Fabrication of multilayered vascular tissues using microfluidic agarose hydrogel platforms.

Vascular tissues fabricated in vitro are useful tools for studying blood vessel-related cellular physiologies and for constructing relatively large 3D tissues. An efficient strategy for fabricating vascular tissue models with multilayered, branched, and thick structures through the in situ hydrogel formation in fluidic channels is proposed. First, an aqueous solution of RGD-alginate containing smooth muscle cells (SMCs) is introduced into channel structures made of agarose hydrogel, forming a cell-embedding Ca-alginate hydrogel layer with a thickness of several hundred micrometers on the channel surface because of the Ca2+ ions diffused from the agarose hydrogel matrix. Next, endothelial cells (ECs) are introduced and cultured for up to seven days to form hierarchically organized, multilayered vascular tissues. The factors affecting the thickness of the Ca-alginate hydrogel layer, and prepared several types of microchannels with different morphologies are examined. The fabricated vascular tissue models are easily recovered from the channel by simply detaching the agarose hydrogel plates. In addition, the effect of O2 tension (20 or 80%) on the viability and elastin production of SMCs during the perfusion culture is evaluated. This technique would pave a new way for vascular tissue engineering because it enables the facile production of morphologically in vivo vascular tissue-like structures that can be employed for various biomedical applications.

Facile fabrication processes for hydrogel-based microfluidic devices made of natural biopolymers.

We present facile strategies for the fabrication of two types of microfluidic devices made of hydrogels using the natural biopolymers, alginate, and gelatin as substrates. The processes presented include the molding-based preparation of hydrogel plates and their chemical bonding. To prepare calcium-alginate hydrogel microdevices, we suppressed the volume shrinkage of the alginate solution during gelation using propylene glycol alginate in the precursor solution along with sodium alginate. In addition, a chemical bonding method was developed using a polyelectrolyte membrane of poly-L-lysine as the electrostatic glue. To prepare gelatin-based microdevices, we used microbial transglutaminase to bond hydrogel plates chemically and to cross-link and stabilize the hydrogel matrix. As an application, mammalian cells (fibroblasts and vascular endothelial cells) were cultivated on the microchannel surface to form three-dimensional capillary-embedding tissue models for biological research and tissue engineering.