layer by layer deposition on LDPE surface (1-5 double layers of polyethyleneimine and poly(acrylic acid)). Surface modification was achieved and confirmed through Fourier Transform Infrared Spectroscopy (FTIR). From I to 5 double layers, the N-halamine content ranged from 3.42 +/- 1.2 to 27.30 +/- 3.5 nmol cm(-2). More than four logarithmic cycles (>99.99%) reduction was reached against L. monocytogenes Scott A after different contact times depending on the level of modification, that varied from 50 to 110 min (from 5 to 2 double layers). Inactivation kinetics followed a sigmoidal behavior. (c) 2013 Elsevier Ltd. All rights reserved