Adenosine triphosphate biosynthesis catalyzed by FoF1 ATP synthase assembled in polymer microcapsules

Oriented Nanoarchitectonics of Bacteriorhodopsin for Enhancing ATP Generation in a Fo F1 -ATPase-Based Assembly System

Energy conversion plays an important role in the metabolism of photosynthetic organisms. Improving energy transformation by promoting a proton gradient has been a great challenge for a long time. In the present study, we realize a directional proton migration through the construction of oriented bacteriorhodopsin (BR) microcapsules coated by F_o F₁ -ATPase molecular motors through layer-by-layer (LBL) assembly. The changes in the conformation of BR under illumination lead to proton transfer in a radial direction, which generates a higher proton gradient to drive the synthesis of adenosine triphosphate (ATP) by F_o F₁ -ATPase. Furthermore, to promote the photosynthetic activity, optically matched quantum dots were introduced into the artificial coassembly system of BR and F_o F₁ -ATPase. Such a design creates a new path for the use of light energy.

Photosystem II-based biomimetic assembly for enhanced photosynthesis

Photosystem II (PSII) is a fascinating photosynthesis-involved enzyme, participating in sunlight-harvest, water splitting, oxygen release, and proton/electron generation and transfer. Scientists have been inspired to couple PSII with synthetic hierarchical structures via biomimetic assembly, facilitating attainment of natural photosynthesis processes, such as photocatalytic water splitting, electron transfer and ATP synthesis, in vivo. In the past decade, there has been significant progress in PSII-based biomimetic systems, such as artificial chloroplasts and photoelectrochemical cells. The biomimetic assembly approach helps PSII gather functions and properties from synthetic materials, resulting in a complex with partly natural and partly synthetic components. PSII-based biomimetic assembly offers opportunities to forward semi-biohybrid research and synchronously inspire optimization of artificial light-harvest micro/nanodevices. This review summarizes recent studies on how PSII combines with artificial structures via molecular assembly and highlights PSII-based semi-natural biosystems which arise from synthetic parts and natural components. Moreover, we discuss the challenges and remaining problems for PSII-based systems and the outlook for their development and applications. We believe this topic provides inspiration for rational designs to develop biomimetic PSII-based semi-natural devices and further reveal the secrets of energy conversion within natural photosynthesis from the molecular level.

Proteomics of Homeobox7 Enhanced Salt Tolerance in Mesembryanthemum crystallinum

Mesembryanthemum crystallinum (common ice plant) is a halophyte species that has adapted to extreme conditions. In this study, we cloned a McHB7 transcription factor gene from the ice plant. The expression of McHB7 was significantly induced by 500 mM NaCl and it reached the peak under salt treatment for 7 days. The McHB7 protein was targeted to the nucleus. McHB7-overexpressing in ice plant leaves through Agrobacterium-mediated transformation led to 25 times more McHB7 transcripts than the non-transformed wild type (WT). After 500 mM NaCl treatment for 7 days, the activities of superoxide dismutase (SOD) and peroxidase (POD) and water content of the transgenic plants were higher than the WT, while malondialdehyde (MDA) was decreased in the transgenic plants. A total of 1082 and 1072 proteins were profiled by proteomics under control and salt treatment, respectively, with 22 and 11 proteins uniquely identified under control and salt stress, respectively. Among the 11 proteins, 7 were increased and 4 were decreased after salt treatment. Most of the proteins whose expression increased in the McHB7 overexpression (OE) ice plants under high salinity were involved in transport regulation, catalytic activities, biosynthesis of secondary metabolites, and response to stimulus. The results demonstrate that the McHB7 transcription factor plays a positive role in improving plant salt tolerance.

Boric Acid-Fueled ATP Synthesis by Fo F1 ATP Synthase Reconstituted in a Supramolecular Architecture

Significant strides toward producing biochemical fuels have been achieved by mimicking natural oxidative and photosynthetic phosphorylation. Here, different from these strategies, we explore boric acid as a fuel for tuneable synthesis of energy-storing molecules in a cell-like supramolecular architecture. Specifically, a proton locked in boric acid is released in a modulated fashion by the choice of polyols. As a consequence, controlled proton gradients across the lipid membrane are established to drive ATP synthase embedded in the biomimetic architecture, which facilitates tuneable ATP production. This strategy paves a unique route to achieve highly efficient bioenergy conversion, holding broad applications in synthesis and devices that require biochemical fuels.

