Collective Shape Actuation of Polymer Double Emulsions by Solvent Evaporation

Controlled evaporation-induced phase separation of droplets containing nanogels and salt molecules

Droplets without protection from surfactants or surfactant-like objects normally experience merging or a coalescence process since it is thermodynamically favored. However, division or replication of droplets is thermodynamically unfavored and comparably more difficult to realize. Herein, we demonstrate that a population of droplets that are composed of nanogels and salt spontaneously undergo a separation process under a slow solvent evaporation condition. Each individual droplet underwent changes in size, shape and eventually developed into two domains, which was caused by the screening effect due to the increased salt concentration as a result of solvent evaporation. The two domains gradually separated into nanogel-rich and salt-rich parts. These two parts eventually evolved into nanogel aggregates and branched structures, respectively. This separation was mainly due to the salting out effect and dewetting. Comparison studies indicate that both the nanogels and salt are indispensable ingredients for the phase separation. These discoveries may have profound applications in the fields of biomimetics and offer new routes for self-replication systems.

An individual droplet containing nanogels and salts can evolve into gel-rich and salt-rich two separate parts upon evaporation.

Nonviral Locally Injected Magnetic Vectors for In Vivo Gene Delivery: A Review of Studies on Magnetofection

Magnetic nanoparticles have been widely used in nanobiomedicine for diagnostics and the treatment of diseases, and as carriers for various drugs. The unique magnetic properties of "magnetic" drugs allow their delivery in a targeted tumor or tissue upon application of a magnetic field. The approach of combining magnetic drug targeting and gene delivery is called magnetofection, and it is very promising. This method is simple and efficient for the delivery of genetic material to cells using magnetic nanoparticles controlled by an external magnetic field. However, magnetofection in vivo has been studied insufficiently both for local and systemic routes of magnetic vector injection, and the relevant data available in the literature are often merely descriptive and contradictory. In this review, we collected and systematized the data on the efficiency of the local injections of magnetic nanoparticles that carry genetic information upon application of external magnetic fields. We also investigated the efficiency of magnetofection in vivo, depending on the structure and coverage of magnetic vectors. The perspectives of the development of the method were also considered.

Core–Shell Droplet Generation Device Using a Flexural Bolt-Clamped Langevin-Type Ultrasonic Transducer

Droplets with a core–shell structure formed from two immiscible liquids are used in various industrial field owing to their useful physical and chemical characteristics. Efficient generation of uniform core–shell droplets plays an important role in terms of productivity. In this study, monodisperse core-shell droplets were efficiently generated using a flexural bolt-clamped Langevin-type transducer and two micropore plates. Water and silicone oil were used as core and shell phases, respectively, to form core–shell droplets in air. When the applied pressure of the core phase, the applied pressure of the shell phase, and the vibration velocity in the micropore were 200 kPa, 150 kPa, and 8.2 mm/s, respectively, the average diameter and coefficient of variation of the droplets were 207.7 μm and 1.6%, respectively. A production rate of 29,000 core–shell droplets per second was achieved. This result shows that the developed device is effective for generating monodisperse core–shell droplets.

Spontaneous Creation of Anisotropic Polymer Crystals with Orientation-Sensitive Birefringence in Liquid Drops

It remains a grand challenge to prepare anisotropic crystal superstructures with sensitive optical properties in polymer science and materials field. This study demonstrates that semicrystalline polymers develop into anisotropic hollow spherulitic crystals spontaneously at interfaces of liquid drops. In contrast to conventional spherulites with centrosymmetric optics and grain boundaries, these anisotropic spherulitic crystals have vanished boundary defects, tunable aspect ratios, and noncentrosymmetric, orientation-sensitive birefringence. The experimental finding is elaborated in poly(l-lactic acid) crystals and is further verified in a broad class of semicrystalline polymers, irrespective of molecular chirality, chemical constitution, or interfacial modification. The facile methods and general mechanism revealed in this study shed light on developing new types of optical microdevices and synthesis of anisotropic semicrystalline particles from liquid emulsions.

On-Demand Generation of Double Emulsions Based on Interface Shearing for Controlled Ultrasound Activation

Stimuli-responsive microcarriers (SRMs) based on multiple emulsions can be widely used in advanced drug delivery, tissue engineering, biosensing, and cell biology. Here a simple and effective compound interface shearing (CIS) method is proposed to one-step produce SRMs for controlled ultrasound (US) activation. In the CIS process, a coaxial needle supplying the core and shell liquids vibrates periodically across a free gas-liquid surface, resulting in the pinch-off of a compound liquid neck for on-demand generation of multiple emulsions. The CIS process is free of confined walls with a pure interface shearing mechanism. Perfectly uniform SRMs with tunable core-shell volume ratios can be produced, following a scaling law of their size as a function of the liquid flow rates and the vibration frequency. US- and magnetic-responsive microcapsules are prepared for magnetic-guided site-targeting delivery, and acid-aided sequential US activation realizes the synergistic delivery of hydrophilic and hydrophobic payloads. It can be concluded that the CIS technique is able to generate multifunctional SRMs at low cost, high uniformity, high flexibility, and effective process control for various fields of potential applications.

Effect of PEGylated Magnetic PLGA-PEI Nanoparticles on Primary Hippocampal Neurons: Reduced Nanoneurotoxicity and Enhanced Transfection Efficiency with Magnetofection

Despite broad application of nanotechnology in neuroscience, the nanoneurotoxicity of magnetic nanoparticles in primary hippocampal neurons remains poorly characterized. In particular, understanding how magnetic nanoparticles perturb neuronal calcium homeostasis is critical when considering magnetic nanoparticles as a nonviral vector for effective gene therapy in neuronal diseases. Here, we address the pressing need to systematically investigate the neurotoxicity of magnetic nanoparticles with different surface charges in primary hippocampal neurons. We found that unlike negative and neutral nanoparticles, positively charged magnetic nanoparticles (magnetic poly(lactic-co-glycolic acid) (PLGA)-polyethylenimine (PEI) nanoparticles, MNP-PLGA-PEI NPs) rapidly elevated cytoplasmic calcium levels in primary hippocampal neurons, mainly via extracellular calcium influx regulated by voltage-gated calcium channels. We went on to show that this perturbation of intracellular calcium homeostasis elicited serious cytotoxicity in primary hippocampal neurons. However, our next experiment demonstrated that PEGylation on the surface of MNP-PLGA-PEI NPs shielded the surface charge, thereby preventing the perturbation of intracellular calcium homeostasis. That is, PEGylated MNP-PLGA-PEI NPs reduced nanoneurotoxicity. Importantly, biocompatible PEGylated MNP-PLGA-PEI NPs under an external magnetic field enhanced transfection efficiency (>7%) of plasmid DNA encoding GFP in primary hippocampal neurons compared to NPs without external magnetic field mediation. Moreover, under an external magnetic field, this system achieved gene transfection in the hippocampus of the C57 mouse. Overall, this study is the first to successfully employ biocompatible PEGylated MNP-PLGA-PEI NPs for transfection using a magnetofection strategy in primary hippocampal neurons, thereby providing a nanoplatform as a new perspective for treating neuronal diseases or modulating neuron activities.