Living cells possess membraneless organelles formed by liquid-liquid phase separation. With the aim of better understanding the general functions of membraneless microcompartments, this paper constructs acellular multicompartment reaction systems using an aqueous multiphase system. Membraneless coacervate droplets are placed within a molecularly crowded environment, where a larger dextran (DEX) droplet is submerged in a polyethylene glycol (PEG) solution. The coacervate droplets are capable of sequestering reagents and enzymes with a long retention time, and demonstrate multistep cascading reactions through the liquid-liquid interfaces. The ability to change phase dynamics is also demonstrated through salt-mediated dissolution of coacervate droplets, which leads to the release and mixing of separately sequestered reagents and enzymes. Finally, as phase-separated materials in membraneless organelles are often substrates and substrate analogues for the enzymes sequestered or excluded in the organelles, this paper explores the interaction between DEX and dextranase, an enzyme that hydrolyzes DEX. The results reveal that dextranase suffers from substrate inhibition when partitioned directly in a DEX phase but that this inhibition can be mitigated and reactions greatly accelerated by compartmentalization of dextranase inside a coacervate droplet that is adjacent to, but phase-separated from, the DEX phase. The insight that compartmentalization of enzymes can accelerate reactions by mitigating substrate inhibition is particularly novel and is an example where artificial membraneless organelle-like systems may provide new insights into physiological cell functions.

Covalent UV/vis-quantifiable bis-aryl hydrazone bond formation was investigated for the preparation of conjugates between α-poly-d-lysine (PDL) and either α-chymotrypsin (α-CT) or horseradish peroxidase (HRP). PDL and the enzymes were first modified via free amino groups with the linking reagents succinimidyl 6-hydrazinonicotinate acetone hydrazone (S-HyNic, at pH 7.6) and succinimidyl 4-formylbenzoate (S-4FB, at pH 7.2), respectively. The modified PDL and enzymes were then conjugated at pH 4.7, whereby polymer chains carrying several enzymes were obtained. Kinetics of the bis-aryl hydrazone bond formation was investigated spectrophotometrically at 354 nm. Retention of the enzymatic activity after conjugate formation was confirmed by using the substrates N-succinimidyl-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide (for α-CT) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, for HRP). Thus, not only a mild and efficient preparation and convenient quantification of a conjugate between the polycationic α-polylysine and enzymes could be shown, but also the complete preservation of the enzymatic activity.

Phase fluorimetry, unlike the more commonly used intensity-based measurements, is not affected by differences in light paths from culture vessels, by optical attenuation through dense 3D cell cultures and hydrogels, and minimizes the dependence on signal intensity for accurate measurements. This work describes the use of phase fluorimetry on oxygen-sensor microbeads to perform oxygen measurements in different microtissue culture environments. In one example, cell spheroids were observed to deplete oxygen from the cell-culture medium filling the bottom of conventional microwells within minutes, whereas oxygen concentrations remained close to ambient levels for several days in hanging-drop cultures. By dispersing multiple oxygen-microsensors in cell-laden hydrogels, we also mapped cell-generated oxygen gradients. The spatial oxygen mapping was sufficiently precise to enable use of computational models of oxygen diffusion and uptake to give estimates of the cellular oxygen uptake rate and the half-saturation constant. The results show the importance of integrated design and analysis of 3D cell cultures from both a biomaterial and oxygen supply aspect. While this paper specifically tests spheroids and cell-laden gel cultures, the described methods should be useful for measuring pericellular oxygen concentrations in many different biomaterials and culture formats.

This paper analyzes the use of a dehydrating oil system to determine binodal curves of an aqueous two phase system (ATPS). Aqueous droplets containing phase-forming polymers are dehydrated at the interface between two immiscible oils. The droplets shrink due to diffusion of water into the oil phase while constantly maintaining a spherical shape. Upon sufficient dehydration, dilute one-phase solutions of phase-forming polymers separate into two phases. Comparison of the droplet diameter at this phase separation point and at the beginning allows facile calculation of the concentration of polymers that determine the binodal curve. The miniaturized droplet dehydration-based binodals obtained in this manner matched the binodals determined by the conventional diluting method but using several orders of magnitude less sample volume (150 nL droplets versus 10 mL vials).

Here, we produce poly(lactide-co-glycolide) (PLGA) based microparticles with varying morphologies, and temperature responsive properties utilizing a Pluronic F127/dextran aqueous two-phase system (ATPS) assisted self-assembly. The PLGA polymer, when emulsified in Pluronic F127/dextran ATPS, forms unique microparticle structures due to ATPS guided-self assembly. Depending on the PLGA concentration, the particles either formed a core-shell or a composite microparticle structure. The microparticles facilitate the simultaneous incorporation of both hydrophobic and hydrophilic molecules, due to their amphiphilic macromolecule composition. Further, due to the lower critical solution temperature (LCST) properties of Pluronic F127, the particles exhibit temperature responsiveness. The ATPS based microparticle formation demonstrated in this study, serves as a novel platform for PLGA/polymer based tunable micro/nano particle and polymersome development. The unique properties may be useful in applications such as theranostics, synthesis of complex structure particles, bioreaction/mineralization at the two-phase interface, and bioseparations.

