ResearchArticle Gel Electrophoresis of Gold-DNA Nanoconjugates

Correspondence should be addressed to W. J. Parak, Wolfgang.parak@physik.uni-marburg.deReceived 20 July 2007; Accepted 13 December 2007Recommended by Marek OsinskiGold-DNA conjugates were investigated in detail by a comprehensive gel electrophoresis study based on 1200 gels. A controllednumber of single-stranded DNA of different length was attached specifically via thiol-Au bonds to phosphine-stabilized colloidalgold nanoparticles. Alternatively, the surface of the gold particles was saturated with single stranded DNA of different length eitherspecifically via thiol-Au bonds or by nonspecific adsorption. From the experimentally determined electrophoretic mobilities, esti-mates for the effective diameters of the gold-DNA conjugates were derived by applying two different data treatment approaches.The first method is based on making a calibration curve for the relation between effective diameters and mobilities with goldnanoparticles of known diameter. The second method is based on Ferguson analysis which uses gold nanoparticles of known di-ameter as reference database. Our study shows that effective diameters derived from gel electrophoresis measurements are affectedwith a high error bar as the determined values strongly depend on the method of evaluation, though relative changes in size uponbinding of molecules can be detected with high precision. Furthermore, in this study, the specific attachment of DNA via gold-thiolbonds to Au nanoparticles is compared to nonspecific adsorption of DNA. Also, the maximum number of DNA molecules thatcan be bound per particle was determined.Copyright © 2007 T. Pellegrino et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.