The nanotechnology of life-inspired systems

Shape-encoded dynamic assembly of mobile micromachines

Field-directed and self-propelled colloidal assembly have been used to build micromachines capable of performing complex motions and functions. However, integrating heterogeneous components into micromachines with specified structure, dynamics and function is still challenging. Here, we describe the dynamic self-assembly of mobile micromachines with desired configurations through pre-programmed physical interactions between structural and motor units. The assembly is driven by dielectrophoretic interactions, encoded in the three-dimensional shape of the individual parts. Micromachines assembled from magnetic and self-propelled motor parts exhibit reconfigurable locomotion modes and additional rotational degrees of freedom that are not available to conventional monolithic microrobots. The versatility of this site-selective assembly strategy is demonstrated on different reconfigurable, hierarchical and three-dimensional micromachine assemblies. Our results demonstrate how shape-encoded assembly pathways enable programmable, reconfigurable mobile micromachines. We anticipate that the presented design principle will advance and inspire the development of more sophisticated, modular micromachines and their integration into multiscale hierarchical systems.

Synthetic asters as elastic and radial skeletons

The radial geometry with rays radiated from a common core occurs ubiquitously in nature for its symmetry and functions. Herein, we report a class of synthetic asters with well-defined core-ray geometry that can function as elastic and radial skeletons to harbor nano- and microparticles. We fabricate the asters in a single, facile, and high-yield step that can be readily scaled up; specifically, amphiphilic gemini molecules self-assemble in water into asters with an amorphous core and divergently growing, twisted crystalline ribbons. The asters can spontaneously position microparticles in the cores, along the radial ribbons, or by the outer rims depending on particle sizes and surface chemistry. Their mechanical properties are determined on single- and multiple-aster levels. We further maneuver the synthetic asters as building blocks to form higher-order structures in virtue of aster-aster adhesion induced by ribbon intertwining. We envision the astral structures to act as rudimentary spatial organizers in nanoscience for coordinated multicomponent systems, possibly leading to emergent, synergistic functions.

Nanosystems capable of organisation and the formation of structures are of interest in nanotechnology. Here, the authors report on synthetic asters made of gemini surfactant which are able to position microparticles based on size and chemical composition which can also be organised into higher order structures.

Single molecule analysis of structural fluctuations in DNA nanostructures

DNA origami is an excellent tool for building complex artificial nanostructures. Functionalization of these structures provides the possibility of precise organization of matter at the nanoscale. In practice, efforts in this endeavour can be impeded by electrostatic repulsion or other dynamics at the molecular scale, resulting in uncompliant local structures. Using single molecule FRET microscopy combined with coarse-grained Brownian dynamics simulations, we investigated here the local structure around the lid of a DNA origami box, which can be opened by specific DNA keys. We found that FRET signals for the closed box depend on buffer ion concentrations and small changes to the DNA structure design. Simulations provided a view of the global and local structure and showed that the distance between the box wall and lid undergoes fluctuations. These results provide methods to vizualise and improve the local structure of three-dimensional DNA origami assemblies and offer guidance for exercising control over placement of chemical groups and ligands.

Sequence Programming with Dynamic Boronic Acid/Catechol Binary Codes

The development of a synthetic code that enables a sequence programmable feature like DNA represents a key aspect toward intelligent molecular systems. We developed herein the well-known dynamic covalent interaction between boronic acids (BAs) and catechols (CAs) into synthetic nucleobase analogs. Along a defined peptide backbone, BA or CA residues are arranged to enable sequence recognition to their complementary strand. Dynamic strand displacement and errors were elucidated thermodynamically to show that sequences are able to specifically select their partners. Unlike DNA, the pH dependency of BA/CA binding enables the dehybridization of complementary strands at pH 5.0. In addition, we demonstrate the sequence recognition at the macromolecular level by conjugating the cytochrome c protein to a complementary polyethylene glycol chain in a site-directed fashion.

Spatial Organization in Proteinaceous Membrane-Stabilized Coacervate Protocells

As a model protocell, the membrane-free coacervate microdroplet is widely utilized in functional studies to provide insights into the physicochemical properties of the cell and to engineer cytomimetic soft technologies; however, the lack of a discrete membrane contributes to its instability and limits further application. Herein, a strategy is developed to fabricate a hybrid protocell based on the self-assembly of a proteinaceous membrane at the surface of coacervate microdroplets driven by a combination of electrostatic adhesion and steric/hydrophilic surface buoyancy. The semipermeable proteinaceous membrane can enhance coacervate stability obviously without compromising sequestration behavior. Significantly, such hybrid protocells demonstrate spatial organization whereby various functional enzymes can be located in discrete regions, which facilitates an on/off modulation for a cascade enzymatic reaction along with enhanced chemical communication between subpopulations.

