The DNA is one of the most important polymers in live- carrying the genetic information of any living system. For diseases like cancer and blood disorders gene therapy is one of the most promising methods for cure or relieve of symptoms. One important step in gene therapy is to compact DNA molecules enabling the entering into cells. Inspired by histones in nature, an increasing number of synthetic agents for compaction are investigated, such as multivalent ions, alcohols, cationic and non-ionic surfactants, lipids, polyelectrolytes and neutral polymers. Decompaction is usually achieved by an internal change in pH or salt concentration. A novel, promising route has recently been taken with azo-benzene containing surfactant [1]. It can be switched between a hydrophobic trans (visible light) and a hydrophilic cis (UV light) state, leading to completely reversible DNA compaction and decompaction. Further investigations [2,3,4,5] showed that the optical triggering works for a series of different azo-containing systems, although the problem of the toxicity of the corresponding compounds remains [6]. Here we take a step towards biocompatibility and reduce the toxicity of the system, by attaching a poly(amido)amine backbone to the azo-benzene switch. We show, by using dynamic light scattering of DNA in solution and AFM analysis of single DNA coils on mica, that within a defined region of surfactant concentration light-induced compaction/decompaction can be achieved. We further use molecular dynamics simulations to study the surfactant-DNA interaction at the atomistic level. Our results indicate that the azo-poly(amido)amine molecule functions quite differently from common monovalent cationic surfactants. We discuss the implications of our finding with respect to optimizing the compaction/decompaction protocol. References: [1] A.L.M. Le Ny, JACS 2006, 128, 6400. [2] M. Sollogoub, ChemBioChem 2008, 9, 1201. [3] A.L.M. Le Ny, Biophys. Chem. 2009, 142, 76. [4] Y. Zakrevskyy, Phys.Rev.E 2011, 84, 021909. [5] Y. Zakrevskyy, J. Chem. Phys. 2014, 140, 044907. [6] Y. Zakrevskyy, J. Chem. Phys. 2014, 140, 044906.

Optically controlled shape of soft nano-objects

251st National Meeting (2016)

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