RESUMEN

The key problem that hinders the water transportation performance and application of microchannels is the annoying gaslock. Realizing liquid transport without the gaslock requires a specially designed pump and a channel system, as well as the reduction of gas concentration in liquids. In nature, to eat viscous nectar with high efficiency, hummingbirds use their open geometric tongue for nectar-sucking. Inspired by hummingbirds' tongue, we report a bionic open microchannel that discharges unwanted gas inside the microchannel from the opening without influencing its fluidic performance. The opening can also be used for extrusion of oil droplets in microchannels, indicating great potential applications in oil-water separation and chemical slow release, especially for bubble discharge in microchannels. Most significantly, a mimicked "leaf" with our bionic open microchannnels exhibits marvelous "transpiration" performance when irradiated by a laser. Our work provides a new strategy for the fabrication of open microchannels and sheds light on potential applications of multiphase phenomena in microchannels including oil-water separation, phase change heat and mass transfer, solar vapor generation, and precisely controllable drug delivery.

Asunto(s)

Néctar de las Plantas , Agua , Gases , Rayos Láser

RESUMEN

High-throughput enzyme screening for desired functionality is highly demanded. This paper utilizes a newly developed microfluidic pneumatic printing platform for high-throughput enzyme screening applications. The novel printing platform can achieve distinct features including a disposable cartridge, which avoids crosstalk; a flexible cartridge design, allowing for integration of multiple channels; and fast printing speed with submicroliter spot size. Moreover, a polydimethylsiloxane (PDMS)-based sandwich structure has been proposed and used during the printing and imaging, which can lead to better results, including reduced evaporation as well as a uniform light path during imaging. Using this microfluidic pneumatic printed PDMS sandwiched microdroplet array platform, we have demonstrated the capability of high-throughput generation of a combinatorial droplet array with concentration and volume gradients. Furthermore, the potential for enzymatic study has been validated by quantified cellulose reaction implemented with the printing platform.

Asunto(s)

Celulasa/metabolismo , Ensayos Analíticos de Alto Rendimiento/métodos , Microfluídica/métodos , Impresión , Celulosa/metabolismo , Luz , Programas Informáticos

RESUMEN

BACKGROUND: A key challenge in the manufacturing of polymeric colloids is producing nanoparticles with good batch-to-batch consistency. OBJECTIVE: Develop a robust microfluidics method for the preparation of PEG-PLGA nanoparticles using dimethyl sulfoxide (DMSO) as the organic phase solvent for the encapsulation of DMSO soluble agents. METHODS: Microfluidic process parameters, total flow rate (10 mL/min), flow rate ratio (1:1) of the aqueous phase and the organic polymer solution, and polymer concentration (5 mg/ml). Polyvinyl alcohol (PVA) or human serum albumin (HSA) was included in the aqueous phase. Dynamic light scattering and transmission electron microscopy were used to investigate the size and morphology of particles. RESULTS: PLGA nanoparticles made using DMSO with the aqueous solvent containing PVA (2%) had an average size of 60 nm while PLGA-PEG nanoparticles made with and without PVA (2%) had an average size of 70 and 100 nm, respectively. PLGA-PEG nanoparticles generated with or without PVA had a high batch-to-batch coefficient of variation for the particle size of 20% while for PLGA nanoparticles with PVA it was 4%. HSA added to the aqueous phase reduced the size and the zeta potential of PEG-PLGA nanoparticles as well the batch-to-batch coefficient of variation for particle size to < 5%. Nanoparticles were stable in solution and after lyophilized in the presence of sucrose. CONCLUSION: Albumin was involved in the self-assembly of PEG-PLGA nanoparticles altering the physicochemical properties of nanoparticles. Adding protein to the aqueous phase in the microfluidic fabrication process may be a valuable tool for tuning the properties of nanoparticles and improving batch-to-batch consistency.

Asunto(s)

Poliésteres/síntesis química , Polietilenglicoles/síntesis química , Alcohol Polivinílico/química , Albúmina Sérica Humana/química , Humanos , Técnicas Analíticas Microfluídicas , Nanopartículas , Tamaño de la Partícula , Poliésteres/química , Polietilenglicoles/química

RESUMEN

Despite recent progresses in the field of microfluidics, the effect of liquid pressure on the detection accuracy has been rarely studied. Here, we perform a quantitative analysis of such effect, by utilizing the sensitive optical responses of graphene to the refractive index (RI) change of its surrounding environment. We utilize a reflection coupling configuration by combining the total internal reflection (TIR) and ultrasonic waves. The high-performance graphene is processed on common glasses by using the solution-processable oxidation-reduction method. We find that the RI change of water caused by a pressure as small as 500 Pa generated by the liquid level change in the microfluidics can be measured directly. The detection accuracy and response time limits are approximately 280 Pa and 100 ns, respectively. The Maxwell's boundary conditions, Fresnel's law, and Pascal's law are used in theoretical analyses. This work highlights the importance of liquid pressure in microfluidics and provides guidance in designing and accurate detection of microfluidic devices.

