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Rhodamine molecules are setting benchmarks in fluorescence microscopy. Herein, we report the deuterium (d12) congeners of tetramethyl(silicon)rhodamine, obtained by isotopic labelling of the four methyl groups, which improves photophysical (i.e. brightness, lifetimes) and chemical (i.e. bleaching) properties. We explore this finding for SNAP- and Halo-tag labelling, and highlight enhanced properties in several applications, such as Forster resonance energy transfer, fluorescence activated cell sorting, fluorescence lifetime microscopy and stimulated emission depletion nanoscopy. We envision deuteration as a generalizable concept to improve existing and develop new Chemical Biology Probes.

DNA origami, a method of folding DNA into precise nanostructures, has emerged as a powerful tool to design complex nanoscale shapes with movable parts. DNA origami has great potential as a drug delivery system that can encapsulate and protect a range of cargos spanning small molecules through large proteins, while remaining stable in a variety of ex vivo processing conditions and in vivo environments. DNA origami has been utilized for drug delivery applications, but the vast majority of these structures have been flexible, flat 2D or solid 3D nanostructures. There is a crucial need for a hollow and completely enclosed design capable of holding any type of cargo. In this paper, we present the design and assembly of a hollow DNA origami "box" with two actuatable lids. We characterize isothermal conditions for structural assembly in minutes that eliminates the need for a thermocycler. The stability of these structures is outstanding, remaining stable at body temperature and low pH for weeks and in the presence of solvents and biological fluids over several days. We demonstrate that passive loading of small molecules is charge dependent. We also outline an approach to design staple extensions pointing into the cavity or outside of the hollow DNA origami, allowing for either active loading of protein or the potential for decoration with passivating or targeting molecules. Future work includes fitting this hollow DNA origami structure with alternative lid opening mechanisms to release a variety of different cargos in response to environmental cues. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/586853v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@97179corg.highwire.dtl.DTLVardef@18f0b46org.highwire.dtl.DTLVardef@2d390eorg.highwire.dtl.DTLVardef@fcf35c_HPS_FORMAT_FIGEXP M_FIG C_FIG

Membrane proteins carry out a wide variety of biological functions. The reproduction of their specific properties in a technically controlled environment is of significant interest. Here, a method is presented that allows the self-assembly of a macroscopically large, freely transportable membrane with Outer membrane porin G from Escherichia Coli. The technique does not use protein specific characteristics and therefore could represent a path to the generation of extended layers of membranes with integrated, arbitrary membrane proteins. The composition of the membrane, its lipid and protein content, is experimentally controlled. Such in-vitro systems are relevant for the study of membrane-protein function and structure and the self-assembly of membrane-based protein complexes. They might become important for the incorporation of lipid-membranes into technical devices.

Respiratory monitoring in daily-life settings is important for health assessment, yet extracting physiologically interpretable information from breathing signals under natural conditions remains challenging, as breathing is inherently dynamic and strongly modulated by behavior. Here, a portable breathing monitoring device based on a flexible lead zirconate titanate sensor is developed to address this challenge. By exploiting polarity-opposed piezoelectric and pyroelectric responses through sensor orientation, the recorded breathing waveform exhibits a characteristic dual-component structure, consisting of a narrow transient spike followed by a broad quasi-steady peak within each breathing phase. This intrinsic waveform structure enables phase-resolved quantification of how breathing effort is distributed between transient and quasi-steady components during inhalation and exhalation. Pilot measurements in healthy subjects and patients with chronic obstructive pulmonary disease or asthma reveal systematic shifts toward transient-enhanced breathing in patients, providing clearer differentiation than conventional descriptors based on breathing duration or amplitude. By transforming complex breathing dynamics into stable and physiologically meaningful signal components under daily-life conditions, this dual-response sensing approach enables more robust access to function-related changes in natural breathing.

