We report the characterization of gold nanoparticles modified with thiol-terminated single stranded DNA using analytical ultracentrifugation and dynamic light scattering. Sedimentation coefficients of nominally 10 and 20 nm diameter gold nanoparticles modified with thiol-terminated thymidine homo-oligonucleotides, 5 to 30 bases in length, were determined with analytical ultracentrifugation. The sedimentation coefficients of the gold nanoparticles were found to decrease with increasing coverage of DNA and increasing number of thymidine nucleotides (dT). It was found that sedimentation coefficients for DNA modified gold particles were most closely predicted when the strands were modeled as fully extended chains (FEC). Calculation of apparent particle density from the measured sedimentation coefficient revealed that as the bare particle size decreased a significant hydration layer greatly begins to reduce the apparent density of bare and short DNA chain modified gold particles.
Pub Type: Journals
gold nanoparticles, ssDNA modified, analytical ultracentrifugation, hydration effects.