Spatiotemporal control of signal-driven enzymatic reaction in artificial cell-like polymersomes

Salt-Bridge-Mediated Coacervate-to-Vesicle Transformation in Arginine-Rich Coacervates

Polypeptide-based liquid-liquid phase separation (LLPS) has received considerable attention as it governs the formation of membraneless organelles in cells. However, the detailed mechanistic understanding of how one of the most prevalent cationic amino acids in proteins, arginine, interacts with various biomolecules to induce phase separation and undergo morphogenesis remains to be resolved. Herein, we report the phase separation behavior and transformation of arginine-rich coacervates into vesicular structures upon introducing polyphosphates. Transformation into vesicles was shown to occur independent of the initial anionic counterparts and was driven by salt-bridge interactions between guanidinium groups of arginine residues and phosphates. We also investigate the role of intermolecular forces and ionic effects on the morphological transformation and further exploit their potential in the assembly of artificial tissue-like constructs. Overall, our findings underpin a unifying principle for vesicle transformation from arginine-rich coacervates and their potency for reconstituting hierarchical biological microcompartments.

Polymeric Nanoarchitectures: Advanced Cargo Systems for Biological Applications

Polymeric nanoarchitectures are crafted from amphiphilic block copolymers through a meticulous self-assembly process. The composition of these block copolymers is finely adjustable, bestowing precise control over the characteristics and properties of the resultant polymeric assemblies. These nanoparticles have garnered significant attention, particularly in the realm of biological sciences, owing to their biocompatibility, favorable pharmacokinetics, and facile chemically modifiable nature. Among the myriad of polymeric nanoarchitectures, micelles and polymersomes stand out as frontrunners, exhibiting much potential as cargo carrier systems for diverse bio-applications. This review elucidates the design strategies employed for amphiphilic block copolymers and their resultant assemblies, specifically focusing on micelles and polymersomes. Subsequently, it discusses their wide-ranging bio-applications, spanning from drug delivery and diagnostics to bioimaging and artificial cell applications. Finally, a reflective analysis will be provided, highlighting the current landscape of polymeric cargo carriers, and discussing the opportunities and challenges that lie ahead. With this review, it is aimed to summarize the recent advances in polymeric assemblies and their applications in the biomedical field.

Cell-free systems: A synthetic biology tool for rapid prototyping in metabolic engineering

Microbial cell factories provide sustainable alternatives to petroleum-based chemical production using cost-effective substrates. A deep understanding of their metabolism is essential to harness their potential along with continuous efforts to improve productivity and yield. However, the construction and evaluation of numerous genetic variants are time-consuming and labor-intensive. Cell-free systems (CFSs) serve as powerful platforms for rapid prototyping of genetic circuits, metabolic pathways, and enzyme functionality. They offer numerous advantages, including minimizing unwanted metabolic interference, precise control of reaction conditions, reduced labor, and shorter Design-Build-Test-Learn cycles. Additionally, the introduction of in vitro compartmentalization strategies in CFSs enables ultra-high-throughput screening in physically separated spaces, which significantly enhances prototyping efficiency. This review highlights the latest examples of using CFS to overcome prototyping limitations in living cells with a focus on rapid prototyping, particularly regarding gene regulation, enzymes, and multienzymatic reactions in bacteria. Finally, this review evaluates CFSs as a versatile prototyping platform and discusses its future applications, emphasizing its potential for producing high-value chemicals through microbial biosynthesis.

Synthetic Biomolecular Condensates: Phase-Separation Control, Cytomimetic Modelling and Emerging Biomedical Potential

Liquid-liquid phase separation towards the formation of synthetic coacervate droplets represents a rapidly advancing frontier in the fields of synthetic biology, material science, and biomedicine. These artificial constructures mimic the biophysical principles and dynamic features of natural biomolecular condensates that are pivotal for cellular regulation and organization. Via adapting biological concepts, synthetic condensates with dynamic phase-separation control provide crucial insights into the fundamental cell processes and regulation of complex biological pathways. They are increasingly designed with the ability to display more complex and ambitious cell-like features and behaviors, which offer innovative solutions for cytomimetic modeling and engineering active materials with sophisticated functions. In this minireview, we highlight recent advancements in the design and construction of synthetic coacervate droplets; including their biomimicry structure and organization to replicate life-like properties and behaviors, and the dynamic control towards engineering active coacervates. Moreover, we highlight the unique applications of synthetic coacervates as catalytic centers and promising delivery vehicles, so that these biomimicry assemblies can be translated into practical applications.