Fatty acid based transient nanostructures for temporal regulation of artificial peroxidase activity

Natural systems access transient high energy self-assembled structures for temporal regulation of different biological functions through dissipative processes. Compartmentalization within self-assembled structures is used by living systems to organize vital biochemical reactions that define cellular metabolism. Herein, we demonstrate a simple fatty acid based system where a redox active base (dimethylaminomethyl ferrocene, Fc-NMe2 ) acts as a countercation to access unique hexagonal compartments resulting in the formation of a self-supporting gel. An oxidizing environment helps in the dissipation of energy by converting Fc-NMe2 to oxidized waste and the gel autonomously undergoes transition to a sol. Hence, the system requires the addition of the fuel Fc-NMe2 to access the temporal gel state. Notably, these transient compartments were able to temporally upregulate and downregulate hemin-catalyzed oxidation reactions mimicking peroxidase, a ubiquitous enzyme in extant biology. An order of magnitude variation in k cat values was observed with time and the chemical reaction persists as long as the gel state was present.

Thermodynamic efficiency in dissipative chemistry

Chemical processes in closed systems inevitably relax to equilibrium. Living systems avoid this fate and give rise to a much richer diversity of phenomena by operating under nonequilibrium conditions. Recent experiments in dissipative self-assembly also demonstrated that by opening reaction vessels and steering certain concentrations, an ocean of opportunities for artificial synthesis and energy storage emerges. To navigate it, thermodynamic notions of energy, work and dissipation must be established for these open chemical systems. Here, we do so by building upon recent theoretical advances in nonequilibrium statistical physics. As a central outcome, we show how to quantify the efficiency of such chemical operations and lay the foundation for performance analysis of any dissipative chemical process.

Phase Separation in Supramolecular Hydrogels Based on Peptide Self-Assembly from Enzyme-Coated Nanoparticles

Spatial localization of biocatalysts, such as enzymes, has recently proven to be an effective process to direct supramolecular self-assemblies in a spatiotemporal way. In this work, silica nanoparticles (NPs) functionalized covalently by alkaline phosphatase (NPs@AP) induce the localized growth of self-assembled peptide nanofibers from NPs by dephosphorylation of Fmoc-FFpY peptides (Fmoc: fluorenylmethyloxycarbonyl; F: phenylalanine; Y: tyrosine; p: phosphate group). The fibrillary nanoarchitecture around NPs@AP underpins a homogeneous hydrogel, which unexpectedly undergoes a macroscopic shape change over time. This macroscopic change is due to a phase separation leading to a dense phase (in NPs and nanofibers) in the center of the vial and surrounded by a dilute one, which still contains NPs and peptide self-assemblies. We thus hypothesize that the phase separation is not a syneresis process. Such a change is only observed when the enzymes are localized on the NPs. The dense phase contracts with time until reaching a constant volume after several days. For a given phosphorylated peptide concentration, the dense phase contracts faster when the NPs@AP concentration is increased. For a given NPs@AP concentration, it condenses faster when the peptide concentration increases. We hypothesize that the appearance of a dense phase is not only due to attractive interactions between NPs@AP but also to the strong interactions of self-assembled peptide nanofibers with the enzymes, covalently fixed on the NPs.

Adenosine Triphosphate Templated Self-Assembly of Cationic Porphyrin into Chiral Double Superhelices and Enzyme-Mediated Disassembly

Self-assembly of small molecules through noncovalent interactions into nanoscale architectures has been extensively studied in supramolecular chemistry. However, it is still challenging to develop a biologically inspired self-assembly system that functions in water with complex structure and dynamics by analogy with those found in nature. Here, we report a new water-soluble cationic porphyrin that undergoes adenosine triphosphate (ATP)-templated self-assembly into right-handed double-helical supramolecular structures. Direct observation of the porphyrin-ATP assembly by transmission electron microscopy has been accomplished. The assemblies consist of superhelical fibers with length greater than 1 μm and width ∼46 nm. The chiral superhelical fibers show reversible disassembly to monomers upon hydrolysis of ATP catalyzed by alkaline phosphatase (ALP), and the nanofibers can be re-formed with subsequent addition of ATP. Moreover, transient self-assembly of a chiral double helix is formed when ALP is present to consume ATP.

