Daisuke Kiriya

Metre-long cell-laden microfibres exhibit tissue morphologies and functions

Artificial reconstruction of fibre-shaped cellular constructs could greatly contribute to tissue assembly in vitro. Here we show that, by using a microfluidic device with double-coaxial laminar flow, metre-long core-shell hydrogel microfibres encapsulating ECM proteins and differentiated cells or somatic stem cells can be fabricated, and that the microfibres reconstitute intrinsic morphologies and functions of living tissues. We also show that these functional fibres can be assembled, by weaving and reeling, into macroscopic cellular structures with various spatial patterns. Moreover, fibres encapsulating primary pancreatic islet cells and transplanted through a microcatheter into the subrenal capsular space of diabetic mice normalized blood glucose concentrations for about two weeks. These microfibres may find use as templates for the reconstruction of fibre-shaped functional tissues that mimic muscle fibres, blood vessels or nerve networks in vivo.

Cellular building unit integrated with microstrand-shaped bacterial cellulose

In bottom-up tissue engineering, a method to integrate a pathway of nutrition and oxygen into the resulting macroscopic tissue has been highly desired, but yet to be established. This paper presents a cellular building unit made from microstrand-shaped bacterial cellulose (BC microstrand) covered with mammalian cells. The BC microstrands are fabricated by encapsulating Acetobacter xylinum with a calcium alginate hydrogel microtube using a double co-axial microfluidic device. The mechanical strength and porous property of the BC microstrands can be regulated by changing the initial density of the bacteria. By folding or reeling the building unit, we demonstrated the multiple shapes of millimeter-scale cellular constructs such as coiled and ball-of-yarn-shaped structures. Histological analysis of the cellular constructs indicated that the BC microstrand served as a pathway of nutrition and oxygen to feed the cells in the central region. These findings suggest that our approach facilitates creating functional macroscopic tissue used in various fields such as drug screening, wound healing, and plastic surgery.

Core-shell gel wires for the construction of large area heterogeneous structures with biomaterials

This paper describes core-shell hydrogel wires for constructing 3D heterogeneous hydrogel microstructures containing biomaterials. A core hydrogel layer contains biomaterials such as cells, and a shell hydrogel layer covers the core to realize a mechanically-robust hydrogel wire. Using this core-shell gel wires, we demonstrate a woven sheet with heterogeneous gel wires by using our stereolithographically-made weaving machine. We also fabricate a reeled-up tube-like cell-containing structure by a glass tube spindle, inspired by tools from fiber industry. We show that our core-shell gel wires and weaving methods are powerful approach to arrange heterogeneous biomaterials in three dimensions.

Living cell fabric

This paper describes a centimeter-scale living cell fabric made of cell-containing core-shell hydrogel fibers, “cell fiber.” We improved core-shell fiber applicable to various types of cells, and precisely characterized their biofunctions and mechanical properties. Using these cell fibers, we demonstrate a centimeter-scale living cell fabric woven by our micro weaving machine. We believe that our weaving approach using cell fibers would be a powerful method for constructing large-scale 3D-patterned functional tissues.

MEMS meets supramolecules: Aligning supramolecular fibers within hydrogel strand using a microfluidic channel

This paper describes the formation of a micro-scale gel strand constructed with self-assembled supramolecular nanofibers fabricated in a microfluidic channel. The supramolecular nanofibers are highly aligned along the axis of the gel strand; this morphology is very different from the bulk gel. Moreover, we found that small molecules are able to diffuse along the supramolecular-nanofibers axis. We believe that these gel strands could be a useful material to transport small molecules based on the supramolecular interaction.

Biofilms in hydrogel core-shell fibers

This paper describes a hydrogel microfiber encapsulating bacteria using an axisymmetric microfluidic device that creates co-axial laminar flow. Since the encapsulated bacteria proliferate at high density in the core of the microfiber, they easily form biofilms; these films are suggested to be important for the cell viability and high-level bacterial secretion. Here, we succeeded in preparing densely packed bacteria in the hydrogel microfiber, and found they proliferated and formed biofilm. We believe this microfiber will be a useful material in the field of bioreactors and microbial sensors.

Propelling microobjects using a stationary DC voltage

We report a method for propelling microobjects under a DC voltage without switching the direction of the voltage. In this study, a stationary DC voltage (about 100 V) was applied to the microobjects (glass beads) in oil using ITO electrodes. The glass beads exhibited random or oscillatory motion when few beads less than four beads were placed between the electrodes; on the other hand, the mass of beads much more than four beads exhibited unidirectional motion as a group. This technique can be applied to transportation of microobjects under simple patterned-electrodes in microsystems without waveform generators.

Inorganic/Parylene composite thin film toward 3D robust structures

We report a composite thin film consisting of inorganic calcium carbonate (CaCO3) crystals and organic Parylene. The CaCO3 crystals were grown on a surface of poly(vinyl alcohol) (PVA) on Parylene and covered the whole region of organic surface homogeneously. The thickness of CaCO3 crystals was about 180 nm and that of organic layers of Parylene with PVA was about 2 μm. Importantly, the thin film shows synergistic properties of CaCO3 crystals and Parylene; the film shows transparency, handleability, shape adjustability and resistivity for fire. Our results indicate that our approach should be useful for harnessing both inorganic and organic properties synergistically.

Microfluidic control of internal morphology of hydrogel fiber

This paper describes a morphology control of nanofiber assemblies in a microfluidic channel; nanofibers show some arrangements in a microfluidic channel depending on flow rates. By curing these morphological flows, we obtained hydrogel fibers with similar morphologies of the flows. Our research indicates that we can control the internal morphologies of materials using microfluidic channels.