Molecular communication relays for dynamic cross-regulation of self-sorting fibrillar self-assemblies.

Structures in living systems cross-regulate via exchange of molecular information to assemble or disassemble on demand and in a coordinated, signal-triggered fashion. DNA strand displacement (DSD) reaction networks allow rational design of signaling and feedback loops, but combining DSD with structural nanotechnology to achieve self-reconfiguring hierarchical system states is still in its infancy. We introduce modular DSD networks with increasing amounts of regulatory functions, such as negative feedback, signal amplification, and signal thresholding, to cross-regulate the transient polymerization/depolymerization of two self-sorting DNA origami nanofibrils and nanotubes. This is achieved by concatenation of the DSD network with molecular information relays embedded on the origami tips. The two origamis exchange information and display programmable transient states observable by TEM and fluorescence spectroscopy. The programmability on the DSD and the origami level is a viable starting point toward more complex lifelike behavior of colloidal multicomponent systems featuring advanced signal processing functions.

Inside a Shell-Organometallic Catalysis Inside Encapsulin Nanoreactors.

Compartmentalization of chemical reactions inside cells are a fundamental requirement for life. Encapsulins are self-assembling protein-based nanocompartments from the prokaryotic repertoire that present a highly attractive platform for intracellular compartmentalization of chemical reactions by design. Using single-molecule Förster resonance energy transfer and 3D-MINFLUX analysis, we analyze fluorescently labeled encapsulins on a single-molecule basis. Furthermore, by equipping these capsules with a synthetic ruthenium catalyst via covalent attachment to a non-native host protein, we are able to perform in vitro catalysis and go on to show that engineered encapsulins can be used as hosts for transition metal catalysis inside living cells in confined space.

Switchable supracolloidal 3D DNA origami nanotubes mediated through fuel/antifuel reactions.

3D DNA origami provide access to the de novo design of monodisperse and functional bio(organic) nanoparticles, and complement structural protein engineering and inorganic and organic nanoparticle synthesis approaches for the design of self-assembling colloidal systems. We show small 3D DNA origami nanoparticles, which polymerize and depolymerize reversibly to nanotubes of micrometer lengths by applying fuel/antifuel switches. 3D DNA nanocylinders are engineered as a basic building block with different numbers of overhang strands at the open sides to allow for their assembly via fuel strands that bridge both overhangs, resulting in the supracolloidal polymerization. The influence of the multivalent interaction patterns and the length of the bridging fuel strand on efficient polymerization and nanotube length distribution is investigated. The polymerized multivalent nanotubes disassemble through toehold-mediated rehybridization by adding equimolar amounts of antifuel strands. Finally, Förster resonance energy transfer yields in situ insights into the kinetics and reversibility of the nanotube polymerization and depolymerization.

Hierarchical cross-linking for synergetic toughening in crustacean-mimetic nanocomposites.

The twisted plywood structure as found in crustacean shells possesses excellent mechanical properties with high stiffness and toughness. Synthetic mimics can be produced by evaporation-induced self-assembly of cellulose nanocrystals (CNCs) with polymer components into bulk films with a cholesteric liquid crystal structure. However, these are often excessively brittle and it has remained challenging to make materials combining high stiffness and toughness. Here, we describe self-assembling cholesteric CNC/polymer nanocomposites with a crustacean-mimetic structure and tunable photonic band gap, in which we engineer combinations of thermo-activated covalent and supramolecular hydrogen-bonded crosslinks to tailor the energy dissipation properties by precise molecular design. Toughening occurs upon increasing the polymer fractions in the nanocomposites, and, critically, combinations of both molecular bonding mechanisms lead to a considerable synergetic increase of stiffness and toughness - beyond the common rule of mixtures. Our concept following careful molecular design allows one to enter previously unreached areas of mechanical property charts for cholesteric CNC-based nanocomposites. The study shows that the subtle engineering of molecular energy dissipation units using sophisticated chemical approaches enables efficient enhancing of the properties of bioinspired CNC/polymer nanocomposites, and opens the design space for future molecular enhancement using tailor-made interactions.

Vitrimer Chemistry Meets Cellulose Nanofibrils: Bioinspired Nanopapers with High Water Resistance and Strong Adhesion.

Nanopapers containing cellulose nanofibrils (CNFs) are an emerging and sustainable class of high performance materials. The diversification and improvement of the mechanical and functional property space critically depend on integration of CNFs with rationally designed, tailor-made polymers following bioinspired nanocomposite designs. Here we combine for the first time CNFs with colloidal dispersions of vitrimer nanoparticles (VP) into mechanically coherent nanopaper materials. Vitrimers are permanently cross-linked polymer networks that undergo temperature-induced bond shuffling through an associative mechanism and which allow welding and reshaping on the macroscale. The choice of low glass transition, hydrophobic vitrimers derived from fatty acids and polydimethylsiloxane (PDMS), and achieving dynamic reshuffling of cross-links through transesterification reactions enables excellent compatibility and covalent attachment onto the CNF surfaces. Moreover, the resulting films are ductile, stretchable and offer high water resistance. The success of imparting the vitrimeric polymeric behavior into the nanocomposite, as well as the curing mechanism of the vitrimer, is highlighted through thorough analysis of structural and mechanical properties. The dynamic exchange chemistry of the vitrimers enables efficient welding of two nanocomposite parts as characterized by good bonding strength during single lap shear tests. In the future, we expect that the dynamic character of vitrimers becomes a promising option for the design of mechanically adaptive bioinspired nanocomposites and for shaping and reshaping such materials.

3D DNA Origami Nanoparticles: From Basic Design Principles to Emerging Applications in Soft Matter and (Bio-)Nanosciences.

Scaffold-based lattice-engineered 3D DNA origami is a powerful and versatile technique for the rational design and build-up of arbitrarily structured and monodisperse DNA-based 3D nanoobjects. Relying on the unsurpassed molecular programmability of sequence-specific DNA hybridization, a long DNA single strand (termed scaffold) is assembled with many short single-stranded oligomers (termed staples), which organize the scaffold into a 3D lattice in a single step, thereby leading to 3D nanoparticulate structures of the highest precision in high yields. Applications of 3D DNA origami are increasingly wide-spread and interface with numerous fields of sciences, for example, anisometric or anisotropically functionalized nanoparticles, fundamental investigations of superstructure formation, biomedicine, (bio)physics, sensors, and optical materials. This Minireview discusses the fundamentals and recent advances from structure formation to selected applications, with a mission to promote cross-disciplinary exchange.