Scaffolded DNA origami has become a valuable nanoscale tool for applications in biomedical and physical sciences. Critical to leveraging the modular and programmable properties of DNA origami nanodevices is access to the scaffold strand, a long single-stranded DNA (ssDNA) of precise length and sequence, which is folded into a compact shape via piecewise base-pairing with many staple strands, short ssDNA oligonucleotides. Current methods to produce and manipulate long ssDNA scaffolds can be costly, time-consuming, and cumbersome. In contrast, methods to produce and manipulate the sequence of double-stranded DNA (dsDNA) are efficient and scalable. Here, we present a method for the rapid isolation of target ssDNA sequences from a variety of dsDNA sources using oligonucleotides as blocking strands that bind continuously to the undesired strand, thereby releasing the target scaffold strand. We report successful ssDNA isolation from linear and supercoiled dsDNAs of various sequences and lengths, ranging from 769 to 15,101 nucleotides. In addition to isolating ssDNA, we demonstrated this approach enables folding of DNA origami directly from dsDNA templates using both blocking and staple strands in a single-pot thermally controlled reaction. Furthermore, we explore multi-scaffold and gene-encoding DNA origami structures, expanding the framework for application-based designs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/709872v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1cc75dcorg.highwire.dtl.DTLVardef@4df8e2org.highwire.dtl.DTLVardef@10ed113org.highwire.dtl.DTLVardef@1c05bdd_HPS_FORMAT_FIGEXP M_FIG C_FIG

DNA nanostructures are typically assembled by thermal annealing in buffers containing magnesium. We demonstrate the assembly of DNA nanostructures at constant temperatures ranging from 4 {degrees}C to 50 {degrees}C in solutions containing different metal ions. The choice of metal ions and the assembly temperature influence the isothermal assembly of several DNA motifs and designed three-dimensional DNA crystals. Molecular dynamics simulations show more fluctuations of the DNA structure in select monovalent ions (Na+ and K+) compared to divalent ions (Mg2+ and Ca2+). A key highlight is the successful assembly of DNA motifs in nickel-containing buffer at temperatures below 40 {degrees}C, otherwise unachievable at higher temperatures, or using an annealing protocol. DNA nanostructures isothermally assembled in different ions do not affect the viability of fibroblasts, myoblasts, and myotubes and or the immune response in myoblasts. The use of ions other than the typically-used magnesium holds key potential in biological and materials science applications that require minimal amounts of magnesium.

DNA nanostructures are a class of self-assembling nanomaterials with a wide range of potential applications in biomedicine and nanotechnology. The history of DNA nanotechnology can be traced back to the 1980s with the development of simple DNA polyhedra using either human intuition or simple algorithms. Today the field is dominated by DNA origami constructs to such an extent that the original algorithms used to design non-origami nanostructures have been lost. In this work we describe Arktos: an algorithm developed to design simple DNA polyhedra without the use of DNA origami. Arktos designs sequences predicted to fold into a desired structure using simulated annealing optimization. As a proof-of-concept, we used Arktos to design a simple DNA tetrahedron. The generated oligonucleotide sequences were synthesized and experimentally validated via polyacrylamide gel electrophoresis, indicating that they fold into the desired structure. These results demonstrate that Arktos can be used to design custom DNA polyhedra as per the needs of the research community.

DNA base pairs can both encode biological information and be used as a programmable material to build nanostructures with potential application in nanofabrication, data processing and storage, biosensing and drug delivery. Over several decades development of these DNA origami nanostructures has led to increasingly advanced self-assembling nanostructures and molecular machines actuated by various mechanisms such as toehold-mediated strand displacement (TMSD), magnetism and even light. However, scalability remains challenging as using larger scaffold strands can increase the likelihood of kinetic traps and misfolded conformations. Here we describe a repeatable DNA nanohinge system to increase the scalability of existing nanohinge designs for hierarchical assembly of more complex structures with greater degrees of mobility and functionality. The components of this system, comprising two distinct nanohinges, were designed in caDNAno. Structure conformation and stability were simulated using CanDo and MrDNA, and hinge assembly was validated by TEM. Electron micrographs revealed hinge-shaped nanostructures capable of self-assembly into more complex structures, as well as actuation using TMSD through a reversible locking mechanism incorporated into the design. Our work expands the existing utility of DNA nanohinges as building blocks for scalable DNA nanostructures and demonstrates the feasibility of polymerizing hinges in a novel manner for higher order assembly. The enhanced functionality of our dual hinge systems can be employed in future applications requiring greater control and mobility of DNA nanostructures.