Biomimetic Chlorosomes: Oxygen-Independent Photocatalytic Nanoreactors for Efficient Combination Photoimmunotherapy

Photocatalytic therapy for hypoxic tumors often suffers from inefficiencies due to its dependence on oxygen and the risk of uncontrolled activation. Inspired by the oxygen-independent and precisely regulated photocatalytic functions of natural light-harvesting chlorosomes, chlorosome-mimetic nanoreactors, termed Ru-Chlos, are engineered by confining the aggregation of photosensitive ruthenium-polypyridyl-silane monomers. These Ru-Chlos exhibit markedly enhanced photocatalytic performance compared to their monomeric counterparts under acidic conditions, while notably bypassing the consumption of oxygen or hydrogen peroxide. The photocatalytic activity of Ru-Chlos is finely tunable through light-responsive disassembly of the Ru-bridged matrix, with tunability governed by pre-irradiation duration. Utilization of Ru-Chlos loading prodrug [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) for phototherapy facilitates the generation of toxic radicals (oxABTS) and the photocatalytic conversion of endogenous NADH to NAD+, inducing oxidative stress in hypoxic cancer cells. Simultaneously, the light-responsive degradation of Ru-Chlos produces Ru-based toxins that further contribute to the therapeutic effect. This dual-action mechanism elicits potent immunogenic cell death effects and significantly enhances antitumor efficacy with the aid of a PD-l blockade. These biomimetic chlorosomes highlight their potential to advance oxygen-independent photocatalytic nanoreactors with controlled activity for novel cancer photoimmunotherapy strategies.

Photoreceptor-Like Signal Transduction Between Polymer-Based Protocells

Deciphering inter- and intracellular signaling pathways is pivotal for understanding the intricate communication networks that orchestrate life's dynamics. Communication models involving bottom-up construction of protocells are emerging but often lack specialized compartments sufficiently robust and hierarchically organized to perform spatiotemporally defined signaling. Here, the modular construction of communicating polymer-based protocells designed to mimic the transduction of information in retinal photoreceptors is presented. Microfluidics is used to generate polymeric protocells subcompartmentalized by specialized artificial organelles. In one protocell population, light triggers artificial organelles with membrane-embedded photoresponsive rotary molecular motors to set off a sequence of reactions starting with the release of encapsulated signaling molecules into the lumen. Intercellular communication is mediated by signal transfer across membranes to protocells containing catalytic artificial organelles as subcompartments, whose signal conversion can be modulated by environmental calcium. Signal propagation also requires selective permeability of the diverse compartments. By segregating artificial organelles in distinct protocells, a sequential chain of reactions mediating intercellular communication is created that is further modulated by adding extracellular messengers. This connective behavior offers the potential for a deeper understanding of signaling pathways and faster integration of proto- and living cells, with the unique advantage of controlling each step by bio-relevant signals.

Peptide-Induced Division of Polymersomes for Biomimetic Compartmentalization

Polymersomes are synthetic vesicles that mimic the architecture of cellular compartments such as the cell membrane and organelles. These biomimetic compartments facilitate the creation of cell-like chemical systems, including microreactors and synthetic organelles. However, the construction of hierarchical multi-compartment systems remains challenging and typically requires the encapsulation of pre-formed vesicles within a host compartment. Here, we report the formation of multicompartment polymersomes with a vesicle-in-vesicle architecture achieved through self-division induced by short peptides incorporated into the vesicle membrane. A phenylalanine-phenylalanine-methionine (FFM) tripeptide was designed and encapsulated into the polymersome via microfluidics. We demonstrate that vesicle self-division occurs due to peptide incorporation into the membrane in response to pH changes. This self-division creates internal vesicles capable of colocalizing enzymes. The hybrid polymer-peptide system described here provides a straightforward method for developing subcompartmentalized systems, paving the way for engineering microreactors with life-like properties.

