The interaction of DNA with metal nanoparticles is of interest due to the application of nanoparticles as labels in biomolecular diagnostics and for the construction of nanoelectronic devices by molecular nanotechnology. The experimental arrangement was based on static micro mixers made lithographically by Si/glass technology. Four educt components were used in the experiments: (1) HAuCl4-solution, (2) ascorbic acid solution, (3) buffer and (4) DNA solution. The colloidal product solutions were characterized by spectrophotometry, differential centrifugal sedimentation (DCS) and SEM. The rate of nanoparticle formation as well as the optical properties of the product solution and the size and aggregation tendency were influenced by the conditions in the micro flow-through process. The addition of DNA leads always to a decrease in the reaction rate. Simultaneously, smaller particles became stabilized by DNA and aggregation was partially suppressed by the biomolecular effector. The effect was reflected by the optical properties as well as by the centrifuge data and SEM images. In the absence of DNA and at higher concentrations of DNA some larger aggregates of nanoparticles were found beside single nanoparticles. Particular types of aggregates appeared at a low concentration of DNA (0.046 μg/μl). At these conditions, network like structures were observed, whereas more compact aggregate structures arose at higher DNA contents. DNA affects the formation of gold nanoparticles during the reaction in a micro flow-through system assemblies.

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