Programmable responsive hydrogels inspired by classical conditioning algorithm

Living systems have inspired research on non-biological dynamic materials and systems chemistry to mimic specific complex biological functions. Upon pursuing ever more complex life-inspired non-biological systems, mimicking even the most elementary aspects of learning is a grand challenge. We demonstrate a programmable hydrogel-based model system, whose behaviour is inspired by associative learning, i.e., conditioning, which is among the simplest forms of learning. Algorithmically, associative learning minimally requires responsivity to two different stimuli and a memory element. Herein, nanoparticles form the memory element, where a photoacid-driven pH-change leads to their chain-like assembly with a modified spectral behaviour. On associating selected light irradiation with heating, the gel starts to melt upon the irradiation, originally a neutral stimulus. A logic diagram describes such an evolution of the material response. Coupled chemical reactions drive the system out-of-equilibrium, allowing forgetting and memory recovery. The findings encourage to search non-biological materials towards associative and dynamic properties.

Living systems inspired research on systems chemistry to mimic specific complex biological functions, but mimicking even the most elementary aspects of learning is a grand challenge. Here the authors demonstrate a programmable hydrogel-based model system, whose behaviour is inspired by associative learning.

Dissipative Catalysis with a Molecular Machine

We report on catalysis by a fuel-induced transient state of a synthetic molecular machine. A [2]rotaxane molecular shuttle containing secondary ammonium/amine and thiourea stations is converted between catalytically inactive and active states by pulses of a chemical fuel (trichloroacetic acid), which is itself decomposed by the machine and/or the presence of additional base. The ON-state of the rotaxane catalyzes the reduction of a nitrostyrene by transfer hydrogenation. By varying the amount of fuel added, the lifetime of the rotaxane ON-state can be regulated and temporal control of catalysis achieved. The system can be pulsed with chemical fuel several times in succession, with each pulse activating catalysis for a time period determined by the amount of fuel added. Dissipative catalysis by synthetic molecular machines has implications for the future design of networks that feature communication and signaling between the components.

Coupling pH-Regulated Multilayers with Inorganic Surfaces for Bionic Devices and Infochemistry

This article summarizes more than 10 years of cooperation with Prof. Helmuth Möhwald. Here we describe how the research moved from light-regulated feedback sustainable systems and control biodevices to the current focus on infochemistry in aqueous solution. An important advanced characteristic of such materials and devices is the pH concentration gradient in aqueous solution. A major part of the article focuses on the use of localized illumination for proton generation as a reliable, minimal-reagent-consuming, stable light-promoted proton pump. The in situ scanning vibration electrode technique (SVET) and scanning ion-selective electrode technique (SIET) are efficient for the spatiotemporal evolution of ions on the surface. pH-sensitive polyelectrolyte (PEs) multilayers with different PE architectures are composed with a feedback loop for bionic devices. We show here that pH-regulated PE multilayers can change their properties-film thickness and stiffness, permeability, hydrophilicity, and/or fluorescence-in response to light or electrochemical or biological processes instead of classical acid/base titration.

Programmable dynamic steady states in ATP-driven nonequilibrium DNA systems

Inspired by the dynamics of the dissipative self-assembly of microtubules, chemically fueled synthetic systems with transient lifetimes are emerging for nonequilibrium materials design. However, realizing programmable or even adaptive structural dynamics has proven challenging because it requires synchronization of energy uptake and dissipation events within true steady states, which remains difficult to orthogonally control in supramolecular systems. Here, we demonstrate full synchronization of both events by ATP-fueled activation and dynamization of covalent DNA bonds via an enzymatic reaction network of concurrent ligation and cleavage. Critically, the average bond ratio and the frequency of bond exchange are imprinted into the energy dissipation kinetics of the network and tunable through its constituents. We introduce temporally and structurally programmable dynamics by polymerization of transient, dynamic covalent DNA polymers with adaptive steady-state properties in dependence of ATP fuel and enzyme concentrations. This approach enables generic access to nonequilibrium soft matter systems with adaptive and programmable dynamics.