Layer-by-Layer Assembly: Recent Progress from Layered Assemblies to Layered Nanoarchitectonics

As an emerging concept for the development of new materials with nanoscale features, nanoarchitectonics has received significant recent attention. Among the various approaches that have been developed in this area, the fixed-direction construction of functional materials, such as layered fabrication, offers a helpful starting point to demonstrate the huge potential of nanoarchitectonics. In particular, the combination of nanoarchitectonics with layer-by-layer (LbL) assembly and a large degree of freedom in component availability and technical applicability would offer significant benefits to the fabrication of functional materials. In this Minireview, recent progress in LbL assembly is briefly summarized. After introducing the basics of LbL assembly, recent advances in LbL research are discussed, categorized according to physical, chemical, and biological innovations, along with the fabrication of hierarchical structures. Examples of LbL assemblies with graphene oxide are also described to demonstrate the broad applicability of LbL assembly, even with a fixed material.

Molecular Assemblies of Biomimetic Microcapsules

Layer-by-layer (LbL) assembly is a most commonly used method to prepare various microcapsules based on the electrostatic interactions, hydrogen bonding, covalent bonding, and so on. Among these interactions, Schiff base bond formed in covalent assembly not only has an advantage in stability, but also enables the assembled microcapsules with autofluorescence and pH sensitivity. In this Article, we will mainly describe the construction of biomimetic microcapsules through Schiff base mediated LbL assembly. The structures and properties of the assembled microcapsules are introduced and their applications as drug carriers are highlighted.

Molecular Assembly of Rotary and Linear Motor Proteins

Molecular machines are an important and emerging frontier in research encompassing interdisciplinary subjects of chemistry, physics, biology, and nanotechnology. Although there has been major interest in creating synthetic molecular machines, research on natural molecular machines is also crucial. Biomolecular motors are natural molecular machines existing in nearly every living systems. They play a vital role in almost every essential process ranging from intracellular transport to cell division, muscle contraction and the biosynthesis of ATP that fuels life processes. The construction of biomolecular motor-based biomimetic systems can help not only to deeply understand the mechanisms of motor proteins in the biological process but also to push forward the development of bionics and biomolecular motor-based devices or nanomachines. From combination of natural biomolecular motors with supramolecular chemistry, great opportunities could emerge toward the development of intelligent molecular machines and biodevices. In this Account, we describe our efforts to design and reconstitute biomolecular motor-based active biomimetic systems, in particular, the combination of motor proteins with layer-by-layer (LbL) assembled cellular structures. They are divided into two parts: (i) reconstitution of rotary molecular motor F_OF₁-ATPase, which is coated on the surface of LbL assembled microcapsules or multilayers and synthesizes adenosine triphosphate (ATP) through creating a proton gradient; (ii) molecular assembly of linear molecular motors, the kinesin-based active biomimetic systems, which are coated on a planar surface or LbL assembled tubular structure and drive the movement of microtubules. LbL assembled structures offer motor proteins with an environment that resembles the natural cell. This enables high activity and optimized function of the motor proteins. The assembled biomolecular motors can mimic their functionalities from the natural system. In addition, LbL assembly provides facile integration of functional components into motor protein-based active biomimetic systems and achieves the manipulation of F_OF₁-ATPase and kinesin. For F_OF₁-ATPase, the light-driven proton gradient and controlled ATP synthesis are highlighted. For kinesin, the strategies used for the direction and velocity control of kinesin-based molecular shuttles are discussed. We hope this research can inspire new ideas and propel the actual applications of biomolecular motor-based devices in the future.

Janus-micromotor-based on-off luminescence sensor for active TNT detection

An active TNT (2,4,6-trinitrotoluene) catalytic sensor based on Janus upconverting nanoparticle (UCNP)-functionalized micromotor capsules, displaying "on-off" luminescence with a low limit of detection has been developed. The Janus capsule motors were fabricated by layer-by-layer assembly of UCNP-functionalized polyelectrolyte microcapsules, followed by sputtering of a platinum layer onto one half of the capsule. By catalytic decomposition of hydrogen peroxide to oxygen bubbles, the Janus UCNP capsule motors are rapidly propelled with a speed of up to 110 μm s^-1. Moreover, the Janus motors display efficient on-off luminescent detection of TNT. Owing to the unique motion of the Janus motor with bubble generation, the likelihood of collision with TNT molecules and the reaction rate between them are increased, resulting in a limit of detection as low as 2.4 ng mL^-1 TNT within 1 minute. Such bubble-propelled Janus UCNP capsule motors have great potential for contaminated water analysis.

