DNA-Controlled Spatiotemporal Patterning of a Cytoskeletal Active Gel.

Living cells move and change their shape because signaling chemical reactions modify the state of their cytoskeleton, an active gel that converts chemical energy into mechanical forces. To create life-like materials, it is thus key to engineer chemical pathways that drive active gels. Here we describe the preparation of DNA-responsive surfaces that control the activity of a cytoskeletal active gel composed of microtubules: A DNA signal triggers the release of molecular motors from the surface into the gel bulk, generating forces that structure the gel. Depending on the DNA sequence and concentration, the gel forms a periodic band pattern or contracts globally. Finally, we show that the structuration of the active gel can be spatially controlled in the presence of a gradient of DNA concentration. We anticipate that such DNA-controlled active matter will contribute to the development of life-like materials with self-shaping properties.

DNA-inspired oligomers: from oligophosphates to functional materials.

To exert its role of a functional polymer, DNA relies on a molecular self-assembly process that is driven by the interactions of only four units placed in a defined order. Extending the structural diversity of recognition motifs in DNA, to and beyond analogues of the nucleobases, will open doors to self-assembled materials with advanced programmable properties. DNA-inspired systems are becoming useful for numerous applications unachievable by the nucleic acids in their native composition. Potential applications of rationally designed oligo- and polyphosphodiesters reside in the areas of drug delivery, diagnostic signalling and imaging, in systems for efficient energy transfer or the precise ordering on the nanoscale. The field of DNA-inspired phosphodiesters highlights the general value and utility of precision in the composition of oligomers and polymers. In this tutorial review, we will summarize the approaches of directing the self-assembly of DNA-inspired, sequence-specific polyphosphodiesters into soft materials with unique properties. These data expose the so far underexploited potential of DNA-derived systems in solving some of the key issues in various technological areas, such as advanced biomaterials, morphologically defined soft matter or the controlled polymer folding and assembly. Moreover, precise positioning of structurally diverse molecules within a polymer chain creates unmatched opportunities for encoding information on the molecular level and transmitting it further to the microscopic and even macroscopic level via noncovalent interactions.

Pathway Diversity in the Self-Assembly of DNA-Derived Bioconjugates.

The pathway diversity of the self-assembly of amphiphilic DNA-pyrene conjugates is described. The hydrophobic pyrene units drive the self-assembly of the anionic oligomers in an aqueous environment into ribbon-shaped, DNA-grafted supramolecular polymers. Isothermal mixing of two types of sorted ribbons, each of which contains only one of two kinds of complementary oligonucleotides, results in the formation of tight networks. Thermal disassembly of these kinetically trapped networks and subsequent reassembly of the liberated components leads to mixed supramolecular polymers, which now contain both types of oligonucleotides. The scrambling of the oligonucleotides prevents the interaction between ribbons and, thus, network formation. The results show that a high local density of DNA strands in linear arrays favors hybridization among sorted polymers, whereas hybridization among mixed arrays is prevented. The lack of DNA hybridization among mixed ribbons is ascribed to the electrostatic repulsion between identical, hence noncomplementary, oligonucleotides. The findings highlight the importance of kinetically trapped states on the structural and functional properties of supramolecular polymers containing orthogonal self-assembly motifs.

From ribbons to networks: hierarchical organization of DNA-grafted supramolecular polymers.

DNA-grafted supramolecular polymers (SPs) allow the programmed organization of DNA in a highly regular, one-dimensional array. Oligonucleotides are arranged along the edges of pyrene-based helical polymers. Addition of complementary oligonucleotides triggers the assembly of individual nanoribbons resulting in the development of extended supramolecular networks. Network formation is enabled by cooperative coaxial stacking interactions of terminal GC base pairs. The process is accompanied by structural changes in the pyrene polymer core that can be followed spectroscopically. Network formation is reversible, and disassembly into individual ribbons is realized either via thermal denaturation or by addition of a DNA separator strand.

DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers.

The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5'-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.

Activating charge-transfer state formation in strongly-coupled dimers using DNA scaffolds.

Strongly-coupled multichromophoric assemblies orchestrate the absorption, transport, and conversion of photonic energy in natural and synthetic systems. Programming these functionalities involves the production of materials in which chromophore placement is precisely controlled. DNA nanomaterials have emerged as a programmable scaffold that introduces the control necessary to select desired excitonic properties. While the ability to control photophysical processes, such as energy transport, has been established, similar control over photochemical processes, such as interchromophore charge transfer, has not been demonstrated in DNA. In particular, charge transfer requires the presence of close-range interchromophoric interactions, which have a particularly steep distance dependence, but are required for eventual energy conversion. Here, we report a DNA-chromophore platform in which long-range excitonic couplings and short-range charge-transfer couplings can be tailored. Using combinatorial screening, we discovered chromophore geometries that enhance or suppress photochemistry. We combined spectroscopic and computational results to establish the presence of symmetry-breaking charge transfer in DNA-scaffolded squaraines, which had not been previously achieved in these chromophores. Our results demonstrate that the geometric control introduced through the DNA can access otherwise inaccessible processes and program the evolution of excitonic states of molecular chromophores, opening up opportunities for designer photoactive materials for light harvesting and computation.

Functional DNA-grafted supramolecular polymers - chirality, cargo binding and hierarchical organization.

The synthesis, characterization and functionalization of DNA-grafted supramolecular polymers are described. Cargo loading of the helical supramolecular assemblies with gold nanoparticles is demonstrated.

Silica Mineralization of DNA-Inspired 1D and 2D Supramolecular Polymers.

The preparation of hybrid materials from supramolecular polymers through the sol-gel process is presented. Supramolecular polymers are assembled from phosphodiester-linked pyrene oligomers and act as water-soluble one- or two-dimensional templates for silicification. The fibrillary and planar morphologies of the assemblies, as well as the excitonic interactions between the chromophores, remain unaffected by the silicification process.