A highly sensitive 27 MHz quartz crystal microbalance instrument with an automatic flow injection system was developed to obtain realistic minimal frequency noise (±0.05 Hz) and to obtain a stable signal baseline (±1 Hz/h) by controlling the temperature of each part in the quartz crystal microbalance (QCM) system using three Peltier devices with a resolution of ±0.001 °C and by optimizing the flow system to prevent fluctuation of the internal pressure of the QCM. The improved QCM with an automatic flow injection system enabled detection of small mass changes such as binding of biotin to a streptavidin-immobilized QCM with a high signal-to-noise ratio. We also applied this device to enzyme reactions of one-base elongation by DNA polymerase (Klenow fragment, KF). We immobilized dsDNAs including the protruding end of dA, dG, dT, or dC on the QCM electrode and ran complementary dNTP monomers with KF into the QCM flow cell. We could directly detect the enzymatic one-base elongation of DNA as a small mass increase, and we found the difference in the reaction rate for each monomer.

Simultaneous detection of multiple analytes from a single sample (multiplexing), particularly when done at the point of need, can guide complex decision-making without increasing the required sample volume or cost per test. Despite recent advances, multiplexed analyte sensing still typically faces the critical limitation of measuring only one type of molecule (e.g., small molecules or nucleic acids) per assay platform. Here, we address this bottleneck with a customizable platform that integrates cell-free expression (CFE) with a polymer-based aqueous two-phase system (ATPS), producing membrane-less protocells containing transcription and translation machinery used for detection. We show that multiple protocells, each performing a distinct sensing reaction, can be arrayed in the same microwell to detect chemically diverse targets from the same sample. Furthermore, these protocell arrays are compatible with human biofluids, maintain function after lyophilization and rehydration, and can produce visually interpretable readouts, illustrating this platform’s potential as a minimal-equipment, field-deployable, multi-analyte detection tool.

of extracellular DNA in tissues and in circulation. [5] Extracellular DNA is capable of engaging with the immune system as depicted in Figure 1; therefore, as synthetic DNA-based biomaterials emerge, their potential immune responses must be considered. DNA sensors are mediators of extracellular DNA immune responses observed in vivo, including cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) and toll-like receptors (TLRs). Defining novel DNA sensors and their mechanisms is an active area of investigation. [6] Likewise, the structural and chemical properties of DNA that triggers DNA sensors continue to be uncovered. [6] This review summarizes known DNA interaction modalities with the immune system, the sources of extracellular DNA, and, finally, the relevant and emerging biotechnologies that incorporate DNA molecules. A focus is geared toward innate immune responses and doublestranded DNA (dsDNA). Leveraging the immunomodulatory capacity of DNA enables tailoring materials to initiate specific immune outcomes depending on the application, for instance, priming aggressive immune responses for localized tumor-interfacing biomaterials or immunosuppressive functions to prevent chronic inflammation on implant surfaces. Achieving this requires an improved understanding of the DNA properties, such as backbone chemistry, base pair sequence, charge, and length, that can function as design levers for the immune response. The Role of Extracellular DNA in the Immune ResponseThe immune system is designed to protect the host against infections by distinguishing between self-and non-self motifs, and by identifying pathogen and damage signals. Upon recognition of a "non-self" or foreign molecule, an array of effector functions are triggered and orchestrated by immune cells to achieve pathogen clearance and restore homeostasis. [7] These immunoactivating defense mechanisms include the release of proinflammatory cytokines, immune cell recruitment, programmed cell death, and phagocytosis. Ideally, immunoactivating responses are supplanted by immunosuppressive functions once the pathogen or agonist is resolved. This immune resolution is necessary to coordinate healing and anti-inflammatory functions such as diminished chemokine and cytokine secretion, replacement Man-made DNA materials hold the potential to modulate specific immune pathways toward immunoactivating or immunosuppressive cascades. DNAbased biomaterials introduce DNA into the extracellular environment during implantation or delivery, and subsequently intracellularly upon phagocytosis or degradation of the material. Therefore, the immunogenic functionality of biological and synthetic extracellular DNA should be considered to achieve desired immune responses. In vivo, extracellular DNA from both endogenous and exogenous sources holds immunoactivating functions which can be traced back to the molecular features of DNA, such as sequence and length. Extracellular DNA is recognized as damage-associated molecular patterns (DAMPs), or pathogen-associated mole...