Bacterial pilin nanowires are protein complexes, suggested to possess electroactive capabilities forming part of the cells bioenergetic programming. Their role is thought to be linked to facilitating electron transfer with the external environment to permit metabolism and cell-to-cell communication. There is a significant debate, with varying hypotheses as to the nature of the proteins currently lying between type-IV pilin-based nanowires and polymerised cytochrome-based filaments. Importantly, to date, there is a very limited structure-function analysis of these structures within whole bacteria. In this work, we engineered Cupriavidus necator H16, a model autotrophic organism to express differing aromatic modifications of type-IV pilus proteins to establish structure-function relationships on conductivity and the effects this has on pili structure. This was achieved via a combination of high-resolution PeakForce tunnelling atomic force microscopy (PeakForce TUNA) technology, alongside conventional electrochemical approaches enabling the elucidation of conductive nanowires emanating from whole bacterial cells for the first time. This work is the first example of functional type-IV pili protein nanowires produced under aerobic conditions using a CN chassis. This work has far-reaching consequences in understanding the basis of bio-electrical communication between cells and with their external environment. O_FIG O_LINKSMALLFIG WIDTH=182 HEIGHT=200 SRC="FIGDIR/small/510814v2_ufig1.gif" ALT="Figure 1"> View larger version (90K): org.highwire.dtl.DTLVardef@134d026org.highwire.dtl.DTLVardef@4d84f3org.highwire.dtl.DTLVardef@15379fcorg.highwire.dtl.DTLVardef@16d942c_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract displaying theoretical PilA monomer models (left), PeakForce TUNA atomic force microscopy contact current images (right) of wild-type (top) and modified with increased tyrosine content (bottom) PilA filaments expressed by Cupriavidus necator H16 cells.

Procedures were devised for the reversible decondensation and recondensation of purified mitotic chromosomes. Computational methods were developed for the quantitative analysis of chromosome morphology in high throughput, enabling the recording of condensation behavior of thousands of individual chromosomes. Established physico-chemical theory for ionic hydrogels was modified for application to chromosomal material and shown to accurately predict the observed condensation behavior. The theory predicts a change of state (a "volume phase transition") in the course of condensation, and such a transition was shown to occur. These findings, together with classical cytology showing loops of chromatin, lead to the description of mitotic chromosome structure in terms of two simple principles: contraction of length of chromatin fibers by the formation of loops, radiating from a central axis; and condensation of the chromosomal material against the central axis through a volume phase transition. One sentence summaryThe mitotic chromosome is an axially scaffolded ionic hydrogel, undergoing a volume phase transition to achieve a condensed state.

Fabrication of nanoscale DNA devices to generate 3D nano-objects with precise control of shape, size, and presentation of ligands has shown tremendous potential for therapeutic applications. The interactions between different topologies of 3D DNA nanostructures and the cell membranes are crucial for designing efficient tools for interfacing DNA devices with biological systems. The practical applications of these DNA nanocages are still limited in cellular and biological systems owing to the limited understanding of interactions of different surface topologies of DNA nanodevices with cell membranes. The correlation between the geometry of DNA nanostructures and their internalization efficiency remains elusive. We investigated the influence of the shape and size of 3D DNA nanostructure on their cellular internalization efficiency. We found that of different geometries designed, one particular geometry, i.e., the tetrahedral shape, is more favoured over other geometries for their cellular uptake in 2D and 3D cell models. This is also replicable for cellular processes like 3D cell invasion assays in 3D spheroid models and passing the epithelial barriers in in-vivo zebrafish model systems. Our work establishes ground rules for the rational designing of DNA nanodevices for their upcoming biological and biomedical applications.

