Biotic communities inspired proteinosome-based aggregation for enhancing utilization rate of enzyme

Liquid-to-gel transitions of phase-separated coacervate microdroplets enabled by endogenous enzymatic catalysis

Biomolecular condensates formed by liquid-liquid phase separation (LLPS) play a crucial role in organizing biochemical processes within living cells. The phase transition of these condensates from a functional liquid-like state to a pathological gel-like or solid-like state is believed to be linked to cellular dysfunction and various diseases. Here, we present a biomimetic model to demonstrate that endogenous enzyme-catalyzed crosslinking within condensate-mimicked coacervate microdroplets can promote a liquid-to-gel phase transition. We identify the transformation in physical characteristics of the densely packed microdroplets including reduced internal mobility, increased storage modulus, selective blocking of large nanoparticles, and enhanced salt resistance. The reversible dynamics of gel-like microdroplets mediated by ionic strength exhibited a limited release and recapture of sequestered positively charged guest molecules. Furthermore, we validate that the phase transition contributes to a restricted biochemical process through an enzymatic cascade. Overall, this work represents an adaptive in vitro platform for exploring the phase transitions associated with the physiological functions of biomolecular condensates and offers chemical insights and perspectives for investigating potential mechanisms involved in phase transitions.

Alternating Binary Droplets-Based Protocell Networks Driven by Heterogeneous Liquid-Liquid Phase Separation

As the emergence of prototissues promotes the evolutionary transformations of protolife, tissue-like networks derived from cytomimetic systems have been studied by using artificial cells as building blocks to mimic prototissues at a higher organizational level. However, liquid-like networks originating from liquid-liquid phase separation (LLPS), especially heterogeneous LLPS, are less reported. Herein, we report a binary liquid droplet-based protocell network composed of coacervates and aqueous two-phase systems (ATPS) droplets arranged in an alternating sequence, integrating both associative and segregative LLPS. This network with worm-like chains can be specifically achieved only when the attached droplets are partially engulfed, mediated by the interfacial tension between coacervate and ATPS droplets. Notably, the interconnected droplets within the network are capable of spatially self-sorting of biomacromolecules into separate domains, thereby facilitating biomacromolecular extraction and biological reactions within designated droplets. Upon changes in the external environment, the network can be reconfigured to enable morphological regulation of trienzymatic cascade reactions. Overall, this work highlights that an all-aqueous network, coupling both associative and segregative LLPS, can be engineered as a possible route toward a hybrid prototissue-like system, offering new insights into the design of higher-ordered biomimetic systems utilizing liquid soft matter.

Programmed Fabrication of Vesicle-Based Prototissue Fibers with Modular Functionalities

Multicellular organisms have hierarchical structures where multiple cells collectively form tissues with complex 3D architectures and exhibit higher-order functions. Inspired by this, to date, multiple protocell models have been assembled to form tissue-like structures termed prototissues. Despite recent advances in this research area, the programmed assembly of protocells into prototissue fibers with emergent functions still represents a significant challenge. The possibility of assembling prototissue fibers will open up a way to a novel type of prototissue subunit capable of hierarchical assembly into unprecedented soft functional materials with tunable architectures, modular and distributed functionalities. Herein, the first method to fabricate freestanding vesicle-based prototissue fibers with controlled lengths and diameters is devised. Importantly, it is also shown that the fibers can be composed of different specialized modules that, for example, can endow the fiber with magnetotaxis capabilities, or that can work synergistically to take an input diffusible chemical signals and transduce it into a readable fluorescent output through a hosted enzyme cascade reaction. Overall, this research addresses an important challenge of prototissue engineering and will find important applications in 3D bio-printing, tissue engineering, and soft robotics as next-generation bioinspired materials.

Biomimetic Materials to Fabricate Artificial Cells

As the foundation of life, a cell is generally considered an advanced microreactor with a complicated structure and function. Undeniably, this fascinating complexity motivates scientists to try to extricate themselves from natural living matter and work toward rebuilding artificial cells in vitro. Driven by synthetic biology and bionic technology, the research of artificial cells has gradually become a subclass. It is not only held import in many disciplines but also of great interest in its synthesis. Therefore, in this review, we have reviewed the development of cell and bionic strategies and focused on the efforts of bottom-up strategies in artificial cell construction. Different from starting with existing living organisms, we have also discussed the construction of artificial cells based on biomimetic materials, from simple cell scaffolds to multiple compartment systems, from the construction of functional modules to the simulation of crucial metabolism behaviors, or even to the biomimetic of communication networks. All of them could represent an exciting advance in the field. In addition, we will make a rough analysis of the bottlenecks in this field. Meanwhile, the future development of this field has been prospecting. This review may bridge the gap between materials engineering and life sciences, forming a theoretical basis for developing various life-inspired assembly materials.

