The brain is one of the most important and complex organs in the human body. Although various neural network models have been proposed for in vitro 3D neuronal networks, it has been difficult to mimic functional and structural complexity of the in vitro neural circuit. Here, a microfluidic model of a simplified 3D neural circuit is reported. First, the microfluidic device is filled with Matrigel and continuous flow is delivered across the device during gelation. The fluidic flow aligns the extracellular matrix (ECM) components along the flow direction. Following the alignment of ECM fibers, neurites of primary rat cortical neurons are grown into the Matrigel at the average speed of 250 μm d(-1) and form axon bundles approximately 1500 μm in length at 6 days in vitro (DIV). Additionally, neural networks are developed from presynaptic to postsynaptic neurons at 14 DIV. The establishment of aligned 3D neural circuits is confirmed with the immunostaining of PSD-95 and synaptophysin and the observation of calcium signal transmission.

We synthesized a series of Seoul-Fluor-based lipid droplet bioprobes with a linear range of lipophilicity and identified SF44 and SF58 as SF-based LD bioprobes in microalgae for biofuel research as well as in mammalian cells. Unlike Nile Red, SF-based bioprobes can stain algal LDs with excellent efficiency under the non-invasive and non-cytotoxic conditions.

Soft lithography and other techniques have been developed to investigate biological and chemical phenomena as an alternative to photolithography-based patterning methods that have compatibility problems. Here, a simple approach for nonlithographic patterning of liquids and gels inside microchannels is described. Using a design that incorporates strategically placed microstructures inside the channel, microliquids or gels can be spontaneously trapped and patterned when the channel is drained. The ability to form microscale patterns inside microfluidic channels using simple fluid drain motion offers many advantages. This method is geometrically analyzed based on hydrodynamics and verified with simulation and experiments. Various materials (i.e., water, hydrogels, and other liquids) are successfully patterned with complex shapes that are isolated from each other. Multiple cell types are patterned within the gels. Capillarity guided patterning (CGP) is fast, simple, and robust. It is not limited by pattern shape, size, cell type, and material. In a simple three-step process, a 3D cancer model that mimics cell-cell and cell-extracellular matrix interactions is engineered. The simplicity and robustness of the CGP will be attractive for developing novel in vitro models of organ-on-a-chip and other biological experimental platforms amenable to long-term observation of dynamic events using advanced imaging and analytical techniques.

Neural circuits, groups of neurons connected in directional manner, play a central role in information processing. Advances in neuronal biology research is limited by a lack of appropriate in vitro methods to construct and probe neuronal networks. Here, we describe a microfluidic culture platform that directs the growth of axons using “neural diode” structures to control neural connectivity. This platform is compatible with live cell imaging and can be used to (i) form pre-synaptic and postsynaptic neurons by directional axon growth and (ii) localize physical and chemical treatment to pre- or postsynaptic neuron groups (i.e. virus infection and etc.). The “neural diode” design consist of a microchannel that split into two branches: one is directed straight toward while the other returns back toward the starting point in a closed loop to send the axons back to the origin. We optimized the “neural diode” pattern dimension and design to achieve close to 70% directionality with a single unit of the “diode”. When repeated 3 times, near perfect (98–100% at wide range of cell concentrations) directionality can be achieved. The living neural circuit was characterized using Ca imaging and confirmed their function. The platform also serves as a straightforward, reproducible method to recapitulate a variety of neural circuit in vitro that were previously observable only in brain slice or in vivo models. The microfluidic neural diode may lead to better models for understanding the neural circuit and neurodegenerative diseases.