Tunable and scalable fabrication of block copolymer-based 3D polymorphic artificial cell membrane array

Bottom-up development of lipid-based synthetic cells for practical applications

Synthetic cells (SCs) can be engineered from the bottom up to recapitulate the functional properties of natural cells while performing specialized tasks such as drug delivery, biosensors, bioproduction, vaccine development, and even environmental remediation. Recent advances in synthetic biology, biomaterials, and microfluidics have enabled the development of increasingly sophisticated SCs. Transitioning from proof-of-concept demonstrations to practical applications requires a deep understanding of the design principles, materials, and fabrication techniques involved. This review provides a comprehensive overview of the current state of bottom-up SC technology and highlights the most promising approaches and applications. Challenges in the implementation of SCs and their prospects for future applications are also discussed.

Exploring the Application of Advanced Chromatographic Methods to Characterize the Surface Physicochemical Properties and Transition Phenomena of Polystyrene-b-poly(4-vinylpyridine)

The linear diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) is an important copolymer recently used in many applications such as optoelectronics, sensors, catalysis, membranes, energy conversion, energy storage devices, photolithography, and biomedical applications. (1) Background: The surface thermodynamic properties of PS-P4VP copolymers are of great importance in many chemical and industrial processes. (2) Methods: The inverse gas chromatography (IGC) at infinite dilution was used for the experimental determination of the retention volumes of organic solvents adsorbed on copolymer surfaces as a function of temperature. This led to the variations in the free energy of interaction necessary to the evaluation of the London dispersive and polar acid-base surface energies, the polar enthalpy and entropy, the Lewis acid-base constants, and the transition temperatures of the PS-P4VP copolymer. (3) Results: The application of the thermal Hamieh model led to an accurate determination of the London dispersive surface energy of the copolymer that showed non-linear variations versus the temperature, highlighting the presence of two transition temperatures. It was observed that the Lewis acid-base parameters of the copolymer strongly depend on the temperature, and the Lewis base constant of the solid surface was shown to be higher than its acid constant. (4) Conclusions: An important effect of the temperature on the surface thermodynamic properties of PS-P4VP was proven and new surface correlations were determined.

A nondestructive membrane engineering method using an amphiphilic polymer

The cellular signaling process or ion transport is mediated by membrane proteins (MPs) located on the cell surface, and functional studies of MPs have mainly been conducted using cells endogenously or transiently expressing target proteins. Reconstitution of purified MPs in the surface of live cells would have advantages of short manipulation time and ability to target cells in which gene transfection is difficult. However, direct reconstitution of MPs in live cells has not been established. The traditional detergent-mediated reconstitution method of MPs into a lipid bilayer cannot be applied to live cells because this disrupts and reforms the lipid bilayer structure, which is detrimental to cell viability. In this study, we demonstrated that GPCRs (prostaglandin E2 receptor 4 [EP4] and glucagon-like peptide-1 receptor [GLP1R]) or serotonin receptor 3A (5HT3A), a ligand-gated ion channel, stabilized with amphiphilic poly-γ-glutamate (APG), can be reconstituted into mammalian cell plasma membranes without affecting cell viability. Furthermore, 5HT3A reconstituted in mammalian cells showed ligand-dependent Ca2+ ion transport activity. APG-mediated reconstitution of GPCR in synthetic liposomes showed that electrostatic interaction between APG and membrane surface charge contributed to the reconstitution process. This APG-mediated membrane engineering method could be applied to the functional modification of cell membranes with MPs in live cells.

Fabrication of polymeric microspheres for biomedical applications

Polymeric microspheres (PMs) have attracted great attention in the field of biomedicine in the last several decades due to their small particle size, special functionalities shown on the surface and high surface-to-volume ratio. However, how to fabricate PMs which can meet the clinical needs and transform laboratory achievements to industrial scale-up still remains a challenge. Therefore, advanced fabrication technologies are pursued. In this review, we summarize the technologies used to fabricate PMs, including emulsion-based methods, microfluidics, spray drying, coacervation, supercritical fluid and superhydrophobic surface-mediated method and their advantages and disadvantages. We also review the different structures, properties and functions of the PMs and their applications in the fields of drug delivery, cell encapsulation and expansion, scaffolds in tissue engineering, transcatheter arterial embolization and artificial cells. Moreover, we discuss existing challenges and future perspectives for advancing fabrication technologies and biomedical applications of PMs.

Looking both ways: Electroactive biomaterials with bidirectional implications for dynamic cell-material crosstalk

Cells exist in natural, dynamic microenvironmental niches that facilitate biological responses to external physicochemical cues such as mechanical and electrical stimuli. For excitable cells, exogenous electrical cues are of interest due to their ability to stimulate or regulate cellular behavior via cascade signaling involving ion channels, gap junctions, and integrin receptors across the membrane. In recent years, conductive biomaterials have been demonstrated to influence or record these electrosensitive biological processes whereby the primary design criterion is to achieve seamless cell-material integration. As such, currently available bioelectronic materials are predominantly engineered toward achieving high-performing devices while maintaining the ability to recapitulate the local excitable cell/tissue microenvironment. However, such reports rarely address the dynamic signal coupling or exchange that occurs at the biotic-abiotic interface, as well as the distinction between the ionic transport involved in natural biological process and the electronic (or mixed ionic/electronic) conduction commonly responsible for bioelectronic systems. In this review, we highlight current literature reports that offer platforms capable of bidirectional signal exchange at the biotic-abiotic interface with excitable cell types, along with the design criteria for such biomaterials. Furthermore, insights on current materials not yet explored for biointerfacing or bioelectronics that have potential for bidirectional applications are also provided. Finally, we offer perspectives aimed at bringing attention to the coupling of the signals delivered by synthetic material to natural biological conduction mechanisms, areas of improvement regarding characterizing biotic-abiotic crosstalk, as well as the dynamic nature of this exchange, to be taken into consideration for material/device design consideration for next-generation bioelectronic systems.