Supramolecularly Assembled Nanocomposites as Biomimetic Chloroplasts for Enhancement of Photophosphorylation

Prototypes of natural biosystems provide opportunities for artificial biomimetic systems to break the limits of natural reactions and achieve output control. However, mimicking unique natural structures and ingenious functions remains a challenge. Now, multiple biochemical reactions were integrated into artificially designed compartments via molecular assembly. First, multicompartmental silica nanoparticles with hierarchical structures that mimic the chloroplasts were obtained by a templated synthesis. Then, photoacid generators and ATPase-liposomes were assembled inside and outside of silica compartments, respectively. Upon light illumination, protons produced by a photoacid generator in the confined space can drive the liposome-embedded enzyme ATPase towards ATP synthesis, which mimics the photophosphorylation process in vitro. The method enables fabrication of bioinspired nanoreactors for photobiocatalysis and provides insight for understanding sophisticated biochemical reactions.

Proton-consumed nanoarchitectures toward sustainable and efficient photophosphorylation

At present, photophosphorylation in natural or artificial systems is accomplished by the production of protons or their pumping across the biomembranes. Herein, different from this strategy above, we demonstrate a designed system which can effectively enhance photophosphorylation by photo-induced proton-scavenging through molecular assembly. Upon the introduction of photobase generators, a (photo-) chemical reaction occurs to produce hydroxyl ions. Accompanying the further extramembranous acid-base neutralization reaction, an outbound flow of protons is generated to drive the reconstituted adenosine triphosphate (ATP) synthase to produce ATP. That is, contrary to biochemistry, the proton gradient to drive photophosphorylation derives from the scavenging of protons present in the external medium by hydroxyl ions, produced by the partially photo-induced splitting of photobase generator. Such assembled system holds great potential in ATP-consuming bioapplications.

Supramolecular Assembly of Photosystem II and Adenosine Triphosphate Synthase in Artificially Designed Honeycomb Multilayers for Photophosphorylation

Plant thylakoids have a typical stacking structure, which is the site of photosynthesis, including light-harvesting, water-splitting, and adenosine triphosphate (ATP) production. This stacking structure plays a key role in exchange of substances with extremely high efficiency and minimum energy consumption through photosynthesis. Herein we report an artificially designed honeycomb multilayer for photophosphorylation. To mimic the natural thylakoid stacking structure, the multilayered photosystem II (PSII)-ATP synthase-liposome system is fabricated via layer-by-layer (LbL) assembly, allowing the three-dimensional distributions of PSII and ATP synthase. Under light illumination, PSII splits water into protons and generates a proton gradient for ATP synthase to produce ATP. Moreover, it is found that the ATP production is extremely associated with the numbers of PSII layers. With such a multilayer structure assembled via LbL, one can better understand the mechanism of PSII and ATP synthase integrated in one system, mimicking the photosynthetic grana structure. On the other hand, such an assembled system can be considered to improve the photophosphorylation.

Polyelectrolyte multilayer-cushioned fluid lipid bilayers: a parachute model

Lipid bilayer membranes supported on polyelectrolyte multilayers are widely used as a new biomembrane model that connects biological and artificial materials since these ultrathin polyelectrolyte supports may mimic the role of the extracellular matrix and cell skeleton in living systems. Polyelectrolyte multilayers were fabricated by a layer-by-layer self-assembly technique. A quartz crystal microbalance with dissipation was used in real time to monitor the interaction between phospholipids and polyelectrolytes in situ on a planar substrate. The surface properties of polyelectrolyte films were investigated by the measurement of contact angles and zeta potential. Phospholipid charge, buffer pH and substrate hydrophilicity were proved to be essential for vesicle adsorption, rupture, fusion and formation of continuous lipid bilayers on the polyelectrolyte multilayers. The results clearly demonstrated that only the mixture of phosphatidylcholine and phosphatidic acid (4 : 1) resulted in fluid bilayers on chitosan and alginate multilayers with chitosan as a top layer at pH 6.5. A coarse-grained molecular simulation study elucidated that the exact mechanism of the formation of fluid lipid bilayers resembles a "parachute" model. As the closest model to the real membrane, polyelectrolyte multilayer-cushioned fluid lipid bilayers can be appropriate candidates for application in biomedical fields.

