Based on their interesting properties, metal nanoparticles show the potential as an analytical tool in electronic (Burmeister et al. 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 et al. 2007), and laser technology (Csaki et al. 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 250 nm. 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.
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Funding of research project “Jenaer Biochip Initiative” (JBCI) within the framework “Unternehmen Region—Inno Profile” from the Federal Ministry of Education and Research, Germany (BMBF) is gratefully acknowledged. This work was supported by the DFG (FR 1348/5-2). We thank Nanoprobes for the kind support with EnzMet enhancement kit, Richard Powell, Vishwas Joshi, Wenqiu Liu, and James Hainfeld for helpful discussions, James Vesenka for the help with AFM measurements, and Daniell Malsch for the discussions about volume measurement as well as Franka Jahn for SEM imaging. Development of the enzyme metallographic reagent was supported by Small Business Innovation Research Grant 5R44 GM064257-03 from the National Institute of General Medical Sciences (NIH), USA.
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