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Microfluidic guillotine reveals multiple timescales and mechanical modes of wound response in Stentor coeruleusAbstract Background Wound healing is one of the defining features of life and is seen not only in tissues but also within individual cells. Understanding wound response at the single-cell level is critical for determining fundamental cellular functions needed for cell repair and survival. This understanding could also enable the engineering of single-cell wound repair strategies in emerging synthetic cell research. One approach is to examine and adapt self-repair mechanisms from a living system that already demonstrates robust capacity to heal from large wounds. Towards this end, Stentor coeruleus , a single-celled free-living ciliate protozoan, is a unique model because of its robust wound healing capacity. This capacity allows one to perturb the wounding conditions and measure their effect on the repair process without immediately causing cell death, thereby providing a robust platform for probing the self-repair mechanism. Results Here we used a microfluidic guillotine and a fluorescence-based assay to probe the timescales of wound repair and of mechanical modes of wound response in Stentor . We found that Stentor requires ~ 100–1000 s to close bisection wounds, depending on the severity of the wound. This corresponds to a healing rate of ~ 8–80 μm 2 /s, faster than most other single cells reportedmore »
Fabrication of 3D Micro-Blades for the Cutting of Biological Structures in a Microfluidic GuillotineMicro-blade design is an important factor in the cutting of single cells and other biological structures. This paper describes the fabrication process of three-dimensional (3D) micro-blades for the cutting of single cells in a microfluidic “guillotine” intended for fundamental wound repair and regeneration studies. Our microfluidic guillotine consists of a fixed 3D micro-blade centered in a microchannel to bisect cells flowing through. We show that the Nanoscribe two-photon polymerization direct laser writing system is capable of fabricating complex 3D micro-blade geometries. However, structures made of the Nanoscribe IP-S resin have low adhesion to silicon, and they tend to peel off from the substrate after at most two times of replica molding in poly(dimethylsiloxane) (PDMS). Our work demonstrates that the use of a secondary mold replicates Nanoscribe-printed features faithfully for at least 10 iterations. Finally, we show that complex micro-blade features can generate different degrees of cell wounding and cell survival rates compared with simple blades possessing a vertical cutting edge fabricated with conventional 2.5D photolithography. Our work lays the foundation for future applications in single cell analyses, wound repair and regeneration studies, as well as investigations of the physics of cutting and the interaction between the micro-blade and biological structures.
The giant unicellular ciliate Stentor coeruleus can be cut into pieces and each piece will regenerate into a healthy, full-sized individual. The molecular mechanism for how Stentor regenerates is a complete mystery, however, the process of regeneration shows striking similarities to the process of cell division. On a morphological level, the process of creating a second mouth in a division or a new oral apparatus in regeneration have the same steps and occur in the same order. On the transcriptional level, genes encoding elements of the cell division and cell cycle regulatory machinery, including Aurora kinases, are differentially expressed during regeneration. This suggests that there may be some common regulatory mechanisms involved in both regeneration and cell division. If the cell cycle machinery really does play a role in regeneration, then inhibition of proteins that regulate the timing of cell division may also affect the timing of regeneration in Stentor. Here we show that two well-characterized Aurora kinase A+B inhibitors that affect the timing of oral apparatus regeneration. ZM447439 slows down the regeneration of the oral apparatus by at least one hour. PF03814735 completely suppresses the regeneration of the oral apparatus until the drug is removed. Here we provide themore »