RESUMEN

Massively parallel single-cell RNA sequencing can precisely resolve cellular diversity in a high-throughput manner at low cost, but unbiased isolation of intact single cells from complex tissues such as adult mammalian brains is challenging. Here, we integrate sucrose-gradient-assisted purification of nuclei with droplet microfluidics to develop a highly scalable single-nucleus RNA-seq approach (sNucDrop-seq), which is free of enzymatic dissociation and nucleus sorting. By profiling ∼18,000 nuclei isolated from cortical tissues of adult mice, we demonstrate that sNucDrop-seq not only accurately reveals neuronal and non-neuronal subtype composition with high sensitivity but also enables in-depth analysis of transient transcriptional states driven by neuronal activity, at single-cell resolution, in vivo.

Asunto(s)

Núcleo Celular/metabolismo , Corteza Cerebral/metabolismo , Secuenciación de Nucleótidos de Alto Rendimiento , Neuronas/metabolismo , ARN/genética , Convulsiones/genética , Análisis de Secuencia de ARN/métodos , Análisis de la Célula Individual/métodos , Transcripción Genética , Animales , Núcleo Celular/patología , Centrifugación por Gradiente de Densidad , Corteza Cerebral/patología , Corteza Cerebral/fisiopatología , Modelos Animales de Enfermedad , Células Madre Embrionarias Humanas/metabolismo , Humanos , Cinética , Masculino , Ratones , Ratones Endogámicos C57BL , Técnicas Analíticas Microfluídicas , Células 3T3 NIH , Inhibición Neural , Neuronas/patología , Pentilenotetrazol , ARN/metabolismo , Convulsiones/metabolismo , Convulsiones/patología , Convulsiones/fisiopatología , Transmisión Sináptica , Transfección

RESUMEN

Fiber-based techniques hold great potential toward the development of structures that mimic the architecture of fibrous tissues, such as tendon. Microfluidics and polyelectrolyte complexation are among the most widely used techniques for the fabrication of fibrous structures. In this work, we combined both techniques to generate hydrogel fibers with a fibrillar-like structure. For this, either methacrylated hyaluronic acid (MA-HA) or chondroitin sulfate (MA-CS) were mixed with alginate (ALG), being all negatively charged polysaccharides, combined with chitosan (CHT), which is positively charged, and separately injected into a microfluidic device. Through a continuous injection into a coagulation bath and subsequent photo-cross-linking, we could obtain multicomponent hydrogel fibers, which exhibited smaller fibrils aligned in parallel, whenever CHT was present. The biological performance was assessed upon encapsulation and further culture of tendon cells. Overall, the reported process did not affect cell viability and cells were also able to maintain their main function of producing extracellular matrix up to 21 days in culture. In summary, we developed a novel class of photo-cross-linkable multicomponent hydrogel fibers than can act as bioactive modulators of cell behavior.

RESUMEN

Directional liquid transportation is important for a variety of biological processes and technical applications. Although surface engineering through asymmetric chemical modification or geometrical patterning facilitates effective liquid manipulation and enables water droplet self-transportation on synthetic surfaces, self-transportation of oil droplets poses a major challenge because of their low surface tension. We report oil droplet self-transportation on oleophobic surfaces that are microtextured with radial arrays of undercut stripes. More significantly, we observe three modes of oil motion on various sample surfaces, namely, inward transportation, pinned, and outward spreading, which can be switched by the structure parameters, including stripe intersection angle and width. Accompanying theoretical modeling provides an in-depth mechanistic understanding of the structure-droplet motion relationship. Finally, we reveal how to optimize the texture parameters to maximize oil droplet self-transportation capability and demonstrate spontaneous droplet movement for liquids down to a surface tension of 22.4 mN/m. The surfaces presented here open up new avenues for power-free liquid transportation and oil contamination self-removal applications in various analytical and fluidic devices.

Asunto(s)

Aceites/química , Interacciones Hidrofóbicas e Hidrofílicas , Microscopía Electrónica de Rastreo , Modelos Químicos , Propiedades de Superficie , Imagen de Lapso de Tiempo

RESUMEN

Paracetamol (PCM)-loaded composite nanoparticles (NPs) composed of a biodegradable poly(d,l-lactide) (PLA) polymer matrix filled with organically modified montmorillonite (MMT) nanoparticles were fabricated by antisolvent nanoprecipitation in a microfluidic co-flow glass capillary device. The incorporation of MMT in the polymer improved both the drug encapsulation efficiency and the drug loading, and extended the rate of drug release in simulated intestinal fluid (pH 7.4). The particle size increased on increasing both the drug loading and the concentration of MMT in the polymer matrix, and decreased on increasing the aqueous to organic flow rate ratio. The drug encapsulation efficiency in the NPs was higher at higher aqueous to organic flow rate ratio due to faster formation of the NPs. The PCM-loaded PLA NPs containing 2 wt% MMT in PLA prepared at an aqueous to organic flow rate ratio of 10 with an orifice size of 200 µm exhibited a spherical shape with a mean size of 296 nm, a drug encapsulation efficiency of 38.5% and a drug loading of 5.4%. The encapsulation of MMT and PCM in the NPs was confirmed by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis and attenuated total reflection-Fourier transform infrared spectroscopy.

