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Although a microfluidic neuronal culture technique that utilised a microchannel structure to generate a motor nerve organoid consisted of neurospheres and fascicles of motor neuronal axons derived from human induced pluripotent stem cells (iPSCs) was reported recently, the lengths of the axonal fascicles were limited to less than 1 cm, which corresponded to the microchannel length. In this study, the authors fabricated microfluidic devices composed of a polydimethylsiloxane chip with a glass substrate and 20-mm-long and 150-μm-wide microchannels to obtain centimetre-long axonal fascicles. They investigated the effects of microchannel height on fascicle length by using three different microchannel heights (120, 150, and 220 μm), neurospheres containing 80,000 motor neuronal cells derived from a human iPSCs cell line (409B2), and N2B27 medium. Maximum and average fascicle lengths of 2 and 1.25 cm, respectively, were successfully achieved with 150-μm-high microchannels. The fascicles grew in length, with an increase in the number of days spent in the culture (ranging from 0.44 to 0.60 mm per day), growing to over 1 cm around the 23rd day of culture. The difference in fascicle length obtained with 120-μm and 150-μm-high microchannels suggests that height significantly affects the length of the axonal fascicle of the nerve organoid.

In spite of wide-ranging previous studies on synthetic macrocycles, the installation of open–close functions into the frameworks remains a challenge. We present a new polyaromatic macrocycle capable of switching between open and closed forms in response to external stimuli, namely, base and acid. The macrocycle, which is prepared in three steps, has a well-defined hydrophobic cavity with a length of around 1 nm, surrounded by four pH-responsive acridinium panels. The open and closed structures were confirmed by single-crystal X-ray analysis. The cylindrical cavity can bind long hydrophilic molecules up to 2.7 nm in length in neutral water and then release the bound guests through a reversible open-to-closed structural change upon simple addition of base.