Natsuko Hosoda

Enzymatically fabricated and degradable microcapsules for production of multicellular spheroids with well-defined diameters of less than 150 μm

Microcapsules with a single, spherical hollow core less than 150 microm in diameter were developed to obtain multicellular spheroids with well-defined sizes of less than 150 microm in diameter. An aqueous solution of phenolic hydroxyl derivative of carboxymethylcellulose (CMC-Ph) containing human hepatoma cell line (HepG2) cells and horse radish peroxidase (HRP) was injected into a coflowing stream of liquid paraffin, containing H(2)O(2), resulting in cell-enclosing CMC-Ph microparticles, 135 microm in diameter, via a peroxidase-catalyzed crosslinking reaction. The CMC-Ph microparticles were then coated with a phenolic hydroxyl derivative of alginate (Alg-Ph) gel membrane several dozen micrometers in thickness, crosslinked via the same enzymatic reaction process, followed by further crosslinking between the carboxyl groups of alginate by Sr(2+). A hollow core structure was achieved by immersing the resultant microcapsules in a medium containing cellulase, which degrades the enclosed CMC-Ph microparticles. The HepG2 cells in the microcapsules then grew and completely filled the hollow core. Multicellular spheroids the same size as the CMC-Ph microparticles, with living cells at their outer surface, were collected within 1 min by soaking them in a medium containing alginate lyase to degrade the Alg-Ph gel microcapsule membrane.

Roles of adsorbed film and gel layer in hydration lubrication for articular cartilage

Abstract To maintain low friction and low wear in natural synovial joints, adsorbed film formation on articular cartilage surface appears to play an important role in mixed or boundary lubrication regime where local direct contact occurs. Furthermore, the proteoglycan gel layer at the uppermost superficial zone in articular cartilage appears to play an important role in preserving low friction and low wear by the hydration lubrication mechanism even after removal of adsorbed film. However, the interaction or synergistic action between adsorbed film and hydrated film/surface has not yet been clarified. To examine the roles of adsorbed film and gel layer on articular cartilage surface in hydration lubrication, the changes in friction were observed in the reciprocating test of articular cartilage against a glass plate, at repeated rubbing including restarting after interrupting—unloading process. It is noticed that at restarting immediately after loading, hydration lubrication is expected to become effective. The lubricating roles of protein-adsorbed film in hydration lubrication are discussed on the basis of experimental results in both cases with and without surface gel layer. The comparison of albumin and γ -globulin is described in connection with the existence of a gel layer.

Finite Element Analysis of Articular Cartilage Model Considering the Configuration and Biphasic Property of the Tissue

Articular cartilage tissue has high water content from 70 to 80% and shows biphasic behavior in which both solid and fluid properties should be considered. Furthermore, the mechanical behavior of cartilage shows depth-dependence. Therefore it is necessary to consider not only the average tissue property but also the local one to explain mechanical and functional behavior.