The interosseous membrane (IOM), a ligament-like structure spanning the radius and ulna, reduces strain in the ulna and structurally stiffens the radio-ulnar complex of the forearm. Using two-photon and second-harmonic-imaging we measured collagen and elastin signal intensity to test the hypothesis that their spatial distributions correspond to predominant loading patterns in the IOM. Distinct spatial gradients in collagen and elastin, as well as cruciate ligament-like architectures, were observed at the submicron and the micron to mesoscopic length scales. Quantitative analysis revealed anisotropies in the elastin-collagen composite comprising the IOM, with elastin 4-6 times higher than collagen concentrations at radius/ulna - IOM interfaces, and organized in the tensile loading direction, i.e. along the major Centroidal Axis, of the IOM. Hence, the IOM exhibits a composite structure comprising elastin and collagen, with spatial distribution of elastin higher than collagen at bone-IOM interfaces and decreasing from the interface with the ulna to that of the radius. These increased concentrations of elastin at interfaces are expected to confer elasticity (spring function). In contrast, peaks in collagen concentrations represent collagens organization into fibers, parallel to the length of the IOM, bridging the radius and ulna, and conferring toughness and damping function to the IOM and forearm construct. Mapping the cross-scale elastin and collagen composition of the IOM gives unprecedented insight into its emergent properties and associated mechanical function, an understanding of which may guide future surgical treatments, implant and medical textile design and manufacture, as well as physical therapy protocols to promote healing.

Liposomes are widely used as synthetic analogues of cell membranes and for drug delivery. Lipid-binding DNA nanostructures can modify the shape, porosity and reactivity of liposomes, mediated by cholesterol-modifications. DNA nanostructures can also be designed to switch conformations by DNA strand displacement. However, the optimal conditions to facilitate stable, high-yield DNA-lipid binding while allowing controlled switching by strand-displacement are not known. Here we characterised the effect of cholesterol arrangement, DNA structure, buffer and lipid composition on DNA-lipid binding and strand displacement. We observed that binding was inhibited below pH 4, and above 200 mM NaCl or 40 mM MgCl2, was independent of lipid type, and increased with membrane cholesterol content. For simple motifs, binding yield was slightly higher for double-stranded DNA than single-stranded. For larger DNA origami tiles, 4 - 8 cholesterol modifications were optimal, while edge positions and longer spacers increased yield of lipid-binding. Strand displacement achieved controlled removal of DNA tiles from membranes, but was inhibited by overhang domains, which are used to prevent cholesterol aggregation. These findings provide design guidelines for integrating strand-displacement switching with lipid-binding DNA nanostructures. This paves the way for achieving dynamic control of membrane morphology, enabling broader applications in nanomedicine and biophysics.

Active enzymes during catalyzing chemical reactions, have been found to generate significant mechanical fluctuations, which can influence the dynamics of their surroundings. These phenomena open new avenues for controlling mass transport in complex and dynamically inhomogeneous environments through localized chemical reactions. To explore this potential, we studied the uptake of transferrin molecules in retinal pigment epithelium (RPE) cells via clathrin-mediated endocytosis. In the presence of enzyme catalysis in the extracellular matrix, we observed a significant enhancement in the transport of fluorophore-tagged transferrin inside the cells. Fluorescence correlation spectroscopy measurements showed substantial increase in transferrin diffusion in the presence of active fluctuations. This study sheds light on the possibility that enzyme-substrate reactions within the extracellular matrix may induce long-range mechanical influences, facilitating targeted material delivery within intracellular milieu more efficiently than passive diffusion. These insights are expected to contribute to the development of better therapeutic strategies by overcoming limitations imposed by slow molecular diffusion under complex environments.