Use of Photoacids and Photobases To Control Dynamic Self-Assembly of Gold Nanoparticles in Aqueous and Nonaqueous Solutions

Dynamic self-assembly of nanoparticles (NPs) for the formation of aggregates takes place out of thermodynamic equilibrium and is sustained by external energy supply. Herein, we present light energy driven dynamic self-assembly process of AuNPs, decorated with pH sensitive ligands. The process is being controlled by the use of photoacids and photobases that undergo excited state proton or hydroxide transfer, respectively, due to their large p K_a change between their ground and excited electronic states. The unique design is underlined by record subsecond conversion rates between the assembled and disassembled AuNPs states, and the ability to control the process using only light of different wavelengths. Measurements in both aqueous and nonaqueous solutions resulted in different self-assembly mechanisms, hence showing the wide versatility of photoacids and photobases for dynamic processes.

Biocomputing with Nanostructures on Lipid Bilayers

Biocomputation is the algorithmic manipulation of biomolecules. Nanostructures, most notably DNA nanostructures and nanoparticles, become active substrates for biocomputation when modified with stimuli-responsive, programmable biomolecular ligands. This approach-biocomputing with nanostructures ("nano-bio computing")-allows autonomous control of matter and information at the nanoscale; their dynamic assemblies and beneficial properties can be directed without human intervention. Recently, lipid bilayers interfaced with nanostructures have emerged as a new biocomputing platform. This new nano-bio interface, which exploits lipid bilayers as a chemical circuit board for information processing, offers a unique reaction space for realizing nanostructure-based computation at a previously unexplored dimension. In this Concept, recent advances in nano-bio computing are briefly reviewed and the newly emerging concept of biocomputing with nanostructures on lipid bilayers is introduced.

Propagation of Oscillating Chemical Signals through Reaction Networks

Akin to electronic systems that can tune to and process signals of select frequencies, systems/networks of chemical reactions also "propagate" time-varying concentration inputs in a frequency-dependent manner. Whereas signals of low frequencies are transmitted, higher frequency inputs are dampened and converted into steady-concentration outputs. Such behavior is observed in both idealized reaction chains as well as realistic signaling cascades, in the latter case explaining the experimentally observed responses of such cascades to input calcium oscillations. These and other results are supported by numerical simulations within the freely available Kinetix web application we developed to study chemical systems of arbitrary architectures, reaction kinetics, and boundary conditions.

Fuel-Responsive Allosteric DNA-Based Aptamers for the Transient Release of ATP and Cocaine

We show herein that allostery offers a key strategy for the design of out-of-equilibrium systems by engineering allosteric DNA-based nanodevices for the transient loading and release of small organic molecules. To demonstrate the generality of our approach, we used two model DNA-based aptamers that bind ATP and cocaine through a target-induced conformational change. We re-engineered these aptamers so that their affinity towards their specific target is controlled by a DNA sequence acting as an allosteric inhibitor. The use of an enzyme that specifically cleaves the inhibitor only when it is bound to the aptamer generates a transient allosteric control that leads to the release of ATP or cocaine from the aptamers. Our approach confirms that the programmability and predictability of nucleic acids make synthetic DNA/RNA the perfect candidate material to re-engineer synthetic receptors that can undergo chemical fuel-triggered release of small-molecule cargoes and to rationally design non-equilibrium systems.

Colloidal systems chemistry. Replication, reproduction and selection at nanoscale

Development of synthetic systems carrying life-like features is a long-standing challenge in chemistry and material science. Poor understanding of mechanisms ruling the emergence of life-like features in an inanimate matter makes the challenge even more exciting. The growing field of systems chemistry takes the lead in defining life-like dynamic signatures in minimalistic (macro)molecular systems through the development of multicomponent synthetic models using tools from organic and supramolecular chemistry. Recent progress in nanoscience makes available a range of novel materials that can undoubtedly enrich systems chemistry. Therefore, with the aim of placing nano- and colloidal science within the context of systems chemistry, the recent experimental and theoretical developments dealing with the use of nanoparticles and their assemblies in the realisation of the concepts such as replication, reproduction and selection are discussed.

A chemically fuelled self-replicator

The continuous consumption of chemical energy powers biological systems so that they can operate functional supramolecular structures. A goal of modern science is to understand how simple chemical mixtures may transition from non-living components to truly emergent systems and the production of new lifelike materials and machines. In this work a replicator can be maintained out-of-equilibrium by the continuous consumption of chemical energy. The system is driven by the autocatalytic formation of a metastable surfactant whose breakdown products are converted back into building blocks by a chemical fuel. The consumption of fuel allows the high-energy replicators to persist at a steady state, much like a simple metabolic cycle. Thermodynamically-driven reactions effect a unidirectional substrate flux as the system tries to regain equilibrium. The metastable replicator persists at a higher concentration than achieved even transiently in a closed system, and its concentration is responsive to the rate of fuel supply.