Engineering pH-Responsive, Self-Healing Vesicle-Type Artificial Tissues with Higher-Order Cooperative Functionalities

Multicellular organisms demonstrate a hierarchical organization where multiple cells collectively form tissues, thereby enabling higher-order cooperative functionalities beyond the capabilities of individual cells. Drawing inspiration from this biological organization, assemblies of multiple protocells are developed to create novel functional materials with emergent higher-order cooperative functionalities. This paper presents new artificial tissues derived from multiple vesicles, which serve as protocellular models. These tissues are formed and manipulated through non-covalent interactions triggered by a salt bridge. Exhibiting pH-sensitive reversible formation and destruction under neutral conditions, these artificial vesicle tissues demonstrate three distinct higher-order cooperative functionalities: transportation of large cargoes, photo-induced contractions, and enhanced survivability against external threats. The rapid assembly and disassembly of these artificial tissues in response to pH variations enable controlled mechanical task performance. Additionally, the self-healing property of these artificial tissues indicates robustness against external mechanical damage. The research suggests that these vesicles can detect specific pH environments and spontaneously assemble into artificial tissues with advanced functionalities. This leads to the possibility of developing intelligent materials with high environmental specificity, particularly for applications in soft robotics.

Constructing a CdS QDs/silica gel composite with high photosensitivity and prolonged recyclable operability for enhanced visible-light-driven NADH regeneration

Visible-light-driven nicotinamide adenine dinucleotide (NADH) regeneration is one of the most effective measures, and cadmium sulfide (CdS) materials are typically used as low-cost photocatalysts. The CdS photocatalysts, however, still suffer from low regeneration efficiency and poor cycle stability. In this work, the CdS quantum dots (QDs) less than 10 nm embedded onto silica gel (CdS QDs/Silica gel) were constructed for visible-light-driven NADH regeneration by a successive ionic layer adsorption reaction and ball milling method. Results demonstrate that the photosensitivity of the CdS QDs/Silica gel composite was 31 times higher than that of the bulk CdS. Moreover, the conduction band (CB) edge of the CdS QDs/Silica gel composite is -1.34 eV, which is more negative 0.5 eV than that of the bulk CdS. The obtained CdS QDs/Silica gel composites showed the highest NADH regeneration yields of 68.8% under visible-light (LED, 420 nm) illumination and can be reused for over 40 cycles. Finally, the bioactivity of NADH toward enzyme catalysis is further confirmed by the hydrogenation of benzaldehyde to benzyl alcohol catalyzed with an alcohol dehydrogenase as enzyme catalysis.

Synthetic-Cell-Based Multi-Compartmentalized Hierarchical Systems

In the extant lifeforms, the self-sustaining behaviors refer to various well-organized biochemical reactions in spatial confinement, which rely on compartmentalization to integrate and coordinate the molecularly crowded intracellular environment and complicated reaction networks in living/synthetic cells. Therefore, the biological phenomenon of compartmentalization has become an essential theme in the field of synthetic cell engineering. Recent progress in the state-of-the-art of synthetic cells has indicated that multi-compartmentalized synthetic cells should be developed to obtain more advanced structures and functions. Herein, two ways of developing multi-compartmentalized hierarchical systems, namely interior compartmentalization of synthetic cells (organelles) and integration of synthetic cell communities (synthetic tissues), are summarized. Examples are provided for different construction strategies employed in the above-mentioned engineering ways, including spontaneous compartmentalization in vesicles, host-guest nesting, phase separation mediated multiphase, adhesion-mediated assembly, programmed arrays, and 3D printing. Apart from exhibiting advanced structures and functions, synthetic cells are also applied as biomimetic materials. Finally, key challenges and future directions regarding the development of multi-compartmentalized hierarchical systems are summarized; these are expected to lay the foundation for the creation of a "living" synthetic cell as well as provide a larger platform for developing new biomimetic materials in the future.

A Photo-degradable Crosslinker for the Development of Light-responsive Protocell Membranes

The achievement of light-responsive behaviours is an important target for protocell engineering to allow control of fundamental protocellular processes such as communication via diffusible chemical signals, shape changes or even motility at the flick of a switch. As a step towards this ambitious goal, here we describe the synthesis of a novel poly(ethylene glycol)-based crosslinker, reactive towards nucleophiles, that effectively degrades with UV light (405 nm). We demonstrate its utility for the fabrication of the first protocell membranes capable of light-induced disassembly, for the photo-generation of patterns of protocells, and for the modulation of protocell membrane permeability. Overall, our results not only open up new avenues towards the engineering of spatially organised, communicating networks of protocells, and of micro-compartmentalised systems for information storage and release, but also have important implications for other research fields such as drug delivery and soft materials chemistry.