Coacervate Droplets as Biomimetic Models for Designing Cell-Like Microreactors

Coacervates are versatile compartments formed by liquid-liquid phase separation. Their dynamic behavior and molecularly crowded microenvironment make them ideal materials for creating cell-like systems such as synthetic cells and microreactors. Recently, combinations of synthetic and natural molecules have been exploited via simple or complex coacervation to create compartments that can be used to build hierarchical chemical systems with life-like properties. This review highlights recent advances in the design of coacervate compartments and their application as biomimetic compartments for the design of cell-like chemical reactors and cell mimicking systems. It first explores the variety of materials used for coacervation and the influence of their chemical structure on their controlled dynamic behavior. Then, the applications of coacervates as cell-like systems are reviewed, focusing on how they can be used as cell-like microreactors through their ability to sequester molecules and provide a distinct and regulatory microenvironment for chemical reactions in aqueous media.

Spatially-Resolved Organoid Transfection by Porous Silicon-Mediated Optoporation

Engineering the spatial organisation of organotypic cultures is pivotal for refining tissue models that are useful for gaining deeper insights into complex, non-cell autonomous processes. These advanced models are key to improving the understanding of fundamental biological mechanisms and therapeutic strategies. Controlling gene regulation through spatially-resolved delivery of nucleic acids provides an attractive approach to produce such tissue models. An emerging strategy for spatially-resolved transfection uses photosensitizing nanoparticles coupled with laser pulses to optoporate cells in culture and locally mediate gene delivery. However, localized optoporation in 3D systems remains challenging. Here we propose a solution to this longstanding hurdle, demonstrating that porous silicon nanoparticles are a safe and bioresorbable photosensitising nanomaterial capable of spatially-resolved transfection of mRNA in MCF-7 organoids by near-infrared two-photon optoporation. Functionalization with an azobenzene-lysine photo-switchable moiety enhances the transfection efficiency of the nanoparticles up to 84% in a 2D cell system. Moreover, the nanoparticles enable spatially selective mRNA transfection to MCF-7 spheroids, demonstrating targeted  gene delivery in complex 3D cellular environments. The approach for spatially-resolved 3D optoporation offers a way forward for the design of tailored spheroids and organoids by spatially selective nucleic acids delivery.

Droplet-based microfluidics for drug delivery applications

The microfluidic method primainly utilizes two incompatible liquids as continuous phase and dispersed phase respectively. It controls the formation of droplets by managing the microchannel structure and the flow rate ratio of the two phases. Droplet-based microfluidics is a rapidly expanding interdisciplinary research field encompassing physics, biochemistry, and Microsystems engineering. Droplet microfluidics offer a diverse and practical toolset that enables chemical and biological experiments to be conducted at high speeds and with greater efficiency compared to traditional instruments. The applications of droplet-based microfluidics are vast, including areas such as drug delivery, owing to its compatibility with numerous chemical and biological reagents and its ability to carry out various operations. This technology has been extensively researched due to its promising features. In this review, we delve into the materials used in droplet generation-based microfluidic devices, manufacturing techniques, methods for droplet generation in channels, and, finally, we summarize the applications of droplet generation-based microfluidics in drug delivery vectors, encompassing nanoparticles, microspheres, microcapsules, and hydrogel particles. We also discuss the challenges and future prospects of this technology across a wide array of applications.

Recent Applications of Amphiphilic Copolymers in Drug Release Systems for Skin Treatment

Amphiphilic copolymers (ACs) are versatile systems with self-assembling and aggregating properties, enabling the formation of nanomaterials (NMs) such as micelles, vesicles, nanocapsules, and nanogels. These materials have been extensively explored for the delivery of various drugs and active compounds, enhancing the solubility and permeation of poorly water-soluble drugs into skin tissue. This improvement facilitates the treatment of skin diseases, including chronic conditions like cancer, as well as infections caused by bacteria, fungi, and viruses. This review summarizes recent applications of ACs in skin treatment, with a particular focus on their use in anti-cancer drug therapy. It covers the synthesis, classification, and characterization of ACs using various experimental techniques. Additionally, it discusses recent research on different drug delivery pathways using ACs, including encapsulation efficiency, release behavior, characteristics, applications, and responses to various chemical and physical stimuli (both in vivo and in vitro). Furthermore, this review provides a comprehensive analysis of the effects of ACs NMs on several skin diseases, highlighting their potential as alternative treatments.

