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It is self-evident that our chests expand and contract during breathing but, surprisingly, exactly how individual alveoli change shape over the respiratory cycle is still a matter of debate. Some argue that all the alveoli expand and contract rhythmically. Others claim that the lung volume change is due to groups of alveoli collapsing and reopening during ventilation. Although this question might seem to be an insignificant detail for healthy individuals, it might be a matter of life and death for patients with compromised lungs. Past analyses were based on static post-mortem preparations primarily due to technological limitations, and therefore, by definition, incapable of providing dynamic information. In contrast, this study provides the first comprehensive dynamic data on how the shape of the alveoli changes, and, further, provides valuable insights into the optimal lung volume for efficient gas exchange. It is concluded that alveolar micro-dynamics is nonlinear; and at medium lung volume, alveoli expand more than the ducts., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Arginine-rich cell-penetrating peptides (CPPs) have emerged as valuable tools for the intracellular delivery of bioactive molecules, but their membrane perturbation during cell penetration is not fully understood. Here, nona-arginine (R 9 )-mediated membrane reorganization that facilitates the translocation of peptides across laterally heterogeneous membranes is directly visualized. The electrostatic binding of cationic R 9 to anionic phosphatidylserine (PS)-enriched domains on a freestanding lipid bilayer induces lateral lipid rearrangements; in particular, in real-time it is observed that R 9 fluidizes PS-rich liquid-ordered (L o ) domains into liquid-disordered (L d ) domains, resulting in the membrane permeabilization. The experiments with giant unilamellar vesicles (GUVs) confirm the preferential translocation of R 9 through L d domains without pore formation, even when L o domains are more negatively charged. Indeed, whenever R 9 comes into contact with negatively charged L o domains, it dissolves the L o domains first, promoting translocation across phase-separated membranes. Collectively, the findings imply that arginine-rich CPPs modulate lateral membrane heterogeneity, including membrane fluidization, as one of the fundamental processes for their effective cell penetration across densely packed lipid bilayers., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Living cells efflux intracellular ions for maintaining cellular life, so intravital measurements of specific ion signals are of significant importance for studying cellular functions and pharmacokinetics. In this work, de novo synthesis of artificial K + -selective membrane and its integration with polyelectrolyte hydrogel-based open-junction ionic diode (OJID) is demonstrated, achieving a real-time K + -selective ion-to-ion current amplification in complex bioenvironments. By mimicking biological K + channels and nerve impulse transmitters, in-line K + -binding G-quartets are introduced across freestanding lipid bilayers by G-specific hexylation of monolithic G-quadruplex, and the pre-filtered K + flow is directly converted to amplified ionic currents by the OJID with a fast response time at 100 ms intervals. By the synergistic combination of charge repulsion, sieving, and ion recognition, the synthetic membrane allows K + transport exclusively without water leakage; it is 250× and 17× more permeable toward K + than monovalent anion, Cl - , and polyatomic cation, N-methyl-d-glucamine + , respectively. The molecular recognition-mediated ion channeling provides a 500% larger signal for K + as compared to Li + (0.6× smaller than K + ) despite the same valence. Using the miniaturized device, non-invasive, direct, and real-time K + efflux monitoring from living cell spheroids is achieved with minimal crosstalk, specifically in identifying osmotic shock-induced necrosis and drug-antidote dynamics., (© 2023 Wiley-VCH GmbH.)

As biomolecules essential for sustaining life, proteins are generated from long chains of 20 different α-amino acids that are folded into unique 3D structures. In particular, many proteins have molecular recognition functions owing to their binding pockets, which have complementary shapes, charges, and polarities for specific targets, making these biopolymers unique and highly valuable for biomedical and biocatalytic applications. Based on the understanding of protein structures and microenvironments, molecular complementarity can be exhibited by synthesizable and modifiable materials. This has prompted researchers to explore the proteomimetic potentials of a diverse range of materials, including biologically available peptides and oligonucleotides, synthetic supramolecules, inorganic molecules, and related coordination networks. To fully resemble a protein, proteomimetic materials perform the molecular recognition to mediate complex molecular functions, such as allosteric regulation, signal transduction, enzymatic reactions, and stimuli-responsive motions; this can also expand the landscape of their potential bio-applications. This review focuses on the recognitive aspects of proteomimetic designs derived for individual materials and their conformations. Recent progress provides insights to help guide the development of advanced protein mimicry with material heterogeneity, design modularity, and tailored functionality. The perspectives and challenges of current proteomimetic designs and tools are also discussed in relation to future applications., (© 2023 Wiley-VCH GmbH.)