Molecular Assembly of Polysaccharide-Based Microcapsules and Their Biomedical Applications

Advanced multifunctional microcapsules have revealed great potential in biomedical applications owing to their tunable size, shape, surface properties, and stimuli responsiveness. Polysaccharides are one of the most acceptable biomaterials for biomedical applications because of their outstanding virtues such as biocompatibility, biodegradability, and low toxicity. Many efforts have been devoted to investigating novel molecular design and efficient building blocks for polysaccharide-based microcapsules. In this Personal Account, we first summarize the common features of polysaccharides and the main principles of the design and fabrication of polysaccharide-based microcapsules, and further discuss their applications in biomedical areas and perspectives for future research.

Controllable Multicompartmental Capsules with Distinct Cores and Shells for Synergistic Release

A facile and flexible approach is developed for controllable fabrication of novel multiple-compartmental calcium alginate capsules from all-aqueous droplet templates with combined coextrusion minifluidic devices for isolated coencapsulation and synergistic release of diverse incompatible components. The multicompartmental capsules exhibit distinct compartments, each of which is covered by a distinct part of a heterogeneous shell. The volume and number of multiple compartments can be well-controlled by adjusting flow rates and device numbers for isolated and optimized encapsulation of different components, while the composition of different part of the heterogeneous shell can be individually tailored by changing the composition of droplet template for flexibly tuning the release behavior of each component. Two combined devices are first used to fabricate dual-compartmental capsules and then scaled up to fabricate more complex triple-compartmental capsules for coencapsulation. The synergistic release properties are demonstrated by using dual-compartmental capsules, which contain one-half shell with a constant release rate and the other half shell with a temperature-dependent release rate. Such a heterogeneous shell provides more flexibilities for synergistic release with controllable release sequence and release rates to achieve advanced and optimized synergistic efficacy. The multicompartmental capsules show high potential for applications such as drug codelivery, confined reactions, enzyme immobilizations, and cell cultures.

The effect of top-layer chemistry on the formation of supported lipid bilayers on polyelectrolyte multilayers: primary versus quaternary amines

The influence of the surface chemistry of PEMs on the formation of lipid bilayers is studied here for PEMs with different cationic amines as a top layer, and polystyrene sulfonate (PSS) as a polyanion.

Dipeptide concave nanospheres based on interfacially controlled self-assembly: from crescent to solid

Concave nanospheres based on the self-assembly of simple dipeptides not only provide alternatives for modeling the interactions between biomacromolecules, but also present a range of applications for purification and separation, and delivery of active species.

Self-propelled Janus mesoporous silica nanomotors with sub-100 nm diameters for drug encapsulation and delivery

The synthesis of an innovative self-propelled Janus nanomotor with a diameter of about 75 nm that can be used as a drug carrier is described. The Janus nanomotor is based on mesoporous silica nanoparticles (MSNs) with chromium/platinum metallic caps and propelled by decomposing hydrogen peroxide to generate oxygen as a driving force with speeds up to 20.2 μm s(-1) (about 267 body lengths per second). The diffusion coefficient (D) of nanomotors with different H2 O2 concentrations is calculated by tracking the movement of individual particles recorded by means of a self-assembled fluorescence microscope and is significantly larger than free Brownian motion. The traction of a single Janus MSN nanomotor is estimated to be about 13.47×10(-15) N. Finally, intracellular localization and drug release in vitro shows that the amount of Janus MSN nanomotors entering the cells is more than MSNs with same culture time and particle concentrations, meanwhile anticancer drug doxorubicin hydrochloride loaded in Janus MSNs can be slowly released by biodegradation of lipid bilayers in cells.

Enzyme nanoarchitectonics: organization and device application

Fabrication of ultrasmall functional machines and their integration within ultrasmall areas or volumes can be useful for creation of novel technologies. The ultimate goal of the development of ultrasmall machines and device systems is to construct functional structures where independent molecules operate as independent device components. To realize exotic functions, use of enzymes in device structures is an attractive solution because enzymes can be regarded as efficient machines possessing high reaction efficiencies and specificities and can operate even under ambient conditions. In this review, recent developments in enzyme immobilization for advanced functions including device applications are summarized from the viewpoint of micro/nano-level structural control, or nanoarchitectonics. Examples are roughly classified as organic soft matter, inorganic soft materials or integrated/organized media. Soft matter such as polymers and their hybrids provide a medium appropriate for entrapment and encapsulation of enzymes. In addition, self-immobilization based on self-assembly and array formation results in enzyme nanoarchitectures with soft functions. For the confinement of enzymes in nanospaces, hard inorganic mesoporous materials containing well-defined channels play an important role. Enzymes that are confined exhibit improved stability and controllable arrangement, which are useful for formation of functional relays and for their integration into artificial devices. Layer-by-layer assemblies as well as organized lipid assemblies such as Langmuir-Blodgett films are some of the best media for architecting controllable enzyme arrangements. The ultrathin forms of these films facilitate their connection with external devices such as electrodes and transistors. Artificial enzymes and enzyme-mimicking catalysts are finally briefly described as examples of enzyme functions involving non-biological materials. These systems may compensate for the drawbacks of natural enzymes, such as their instabilities under harsh conditions. We believe that enzymes and their mimics will be freely coupled, organized and integrated upon demand in near future technologies.