Encapsulins, self-assembling icosahedral protein nanocages derived from prokaryotes, represent a versatile set of tools for nanobiotechnology. However, a comprehensive understanding of the mechanisms underlying encapsulin self-assembly, disassembly, and reassembly is lacking. Here, we characterise the disassembly/reassembly properties of three encapsulin nanocages that possess different structural architectures: T = 1 (24 nm), T = 3 (32 nm), and T = 4 (42 nm). Using spectroscopic techniques and electron microscopy, encapsulin architectures were found to exhibit varying sensitivities to the denaturant guanidine hydrochloride (GuHCl), extreme pH, and elevated temperature. While all encapsulins showed the capacity to reassemble following GuHCl-induced disassembly (within 75 min), only the smallest T = 1 nanocage reassembled after disassembly in basic pH (within 15 min). Furthermore, atomic force microscopy revealed that all encapsulins showed a significant loss of structural integrity after undergoing sequential disassembly/reassembly steps. These findings provide insights into encapsulins disassembly/reassembly dynamics, thus informing their future design, modification, and application.

The silicification of DNA origami nanostructures offers a powerful strategy for enhancing their mechanical stability and resistivity against detrimental environmental conditions. In the past years, several studies have investigated different aspects of the silica coating procedure, leading to several different silicification protocols. Until now, the silica coating generally served as a protective layer or as the base for the further deposition of inorganic materials. However, it did not carry any additional functionality itself. Here, we present two different approaches for the customization of the silica coating on DNA origami nanostructures. Firstly, we developed a custom synthesized silica precursor carrying a fluorescein molecule to endow the silica coating of both DNA origami monomers and crystals with fluorescence and show the applicability of this novel silicification for the stabilization and tracking of DNA origami nanostructures intracellularly. Secondly, we employ a silica precursor containing a disulfide bridge to develop a silica coating that is dissolvable in a reducing environment. We anticipate that the results presented in this study will expand the toolbox of silicification in DNA nanotechnology and will further pave the way towards applications in drug delivery and material science.

Extracellular vesicles (EVs) have emerged as promising therapeutic entities in part due to their potential to regulate multiple signaling pathways in target cells. This potential is derived from the broad array of constituent and/or cargo molecules associated with EVs. Among these, microRNAs (miRNAs) are commonly implicated as important and have been associated with a wide variety of EV-induced biological phenomena. While controlled loading of single miRNAs is a well-documented approach for enhancing EV bioactivity, loading of multiple miRNAs has not been fully leveraged to maximize the potential of EV-based therapies. Here, an established approach to extrinsic nucleic acid loading of EVs, sonication, was utilized to enable controlled loading of multiple miRNAs in HEK293T EVs. Combinations of carefully chosen miRNAs were compared to single miRNAs with respect to anti-inflammatory outcomes in assays of increasing stringency, with the combination of miR-146a, miR-155, and miR-223 found to have the most potential amongst tested groups.

