Yang Liu

Publications (7) View all

• Article: Impact of the composition of alginate and gelatin derivatives in bio-conjugated hydrogels on the fabrication of cell sheets and spherical tissues with living cell sheaths.

  Yang Liu, Shinji Sakai, Masahito Taya
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  ABSTRACT: Gelatin and alginate derivatives possessing phenolic hydroxyl moieties (Gelatin-Ph and Alg-Ph) were dissolved in an aqueous solution and conjugated via a horseradish peroxidase-catalyzed cross-linking, resulting in hydrogelation. The objective of creating the hydrogels was to prepare cell sheets and spherical tissues wrapped with living cell sheaths. An increase in the content of Gelatin-Ph in the hydrogel improved cellular adhesion on the hydrogel surface but hindered the degradability by alginate lyase. A hydrogel meeting desired characteristics was obtained from a solution containing Gelatin-Ph and Alg-Ph at 0.5 and 1.5% (w/v), respectively. Human aortic endothelial (HAE) cells and mouse embryo fibroblast 10T1/2 cells grew on the hydrogels and could be harvested as cell sheets by treatment with alginate lyase. 10T1/2 cells, enclosed in Alg-Ph/Gelatin-Ph microcapsules, composed of the conjugate hydrogel, elongated on the inner surface of the microcapsules and grew three times faster than those enclosed in Alg-Ph microcapsules. Alg-Ph/Gelatin-Ph microcapsules not only supported growth of the enclosed cells into spherical tissues, but also provided a cell-adhesive outer surface for fabricating an HAE cell layer. Finally, spherical tissues of 10T1/2 cells wrapped with living HAE cell sheaths were obtained by treatment with alginate lyase.
  Acta biomaterialia 02/2013; · 3.98 Impact Factor
• Article: Horseradish peroxidase/catalase-mediated cell-laden alginate-based hydrogel tube production in two-phase coaxial flow of aqueous solutions for filament-like tissues fabrication.

  Shinji Sakai, Yang Liu, Emma Jane Mah, Masahito Taya
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  ABSTRACT: We report a method for preparing cell-laden hydrogel tubes. This method uses a coaxial double-orifice spinneret, simpler than triple-orifice spinnerets which have been used for preparing similar constructs. The intended application was to create a template for preparing filament-like structures composed of two heterogeneous living cell layers. An aqueous solution containing an alginate derivative possessing phenolic hydroxyl moieties (Alg-Ph), catalase and horseradish peroxidase (HRP) was extruded into an ambient flow of H(2)O(2) aqueous solution. This operation enabled the Alg-Ph solution to be gellable through a HRP-catalyzed reaction, cross-linking the Ph moieties together. By altering flow rates of the Alg-Ph and H(2)O(2) solutions along with the concentrations of catalase and H(2)O(2), the diameter and membrane thickness of the hydrogel tubes were controllable between 250-550 µm and 70-140 µm, respectively. The viability of the HeLa cells enclosed in the hydrogel tubes with a diameter of 300 µm and a membrane thickness of 80 µm was 95.4%. Subsequently, the enclosed HeLa cells grew and filled the hollow core. A filament-like structure of HeLa cells covered with a layer of fibroblast 10T1/2 cells was obtained when confluency of fibroblast 10T1/2 cells was reached and the hydrogel matrix was degraded with alginate lyase.
  Biofabrication 01/2013; 5(1):015012. · 3.48 Impact Factor
• Article: Enzymatically-gelled amylopectin-based substrates enable on-demand harvesting cells with preserving cell-to-cell connection using saliva.

  Shinji Sakai, Yang Liu, Masahito Taya
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  ABSTRACT: The possibility of on-demand harvesting of cells using human saliva was investigated for amylopectin-based hydrogel substrate obtained through enzymatic reaction. The human epithelial cells grown on the surface of the hydrogels detached within 10 min with preserving cell-to-cell connection by soaking in the medium containing human saliva at 5% (v/v).
  Journal of Bioscience and Bioengineering 11/2012; · 1.79 Impact Factor
• Article: Production of endothelial cell-enclosing alginate-based hydrogel fibers with a cell adhesive surface through simultaneous cross-linking by horseradish peroxidase-catalyzed reaction in a hydrodynamic spinning process.

  Yang Liu, Shinji Sakai, Masahito Taya
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  ABSTRACT: We developed an alginate-based hydrogel fiber enabling to enclose endothelial cells, degradable on-demand by alginate lyase, and having a cell adhesive surface. The hydrogel fiber was obtained by extruding an aqueous solution of 4% (w/v) alginate derivative possessing phenolic hydroxyl moieties (Alg-Ph) and horseradish peroxidase (HRP) into a flow of aqueous solution containing 0.3 mM H(2)O(2) and gelatin derivative possessing Ph moieties (Gelatin-Ph). In the process, cross-linking of Alg-Ph resulting in a hydrogel fiber and immobilization of Gelatin-Ph on the surface of the hydrogel fiber were simultaneously accomplished by an HRP-catalyzed cross-linking reaction between Ph moieties. The diameter of the hydrogel fiber and the quantity of immobilized Gelatin-Ph on the fiber were controllable by changing the flow rates of the solutions and the concentration of HRP in the Alg-Ph-containing solution, respectively. The viability of the human endothelial cells enclosed in the hydrogel fibers obtained by 10 s of flowing in the H(2)O(2)-containing solution was 87.1%. In addition, the cells harvested from the hydrogel fibers through degradation using alginate lyase grew on tissue culture dishes in the same fashion as the cells seeded by a conventional subculture protocol. Human smooth muscle cells adhered, grew and achieved confluence on the surface of the hydrogel fibers. By degrading the hydrogel fibers using alginate lyase, a tubular cell construct was successfully obtained.
  Journal of Bioscience and Bioengineering 05/2012; 114(3):353-9. · 1.79 Impact Factor
• Article: Rapidly serum-degradable hydrogel templating fabrication of spherical tissues and curved tubular structures.

  Shinji Sakai, Hitomi Inagaki, Yang Liu, Tomohiro Matsuyama, Takanori Kihara, Jun Miyake, Koei Kawakami, Masahito Taya
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  ABSTRACT: Development of the techniques for fabricating three-dimensional tissues still poses significant challenges for tissue engineering. We used hydrogels obtained from phenol-substituted amylopectin (AP-Ph) as templates for preparing multicellular spherical tissues (MSTs) and endothelialized curved tubular structures in type I collagen gel. AP-Ph hydrogel microparticles of diameter 200 µm and fibers of diameter 500 µm disappeared within hours of soaking in a serum-containing medium. HeLa cells and human endothelial cells were enclosed in the microparticles and hydrogel fibers, respectively, and then embedded in Ca-alginate microcapsules or the collagen gel. The enclosed cells were released in cavities formed by hydrogel degradation in the serum-containing medium. The released HeLa cells in the spherical cavities grew and formed MSTs, eventually filling the cavities. The spherical tissues were easily harvested by liquefying the Ca-alginate hydrogel microcapsule membrane by chelation using sodium citrate. The released endothelial cells grew on the tubular cavity surfaces and formed tubular structures. An endothelial cell network was formed by cell migration into the collagen gel. These results demonstrate the potential of serum-degradable AP-Ph hydrogels in constructing three-dimensional tissues. Biotechnol. Bioeng. 2012; 109: 2911-2919. © 2012 Wiley Periodicals, Inc.
  Biotechnology and Bioengineering 05/2012; 109(11):2911-9. · 3.95 Impact Factor