Asunto(s)

Acetaminofén/farmacocinética , Bentonita/química , Vidrio/química , Microfluídica/métodos , Nanopartículas/química , Poliésteres/química , Acetaminofén/química , Analgésicos no Narcóticos/química , Analgésicos no Narcóticos/farmacocinética , Rastreo Diferencial de Calorimetría , Preparaciones de Acción Retardada/química , Preparaciones de Acción Retardada/farmacocinética , Portadores de Fármacos/química , Liberación de Fármacos , Concentración de Iones de Hidrógeno , Microscopía Electrónica de Transmisión , Nanopartículas/ultraestructura , Tamaño de la Partícula , Solventes/química , Espectrometría por Rayos X , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos X

RESUMEN

The development of long-term human organotypic liver-on-a-chip models for successful prediction of toxic response is one of the most important and urgent goals of the NIH/DARPA's initiative to replicate and replace chronic and acute drug testing in animals. For this purpose, we developed a microfluidic chip that consists of two microfluidic chambers separated by a porous membrane. The aim of this communication is to demonstrate the recapitulation of a liver sinusoid-on-a-chip, using human cells only for a period of 28 days. Using a step-by-step method for building a 3D microtissue on-a-chip, we demonstrate that an organotypic in vitro model that reassembles the liver sinusoid microarchitecture can be maintained successfully for a period of 28 days. In addition, higher albumin synthesis (synthetic) and urea excretion (detoxification) were observed under flow compared to static cultures. This human liver-on-a-chip should be further evaluated in drug-related studies.

Asunto(s)

Hígado/fisiología , Microfluídica/métodos , Técnicas de Cultivo de Órganos/métodos , Evaluación Preclínica de Medicamentos/métodos , Humanos , Modelos Biológicos , Factores de Tiempo

RESUMEN

RE-1 silencing transcription factor (REST), a master negative regulator of neuronal differentiation, controls neurogenesis by preventing the differentiation of neural stem cells. Here we focused on the role of REST in the early steps of differentiation and maturation of adult hippocampal progenitors (AHPs). REST knockdown promoted differentiation and affected the maturation of rat AHPs. Surprisingly, REST knockdown cells enhanced the differentiation of neighboring wild-type AHPs, suggesting that REST may play a non-cell-autonomous role. Gene expression analysis identified Secretogranin II (Scg2) as the major secreted REST target responsible for the non-cell-autonomous phenotype. Loss-of-function of Scg2 inhibited differentiation in vitro, and exogenous SCG2 partially rescued this phenotype. Knockdown of REST in neural progenitors in mice led to precocious maturation into neurons at the expense of mushroom spines in vivo. In summary, we found that, in addition to its cell-autonomous function, REST regulates differentiation and maturation of AHPs non-cell-autonomously via SCG2. SIGNIFICANCE STATEMENT: Our results reveal that REST regulates differentiation and maturation of neural progenitor cells in vitro by orchestrating both cell-intrinsic and non-cell-autonomous factors and that Scg2 is a major secretory target of REST with a differentiation-enhancing activity in a paracrine manner. In vivo, REST depletion causes accelerated differentiation of newborn neurons at the expense of spine defects, suggesting a potential role for REST in the timing of the maturation of granule neurons.

Asunto(s)

Diferenciación Celular/fisiología , Células-Madre Neurales/fisiología , Neuronas/fisiología , Proteínas Represoras/fisiología , Secretogranina II/metabolismo , Animales , Células Cultivadas , Femenino , Hipocampo/citología , Hipocampo/crecimiento & desarrollo , Hipocampo/metabolismo , Ratones , Ratones Endogámicos C57BL , Células-Madre Neurales/metabolismo , Neurogénesis/fisiología , Ratas Wistar

RESUMEN

A size-based blood cell sorting model with a micro-fence structure is proposed in the frame of immersed boundary and lattice Boltzmann method (IB-LBM). The fluid dynamics is obtained by solving the discrete lattice Boltzmann equation, and the cells motion and deformation are handled by the immersed boundary method. A micro-fence consists of two parallel slope post rows which are adopted to separate red blood cells (RBCs) from white blood cells (WBCs), in which the cells to be separated are transported one after another by the flow into the passageway between the two post rows. Effected by the cross flow, RBCs are schemed to get through the pores of the nether post row since they are smaller and more deformable compared with WBCs. WBCs are required to move along the nether post row till they get out the micro-fence. Simulation results indicate that for a fix width of pores, the slope angle of the post row plays an important role in cell sorting. The cells mixture can not be separated properly in a small slope angle, while obvious blockages by WBCs will take place to disturb the continuous cell sorting in a big slope angle. As an optimal result, an adaptive slope angle is found to sort RBCs form WBCs correctly and continuously.

Asunto(s)

Separación Celular/instrumentación , Separación Celular/métodos , Eritrocitos/citología , Leucocitos/citología , Algoritmos , Movimiento Celular , Simulación por Computador , Humanos , Hidrodinámica , Técnicas Analíticas Microfluídicas , Microfluídica/métodos , Modelos Teóricos , Programas Informáticos , Viscosidad