Biomolecular Condensation of Trypsin Prevents Autolysis and Promotes Ca2+-Mediated Activation of Esterase Activity

The presence of Ca2+ ions is known to facilitate the activity of trypsin-like serine proteases via structural stabilization against thermal denaturation and autolysis. Herein, we report a new and hidden regulatory role of Ca2+ in the catalytic pathways of trypsin and α-chymotrypsin under physiological conditions. We discovered that macromolecular crowding promotes spontaneous homotypic condensation of trypsin via liquid-liquid phase separation to yield membraneless condensates over a broad range of concentrations, pH, and temperature, which are stabilized by multivalent hydrophobic interactions. Interestingly, we found that Ca2+ binding in the calcium binding loop reversibly regulates the condensation of trypsin and α-chymotrypsin. Spontaneous condensation effectively prevents autolysis of trypsin and preserves its native-like esterase activity for a prolonged period of time. It has also been found that phase-separated trypsin responds to Ca2+-dependent activation of its esterase activity even after 14 days of storage while free trypsin failed to do so. The present study highlights an important physiological aspect by which cells can spatiotemporally regulate the biocatalytic efficacy of trypsin-like serine proteases via Ca2+-signaling.

Redefining drug therapy: innovative approaches using catalytic compartments

INTRODUCTION

Rapid excretion of drug derivatives often results in short drug half-lives, necessitating frequent administrations. Catalytic compartments, also known as nano- and microreactors, offer a solution by providing confined environments for in situ production of therapeutic agents. Inspired by natural compartments, polymer-based catalytic compartments have been developed to improve reaction efficiency and enable site-specific therapeutic applications.

AREAS COVERED

Polymer-based compartments provide stability, permeability control, and responsiveness to stimuli, making them ideal for generating localized compounds/signals. These sophisticated systems, engineered to carry active compounds and enable selective molecular release, represent a significant advancement in pharmaceutical research. They mimic cellular functions, creating controlled catalytic environments for bio-relevant processes. This review explores the latest advancements in synthetic catalytic compartments, focusing on design approaches, building blocks, active molecules, and key bio-applications.

EXPERT OPINION

Catalytic compartments hold transformative potential in precision medicine by improving therapeutic outcomes through precise, on-site production of therapeutic agents. While promising, challenges like scalable manufacturing, biodegradability, and regulatory hurdles must be addressed to realize their full potential. Addressing these will be crucial for their successful application in healthcare.

Cytoskeleton-modulating nanomaterials and their therapeutic potentials

The cytoskeleton, an intricate network of protein fibers within cells, plays a pivotal role in maintaining cell shape, enabling movement, and facilitating intracellular transport. Its involvement in various pathological states, ranging from cancer proliferation and metastasis to the progression of neurodegenerative disorders, underscores its potential as a target for therapeutic intervention. The exploration of nanotechnology in this realm, particularly the use of nanomaterials for cytoskeletal modulation, represents a cutting-edge approach with the promise of novel treatments. Inorganic nanomaterials, including those derived from gold, metal oxides, carbon, and black phosphorus, alongside organic variants such as peptides and proteins, are at the forefront of this research. These materials offer diverse mechanisms of action, either by directly interacting with cytoskeletal components or by influencing cellular signaling pathways that, in turn, modulate the cytoskeleton. Recent advancements have introduced magnetic field-responsive and light-responsive nanomaterials, which allow for targeted and controlled manipulation of the cytoskeleton. Such precision is crucial in minimizing off-target effects and enhancing therapeutic efficacy. This review explores the importance of research into cytoskeleton-targeting nanomaterials for developing therapeutic interventions for a range of diseases. It also addresses the progress made in this field, the challenges encountered, and future directions for using nanomaterials to modulate the cytoskeleton. The continued exploration of nanomaterials for cytoskeleton modulation holds great promise for advancing therapeutic strategies against a broad spectrum of diseases, marking a significant step forward in the intersection of nanotechnology and medicine.

Synthetic Cells from Droplet-Based Microfluidics for Biosensing and Biomedical Applications

Synthetic cells function as biological mimics of natural cells by mimicking salient features of cells such as metabolism, response to stimuli, gene expression, direct metabolism, and high stability. Droplet-based microfluidic technology presents the opportunity for encapsulating biological functional components in uni-lamellar liposome or polymer droplets. Verified by its success in the fabrication of synthetic cells, microfluidic technology is widely replacing conventional labor-intensive, expensive, and sophisticated techniques justified by its ability to miniaturize and perform batch production operations. In this review, an overview of recent research on the preparation of synthetic cells through droplet-based microfluidics is provided. Different synthetic cells including lipid vesicles (liposome), polymer vesicles (polymersome), coacervate microdroplets, and colloidosomes, are systematically discussed. Efforts are then made to discuss the design of a variety of microfluidic chips for synthetic cell preparation since the combination of microfluidics with bottom-up synthetic biology allows for reproductive and tunable construction of batches of synthetic cell models from simple structures to higher hierarchical structures. The recent advances aimed at exploiting them in biosensors and other biomedical applications are then discussed. Finally, some perspectives on the challenges and future developments of synthetic cell research with microfluidics for biomimetic science and biomedical applications are provided.

