Enzymatic control of metal deposition as key step for a low-background electrical detection for DNA chips
ABSTRACT Electrical detection of DNA using nanoparticle labels in combination with metal enhancement represents an interesting alternative to fluorescence readout schemes. This electrical method is hampered by unspecific metal deposition, resulting in a lower sensitivity of the assay. A novel enhancement technique based on an enzymatic process is introduced. This approach enables highly specific metal deposition only at the enzyme label, without the background that is typical in the case of the conventional metal enhancement process of growing nanoparticles. The enzymatic enhancement leads to a significant increase in sensitivity, and the detection of single base mismatches demonstrates the high specificity of the novel enhancement approach.
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ABSTRACT: Based on their interesting properties, metal nanoparticles show the potential as an analytical tool in electronic (Burmeister etal. 2004), optical (Yguerabide and Yguerabide 1998), and catalytic applications (Liu 2006). Their characteristics depend on the composition, shape, and size of the single particles. These various properties are utilized in many different approaches such as optics, magnetics (Lang etal. 2007), and laser technology (Csaki etal. 2007). We investigated an alternative method for the synthesis of nanoparticles. In this case, an enzyme, horseradish peroxidase, induces a silver deposition and replaces a metal nanoparticle as the reaction seed. Depending on the reaction time, we could obtain particles in a range of few nanometers up to more than 250nm. For a better understanding of the enzymatic silver deposition process, the silver particles produced by this process were analyzed by SEM, TEM, and atomic force microscopy (AFM) on a single particle level after different enhancement times. The AFM images were utilized for the characterization of particle height and volume to study the enzyme kinetics, i.e., the particle growth process. Thereby, two different phases are described: a first growth phase probably induced by the enzyme-related growth, and a second, more unspecific growth based on the metal deposition onto the silver deposits. These findings may help to use the enzyme-induced silver deposition in a quantitative manner for bioanalytical applications.Journal of Nanoparticle Research 01/2009; 11(4):939-946. DOI:10.1007/s11051-008-9496-7 · 2.28 Impact Factor
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ABSTRACT: We have developed a technique for the high-resolution, self-aligning, and high-throughput patterning of antibody binding functionality on surfaces by selectively changing the reactivity of protein-coated surfaces in specific regions of a workpiece with a beam of energetic helium particles. The exposed areas are passivated with bovine serum albumin (BSA) and no longer bind the antigen. We demonstrate that patterns can be formed (1) by using a stencil mask with etched openings that forms a patterned exposure, or (2) by using angled exposure to cast shadows of existing raised microstructures on the surface to form self-aligned patterns. We demonstrate the efficacy of this process through the patterning of anti-lysozyme, anti-Norwalk virus, and anti-Escherichia coli antibodies and the subsequent detection of each of their targets by the enzyme-mediated formation of colored or silver deposits, and also by binding of gold nanoparticles. The process allows for the patterning of three-dimensional structures by inclining the sample relative to the beam so that the shadowed regions remain unaltered. We demonstrate that the resolution of the patterning process is of the order of hundreds of nanometers, and that the approach is well-suited for high throughput patterning.Biointerphases 12/2013; 8(1). DOI:10.1186/1559-4106-8-9 · 2.68 Impact Factor
Article: DNA-TEMPLATED NANOMATERIALS