DNA has the potential to achieve a controllable macromolecular structure, such as hydrogels or droplets formed through liquid-liquid phase separation (LLPS), as the design of its base sequence can result in programmable interactions. Here, we constructed “DNA droplets” via LLPS of sequence-designed DNA nanostructures and controlled their dynamic functions by designing their sequences. Specifically, we were able to adjust the temperature required for the formation of DNA droplets by designing the sequences. In addition, the fusion, fission, and formation of Janus-shaped droplets were controlled by sequence design and enzymatic reactions. Furthermore, modifications of proteins with sequence-designed DNAs allowed for their capture into specific droplets. Overall, our results provide a platform for designing and controlling macromolecular droplets via the information encoded in component molecules and pave the way for various applications of sequence-designed DNA such as cell mimics, synthetic membraneless organelles, and artificial molecular systems.

Controlled synthesis of micro multi-compartmental particles using a centrifuge droplet shooting device (CDSD) is reported. Sodium alginate solutions introduced in a multi-barreled capillary form droplets at the capillary orifice under ultrahigh gravity and gelify in a CaCl(2) solution. The size, shape, and compartmentalization of the particles are controlled. Co-encapsulation of Jurkat cells and magnetic colloids into Janus particles is demonstrated. The Janus particles present sensitive reaction toward magnetic fields, while the viability of the encapsulated cells is 91%.

This paper describes a methodology for the rapid and highly selective detection of cocaine using a membrane protein channel combined with a DNA aptamer. The DNA aptamer recognizes the cocaine molecule with high selectivity. We successfully detected a low concentration of cocaine (300 ng/mL, the drug test cutoff limit) within 60 s using a biological nanopore embedded in a microchip.

Cell-sized liposomes and droplets coated with lipid layers have been used as platforms for understanding live cells, constructing artificial cells, and implementing functional biomedical tools such as biosensing platforms and drug delivery systems. However, these systems are very fragile, which results from the absence of cytoskeletons in these systems. Here, we construct an artificial cytoskeleton using DNA nanostructures. The designed DNA oligomers form a Y-shaped nanostructure and connect to each other with their complementary sticky ends to form networks. To undercoat lipid membranes with this DNA network, we used cationic lipids that attract negatively charged DNA. By encapsulating the DNA into the droplets, we successfully created a DNA shell underneath the membrane. The DNA shells increased interfacial tension, elastic modulus, and shear modulus of the droplet surface, consequently stabilizing the lipid droplets. Such drastic changes in stability were detected only when the DNA shell was in the gel phase. Furthermore, we demonstrate that liposomes with the DNA gel shell are substantially tolerant against outer osmotic shock. These results clearly show the DNA gel shell is a stabilizer of the lipid membrane akin to the cytoskeleton in live cells.iposomes have been used as artificial cell models to understand cell shape, membrane protein function, and lipid− protein interaction, among other biological functions (1-3). In addition, liposomes have been used as a platform for biosensing and as drug delivery systems (DDS) because of their excellent biocompatibility and biodegradability (4). However, liposomes collapse easily against environmental shifts and mechanical forces because of their low bending modulus. The fragility of liposomes causes uncontrolled leakage of the entrapped compounds and thus inhibits their use in biomedical applications and artificial cells experiments.In contrast, cell membranes are tolerant against environmental shifts and mechanical forces. The stability of cell membrane arises from the cytoskeleton underneath the membrane. The major component of cytoskeletons is actin (5). Actin gels show high elasticity (6), which ensures the stability of cell membranes against various forces. For liposomes, the use of actin filaments as a cytoskeleton is not an optimal strategy for the following three reasons: First, although actin bundles and actomyosin rings have been reconstituted in artificial cells (7,8), formation of an actin cortex underneath artificial membranes has been still challenging. Second, actin is hard to modify by chemical and genetic means because of its essentiality for cell growth. Third, the physicochemical properties of actin gels are still unclear (9, 10). Hence, the cytoskeleton of liposomes should be constructed with defined and designable materials. To accomplish this aim, DNA nanotechnology, which uses limited components with high designability in a nanometer scale (11), is a feasible candidate to construct cytoskeleton structures in artificial cells.DNA nanostructure...