Quantitative turbidimetric characterization of stabilized complex coacervate dispersions

Stabilizing complex coacervate microdroplets is desirable due to their various applications, such as bioreactors, drug delivery vehicles, and encapsulants. Here, we present quantitative characterization of complex coacervate dispersion stability inferred by turbidimetry measurements. The stability of the dispersions is shown to be modulated by the concentrations of comb polyelectrolyte (cPE) stabilizers and salt. We demonstrate cPEs as effective stabilizers for complex coacervate dispersions independent of the chemistry or length of the constituent polyelectrolytes, salts, or preparation routes. By monitoring the temporal evolution of dispersion turbidity, we show that cPEs suppress microdroplet coalescence with minimal change in microdroplet sizes over 48 hours, even at salt concentrations up to 300 mM. The number density and average microdroplet size are shown to be controlled by varying the cPE and salt concentrations. Lastly, turbidity maps, akin to binodal phase maps, depict an expansion of the turbid two-phase region and an increase in the salt resistance of the coacervates upon the introduction of cPEs. The coacervate salt resistance is shown to increase by >3×, and this increase is maintained for up to 15 days, demonstrating that cPEs impart higher salt resistance over extended durations.

Controllable enzymatic hydrolysis in reverse Janus emulsion microreactors

HYPOTHESIS

The key feature of living cells is multicompartmentalization for enzymatic reactions. Artificial cell-like multicompartments with micro domains are appealing to mimic the biological counterparts. In addition, establishing a sustainable, efficient, and controllable reaction system for enzymatic hydrolysis is imperative for the production of natural fatty acids from animal and plant-based fats.

EXPERIMENTS

Reverse Janus emulsion microreactors, i.e. (W1 + W2)/O, is constructed through directly using natural fats as continuous phase and aqueous two-phase solutions (ATPS) as inner phases. Enzyme is confined in the compartmented aqueous droplets dominated by the salt of Na2SO4 and polyethylene glycol (PEG). Enzyme catalyzed ester hydrolysis employed as a model reaction is performed under the conditions of agitation-free and mild temperature. Regulation of reaction kinetics is investigated by diverse droplet topology, composition of inner ATPS, and on-demand emulsification.

FINDINGS

Excellent enzymatic activity toward hydrolysis of plant and animal oils achieves 88.5 % conversion after 3 h. Compartmented micro domains contribute to condense and organize the enzymes spatially. Timely removal of the products away from reaction sites of oil/water interface "pushed" the reaction forward. Distribution and transfer of enzyme in two aqueous lobes provide extra freedom in the regulation of hydrolysis kinetics, with equilibrium conversion controlled freely from 14.5 % to 88.5 %. Reversible "open" and "shut" of hydrolysis is acheived by on-demand emulsification and spontaneous demulsification. This paper paves the way to advancing progress in compartmentalized emulsion as a sustainable and high-efficiency platform for biocatalytic applications.

Programmable Enzymatic Reaction Network in Artificial Cell-Like Polymersomes

The ability to precisely control in vitro enzymatic reactions in synthetic cells plays a crucial role in the bottom-up design of artificial cell models that can recapitulate the key cellular features and functions such as metabolism. However, integration of enzymatic reactions has been limited to bulk or microfluidic emulsions without a membrane, lacking the ability to design more sophisticated higher-order artificial cell communities for reconstituting spatiotemporal biological information at multiple length scales. Herein, droplet microfluidics is utilized to synthesize artificial cell-like polymersomes with distinct molecular permeability for spatiotemporal control of enzymatic reactions driven by external signals and fuels. The presence of a competing reverse enzymatic reaction that depletes the active substrates is shown to enable demonstration of fuel-driven formation of sub-microcompartments within polymersomes as well as realization of out-of-equilibrium systems. In addition, the different permeability characteristics of polymersome membranes are exploited to successfully construct a programmable enzymatic reaction network that mimics cellular communication within a heterogeneous cell community through selective molecular transport.