Biopolymers are essential building blocks that constitute cells and tissues with well-defined molecular structures and diverse biological functions. Their three-dimensional (3D) complex architectures are used to analyze, control, and mimic various cells and their ensembles. However, the free-form and high-resolution structuring of various biopolymers remain challenging because their structural and rheological control depend critically on their polymeric types at the submicron scale. Here, direct 3D writing of intact biopolymers is demonstrated using a systemic combination of nanoscale confinement, evaporation, and solidification of a biopolymer-containing solution. A femtoliter solution is confined in an ultra-shallow liquid interface between a fine-tuned nanopipette and a chosen substrate surface to achieve directional growth of biopolymer nanowires via solvent-exclusive evaporation and concurrent solution supply. The evaporation-dependent printing is biopolymer type-independent, therefore, the 3D motor-operated precise nanopipette positioning allows in situ printing of nucleic acids, polysaccharides, and proteins with submicron resolution. By controlling concentrations and molecular weights, several different biopolymers are reproducibly patterned with desired size and geometry, and their 3D architectures are biologically active in various solvents with no structural deformation. Notably, protein-based nanowire patterns exhibit pin-point localization of spatiotemporal biofunctions, including target recognition and catalytic peroxidation, indicating their application potential in organ-on-chips and micro-tissue engineering., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Cell membranes actively change their local compositions, serving essential biological processes such as cellular signaling and endocytosis. Although membrane dynamics is vital in the cellular functions, the complexity of natural membranes has made its fundamental understanding and systematic assessment difficult. Here, a powerful artificial membrane system is developed for real-time visualization of the spatiotemporal dynamics of membrane remodeling. Through well-defined air/oil/water interfaces on grid holes, tens of planar lipid bilayer membranes are easily created, and their reproducibility, controllability, and generality are highlighted. The freestanding membranes are large but also highly stable, facilitating direct long-term monitoring of dynamic membrane reconstitution caused by external stimuli. As an example to demonstrate the superiority of this membrane system, the effect of cholesterol trafficking, which significantly affects biophysical properties of cell membranes, is investigated at different membrane compositions. Cholesterol transport into and out of the membranes at different rates causes anomalous lipid arrangements through cholesterol-mediated phase transitions and decomposition, which have never been witnessed before. Furthermore, enzyme-induced membrane dynamics is successfully shown in this platform; sphingomyelinases locally generate asymmetry between two membrane leaflets. This technique is broadly applicable for exploring the membrane heterogeneity under various membrane-based reactions, providing valuable insight into the membrane dynamics., (© 2020 Wiley-VCH GmbH.)

We report the first in vitro selection of DNA nanostructures that switch their conformation when triggered by change in pH. Previously, most pH-active nanostructures were designed using known pH-active motifs, such as the i-motif or the triplex structure. In contrast, we performed de novo selections starting from a random library and generated nanostructures that can sequester and release Mipomersen, a clinically approved antisense DNA drug, in response to pH change. We demonstrate extraordinary pH-selectivity, releasing up to 714-fold more Mipomersen at pH 5.2 compared to pH 7.5. Interestingly, none of our nanostructures showed significant sequence similarity to known pH-sensitive motifs, suggesting that they may operate via novel structure-switching mechanisms. We believe our selection scheme is general and could be adopted for generating DNA nanostructures for many applications including drug delivery, sensors and pH-active surfaces., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The optical properties of metamaterials made by block copolymer self-assembly are tuned by structural and environmental variations. The plasma frequency red-shifts with increasing lattice constant and blue-shifts as the network filling fraction increases. Infiltration with dielectric liquids leads also to a red-shift of the plasma edge. A 300 nm-thick slab of gyroid-structured gold has a remarkable transmission of 20%., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Metallic single gyroids, a new class of self-assembled nanoplasmonic metamaterials, are analyzed on the basis of a tri-helical metamaterial model. The physical mechanisms underlying the chiral optical behavior of the nanoplasmonic single gyroid are identified and it is shown that the optical chirality in this metallic structure is primarily determined by structural chirality and the connectivity of helices along the main cubic axes., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)