[Zurück]

C. Jochum, N. Adzić, G. Kahl, C. N. Likos:
"Investigating DNA-based dendrimers: theory and experiment";
Vortrag: 5th International Soft Matter Conference (ISMC2019), Edinburgh; 03.06.2019 - 07.06.2019; in: "Conference Booklet of the 5th International Soft Matter Conference (ISMC2019)", (2019), S. 25.

Dendrimers are synthetic macromolecules possessing a highly branched and regular internal structure. Recently, Luo and his co-workers at Cornell University synthesized dendrimer-like DNA (DL-DNA) via enzymatic ligation of Y-shaped DNA building blocks [1]. These charged DNA-based dendrimers are novel macromolecule aggregates, which hold high promise in bringing about targeted self-assembly of soft-matter systems in the bulk and at interfaces. Being charged, these dendrimers are -- in contrast to their neutral counterparts -- conformationally responsive.

Inspired by these findings, we present a joint theoretical-experimental study of this novel class of macromolecules. We employ a bead-spring model in order to describe such dendrimers of varying generation numbers and performed Molecular Dynamics simulations (MD) to determine equilibrium properties and conformational characteristics of all-DNA dendrimers. The obtained results are compared to static (SLS) and dynamic light scattering experiments (DLS) [2]. While the results from MD simulations show favorable agreement with the experimental results, e.g., with SLS data for the radius of gyration, $R_\mathrm{g}$, and with DLS data for the hydrodynamic radius, $R_\mathrm{H}$, they also provide a host of additional information and insight into the molecular structure of DL-DNA at the same time. For instance, our computational results show that DL-DNA molecules are rigid objects with low internal bead concentration and a high percentage of absorbed counterions. We also examine the salt-responsiveness of these macromolecules, finding that despite the strong screening of electrostatic interactions brought about by the added salt, the macromolecules shrink only slightly, their size robustness stemming from the high bending rigidity of the DNA-segments.

In order to simulate large ensembles of DL-DNA, we calculate a coarse-grained potential for the dendrimers within the framework of the introduced model. This is achieved by employing an approach based on the Widom particle-insertion method as well as the umbrella sampling method [3]. With this coarse-grained potential at hand, we investigate the bulk behaviour of DL-DNA systems. These findings are essential to determine if DL-DNA is a viable candidate for the experimental realization of cluster crystals in the bulk, a novel form of solid with multiple site occupancy [4].

The study of these charged dendrimer systems is an important field of research in the area of soft matter due to their potential role for various interdisciplinary applications, ranging from molecular cages and carriers for drug delivery in a living organism to the development of dendrimer- and dendron-based ultra-thin films in the area of nanotechnology [5-6].

Acknowledgements: Supported by FWF (I 2866-N36) and DFG (STI 664/3-1).

[1] Y. Li, Y. Tseng and D. Luo, Nat. Mater., 2004, 3, 38-42.
[2] C. Jochum, N. Adzić, E. Stiakakis, T. L. Derrien, D. Luo, G. Kahl, and C. N. Likos, Nanoscale, 2019, 11, 1604-1617.
[3] B. Mladek and D. Frenkel, Soft Matter, 2011, 7, 1450-1455.
[4] B. Mladek, M. Neumann, G. Kahl, and C. N. Likos, Phys. Rev. Lett., 2006, 96, 045701.
[5] C. Lee, J. MacKay, J. Fréchet, and F. Szoka, Nat. Biotechnol., 2005, 23, 1517-1526.
[6] D. Tully and J. Fréchet, Chem. Commun., 2001, 14, 1229-1239.

https://publik.tuwien.ac.at/files/publik_280019.pdf