Understanding how simple chemical mixtures transition into truly emergent systems is essential to create new lifelike materials. Here, the authors show a self-replicating system that can be maintained out-of-equilibrium by an oxidant fuel in analogy to simple metabolic cycles.

Chemical fuel-driven living and transient supramolecular polymerization

Temporal control over self-assembly process is a desirable trait in the quest towards adaptable and controllable materials. The ability to devise synthetic ways to control the growth, as well as decay of materials has long been a property which only the biological systems could perform seamlessly. A common synthetic strategy which works on the biological principles such as chemical fuel-driven control over temporal self-assembly profile has not been completely realized synthetically. Here we show, we filled this dearth by showing that a chemical fuel driven self-assembling system can not only be grown in a controlled manner, but it can also result in precise control over the assembly and disassembly kinetics. Herein, we elaborate strategies which clearly show that once a chemical fuel driven self-assembly is established it can be made receptive to multiple molecular cues such that the inherent growth and decay characteristics are programmed into the ensemble.

Magnetoliposomes as model for signal transmission

Liposomes containing magnetic nanoparticles (magnetoliposomes) have been extensively explored for targeted drug delivery. However, the magnetic effect of nanoparticles movement is also an attractive choice for the conduction of signals in communication systems at the nanoscale level because of the simple manipulation and efficient control. Here, we propose a model for the transmission of electrical and luminous signals taking advantage of magnetophoresis. The study involved three steps. Firstly, magnetite was synthesized and incorporated into fusogenic large unilamellar vesicles (LUVs) previously associated with a fluorescent label. Secondly, the fluorescent magnetite-containing LUVs delivered their contents to the giant unilamellar vesicles (GUVs), which were corroborated by magnetophoresis and fluorescence microscopy. In the third step, magnetophoresis of magnetic vesicles was used for the conduction of the luminous signal from a capillary to an optical fibre connected to a fluorescence detector. Also, the magnetophoresis effects on subsequent transmission of the electrochemical signal were demonstrated using magnetite associated with CTAB micelles modified with ferrocene. We glimpse that these magnetic supramolecular systems can be applied in micro- and nanoscale communication systems.

Stimuli-responsive self-assembly of nanoparticles

Ligand-protected nanoparticles can serve as attractive building blocks for constructing complex chemical systems.

Gel-based soft actuators driven by light

Gels that display light-induced motile, life-like actions are reviewed and their potential applications as light-driven soft actuators are also discussed.

Quasiperiodic behavior in the electrodeposition of Cu/Sn multilayers: extraction of activation energies and wavelet analysis

The oscillatory electro-deposition of Cu/Sn in the presence of a surfactant shows quasiperiodic behavior, which is described by the coupling between a mainly activation and a mainly diffusion-controlled processes.

Substrate-Induced Self-Assembly of Cooperative Catalysts

Dissipative self-assembly processes in nature rely on chemical fuels that activate proteins for assembly through the formation of a noncovalent complex. The catalytic activity of the assemblies causes fuel degradation, resulting in the formation of an assembly in a high-energy, out-of-equilibrium state. Herein, we apply this concept to a synthetic system and demonstrate that a substrate can induce the formation of vesicular assemblies, which act as cooperative catalysts for cleavage of the same substrate.

Substrate-Induced Self-Assembly of Cooperative Catalysts

Dissipative self-assembly processes in nature rely on chemical fuels that activate proteins for assembly through the formation of a noncovalent complex. The catalytic activity of the assemblies causes fuel degradation, resulting in the formation of an assembly in a high-energy, out-of-equilibrium state. Herein, we apply this concept to a synthetic system and demonstrate that a substrate can induce the formation of vesicular assemblies, which act as cooperative catalysts for cleavage of the same substrate.

Chemically Fueled Dissipative Self-Assembly that Exploits Cooperative Catalysis

In living systems, dissipative processes are driven by the endergonic hydrolysis of chemical fuels such as nucleoside triphosphates. Now, through a simple model system, a transient self-assembled state is realized by utilizing the catalytic effect of histidine on the formation and breaking of ester bonds. First, histidine facilitates the ester bond formation, which then rapidly co-assembles to form a self-supporting gel. An out-of-equilibrium state is realized owing to the cooperative catalysis by the proximal histidines in the assembled state, driving the second pathway and resulting in disassembly to sol. Cooperative effects that use the dual role of imidazoles as nucleophile and as proton donor is utilized to achieve transient assemblies. This simple system mimics the structural journey seen in microtubule formation where the substrate GTP facilitates the non-covalent assembly and triggers a cooperative catalytic process, leading to substrate hydrolysis and subsequent disassembly.