Recent advances of droplet-based microfluidics for engineering artificial cells

Artificial cells, synthetic cells, or minimal cells are microengineered cell-like structures that mimic the biological functions of cells. Artificial cells are typically biological or polymeric membranes where biologically active components, including proteins, genes, and enzymes, are encapsulated. The goal of engineering artificial cells is to build a living cell with the least amount of parts and complexity. Artificial cells hold great potential for several applications, including membrane protein interactions, gene expression, biomaterials, and drug development. It is critical to generate robust, stable artificial cells using high throughput, easy-to-control, and flexible techniques. Recently, droplet-based microfluidic techniques have shown great potential for the synthesis of vesicles and artificial cells. Here, we summarized the recent advances in droplet-based microfluidic techniques for the fabrication of vesicles and artificial cells. We first reviewed the different types of droplet-based microfluidic devices, including flow-focusing, T-junction, and coflowing. Next, we discussed the formation of multi-compartmental vesicles and artificial cells based on droplet-based microfluidics. The applications of artificial cells for studying gene expression dynamics, artificial cell-cell communications, and mechanobiology are highlighted and discussed. Finally, the current challenges and future outlook of droplet-based microfluidic methods for engineering artificial cells are discussed. This review will provide insights into scientific research in synthetic biology, microfluidic devices, membrane interactions, and mechanobiology.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Synthetic Cells Revisited: Artificial Cells Construction Using Polymeric Building Blocks

The exponential growth of research on artificial cells and organelles underscores their potential as tools to advance the understanding of fundamental biological processes. The bottom-up construction from a variety of building blocks at the micro- and nanoscale, in combination with biomolecules is key to developing artificial cells. In this review, artificial cells are focused upon based on compartments where polymers are the main constituent of the assembly. Polymers are of particular interest due to their incredible chemical variety and the advantage of tuning the properties and functionality of their assemblies. First, the architectures of micro- and nanoscale polymer assemblies are introduced and then their usage as building blocks is elaborated upon. Different membrane-bound and membrane-less compartments and supramolecular structures and how they combine into advanced synthetic cells are presented. Then, the functional aspects are explored, addressing how artificial organelles in giant compartments mimic cellular processes. Finally, how artificial cells communicate with their surrounding and each other such as to adapt to an ever-changing environment and achieve collective behavior as a steppingstone toward artificial tissues, is taken a look at. Engineering artificial cells with highly controllable and programmable features open new avenues for the development of sophisticated multifunctional systems.

Ultrasound-nanovesicles interplay for theranostics

Nanovesicles (NVs) are widely used in the treatment and diagnosis of diseases due to their excellent vascular permeability, good biocompatibility, high loading capacity, and easy functionalization. However, their yield and in vivo penetration depth limitations and their complex preparation processes still constrain their application and development. Ultrasound, as a fundamental external stimulus with deep tissue penetration, concentrated energy sources, and good safety, has been proven to be a patient-friendly and highly efficient strategy to overcome the restrictions of traditional clinical medicine. Recent research has shown that ultrasound can drive the generation of NVs, increase their yield, simplify their preparation process, and provide direct therapeutic effects and intelligent control to enhance the therapeutic effect of NVs. In addition, NVs, as excellent drug carriers, can enhance the targeting efficiency of ultrasound-based sonodynamic therapy or sonogenetic regulation and improve the accuracy of ultrasound imaging. This review provides a detailed introduction to the classification, generation, and modification strategies of NVs, emphasizing the impact of ultrasound on the formation of NVs and summarizing the enhanced treatment and diagnostic effects of NVs combined with ultrasound for various diseases.

Advancing Biomimetic Functions of Synthetic Cells through Compartmentalized Cell-Free Protein Synthesis

Synthetic cells are artificial constructs that mimic the structures and functions of living cells. They are attractive for studying diverse biochemical processes and elucidating the origins of life. While creating a living synthetic cell remains a grand challenge, researchers have successfully synthesized hundreds of unique synthetic cell platforms. One promising approach to developing more sophisticated synthetic cells is to integrate cell-free protein synthesis (CFPS) mechanisms into vesicle platforms. This makes it possible to create synthetic cells with complex biomimetic functions such as genetic circuits, autonomous membrane modifications, sensing and communication, and artificial organelles. This Review explores recent advances in the use of CFPS to impart advanced biomimetic structures and functions to bottom-up synthetic cell platforms. We also discuss the potential applications of synthetic cells in biomedicine as well as the future directions of synthetic cell research.

