Droplet breakup mechanisms in premix membrane emulsification and related microfluidic channels

Oriented Interpenetrating Capillary Network with Surface Engineering by Porous ZnO from Wood for Membrane Emulsification

Membrane emulsification technology has garnered increasing interest in emulsion preparation due to controllable droplet size, narrower droplet size distribution, low energy consumption, simple process design and excellent reproducibility. Nevertheless, the pore structure and surface engineering in membrane materials design play a crucial role in achieving high-quality emulsions with high throughput simultaneously. In this work, an oriented interpenetrating capillary network composed of highly aligned and interconnected wood cell lumens has been utilized to fabricate an emulsion membrane. A novel honeycomb porous ZnO layer obtained by a seed prefabrication-hydrothermal growth method was designed to reconstruct wood channel surfaces for enhanced microfluid mixing. The results show that through the unique capillary mesh microstructure of wood, the emulsion droplets were smaller in size, had narrower pore-size distribution, and were easy to obtain under high throughput conditions. Meanwhile, a well-designed ZnO layer could further improve the emulsion quality of a wood membrane, while the emulsifying throughput is still maintained at a higher level. This demonstrates that the convection process of the microfluid in these wood capillary channels was intensified markedly. This study not only develops advanced membrane materials in emulsion preparation, but also introduces a brand-new field for functional applications of wood.

Understanding droplet breakup in a post-array device with sheath-flow configuration

Microfluidic post-array devices have the potential to generate quasi-monodisperse emulsion droplets with high throughput and dispersed phase fractions by splitting droplets with regularly arranged posts. However, the lack of understanding of post-array devices makes it challenging to predict droplet size and quantitatively evaluate the influence of post geometry, hindering their widespread application. Therefore, we investigated the characteristics of droplet breakup through a post array using a series of devices with sheath-flow configurations, in which the dispersed and continuous flow rates could be flexibly tuned. Using a poly(dimethylsiloxane)-glass device fabricated via soft lithography, we found that the volume ratio of the dispersed phase to the continuous phase significantly affects the droplet size, even when the viscosity ratio is close to one. For the first time, we demonstrated that the effective capillary number calculated from the emulsion viscosity and effect of the dispersed phase fraction consistently describes various experimental results. Furthermore, our flow observations and droplet diameter measurement showed two breakup modes: the size-constant obstruction and shear-induced modes with a power-law correlation similar to droplet splitting in a T-junction. Thus, the power-law correlation in microfluidic droplet splitting successfully expresses the droplet generation characteristics in post-array devices. A combination of effective viscosity correction and curve fitting allowed us to evaluate the influence of the material and post-geometry on droplet generation characteristics. This study contributes to the understanding of droplet breakup in post-array devices and extends their unique droplet generation properties to include high-throughput, high-fraction, robust, and continuous emulsification processes.

Development of tetracycline-modified nanoparticles for bone-targeted delivery of anti-tubercular drug

Background: Since the poor response to existing anti-tuberculosis drugs and low drug concentration in local bone tissues, the traditional drug therapy does not result in satisfactory treatment of osteoarticular tuberculosis. Thus, we report a rifapentine release system with imparted bone targeting potential using tetracycline (TC) -modified nanoparticles (NPs). Methods: TC was conjugated to PLGA-PEG copolymer via a DCC/NHS technique. Rifapentine-loaded NPs were prepared by premix membrane emulsification technique. The resulting NPs were characterized in terms of physicochemical characterization, hemolytic study, cytotoxicity, bone mineral binding ability, in vitro drug release, stability test and antitubercular activity. The pharmacokinetic and biodistribution studies were also performed in mice. Results: Rifapentine loaded TC-PLGA-PEG NPs were proved to be 48.8 nm in size with encapsulation efficiency and drug loading of 83.3% ± 5.5% and 8.1% ± 0.4%, respectively. The release of rifapentine from NPs could be maintained for more than 60 h. Most (68.0%) TC-PLGA-PEG NPs could bind to HAp powder in vitro. The cellular studies revealed that NPs were safe for intravenous administration. In vivo evaluations also revealed that the drug concentration of bone tissue in TC-PLGA-PEG group was significantly higher than that in other groups at all time (p < 0.05). Both NPs could improve pharmacokinetic parameters without evident organ toxicity. The minimal inhibitory concentration of NPs was 0.094 μg/mL, whereas this of free rifapentine was 0.25 μg/mL. Conclusion: Rifapentine loaded TC-PLGA-PEG NPs could increase the amount of rifapentine in bone tissue, prolong drug release in systemic circulation, enhance anti-tuberculosis activity, and thereby reducing dose and frequency of drug therapy for osteoarticular tuberculosis.

Optimization of Pea Protein Isolate-Stabilized Oil-in-Water Ultra-Nanoemulsions by Response Surface Methodology and the Effect of Electrolytes on Optimized Nanoemulsions

Nanoemulsions are optically transparent and offer good stability, bioavailability, and control over the targeted delivery and release of lipophilic active components. In this study, pea protein isolate (PPI)-stabilized O/W nanoemulsions were evaluated using response surface methodology to obtain optimized ultra-nanoemulsions of Sauter mean diameter (D3,2) < 100 nm using a high-pressure homogenizer (HPH). Furthermore, the effect of food matrix electrolytes, i.e., the pH and ionic strength, on the emulsion (prepared at optimized conditions) was investigated. The results revealed that the droplet size distribution of emulsions was mainly influenced by the PPI concentration and the interaction of oil concentration and HPH pressure. Moreover, a non-significant increase in droplet size was observed when the nanoemulsions (having an initial D3,2 < 100 nm) were stored at 4 °C for 7 days. Based on the current experimental design, nanoemulsions with a droplet size < 100 nm can effectively be prepared with a high PPI concentration (6.35%), with less oil (1.95%), and at high HPH pressure (46.82 MPa). Such emulsions were capable of maintaining a droplet size below 100 nm even at ionic conditions of up to 400 mM NaCl and at acidic pH.

Research on the Centrifugal Driving of a Water-in-Oil Droplet in a Microfluidic Chip with Spiral Microchannel

Combining the advantages of droplet-based microfluidics and centrifugal driving, a method for centrifugally driving W/O droplets with spiral microchannel is proposed in this paper. A physical model of droplet flow was established to study the flow characteristics of the W/O droplet in the spiral microchannel driven by centrifugal force, and kinematic analysis was performed based on the rigid body assumption. Then, the theoretical formula of droplet flow rate was obtained. The theoretical value was compared with the actual value measured in the experiments. The result shows that the trend of the theoretical value is consistent with the measured value, and the theoretical value is slightly larger than the experimentally measured value caused by deformation. Moreover, it is found that the mode of centrifugal driving with spiral microchannel has better flow stability than the traditional centrifugal driving structure. A larger regulation speed range can be achieved by adjusting the motor speed without using expensive equipment or precise instruments. This study can provide a basis and theoretical reference for the development of droplet-based centrifugal microfluidic chips.