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.

Morphology Engineering of the Asymmetric PS-b-P4VP Block Copolymer: From Porous to Nanodot Oxide Structures

In the present work, we demonstrate the formation of oxide porous and nanodot structures from the same block copolymer (BCP) by the phase inversion of a BCP template. We investigated the effect of solvent annealing time on the ordering of asymmetric, cylinder forming, polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) BCP. Phase separation of PS-b-P4VP was achieved by solvent vapor annealing (SVA) in a solvent atmosphere that is (partially) selective to P4VP to initially generate hexagonally arranged, cylindrical arrays of the expected structure. The morphology of the BCP changed from P4VP hexagonally packed cylinders to an 'inverse' structure with PS cylinders embedded in a P4VP matrix. This suggests that selective swelling occurs over time such that the swollen P4VP phase becomes the majority volume component. Metal ions (Ga3+, In3+) were infiltrated into the BCP templates by a solution-mediated infiltration approach, followed by an ultraviolet-ozone treatment to remove the polymer and oxidize the metallic ions to their oxides. The findings show that a single BCP can be used to create both metal oxide arrays and porous structures of metal oxides by simply varying the duration of the solvent annealing process. The resulting structures were analyzed through several methods including scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, and energy-dispersive X-ray spectroscopy. XPS analyses confirmed the complete elimination of the BCP template and the presence of metal oxides. This study provides important insights into the development of functional BCP materials with inverse structures.

Liquid Phase Infiltration of Block Copolymers

Novel materials with defined composition and structures at the nanoscale are increasingly desired in several research fields spanning a wide range of applications. The development of new approaches of synthesis that provide such control is therefore required in order to relate the material properties to its functionalities. Self-assembling materials such as block copolymers (BCPs), in combination with liquid phase infiltration (LPI) processes, represent an ideal strategy for the synthesis of inorganic materials into even more complex and functional features. This review provides an overview of the mechanism involved in the LPI, outlining the role of the different polymer infiltration parameters on the resulting material properties. We report newly developed methodologies that extend the LPI to the realisation of multicomponent and 3D inorganic nanostructures. Finally, the recently reported implementation of LPI into different applications such as photonics, plasmonics and electronics are highlighted.

Highly Ordered Porous Inorganic Structures via Block Copolymer Lithography: An Application of the Versatile and Selective Infiltration of the "Inverse" P2VP-b-PS System

A facile and versatile strategy was developed to produce highly ordered porous metal oxide structures via block copolymer (BCP) lithography. Phase separation of poly(2-vinylpyridine)-b-polystyrene (P2VP-b-PS) was induced by solvent vapor annealing in a nonselective solvent environment to fabricate cylindrical arrays. In this work, we thoroughly analyzed the effects of the film thickness, solvent annealing time, and temperature on the ordering of a P2VP-majority system for the first time, resulting in "inverse" structures. Reflectometry, atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy were used to characterize the formation of the highly ordered BCP morphology and the subsequently produced metal oxide film. At 40 min solvent annealing time, hexagonally close packed structures were produced with cylinder diameters ∼40 nm. Subsequently, the BCP films were infiltrated with different metal cations. Metal ions (Cr, Fe, Ni, and Ga) selectively infiltrated the P2VP domain, while the PS did not retain any detectable amount of metal precursor. This gave rise to a metal oxide porous structure after a UV/ozone (UVO) treatment. The results showed that the metal oxide structures demonstrated high fidelity compared to the BCP template and cylindrical domains presented a similar size to the previous PS structure. Moreover, XPS analyses revealed the complete elimination of the BCP template and confirmed the presence of the metal oxides. These metal oxides were used as hard masks for pattern transfer via dry etching as a further application. Silicon nanopores were fabricated mimicking the BCP template and demonstrated a pore depth of ∼50 nm. Ultimately, this strategy can be applied to create different inorganic nanostructures for a diverse range of applications, for example, solar cells, diodes, and integrated circuits. Furthermore, by optimizing the etching parameters, deeper structures can be obtained via ICP/RIE processes, leading to many potential applications.

Bio-Inspired Robots and Structures toward Fostering the Modernization of Agriculture

Biomimetics is the interdisciplinary cooperation of biology and technology that offers solutions to practical problems by analyzing biological systems and transferring their principles into applications. This review article focused on biomimetic innovations, including bio-inspired soft robots and swarm robots that could serve multiple functions, including the harvesting of fruits, pest control, and crop management. The research demonstrated commercially available biomimetic innovations, including robot bees by Arugga AI Farming and the Robotriks Traction Unit (RTU) precision farming equipment. Additionally, soft robotic systems have made it possible to mitigate the risk of surface bruises, rupture, the crushing destruction of plant tissue, and plastic deformation in the harvesting of fruits with a soft rind such as apples, cherries, pears, stone fruits, kiwifruit, mandarins, cucumbers, peaches, and pome. Even though the smart farming technologies, which were developed to mimic nature, could help prevent climate change and enhance the intensification of agriculture, there are concerns about long-term ecological impact, cost, and their inability to complement natural processes such as pollination. Despite the problems, the market for bio-inspired technologies with potential agricultural applications to modernize farming and solve the abovementioned challenges has increased exponentially. Future research and development should lead to low-cost FEA robotic grippers and FEA-tendon-driven grippers for crop harvesting. In brief, soft robots and swarm robotics have immense potential in agriculture.