A Self-Regenerating Artificial Cell, that is One Step Closer to Living Cells: Challenges and Perspectives

Controllable, self-regenerating artificial cells (SRACs) can be a vital advancement in the field of synthetic biology, which seeks to create living cells by recombining various biological molecules in the lab. This represents, more importantly, the first step on a long journey toward creating reproductive cells from rather fragmentary biochemical mimics. However, it is still a difficult task to replicate the complex processes involved in cell regeneration, such as genetic material replication and cell membrane division, in artificially created spaces. This review highlights recent advances in the field of controllable, SRACs and the strategies to achieve the goal of creating such cells. Self-regenerating cells start by replicating DNA and transferring it to a location where proteins can be synthesized. Functional but essential proteins must be synthesized for sustained energy generation and survival needs and function in the same liposomal space. Finally, self-division and repeated cycling lead to autonomous, self-regenerating cells. The pursuit of controllable, SRACs will enable authors to make bold advances in understanding life at the cellular level, ultimately providing an opportunity to use this knowledge to understand the nature of life.

Coacervate Droplets for Synthetic Cells

The design and construction of synthetic cells - human-made microcompartments that mimic features of living cells - have experienced a real boom in the past decade. While many efforts have been geared toward assembling membrane-bounded compartments, coacervate droplets produced by liquid-liquid phase separation have emerged as an alternative membrane-free compartmentalization paradigm. Here, the dual role of coacervate droplets in synthetic cell research is discussed: encapsulated within membrane-enclosed compartments, coacervates act as surrogates of membraneless organelles ubiquitously found in living cells; alternatively, they can be viewed as crowded cytosol-like chassis for constructing integrated synthetic cells. After introducing key concepts of coacervation and illustrating the chemical diversity of coacervate systems, their physicochemical properties and resulting bioinspired functions are emphasized. Moving from suspensions of free floating coacervates, the two nascent roles of these droplets in synthetic cell research are highlighted: organelle-like modules and cytosol-like templates. Building the discussion on recent studies from the literature, the potential of coacervate droplets to assemble integrated synthetic cells capable of multiple life-inspired functions is showcased. Future challenges that are still to be tackled in the field are finally discussed.

pH-Responsive Elastin-Like Polypeptide Designer Condensates

Biomolecular condensates are macromolecular complexes formed by liquid-liquid phase separation. They regulate key biological functions by reversibly compartmentalizing molecules in cells, in a stimulus-dependent manner. Designing stimuli-responsive synthetic condensates is crucial for engineering compartmentalized synthetic cells that are able to mimic spatiotemporal control over the biochemical reactions. Here, we design and test a family of condensate-forming, pH-responsive elastin-like polypeptides (ELPs) that form condensates above critical pH values ranging between 4 and 7, for temperatures between 20 and at 37 °C. We show that the condensation occurs rapidly, in sharp pH intervals (ΔpH < 0.3). For eventual applications in engineering synthetic cell compartments, we demonstrate that multiple types of pH-responsive ELPs can form mixed condensates inside micron-sized vesicles. When genetically fused with enzymes, receptors, and signaling molecules, these pH-responsive ELPs could be potentially used as pH-switchable functional condensates for spatially controlling biochemistry in engineered synthetic cells.

A transient vesicular glue for amplification and temporal regulation of biocatalytic reaction networks

Regulation of enzyme activity and biocatalytic cascades on compartmentalized cellular components is key to the adaptation of cellular processes such as signal transduction and metabolism in response to varying external conditions. Synthetic molecular glues have enabled enzyme inhibition and regulation of protein-protein interactions. So far, all the molecular glue systems based on covalent interactions operated under steady-state conditions. To emulate dynamic biological processes under dissipative conditions, we introduce herein a transient supramolecular glue with a controllable lifetime. The transient system uses multivalent supramolecular interactions between guanidinium group-bearing surfactants and adenosine triphosphate (ATP), resulting in bilayer vesicle structures. Unlike the conventional chemical agents for dissipative assemblies, ATP here plays the dual role of providing a structural component for the assembly as well as presenting active functional groups to "glue" enzymes on the surface. While gluing of the enzymes on the vesicles achieves augmented catalysis, oscillation of ATP concentration allows temporal control of the catalytic activities similar to the dissipative cellular nanoreactors. We further demonstrate temporal upregulation and control of complex biocatalytic reaction networks on the vesicles. Altogether, the temporal activation of biocatalytic cascades on the dissipative vesicular glue presents an adaptable and dynamic system emulating heterogeneous cellular processes, opening up avenues for effective protocell construction and therapeutic interventions.