Extracellular vesicles (EVs) are promising tools to transfer macromolecular therapeutic molecules to recipient cells, however, efficient functional intracellular protein delivery by EVs remains challenging. Here, we have developed novel and versatile systems that leverage selected molecular tools to engineer EVs for robust cytosolic protein delivery both in vitro and in vivo. These systems, termed VSV-G plus EV-sorting Domain-Intein-Cargo (VEDIC) and VSV-G-Foldon-Intein-Cargo (VFIC), exploit an engineered mini-intein (intein) protein with self-cleavage activity to link cargo to an EV-sorting domain and release it from the EV membrane inside the EV lumen. In addition, we utilize the fusogenic protein VSV-G to facilitate endosomal escape and cargo release from the endosomal system to the cytosol of recipient cells. Importantly, we demonstrate that the combination of the self-cleavage intein, fusogenic protein and EV-sorting domain are indispensable for efficient functional intracellular delivery of cargo proteins by engineered EVs. As such, nearly 100% recombination and close to 80% genome editing efficiency in reporter cells were observed by EV-transferred Cre recombinase and Cas9/sgRNA RNPs, respectively. Moreover, EV-mediated Cre delivery by VEDIC or VFIC engineered EVs resulted in significant in vivo recombination in Cre-LoxP R26-LSL-tdTomato reporter mice following both local and systemic injections. Finally, we applied these systems for improved treatment of LPS-induced systemic inflammation by delivering a super-repressor of NF-B activity. Altogether, this study describes a platform by which EVs can be utilized as a vehicle for the efficient intracellular delivery of macromolecular therapeutics for treatments of disease. Graphic summary: Development of VEDIC and VFIC systems for high-efficiency intracellular protein delivery in vitro and in vivo.Intein in tripartite fusion protein (EV-sorting Domain-Intein-Cargo) performs C-terminal cleavage during the process of EV-biogenesis, resulting in enriched free cargo proteins inside of vesicles. Together with fusogenic protein, VSV-G, these engineered EVs achieve high-efficiency intracellular delivery of cargo protein (Cre and super repressor of NF-B) or protein complex (Cas9/sgRNA RNPs) both in reporter cells and in mice models. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/535834v4_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@d0da37org.highwire.dtl.DTLVardef@1a6514corg.highwire.dtl.DTLVardef@235c9aorg.highwire.dtl.DTLVardef@194bbfa_HPS_FORMAT_FIGEXP M_FIG C_FIG

Living organisms use biomolecular condensates to respond to dynamic environments and create functional materials with complex architectures. Exploring such phase-separated systems beyond the naturally occurring scenarios may offer valuable insights for emergent synthetic biosystems. Here, we report the self-assembly behavior of a short, disordered peptide sequence (termed CT45) derived from a protein present in the bioad-hesive system of tick ectoparasites. We show that CT45 spontaneously accumulates at polar-nonpolar interfaces, and further undergoes liquid-liquid and liquid-to-solid phase transitions to create mechanically stable structures. When encapsulated within vesicles and presented with a stable oil-water interface, CT45 rapidly forms solid shells, which can be reinforced by up-concentrating the material through osmotic imbalance. Unex-pectedly, when presented with a transient acetone-water interface, CT45 condenses at the evaporating interface and forms interconnected, porous mesoscopic scaffolds. The underlying mechanism is found to be the amphiphilic nature of CT45 leading to in-terfacial accumulation, enhancing intermolecular{pi} -based interactions to trigger phase transitions. The micron-sized shells exhibit appreciable mechanical strength and the porous scaffolds present a highly stable platform capable of retaining molecules. In conclusion, the presented condensate-based microscopic and mesoscopic scaffolds hold significance in customizable condensate architectures, with potential applications in biomedical engineering and synthetic biology.

Ligation of staple strands in DNA origami nanostructures (DONs) can yield enhanced structural stability in critical environments. This process can be viewed as performing hundreds of parallel reactions programmed on a self-assembled nanoscale platform. While previous studies have focused on investigating the collective results of the chemical or enzymatic ligation reactions, herein, the global assessment of individual ligation reactions is achieved using quantitative PCR (qPCR). By mapping enzymatic ligation efficiency on a trapezoidal substructure representing one third of a triangular DON, ligation is shown to preferentially occur at the trapezoid edges rather than at inner sites. Excellent agreement between the experimental ligation yields and docking simulations suggests that this is a result of variations in the ligase docking probability. Interestingly, removing neighboring staple strands increases the local dynamics on inner nick sites and thereby enhances the docking probability of the ligase, resulting in remarkably improved ligation yields. Finally, ligation products involving more than two consecutive sequences can be generated with each enzyme-catalyzed reaction as an independent event. This method provides unprecedented insight into the multiple ligation reactions occurring in parallel within complex DONs and will be an invaluable tool in the translation of DONs from the lab to real-world applications.