Nonequilibrium Spatiotemporal Sensing within Acoustically Patterned Two-Dimensional Protocell Arrays

Acoustically trapped periodic arrays of horseradish peroxidase (HRP)-loaded poly(diallydimethylammonium chloride) / adenosine 5'-triphosphate coacervate microdroplet-based protocells exhibit a spatiotemporal biochemical response when exposed to a codiffusing mixture of substrate molecules (o-phenylenediamine (o-PD) and hydrogen peroxide (H₂O₂)) under nonequilibrium conditions. Unidirectional propagation of the chemical concentration gradients gives rise to time- and position-dependent fluorescence signal outputs from individual coacervate microdroplets, indicating that the organized protocell assembly can dynamically sense encoded information in the advancing reaction-diffusion front. The methodology is extended to arrays comprising spatially separated binary populations of HRP- or glucose oxidase-containing coacervate microdroplets to internally generate a H₂O₂ signal that chemically connects the two protocell communities via a concerted biochemical cascade reaction. Our results provide a step toward establishing a systematic approach to study dynamic interactions between organized protocell consortia and propagating reaction-diffusion gradients, and offer a new methodology for exploring the complexity of protocellular communication networks operating under nonequilibrium conditions.

Switchable Stimuli-Responsive Heterogeneous Catalysis

Heterogeneous catalytic systems based on the use of stimuli-responsive materials can be switched from an “on” active state to an “off” inactive state, which contributes to endowing the catalysts with unique functional properties, such as adaptability, recyclability and precise spatial and temporal control on different types of chemical reactions. All these properties constitute a step toward the development of nature-inspired catalytic systems. Even if this is a niche area in the field of catalysis, it is possible to find in literature intriguing examples of dynamic catalysts, whose systematic analysis and review are still lacking. The aim of this work is to examine the recent developments of stimuli-responsive heterogeneous catalytic systems from the viewpoint of different approaches that have been proposed to obtain a dynamic control of catalytic efficiency. Because of the variety of reactions and conditions, it is difficult to make a quantitative comparison between the efficiencies of the considered systems, but the analysis of the different strategies can inspire the preparation of new smart catalytic systems.

Oscillations, travelling fronts and patterns in a supramolecular system

Supramolecular polymers, such as microtubules, operate under non-equilibrium conditions to drive crucial functions in cells, such as motility, division and organelle transport¹. In vivo and in vitro size oscillations of individual microtubules^2,3 (dynamic instabilities) and collective oscillations⁴ have been observed. In addition, dynamic spatial structures, like waves and polygons, can form in non-stirred systems⁵. Here we describe an artificial supramolecular polymer made of a perylene diimide derivative that displays oscillations, travelling fronts and centimetre-scale self-organized patterns when pushed far from equilibrium by chemical fuels. Oscillations arise from a positive feedback due to nucleation-elongation-fragmentation, and a negative feedback due to size-dependent depolymerization. Travelling fronts and patterns form due to self-assembly induced density differences that cause system-wide convection. In our system, the species responsible for the nonlinear dynamics and those that self-assemble are one and the same. In contrast, other reported oscillating assemblies formed by vesicles⁶, micelles⁷ or particles⁸ rely on the combination of a known chemical oscillator and a stimuli-responsive system, either by communication through the solvent (for example, by changing pH^7-9), or by anchoring one of the species covalently (for example, a Belousov-Zhabotinsky catalyst^6,10). The design of self-oscillating supramolecular polymers and large-scale dissipative structures brings us closer to the creation of more life-like materials¹¹ that respond to external stimuli similarly to living cells, or to creating artificial autonomous chemical robots¹².

Molecular bionics - engineering biomaterials at the molecular level using biological principles

Life and biological units are the result of the supramolecular arrangement of many different types of molecules, all of them combined with exquisite precision to achieve specific functions. Taking inspiration from the design principles of nature allows engineering more efficient and compatible biomaterials. Indeed, bionic (from bion-, unit of life and -ic, like) materials have gained increasing attention in the last decades due to their ability to mimic some of the characteristics of nature systems, such as dynamism, selectivity, or signalling. However, there are still many challenges when it comes to their interaction with the human body, which hinder their further clinical development. Here we review some of the recent progress in the field of molecular bionics with the final aim of providing with design rules to ensure their stability in biological media as well as to engineer novel functionalities which enable navigating the human body.