Control of Enzyme Reactivity in Response to Osmotic Pressure Modulation Mimicking Dynamic Assembly of Intracellular Organelles

In response to variations in osmotic stress, in particular to hypertonicity associated with biological dysregulations, cells have developed complex mechanisms to release their excess water, thus avoiding their bursting and death. When water is expelled, cells shrink and concentrate their internal bio(macro)molecular content, inducing the formation of membraneless organelles following a liquid-liquid phase separation (LLPS) mechanism. To mimic this intrinsic property of cells, functional thermo-responsive elastin-like polypeptide (ELP) biomacromolecular conjugates are herein encapsulated into self-assembled lipid vesicles using a microfluidic system, together with polyethylene glycol (PEG) to mimic cells' interior crowded microenvironment. By inducing a hypertonic shock onto the vesicles, expelled water induces a local increase in concentration and a concomitant decrease in the cloud point temperature (Tcp ) of ELP bioconjugates that phase separate and form coacervates mimicking cellular stress-induced membraneless organelle assemblies. Horseradish peroxidase (HRP), as a model enzyme, is bioconjugated to ELPs and is locally confined in coacervates as a response to osmotic stress. This consequently increases local HRP and substrate concentrations and accelerates the kinetics of the enzymatic reaction. These results illustrate a unique way to fine-tune enzymatic reactions dynamically as a response to a physiological change in isothermal conditions.

Artificial Organelles with Digesting Characteristics: Imitating Simplified Lysosome- and Macrophage-Like Functions by Trypsin-Loaded Polymersomes

Defects in cellular protein/enzyme encoding or even in organelles are responsible for many diseases. For instance, dysfunctional lysosome or macrophage activity results in the unwanted accumulation of biomolecules and pathogens implicated in autoimmune, neurodegenerative, and metabolic disorders. Enzyme replacement therapy (ERT) is a medical treatment that replaces an enzyme that is deficient or absent in the body but suffers from short lifetime of the enzymes. Here, this work proposes the fabrication of two different pH-responsive and crosslinked trypsin-loaded polymersomes as protecting enzyme carriers mimicking artificial organelles (AOs). They allow the enzymatic degradation of biomolecules to mimic simplified lysosomal function at acidic pH and macrophage functions at physiological pH. For optimal working of digesting AOs in different environments, pH and salt composition are considered the key parameters, since they define the permeability of the membrane of the polymersomes and the access of model pathogens to the loaded trypsin. Thus, this work demonstrates environmentally controlled biomolecule digestion by trypsin-loaded polymersomes also under simulated physiological fluids, allowing a prolonged therapeutic window due to protection of the enzyme in the AOs. This enables the application of AOs in the fields of biomimetic therapeutics, specifically in ERT for dysfunctional lysosomal diseases.

Imaging Flow Cytometry for High-Throughput Phenotyping of Synthetic Cells

The reconstitution of basic cellular functions in micrometer-sized liposomes has led to a surge of interest in the construction of synthetic cells. Microscopy and flow cytometry are powerful tools for characterizing biological processes in liposomes with fluorescence readouts. However, applying each method separately leads to a compromise between information-rich imaging by microscopy and statistical population analysis by flow cytometry. To address this shortcoming, we here introduce imaging flow cytometry (IFC) for high-throughput, microscopy-based screening of gene-expressing liposomes in laminar flow. We developed a comprehensive pipeline and analysis toolset based on a commercial IFC instrument and software. About 60 thousands of liposome events were collected per run starting from one microliter of the stock liposome solution. Robust population statistics from individual liposome images was performed based on fluorescence and morphological parameters. This allowed us to quantify complex phenotypes covering a wide range of liposomal states that are relevant for building a synthetic cell. The general applicability, current workflow limitations, and future prospects of IFC in synthetic cell research are finally discussed.