Feedback regulation plays a crucial role in dynamic gene expression in nature, but synthetic translational feedback systems have yet to be demonstrated. Here we use an RNA/protein interaction-based synthetic translational switch to create a feedback system that tightly controls the expression of proteins of interest in mammalian cells. Feedback is mediated by modified ribosomal L7Ae proteins, which bind a set of RNA motifs with a range of affinities. We designed these motifs into L7Ae-encoding mRNA. Newly translated L7Ae binds its own mRNA, inhibiting further translation. This inhibition tightly feedback-regulates the concentration of L7Ae and any fusion partner of interest. A mathematical model predicts system behavior as a function of RNA/protein affinity. We further demonstrate that the L7Ae protein can simultaneously and tunably regulate the expression of multiple proteins of interest by binding RNA control motifs built into each mRNA, allowing control over the coordinated expression of protein networks.

The magnetic actuation of deposited drops has mainly relied on volume forces exerted on the liquid to be transported, which is poorly efficient with conventional diamagnetic liquids such as water and oil, unless magnetosensitive particles are added. Herein, we describe a new and additive‐free way to magnetically control the motion of discrete liquid entities. Our strategy consists of using a paramagnetic liquid as a deformable substrate to direct, using a magnet, the motion of various floating liquid entities, ranging from naked drops to liquid marbles. A broad variety of liquids, including diamagnetic (water, oil) and nonmagnetic ones, can be efficiently transported using the moderate magnetic field (ca. 50 mT) produced by a small permanent magnet. Complex trajectories can be achieved in a reliable manner and multiplexing potential is demonstrated through on‐demand drop fusion. Our paramagnetofluidic method advantageously works without any complex equipment or electric power, in phase with the necessary development of robust and low‐cost analytical and diagnostic fluidic devices.

This paper describes an AND logic operation with amplification and transcription from DNA to RNA, using T7 RNA polymerase. All four operations, (0 0) to (1 1), with an enzyme reaction can be performed simultaneously, using four-droplet devices that are directly connected to a patch-clamp amplifier. The output RNA molecule is detected using a biological nanopore with single-molecule translocation. Channel current recordings can be obtained using the enzyme solution. The integration of DNA logic gates into electrochemical devices is necessary to obtain output information in a human-recognizable form. Our method will be useful for rapid and confined DNA computing applications, including the development of programmable diagnostic devices.

Phase‐separated biomolecular droplets are formed in cells to regulate various biological processes. This phenomenon can be applied to constructing self‐assembled dynamic molecular systems such as artificial cells and molecular robots. Recently, programmable phase‐separated droplets called DNA droplets have been reported as a possible method to construct such dynamic molecular systems. This study reports a computational DNA droplet that can recognize a specific combination of tumor biomarker microRNAs (miRNAs) as molecular inputs and output a DNA logic computing result by physical DNA droplet phase separation. A mixed DNA droplet consisting of three DNA nanostructures with orthogonal sticky‐end sequences and two linker DNAs to cross‐bridge the orthogonal DNA nanostructures is proposed. By the hybridization of miRNAs with the linkers, the cross‐bridging ability is lost, causing the phase‐separation of the mixed DNA droplet into three DNA droplets, resulting in executing a miRNA pattern recognition described by a logical expression ((miRNA‐1 ∧ miRNA‐2) ∧ (miRNA‐3 ∧ ¬miRNA‐4)). This experimentally demonstrates that the computational DNA droplets recognize the above specific pattern of chemically synthesized miRNA sequences as a model experiment. In the future, this method will provide potential applications such as diagnosis and therapy with integration to biomolecular robots and artificial cells.