Cyclodextrin-based microcapsules as bioreactors for ATP biosynthesis

A biomimetic energy converter was fabricated via the assembly of CF0F1-ATPase on lipid-coated hollow nanocapsules composed of α-cyclodextrins/chitosan-graft-poly(ethylene glycol) methacrylate. Upon entrapped GOD into these capsules, the addition of glucose could trigger proton-motive force and then drive the rotation of ATPase to synthesize ATP.

Autonomous movement of controllable assembled Janus capsule motors

We demonstrate the first example of a self-propelled Janus polyelectrolyte multilayer hollow capsule that can serve as both autonomous motor and smart cargo. This new autonomous Janus capsule motor composed of partially coated dendritic platinum nanoparticles (Pt NPs) was fabricated by using a template-assisted layer-by-layer (LbL) self-assembly combined with a microcontact printing method. The resulting Janus capsule motors still retain outstanding delivery capacities and can respond to external stimuli for controllable encapsulation and triggered release of model drugs. The Pt NPs on the one side of the Janus capsule motors catalytically decompose hydrogen peroxide fuel, generating oxygen bubbles which then recoil the movement of the capsule motors in solution or at an interface. They could autonomously move at a maximum speed of above 1 mm/s (over 125 body lengths/s), while exerting large forces exceeding 75 pN. Also, these asymmetric hollow capsules can be controlled by an external magnetic field to achieve directed movement. This LbL-assembled Janus capsule motor system has potential in making smart self-propelling delivery systems.

Protein capsules assembled via isobutyramide grafts: sequential growth, biofunctionalization, and cellular uptake

We report the sequential assembly of proteins via the alternating physical adsorption of human serum albumin (HSA) and chemical grafting with isobutyramide (IBAM) or bromoisobutyramide (BrIBAM) groups. This approach, performed on silica template particles, leads to the formation of noncovalent protein films with controlled growth at the nanometer scale. Further, after template removal, hollow protein capsules with tunable wall thicknesses and high mechanical stability are obtained. The use of BrIBAM, compared to IBAM grafts, leads to significantly thicker capsule walls, highlighting the influence of the bromine atoms in the assembly process, which is discussed in terms of a theoretical model of noncovalent interactions. Another feature of the process is the possibility to functionalize the HSA capsules with other biologically active macromolecules, including enzymes, polysaccharides, or DNA plasmids, demonstrating the versatility of this approach. We also report that BrIBAM-HSA and IBAM-HSA capsules display negligible cytotoxicity in vitro with HeLa cells and that their cellular uptake is dependent on the thickness of the capsule walls. These findings support the potential use of these protein capsules in tailored biological applications such as drug delivery.

Flake-shell capsules: adjustable inorganic structures

Structure-adjustable capsules are fabricated from inorganic components by using a self-template dissolution-regrowth mechanism to give flake-shell silica microcapsules. The capsules shrink under thermal stimulus and their structures can be adjusted by treatment at different pH values. Tuning of shell pore diameters leads to tailored drug release over prolonged periods.

Molecular assembly and application of biomimetic microcapsules

The assembly of multifunctional biomimetic microcapsules at the molecular level is of tremendous interest for biophysical research and the biomedical field. Among the available molecular assembly techniques, layer-by-layer assembly has attracted extensive attention for the fabrication of biomimetic microcapsules because it possesses engineered features including size, shape, thickness, composition and permeation, and the capability of incorporating different types of biomolecules. In this tutorial review, we highlight how biomimetic microcapsules can be fabricated by directly applying lipids and proteins as assembly pairs and how layer-by-layer assembled polyelectrolyte microcapsules can be interfaced with biological components such as phospholipid membranes and proteins. The applications of these biomimetic microcapsules in drug delivery, biosensors, and hybrid nanodevices are also addressed.